WorldWideScience

Sample records for weak annihilation wa

  1. Weak annihilation and new physics in charmless B → MM decays

    Energy Technology Data Exchange (ETDEWEB)

    Bobeth, Christoph [Institute for Advanced Study, Technische Universitaet Muenchen, Garching (Germany); Gorbahn, Martin [University of Liverpool, Department of Mathematical Sciences, Liverpool (United Kingdom); Vickers, Stefan [Excellence Cluster Universe, Technische Universitaet Muenchen, Garching (Germany)

    2015-07-15

    We use currently available data of nonleptonic charmless 2-body B → MM decays (MM = PP, PV,VV) that are mediated by b → (d, s) QCD- and QED-penguin operators to study weak annihilation and new-physics effects in the framework of QCD factorization. In particular we introduce one weak-annihilation parameter for decays related by (u <-> d) quark interchange and test this universality assumption. Within the standard model, the data supports this assumption with the only exceptions in the B → Kπ system, which exhibits the well-known ''ΔA{sub CP} puzzle'', and some tensions in B → K*φ. Beyond the standard model, we simultaneously determine weak-annihilation and new-physics parameters from data, employing model independent scenarios that address the ''ΔA{sub CP} puzzle'', such as QED-penguins and b → s anti uu current-current operators. We discuss also possibilities that allow further tests of our assumption once improved measurements from LHCb and Belle II become available. (orig.)

  2. Weak annihilation cusp inside the dark matter spike about a black hole.

    Science.gov (United States)

    Shapiro, Stuart L; Shelton, Jessie

    2016-06-15

    We reinvestigate the effect of annihilations on the distribution of collisionless dark matter (DM) in a spherical density spike around a massive black hole. We first construct a very simple, pedagogic, analytic model for an isotropic phase space distribution function that accounts for annihilation and reproduces the "weak cusp" found by Vasiliev for DM deep within the spike and away from its boundaries. The DM density in the cusp varies as r -1/2 for s -wave annihilation, where r is the distance from the central black hole, and is not a flat "plateau" profile. We then extend this model by incorporating a loss cone that accounts for the capture of DM particles by the hole. The loss cone is implemented by a boundary condition that removes capture orbits, resulting in an anisotropic distribution function. Finally, we evolve an initial spike distribution function by integrating the Boltzmann equation to show how the weak cusp grows and its density decreases with time. We treat two cases, one for s -wave and the other for p -wave DM annihilation, adopting parameters characteristic of the Milky Way nuclear core and typical WIMP models for DM. The cusp density profile for p -wave annihilation is weaker, varying like ~ r -0.34 , but is still not a flat plateau.

  3. Weak interaction effects in e+e- annihilation with polarised beams

    International Nuclear Information System (INIS)

    Simard, R.

    1977-01-01

    Although the standard gauge model of weak and electromagnetic interactions based on the work of Salam and Weinberg has met with great success, there are experimental facts that will require its extension or its modification to a new gauge model; the discovery of a heavy lepton at SLAC and the absence of parity violation in atoms that is expected from the neutral weak current coupling to electrons are discussed. Three tests are proposed that bear on these questions. First, heavy lepton production in e + e - annihilation when one of the incident beams is longitudinally polarized is considered and the purely leptonic decay of this heavy lepton is examined. An asymmetry in the inclusive angular distribution of one charged lepton (electron or muon) is important in determining the structure of weak interactions of the heavy lepton. In fact, this angular asymmetry easily distinguishes between the cases V - A and V + A for the heavy lepton current. Then, the decay channel L → ν/sub L/ + one hadron is considered (L = heavy lepton) under the same experimental set-up and the inclusive one-hadron angular distribution examined. Parity nonconservation in the decay of the heavy lepton causes a conspicuous forward-backward asymmetry in the cos theta distribution of the inclusive hadron spectrum near the high energy end that can be distinguished easily from other sources of asymmetry. It is easy then to discover the chirality (V - A or V + A) of the heavy lepton current. Finally a test is proposed which provides unambigous and clear evidence for parity violation in e + e - annihilation. It consists in measuring a possible left-right asymmetry of inclusive hadron production with highly transversely polarized e + e - incident beams. If observed, this asymmetry provides evidence of a parity violating neutral current coupling to electrons

  4. Manifestation of neutral weak currents in the e+e-annihilation

    International Nuclear Information System (INIS)

    Rekalo, M.P.; Gakh, G.I.; Korzh, A.P.

    1980-01-01

    The polarization effects, caused by the interference between electromagnetic and neutral weak currents mechanisms, are investigated for the inclusive V-meson production in the e + e - - annihilation. The polarization states of the V-meson are discussed in detail. We use three decriptions of the V-meson polarization. They are: the 4-vector of spin and quadrupole tensor description, the polarization vector description and the density matrix, formalis. The collision of the polarized beams is characterized by the virtual photon and Z-boson density matrix in the helicity representation

  5. Study of the weak annihilation contributions in charmless B{sub s} → VV decays

    Energy Technology Data Exchange (ETDEWEB)

    Chang, Qin [Henan Normal University, Institute of Particle and Nuclear Physics, Henan (China); Central China Normal University, Institute of Particle Physics and Key Laboratory of Quark and Lepton Physics (MOE), Wuhan, Hubei (China); Li, Xiaonan; Sun, Junfeng [Henan Normal University, Institute of Particle and Nuclear Physics, Henan (China); Li, Xin-Qiang [Central China Normal University, Institute of Particle Physics and Key Laboratory of Quark and Lepton Physics (MOE), Wuhan, Hubei (China)

    2017-06-15

    In this paper, in order to probe the spectator-scattering and weak annihilation contributions in charmless B{sub s} → VV (where V stands for a light vector meson) decays, we perform the χ{sup 2}-analyses for the endpoint parameters within the QCD factorization framework, under the constraints from the measured anti B{sub s} → ρ{sup 0}φ, φK{sup *0}, φφ and K{sup *0} anti K{sup *0} decays. The fitted results indicate that the endpoint parameters in the factorizable and nonfactorizable annihilation topologies are non-universal, which is also favored by the charmless B → PP and PV (where P stands for a light pseudo-scalar meson) decays observed in previous work. Moreover, the abnormal polarization fractions f{sub L,} {sub perpendicular} {sub to} (anti B{sub s} → K{sup *0} anti K{sup *0}) = (20.1±7.0)%, (58.4±8.5)% measured by the LHCb collaboration can be reconciled through the weak annihilation corrections. However, the branching ratio of anti B{sub s} → φK{sup *0} decay exhibits a tension between the data and theoretical result, which dominates the contributions to χ{sub min}{sup 2} in the fits. Using the fitted endpoint parameters, we update the theoretical results for the charmless B{sub s} → VV decays, which will be further tested by the LHCb and Belle-II experiments in the near future. (orig.)

  6. Ushairi wa Kiswahili kama Chombo cha Ujenzi wa Utangamano wa ...

    African Journals Online (AJOL)

    Makala haya yanafafanua dhima ya ushairi wa Kiswahili katika kujenga uwiano na utangamano katika jamii. Maendeleo na ustawi wa lugha huenda sambamba na fasihi yake. Ushairi wa Kiswahili kama utanzu wa fasihi, una historia ndefu. Aidha, umaarufu wa ushairi huu hautokani tu na vipengele vya lugha teule ...

  7. 'Mgogoro' wa Ushairi wa Kiswahili bado Upo?: Uchunguzi wa ...

    African Journals Online (AJOL)

    Nyimbo za muziki wa Hip hop na Bongo fleva zimekuwa maarufu nchini Tanzania kuanzia miaka ya 1980. Nyimbo hizi, kama mojawapo ya tanzu au kipera cha ushairi simulizi wa Kiswahili, zimekuwa ni chanzo kizuri cha utafiti kuhusiana na masuala mbalimbali yahusikayo. Miongoni mwa mambo yanayoonekana kuanza ...

  8. WaVPeak: Picking NMR peaks through wavelet-based smoothing and volume-based filtering

    KAUST Repository

    Liu, Zhi

    2012-02-10

    Motivation: Nuclear magnetic resonance (NMR) has been widely used as a powerful tool to determine the 3D structures of proteins in vivo. However, the post-spectra processing stage of NMR structure determination usually involves a tremendous amount of time and expert knowledge, which includes peak picking, chemical shift assignment and structure calculation steps. Detecting accurate peaks from the NMR spectra is a prerequisite for all following steps, and thus remains a key problem in automatic NMR structure determination. Results: We introduce WaVPeak, a fully automatic peak detection method. WaVPeak first smoothes the given NMR spectrum by wavelets. The peaks are then identified as the local maxima. The false positive peaks are filtered out efficiently by considering the volume of the peaks. WaVPeak has two major advantages over the state-of-the-art peak-picking methods. First, through wavelet-based smoothing, WaVPeak does not eliminate any data point in the spectra. Therefore, WaVPeak is able to detect weak peaks that are embedded in the noise level. NMR spectroscopists need the most help isolating these weak peaks. Second, WaVPeak estimates the volume of the peaks to filter the false positives. This is more reliable than intensity-based filters that are widely used in existing methods. We evaluate the performance of WaVPeak on the benchmark set proposed by PICKY (Alipanahi et al., 2009), one of the most accurate methods in the literature. The dataset comprises 32 2D and 3D spectra from eight different proteins. Experimental results demonstrate that WaVPeak achieves an average of 96%, 91%, 88%, 76% and 85% recall on 15N-HSQC, HNCO, HNCA, HNCACB and CBCA(CO)NH, respectively. When the same number of peaks are considered, WaVPeak significantly outperforms PICKY. The Author(s) 2012. Published by Oxford University Press.

  9. ulinganishi wa muundo wa vitomeo katika kamusi mbili za kiswahili

    African Journals Online (AJOL)

    ULINGANISHI WA MUUNDO WA VITOMEO KATIKA KAMUSI MBILI ZA KISWAHILI - KIINGEREZA. E.K.F Chiduo. Abstract. Ulinganishi wa Kamusi Sanifu ya Kiswahili-Kiingereza (KSKK, 1993) na Kamusi ya Kiswahili- Kiingereza (KKK, TUKI 2001) unazingatia mtazamo wa Nkweti-Azel. Mtizamo huu unazingatia vipengelele ...

  10. Towards a quantitative description of hadronic weak decays

    International Nuclear Information System (INIS)

    Bigi, I.I.Y.

    1981-01-01

    We develop a formalism for describing hadronic weak annihilation decays in analogy to the treatment of deep inelastic lepton-nucleon scattering: we write down evolution equations for colour singlet and octet (Qanti q) systems inside mesons of increasing mass. Using D decays as input we can predict weak annihilation decay rates of heavier mesons in a semiquantitative fashion despite our ignorance on bound-state dynamics. (orig.)

  11. CMB bounds on dark matter annihilation: Nucleon energy losses after recombination

    NARCIS (Netherlands)

    Weniger, C.; Serpico, P.D.; Iocco, F.; Bertone, G.

    2013-01-01

    We consider the propagation and energy losses of protons and antiprotons produced by dark matter annihilation at redshifts 100annihilations into quarks, gluons and weak gauge bosons, protons and antiprotons carry about 20% of the energy injected into e± and γ’s,

  12. Annihilation physics of exotic galactic dark matter particles

    Science.gov (United States)

    Stecker, F. W.

    1990-01-01

    Various theoretical arguments make exotic heavy neutral weakly interacting fermions, particularly those predicted by supersymmetry theory, attractive candidates for making up the large amount of unseen gravitating mass in galactic halos. Such particles can annihilate with each other, producing secondary particles of cosmic-ray energies, among which are antiprotons, positrons, neutrinos, and gamma-rays. Spectra and fluxes of these annihilation products can be calculated, partly by making use of positron electron collider data and quantum chromodynamic models of particle production derived therefrom. These spectra may provide detectable signatures of exotic particle remnants of the big bang.

  13. Utafiti Wa Lahaja Za Kiswahili: Uzoefu Wa Uwandani | Ismail ...

    African Journals Online (AJOL)

    Katika ujumla wake, historia ya utafiti, na hasa utafiti wa uwandani, ni historia ya jitihada za binadamu katika kujishughulisha kwake ili ayaelewe masuala mengi mtambuka katika mazingira fungamanishi. Hakuna mtafiti yeyote anayeweza kudai kuwa utafiti wa mada fulani katika eneo fulani umekamilika na ...

  14. Mabadiliko Ya Kifonolojia Na Kimofolojia Wakati Wa Utohozi Wa ...

    African Journals Online (AJOL)

    Mwingiliano wa lugha ya Kiswahili na Kiarabu una historia ndefu kidogo. Inasemekana Waarabu walianza muwasala na 'Waswahili' tangu karne ya kwanza (BK) (Polome 1967:9). Kutokana na muwasala huo wa muda mrefu, lugha hizi mbili (Kiarabu na Kiswahili) zimeathiriana sana. Lakini kuna maoni kwamba Kiarabu ...

  15. Azimuthal Seismic Amplitude Variation with Offset and Azimuth Inversion in Weakly Anisotropic Media with Orthorhombic Symmetry

    Science.gov (United States)

    Pan, Xinpeng; Zhang, Guangzhi; Yin, Xingyao

    2018-01-01

    Seismic amplitude variation with offset and azimuth (AVOaz) inversion is well known as a popular and pragmatic tool utilized to estimate fracture parameters. A single set of vertical fractures aligned along a preferred horizontal direction embedded in a horizontally layered medium can be considered as an effective long-wavelength orthorhombic medium. Estimation of Thomsen's weak-anisotropy (WA) parameters and fracture weaknesses plays an important role in characterizing the orthorhombic anisotropy in a weakly anisotropic medium. Our goal is to demonstrate an orthorhombic anisotropic AVOaz inversion approach to describe the orthorhombic anisotropy utilizing the observable wide-azimuth seismic reflection data in a fractured reservoir with the assumption of orthorhombic symmetry. Combining Thomsen's WA theory and linear-slip model, we first derive a perturbation in stiffness matrix of a weakly anisotropic medium with orthorhombic symmetry under the assumption of small WA parameters and fracture weaknesses. Using the perturbation matrix and scattering function, we then derive an expression for linearized PP-wave reflection coefficient in terms of P- and S-wave moduli, density, Thomsen's WA parameters, and fracture weaknesses in such an orthorhombic medium, which avoids the complicated nonlinear relationship between the orthorhombic anisotropy and azimuthal seismic reflection data. Incorporating azimuthal seismic data and Bayesian inversion theory, the maximum a posteriori solutions of Thomsen's WA parameters and fracture weaknesses in a weakly anisotropic medium with orthorhombic symmetry are reasonably estimated with the constraints of Cauchy a priori probability distribution and smooth initial models of model parameters to enhance the inversion resolution and the nonlinear iteratively reweighted least squares strategy. The synthetic examples containing a moderate noise demonstrate the feasibility of the derived orthorhombic anisotropic AVOaz inversion method, and the

  16. The electroweak interaction in e+e- annihilations

    International Nuclear Information System (INIS)

    Marshall, R.

    1982-04-01

    The role of e + e - annihilation in studying the weak neutral current, at PETRA and PEP, is reviewed. The way in which the vector and axial vector couplings appear in the total cross sections, the angular distributions and the polarisation dependences are discussed. The dependence of external gauge models on the results of PETRA and PEP experiments is examined. (U.K.)

  17. e+e- annihilation in the Weinberg-Salam model

    International Nuclear Information System (INIS)

    Davier, M.

    1980-01-01

    Electron-positron annihilation at high energies is a good probe of the neutral weak interaction and it is foreseen to be a privileged tool for the study of the neutral weak and electromagnetic currents. In these lectures, we analyse in detail the various tests of the gauge structure of these currents with particular emphasis on the SU(2) X U(1) Salam-Weinberg group. These tests include: study of the coupling of all fermions (leptons and quarks) to the neutral weak current, vector boson (Z 0 and W +- ) production. Higgs meson production and finally 3 and 4 boson couplings - a critical test of non-abelian group structure [fr

  18. Weak interactions of the b quark

    International Nuclear Information System (INIS)

    Branco, G.C.; Mohapatra, R.N.

    1978-01-01

    In weak-interaction models with two charged W bosons of comparable mass, there exists a novel possibility for the weak interactions of the b quark, in which the (u-barb)/sub R/ current occurs with maximal strength. It is noted that multimuon production in e + e - annihilation at above Q 2 > or approx. = (12 GeV) 2 will distinguish this scheme from the conventional one. We also present a Higgs system that leads naturally to this type of coupling, in a class of gauge models

  19. Appearance of a Minimal Length in $e^+ e^-$ Annihilation

    CERN Document Server

    Dymnikova, Irina; Ulbricht, Jürgen

    2014-01-01

    Experimental data reveal with a 5$\\sigma$ significance the existence of a characteristic minimal length $l_e$= 1.57 × 10$^{−17}$ cm at the scale E = 1.253 TeV in the annihilation reaction $e^+e^- \\to \\gamma\\gamma(\\gamma)$ . Nonlinear electrodynamics coupled to gravity and satisfying the weak energy condition predicts, for an arbitrary gauge invariant Lagrangian, the existence of spinning charged electromagnetic soliton asymptotically Kerr-Newman for a distant observer with the gyromagnetic ratio g=2 . Its internal structure includes a rotating equatorial disk of de Sitter vacuum which has properties of a perfect conductor and ideal diamagnetic, displays superconducting behavior, supplies a particle with the finite positive electromagnetic mass related to breaking of space-time symmetry, and gives some idea about the physical origin of a minimal length in annihilation.

  20. Neutron mean annihilation time and inverse of the mean annihilation rate in nuclear reactor

    International Nuclear Information System (INIS)

    Hayashi, Masatoshi

    1999-01-01

    There is a dogma in nuclear reactor theory that in a critical reactor the mean annihilation time of neutron is equal to the mean generation time. The author insists that this is a dogma from the basic reexamination of the mean annihilation time of neutron. There are two kinds of neutrons, one participating in chain reactions and the other not participating in chain reactions. The mean annihilation time of neutron is the mean time of the time to annihilation of all neutrons generated in the reactor. The 'prompt neutron life' as a dynamic characteristic parameter proper to nuclear reactor can not be understood as the mean time of neutron to annihilation. The author explains the logic quantitatively with two kinds of nuclear reactors, a bare reactor and an infinite reactor, for which two different mean neutron annihilation times can be defined. Thus, (1) the inverse of the annihilation rate can not simply be considered as the mean annihilation time, (2) the mean annihilation time of a critical reactor is not necessarily equal to the mean generation time, and (3) the prompt neutron life used as a dynamic characteristic parameter of a nuclear reactor can not be understood as the mean time of neutron to annihilation. (M.M.)

  1. 75 FR 41762 - Safety Zone; Annual Kennewick, WA, Columbia Unlimited Hydroplane Races, Kennewick, WA

    Science.gov (United States)

    2010-07-19

    ...-AA00 Safety Zone; Annual Kennewick, WA, Columbia Unlimited Hydroplane Races, Kennewick, WA AGENCY..., Columbia Unlimited Hydroplane Races'' also known as the Tri-City Water Follies Hydroplane Races. The safety... power and responsibilities between the Federal Government and Indian tribes. Energy Effects We have...

  2. Anisotropy of the cosmic gamma-ray background from dark matter annihilation

    International Nuclear Information System (INIS)

    Ando, Shin'ichiro; Komatsu, Eiichiro

    2006-01-01

    High-energy photons from pair annihilation of dark matter particles contribute to the cosmic gamma-ray background (CGB) observed in a wide energy range. Since dark matter particles are weakly interacting, annihilation can happen only in high density regions such as dark matter halos. The precise shape of the energy spectrum of CGB depends on the nature of dark matter particles--their mass and annihilation cross section, as well as the cosmological evolution of dark matter halos. In order to discriminate between the signals from dark matter annihilation and other astrophysical sources, however, the information from the energy spectrum of CGB may not be sufficient. We show that dark matter annihilation not only contributes to the mean CGB intensity, but also produces a characteristic anisotropy, which provides a powerful tool for testing the origins of the observed CGB. We develop the formalism based on a halo model approach to analytically calculate the three-dimensional power spectrum of dark matter clumping, which determines the power spectrum of annihilation signals. We show that the expected sensitivity of future gamma-ray detectors such as the Gamma Ray Large Area Space Telescope (GLAST) should allow us to measure the angular power spectrum of CGB anisotropy, if dark matter particles are supersymmetric neutralinos and they account for most of the observed mean intensity of CGB in GeV region. On the other hand, if dark matter has a relatively small mass, on the order of 20 MeV, and accounts for most of the CGB in MeV region, then the future Advanced Compton Telescope (ACT) should be able to measure the angular power spectrum in MeV region. As the intensity of photons from annihilation is proportional to the density squared, we show that the predicted shape of the angular power spectrum of gamma rays from dark matter annihilation is different from that due to other astrophysical sources such as blazars and supernovae, whose intensity is linearly proportional to

  3. Possible Dark Matter Annihilation Signal in the AMS-02 Antiproton Data.

    Science.gov (United States)

    Cui, Ming-Yang; Yuan, Qiang; Tsai, Yue-Lin Sming; Fan, Yi-Zhong

    2017-05-12

    Using the latest AMS-02 cosmic-ray antiproton flux data, we search for a potential dark matter annihilation signal. The background parameters about the propagation, source injection, and solar modulation are not assumed a priori but based on the results inferred from the recent B/C ratio and proton data measurements instead. The possible dark matter signal is incorporated into the model self-consistently under a Bayesian framework. Compared with the astrophysical background-only hypothesis, we find that a dark matter signal is favored. The rest mass of the dark matter particles is ∼20-80  GeV, and the velocity-averaged hadronic annihilation cross section is about (0.2-5)×10^{-26}  cm^{3} s^{-1}, in agreement with that needed to account for the Galactic center GeV excess and/or the weak GeV emission from dwarf spheroidal galaxies Reticulum 2 and Tucana III. Tight constraints on the dark matter annihilation models are also set in a wide mass region.

  4. Multiwavelength analysis of dark matter annihilation and RX-DMFIT

    International Nuclear Information System (INIS)

    McDaniel, A.; Jeltema, T.; Profumo, S.; Storm, E.

    2017-01-01

    Dark matter (DM) particles are predicted by several well motivated models to yield Standard Model particles through self-annihilation that can potentially be detected by astrophysical observations. In particular, the production of charged particles from DM annihilation in astrophysical systems that contain magnetic fields yields radio emission through synchrotron radiation and X-ray emission through inverse Compton scattering of ambient photons. We introduce RX-DMFIT, a tool used for calculating the expected secondary emission from DM annihilation. RX-DMFIT includes a wide range of customizable astrophysical and particle parameters and incorporates important astrophysics including the diffusion of charged particles, relevant radiative energy losses, and magnetic field modelling. We demonstrate the use and versatility of RX-DMFIT by analyzing the potential radio and X-ray signals for a variety of DM particle models and astrophysical environments including galaxy clusters, dwarf spheroidal galaxies and normal galaxies. We then apply RX-DMFIT to a concrete example using Segue I radio data to place constraints for a range of assumed DM annihilation channels. For WIMP models with M χ ≤ 100 GeV and assuming weak diffusion, we find that the leptonic μ + μ − and τ + τ − final states provide the strongest constraints, placing limits on the DM particle cross-section well below the thermal relic cross-section, while even for the b b-bar channel we find limits close to the thermal relic cross-section. Our analysis shows that radio emission provides a highly competitive avenue for dark matter searches.

  5. Multiwavelength analysis of dark matter annihilation and RX-DMFIT

    Energy Technology Data Exchange (ETDEWEB)

    McDaniel, A.; Jeltema, T.; Profumo, S. [Department of Physics, University of California, 1156 High St. Santa Cruz, CA, 95064 (United States); Storm, E., E-mail: alexmcdaniel@ucsc.edu, E-mail: tesla@ucsc.edu, E-mail: profumo@ucsc.edu, E-mail: e.m.storm@uva.nl [GRAPPA, Institute of Physics, Universiteit van Amsterdam Science Park 904, 1098XH Amsterdam (Netherlands)

    2017-09-01

    Dark matter (DM) particles are predicted by several well motivated models to yield Standard Model particles through self-annihilation that can potentially be detected by astrophysical observations. In particular, the production of charged particles from DM annihilation in astrophysical systems that contain magnetic fields yields radio emission through synchrotron radiation and X-ray emission through inverse Compton scattering of ambient photons. We introduce RX-DMFIT, a tool used for calculating the expected secondary emission from DM annihilation. RX-DMFIT includes a wide range of customizable astrophysical and particle parameters and incorporates important astrophysics including the diffusion of charged particles, relevant radiative energy losses, and magnetic field modelling. We demonstrate the use and versatility of RX-DMFIT by analyzing the potential radio and X-ray signals for a variety of DM particle models and astrophysical environments including galaxy clusters, dwarf spheroidal galaxies and normal galaxies. We then apply RX-DMFIT to a concrete example using Segue I radio data to place constraints for a range of assumed DM annihilation channels. For WIMP models with M {sub χ} ≤ 100 GeV and assuming weak diffusion, we find that the leptonic μ{sup +}μ{sup −} and τ{sup +}τ{sup −} final states provide the strongest constraints, placing limits on the DM particle cross-section well below the thermal relic cross-section, while even for the b b-bar channel we find limits close to the thermal relic cross-section. Our analysis shows that radio emission provides a highly competitive avenue for dark matter searches.

  6. Antideuteron annihilation on nuclei

    International Nuclear Information System (INIS)

    Cugnon, J.

    1992-01-01

    An investigation of antideuteron annihilation on nuclei within an intranuclear cascade (INC) model is presented. Two models are set up to describe the annihilation itself, which either implies the antideuteron as a whole and occurs at a single point, or which may be considered as two independent nucleon-antinucleon annihilation occurring at different points and different times. Particular attention is paid to the energy transferred from the pions issued from the annihilation to the nuclear system and to the possibility of having a multifragmentation of the target. The latter feature is investigated within a percolation model. The pion distribution and the energy distribution are also discussed. Predictions of proton multiplicity distributions are compared with experiment. (orig.)

  7. Cosmic ray neutrino tests for heavier weak bosons and cosmic antimatter

    Science.gov (United States)

    Brown, R. W.; Stecker, F. W.

    1981-01-01

    A program for using high energy neutrino astronomy with large neutrino detectors to directly test for the existence of heavier weak intermediate vector bosons (ivb) and cosmic antimatter is described. Such observations can provide a direct test of baryon symmetric cosmologies. Changes in the total cross section for nu(N) yields mu(X) due to additional propagators are discussed and higher mass resonances in the annihilation channel bar-nu sub e e(-) yields X are analyzed. The annihilation channel is instrumental in the search for antimatter, partcularly if heavier IVB's exist.

  8. Studying the gelation process of titanium isopropoxide by method of positron annihilation spectroscopy; Studium procesu gelacie izopropoxidu titaniciteho metodou pozitronovej anihilacnej spektroskopie

    Energy Technology Data Exchange (ETDEWEB)

    Nyblova, D.; Jesenak, K. [Univerzita Komenskeho, Prirodovedecka fakulta, Katedra anorganickej chemie, 84215 Bratislava (Slovakia); Sausa, O. [Slovenska akademia vied, Fyzikalny ustav, 84511 Bratislava (Slovakia)

    2013-04-16

    Thank to its harmlessness titanium dioxide is widely utilized material. One of the new areas to use titanium dioxide is photocatalysis, which could be the way to e.g. remove organic pollutants from water or air. Titanium dioxide based gels are perspective form of TiO{sub 2} for photocatalysis because of their high porosity thus high surface area. Positron annihilation spectroscopy is a physical method to study microporous structure and electron energy distribution in materials. We studied gelation process of titanium isopropoxide in ethanol with various amount of water catalyzed by hydrochloric acid by positron annihilation lifetime spectroscopy and doppler broadening of annihilation line in this work. Positronium is weakly formed in TiO{sub 2} in general wherefore it cannot be monitored by positron annihilation spectroscopy very well. Gelation process can be monitored through pick-off annihilation of ortho-positronium. (authors)

  9. First search for dark matter annihilations in the Earth with the IceCube detector

    International Nuclear Information System (INIS)

    Aartsen, M.G.; Hill, G.C.; Robertson, S.; Wallace, A.; Whelan, B.J.; Abraham, K.; Bernhard, A.; Coenders, S.; Holzapfel, K.; Huber, M.; Jurkovic, M.; Krings, K.; Resconi, E.; Turcati, A.; Veenkamp, J.; Ackermann, M.; Bernardini, E.; Blot, S.; Bretz, H.P.; Franckowiak, A.; Gluesenkamp, T.; Jacobi, E.; Karg, T.; Kintscher, T.; Kunwar, S.; Mohrmann, L.; Nahnhauer, R.; Satalecka, K.; Spiering, C.; Stasik, A.; Stoessl, A.; Strotjohann, N.L.; Terliuk, A.; Usner, M.; Santen, J. van; Yanez, J.P.; Adams, J.; Aguilar, J.A.; Ansseau, I.; Heereman, D.; Meagher, K.; Meures, T.; O'Murchadha, A.; Pinat, E.; Raab, C.; Ahlers, M.; Braun, J.; Chirkin, D.; Day, M.; Desiati, P.; Diaz-Velez, J.C.; Fahey, S.; Feintzeig, J.; Ghorbani, K.; Gladstone, L.; Griffith, Z.; Halzen, F.; Hanson, K.; Jero, K.; Karle, A.; Kauer, M.; Kelley, J.L.; Kheirandish, A.; Krueger, C.; Mancina, S.; McNally, F.; Merino, G.; Sabbatini, L.; Tobin, M.N.; Tosi, D.; Vandenbroucke, J.; Rossem, M. van; Wandkowsky, N.; Wendt, C.; Westerhoff, S.; Wille, L.; Xu, D.L.; Ahrens, M.; Bohm, C.; Dumm, J.P.; Finley, C.; Flis, S.; Hultqvist, K.; Walck, C.; Wolf, M.; Zoll, M.; Altmann, D.; Anton, G.; Katz, U.; Kittler, T.; Tselengidou, M.; Andeen, K.; Anderson, T.; Dunkman, M.; Eller, P.; Huang, F.; Keivani, A.; Lanfranchi, J.L.; Pankova, D.V.; Quinnan, M.; Tesic, G.; Weiss, M.J.; Archinger, M.; Baum, V.; Boeser, S.; Pino Rosendo, E. del; Di Lorenzo, V.; Eberhardt, B.; Ehrhardt, T.; Foesig, C.C.; Koepke, L.; Krueckl, G.; Peiffer, P.; Sandroos, J.; Steuer, A.; Wiebe, K.; Argueelles, C.; Axani, S.; Collin, G.H.; Conrad, J.M.; Jones, B.J.P.; Moulai, M.; Auffenberg, J.; Bissok, M.; Glagla, M.; Glauch, T.; Haack, C.; Hansmann, B.; Hansmann, T.; Kemp, J.; Konietz, R.; Leuermann, M.; Leuner, J.; Penek, Oe.; Raedel, L.; Reimann, R.; Rongen, M.; Schimp, M.; Schoenen, S.; Schumacher, L.; Stahlberg, M.; Stettner, J.; Vehring, M.; Vogel, E.; Wallraff, M.; Wickmann, S.; Wiebusch, C.H.; Bai, X.; Barwick, S.W.; Yodh, G.; Bay, R.; Filimonov, K.; Price, P.B.; Woschnagg, K.; Beatty, J.J.; Becker Tjus, J.; Bos, F.; Eichmann, B.; Kroll, M.; Mandelartz, M.; Schoeneberg, S.; Tenholt, F.; Becker, K.H.; Bindig, D.; Helbing, K.; Hickford, S.; Hoffmann, R.; Kopper, S.; Lauber, F.; Naumann, U.; Obertacke Pollmann, A.; Soldin, D.; BenZvi, S.; Cross, R.; Berley, D.; Blaufuss, E.; Cheung, E.; Felde, J.; Friedman, E.; Hellauer, R.; Hoffman, K.D.; Maunu, R.; Olivas, A.; Schmidt, T.; Song, M.; Sullivan, G.W.; Besson, D.Z.; Binder, G.; Gerhardt, L.; Klein, S.R.; Miarecki, S.; Tatar, J.

    2017-01-01

    We present the results of the first IceCube search for dark matter annihilation in the center of the Earth. Weakly interacting massive particles (WIMPs), candidates for dark matter, can scatter off nuclei inside the Earth and fall below its escape velocity. Over time the captured WIMPs will be accumulated and may eventually self-annihilate. Among the annihilation products only neutrinos can escape from the center of the Earth. Large-scale neutrino telescopes, such as the cubic kilometer IceCube Neutrino Observatory located at the South Pole, can be used to search for such neutrino fluxes. Data from 327 days of detector livetime during 2011/2012 were analyzed. No excess beyond the expected background from atmospheric neutrinos was detected. The derived upper limits on the annihilation rate of WIMPs in the Earth and the resulting muon flux are an order of magnitude stronger than the limits of the last analysis performed with data from IceCube's predecessor AMANDA. The limits can be translated in terms of a spin-independent WIMP-nucleon cross section. For a WIMP mass of 50 GeV this analysis results in the most restrictive limits achieved with IceCube data. (orig.)

  10. First search for dark matter annihilations in the Earth with the IceCube detector

    Energy Technology Data Exchange (ETDEWEB)

    Aartsen, M.G.; Hill, G.C.; Robertson, S.; Wallace, A.; Whelan, B.J. [University of Adelaide, Department of Physics, Adelaide (Australia); Abraham, K.; Bernhard, A.; Coenders, S.; Holzapfel, K.; Huber, M.; Jurkovic, M.; Krings, K.; Resconi, E.; Turcati, A.; Veenkamp, J. [Technische Universitaet Muenchen, Physik-Department, Garching (Germany); Ackermann, M.; Bernardini, E.; Blot, S.; Bretz, H.P.; Franckowiak, A.; Gluesenkamp, T.; Jacobi, E.; Karg, T.; Kintscher, T.; Kunwar, S.; Mohrmann, L.; Nahnhauer, R.; Satalecka, K.; Spiering, C.; Stasik, A.; Stoessl, A.; Strotjohann, N.L.; Terliuk, A.; Usner, M.; Santen, J. van; Yanez, J.P. [DESY, Zeuthen (Germany); Adams, J. [University of Canterbury, Department of Physics and Astronomy, Private Bag 4800, Christchurch (New Zealand); Aguilar, J.A.; Ansseau, I.; Heereman, D.; Meagher, K.; Meures, T.; O' Murchadha, A.; Pinat, E.; Raab, C. [Universite Libre de Bruxelles, Science Faculty CP230, Brussels (Belgium); Ahlers, M.; Braun, J.; Chirkin, D.; Day, M.; Desiati, P.; Diaz-Velez, J.C.; Fahey, S.; Feintzeig, J.; Ghorbani, K.; Gladstone, L.; Griffith, Z.; Halzen, F.; Hanson, K.; Jero, K.; Karle, A.; Kauer, M.; Kelley, J.L.; Kheirandish, A.; Krueger, C.; Mancina, S.; McNally, F.; Merino, G.; Sabbatini, L.; Tobin, M.N.; Tosi, D.; Vandenbroucke, J.; Rossem, M. van; Wandkowsky, N.; Wendt, C.; Westerhoff, S.; Wille, L.; Xu, D.L. [University of Wisconsin, Department of Physics and Wisconsin IceCube Particle Astrophysics Center, Madison, WI (United States); Ahrens, M.; Bohm, C.; Dumm, J.P.; Finley, C.; Flis, S.; Hultqvist, K.; Walck, C.; Wolf, M.; Zoll, M. [Stockholm University, Department of Physics, Oskar Klein Centre, Stockholm (Sweden); Altmann, D.; Anton, G.; Katz, U.; Kittler, T.; Tselengidou, M. [Friedrich-Alexander-Universitaet Erlangen-Nuernberg, Centre for Astroparticle Physics, Erlangen (Germany); Andeen, K. [Marquette University, Department of Physics, Milwaukee, WI (United States); Anderson, T.; Dunkman, M.; Eller, P.; Huang, F.; Keivani, A.; Lanfranchi, J.L.; Pankova, D.V.; Quinnan, M.; Tesic, G.; Weiss, M.J. [Pennsylvania State University, Department of Physics, University Park, PA (United States); Archinger, M.; Baum, V.; Boeser, S.; Pino Rosendo, E. del; Di Lorenzo, V.; Eberhardt, B.; Ehrhardt, T.; Foesig, C.C.; Koepke, L.; Krueckl, G.; Peiffer, P.; Sandroos, J.; Steuer, A.; Wiebe, K. [University of Mainz, Institute of Physics, Mainz (Germany); Argueelles, C.; Axani, S.; Collin, G.H.; Conrad, J.M.; Jones, B.J.P.; Moulai, M. [Massachusetts Institute of Technology, Department of Physics, Cambridge, MA (United States); Auffenberg, J.; Bissok, M.; Glagla, M.; Glauch, T.; Haack, C.; Hansmann, B.; Hansmann, T.; Kemp, J.; Konietz, R.; Leuermann, M.; Leuner, J.; Penek, Oe.; Raedel, L.; Reimann, R.; Rongen, M.; Schimp, M.; Schoenen, S.; Schumacher, L.; Stahlberg, M.; Stettner, J.; Vehring, M.; Vogel, E.; Wallraff, M.; Wickmann, S.; Wiebusch, C.H. [RWTH Aachen University, III. Physikalisches Institut, Aachen (Germany); Bai, X. [South Dakota School of Mines and Technology, Physics Department, Rapid City, SD (United States); Barwick, S.W.; Yodh, G. [University of California, Department of Physics and Astronomy, Irvine, CA (United States); Bay, R.; Filimonov, K.; Price, P.B.; Woschnagg, K. [University of California, Department of Physics, Berkeley, CA (United States); Beatty, J.J. [Ohio State University, Department of Physics and Center for Cosmology and Astro-Particle Physics, Columbus, OH (United States); Ohio State University, Department of Astronomy, Columbus, OH (United States); Becker Tjus, J.; Bos, F.; Eichmann, B.; Kroll, M.; Mandelartz, M.; Schoeneberg, S.; Tenholt, F. [Ruhr-Universitaet Bochum, Fakultaet fuer Physik and Astronomie, Bochum (Germany); Becker, K.H.; Bindig, D.; Helbing, K.; Hickford, S.; Hoffmann, R.; Kopper, S.; Lauber, F.; Naumann, U.; Obertacke Pollmann, A.; Soldin, D. [University of Wuppertal, Department of Physics, Wuppertal (Germany); BenZvi, S.; Cross, R. [University of Rochester, Department of Physics and Astronomy, Rochester, NY (United States); Berley, D.; Blaufuss, E.; Cheung, E.; Felde, J.; Friedman, E.; Hellauer, R.; Hoffman, K.D.; Maunu, R.; Olivas, A.; Schmidt, T.; Song, M.; Sullivan, G.W. [University of Maryland, Department of Physics, College Park, MD (United States); Besson, D.Z. [University of Kansas, Department of Physics and Astronomy, Lawrence, KS (United States); Binder, G.; Gerhardt, L.; Klein, S.R.; Miarecki, S.; Tatar, J. [University of California, Department of Physics, Berkeley, CA (United States); Lawrence Berkeley National Laboratory, Berkeley, CA (United States); Collaboration: IceCube Collaboration; and others

    2017-02-15

    We present the results of the first IceCube search for dark matter annihilation in the center of the Earth. Weakly interacting massive particles (WIMPs), candidates for dark matter, can scatter off nuclei inside the Earth and fall below its escape velocity. Over time the captured WIMPs will be accumulated and may eventually self-annihilate. Among the annihilation products only neutrinos can escape from the center of the Earth. Large-scale neutrino telescopes, such as the cubic kilometer IceCube Neutrino Observatory located at the South Pole, can be used to search for such neutrino fluxes. Data from 327 days of detector livetime during 2011/2012 were analyzed. No excess beyond the expected background from atmospheric neutrinos was detected. The derived upper limits on the annihilation rate of WIMPs in the Earth and the resulting muon flux are an order of magnitude stronger than the limits of the last analysis performed with data from IceCube's predecessor AMANDA. The limits can be translated in terms of a spin-independent WIMP-nucleon cross section. For a WIMP mass of 50 GeV this analysis results in the most restrictive limits achieved with IceCube data. (orig.)

  11. WA18

    CERN Multimedia

    1977-01-01

    Front view. The target plates are cut from marble (3x3 m slabs surrounded by magnetized iron) and allow the use of the calorimeter as a muon polarimeter. WA18 was CHARM, the experiment of the CERN-Hamburg-Amsterdam-Rome(INFN)-Moskow(ITEP) Collaboration

  12. Multiple gamma lines from semi-annihilation

    International Nuclear Information System (INIS)

    D'Eramo, Francesco; McCullough, Matthew; Thaler, Jesse

    2013-01-01

    Hints in the Fermi data for a 130 GeV gamma line from the galactic center have ignited interest in potential gamma line signatures of dark matter. Explanations of this line based on dark matter annihilation face a parametric tension since they often rely on large enhancements of loop-suppressed cross sections. In this paper, we pursue an alternative possibility that dark matter gamma lines could arise from ''semi-annihilation'' among multiple dark sector states. The semi-annihilation reaction ψ i ψ j → ψ k γ with a single final state photon is typically enhanced relative to ordinary annihilation ψ i ψ-bar i → γγ into photon pairs. Semi-annihilation allows for a wide range of dark matter masses compared to the fixed mass value required by annihilation, opening the possibility to explain potential dark matter signatures at higher energies. The most striking prediction of semi-annihilation is the presence of multiple gamma lines, with as many as order N 3 lines possible for N dark sector states, allowing for dark sector spectroscopy. A smoking gun signature arises in the simplest case of degenerate dark matter, where a strong semi-annihilation line at 130 GeV would be accompanied by a weaker annihilation line at 173 GeV. As a proof of principle, we construct two explicit models of dark matter semi-annihilation, one based on non-Abelian vector dark matter and the other based on retrofitting Rayleigh dark matter

  13. Heavy lepton production in e+e- annihilation

    International Nuclear Information System (INIS)

    Kawamoto, Noboru

    1976-01-01

    We first enumerate several global properties of e + e - annihilation, which were left untouched in previous studies, as evidences of a heavy lepton with the mass of 1.8 GeV. As for the charged energy fraction in e + e - annihilation, we note that the effect of heavy lepton productions superimposed on the linearly decreasing background parametrized as r sub(h)=-0.014√s+0.632 can give a satisfactory fit to the data up to √s -- 8 GeV (where √s is the total c.m. energy). In this case, the charged energy fraction at PEP and PETRA energies is expected to come far below the naive application of the Llewellyn-Smith-Pais lower bound. We also compare the heavy lepton interpretation of the eμ events with other interpretations, and we argue that the 1.8 GeV heavy lepton gives the most plausible interpretation. Finally we discuss the observed eμ cross section and momentum distributions in terms of this heavy lepton with a general structure of the weak current and with an arbitrary mass for the associated neutrino. (auth.)

  14. Antihyperon-hyperon production in antiproton-proton annihilations with PANDA at FAIR

    Energy Technology Data Exchange (ETDEWEB)

    Papenbrock, Michael [Department of Nuclear Physics and Astronomy, Uppsala University, Uppsala (Sweden); Collaboration: PANDA-Collaboration

    2015-07-01

    The production of antihyperon-hyperon pairs in antiproton-proton annihilations involves the annihilation of at least one light (u,d) quark-antiquark pair and the creation of a heavier (s,c,b) pair. Production of strange hyperons occur in an energy region in which QCD is difficult to predict. By studying hyperon production we learn about the strong interaction in this energy region, i.e. the confinement domain. It is an open question what the relevant degrees of freedom are: quarks and gluons, or hadrons. Spin observables is an excellent tool in order to better understand the physical processes. These are accessible via the weak, parity violating decay of the hyperon which results in an angular asymmetry of the decay products. The future PANDA experiment at FAIR is going to be ideally suited to study spin physics on hyperons with both high precision and high statistics. Since hyperons decay weakly and thus have long life-times, their decay vertices are displaced with respect to the production point. This sets high demands on precise track reconstruction. A pattern recognition algorithm is currently under development, with the ability to reconstruct tracks originating in displaced vertices. Simulation studies done by the Uppsala group as well as the status of the development will be presented and discussed.

  15. Muundo wa Mashairi katika Diwani ya Mnyampala (1965) na Nafasi ...

    African Journals Online (AJOL)

    Makala hii pia inadadisi namna mbinu za kimuundo zilivyofanikisha usawiri na ubainishaji wa falsafa ya mtunzi kuhusu ushairi wa Kiswahili na nafasi ya ushairi katika jamii. Makala imeanza kwa kugusia usuli wa historia ya ushairi wa Kiswahili, historia fupi ya maisha ya Mathias Mnyampala na nadharia yake kuhusu ...

  16. Simulation of the annihilation emission of galactic positrons; Modelisation de l'emission d'annihilation des positrons Galactiques

    Energy Technology Data Exchange (ETDEWEB)

    Gillard, W

    2008-01-15

    Positrons annihilate in the central region of our Galaxy. This has been known since the detection of a strong emission line centered on an energy of 511 keV in the direction of the Galactic center. This gamma-ray line is emitted during the annihilation of positrons with electrons from the interstellar medium. The spectrometer SPI, onboard the INTEGRAL observatory, performed spatial and spectral analyses of the positron annihilation emission. This thesis presents a study of the Galactic positron annihilation emission based on models of the different interactions undergone by positrons in the interstellar medium. The models are relied on our present knowledge of the properties of the interstellar medium in the Galactic bulge, where most of the positrons annihilate, and of the physics of positrons (production, propagation and annihilation processes). In order to obtain constraints on the positrons sources and physical characteristics of the annihilation medium, we compared the results of the models to measurements provided by the SPI spectrometer. (author)

  17. Riwaya ya Kiswahili katika ufundishaji wa historia | Mlaga | Kiswahili

    African Journals Online (AJOL)

    Makala haya yanachunguza uwezekano wa riwaya ya Kiswahili kutumika katika ufundishaji wa historia. Makala yamejiegemeza katika kuonesha namna ambavyo riwaya kama utanzu mmojawapo wa fasihi unafaa kufundishia historia. Hivyo basi, hoja mbalimbali zinabainishwa ili kuonesha namna ambavyo riwaya ya ...

  18. Neutrinos from WIMP annihilations obtained using a full three-flavor Monte Carlo approach

    International Nuclear Information System (INIS)

    Blennow, Mattias; Ohlsson, Tommy; Edsjö, Joakim

    2008-01-01

    Weakly interacting massive particles (WIMPs) are one of the main candidates for making up the dark matter in the Universe. If these particles make up the dark matter, then they can be captured by the Sun or the Earth, sink to the respective cores, annihilate, and produce neutrinos. Thus, these neutrinos can be a striking dark matter signature at neutrino telescopes looking towards the Sun and/or the Earth. Here, we improve previous analyses on computing the neutrino yields from WIMP annihilations in several respects. We include neutrino oscillations in a full three-flavor framework as well as all effects from neutrino interactions on the way through the Sun (absorption, energy loss, and regeneration from tau decays). In addition, we study the effects of non-zero values of the mixing angle θ 13 as well as the normal and inverted neutrino mass hierarchies. Our study is performed in an event-based setting which makes these results very useful both for theoretical analyses and for building a neutrino telescope Monte Carlo code. All our results for the neutrino yields, as well as our Monte Carlo code, are publicly available. We find that the yield of muon-type neutrinos from WIMP annihilations in the Sun is enhanced or suppressed, depending on the dominant WIMP annihilation channel. This effect is due to an effective flavor mixing caused by neutrino oscillations. For WIMP annihilations inside the Earth, the distance from source to detector is too small to allow for any significant amount of oscillations at the neutrino energies relevant for neutrino telescopes

  19. Search for heavy neutrinos produced in e+e- annihilation

    International Nuclear Information System (INIS)

    Feldman, G.J.

    1985-05-01

    We report a search for long-lived heavy neutrinos produced by the neutral weak current in e + e - annihilation at 29 GeV at PEP. Data from the Mark II detector are examined for evidence of events with one or more separated vertices in the radial range of 2 mm to 10 cm. No events were found that were consistent with the hypothesis of heavy neutrino production, eliminating the possibility of heavy neutrinos with decay lengths of 1 to 20 cm in mass range 1 to 13 GeV/c 2 . 11 refs

  20. Energetic neutrinos from heavy-neutralino annihilation in the Sun. Ph.D. Thesis

    Science.gov (United States)

    Kamionkowski, Marc

    1991-01-01

    Neutralinos may be captured in the sun and annihilated therein producing high-energy neutrinos. Present limits on the flux of such neutrinos from underground detectors such as IMB and Kamiokande 2 may be used to rule out certain supersymmetric dark matter candidates, while in many other supersymmetric models the rates are large enough that if neutralinos do reside in the galactic halo, observation of a neutrino signal may be possible in the near future. Neutralinos that are either nearly pure Higgsino or a Higgsino/gaugino combination are generally captured in the sun by coherent scattering off nuclei via exchange of the lightest Higgs boson. If the squark mass is not much greater than the neutralino mass, then capture of neutralinos that are primarily gaugino occurs predominantly by spin-dependent scattering off hydrogen in the sun. The neutrino signal from annihilation of WIMPs with masses in the range of 80 to 1000 GeV in the sun should generally be stronger than that from weakly interacting massive particle (WIMP) annihilation in the earth, and detection rates for mixed-state neutralinos are generally higher than those for Higgsinos or gauginos.

  1. Positron annihilation spectroscopy

    International Nuclear Information System (INIS)

    Sundar, C.S.; Viswanathan, B.

    1996-01-01

    An overview of positron annihilation spectroscopy, the experimental techniques and its application to studies on defects and electronic structure of materials is presented. The scope of this paper is to present the requisite introductory material, that will enable a better appreciation of the subsequent specialized articles on the applications of positron annihilation spectroscopy to investigate various problems in materials science. (author). 31 refs., 3 figs

  2. At WA7

    CERN Multimedia

    1977-01-01

    The CERN-Genoa-Annecy(LAPP)- Niels Bohr Institute, Copenhagen-Oslo-University College,London Collaboration set-up the experiment WA7 to study two-body reactions at large transverse momentum. Here, Michel Yvert, Alberto Santronico, Per Carlson

  3. Positron annihilation in vitreous silica glasses

    International Nuclear Information System (INIS)

    Uedono, Akira; Tanigawa, Shoichiro

    1993-01-01

    The annihilation characteristics of positrons in vitreous silica glasses (v-SiO 2 ) were studied by measurements of two-dimensional angular correlation of positron annihilation radiations and positron lifetime spectra. From the measurements, it was found that positrons and positronium (Ps) atoms mainly annihilate from trapped states by vacancy-type defects in v-SiO 2 . For v-SiO 2 specimens with cylindrical porous structures, annihilations of Ps with anisotropic momentum distributions were observed. This fact was attributed to the momentum uncertainty due to localization of Ps in a finite dimension of pores. This investigation showed possibilities for the detection of microstructures in v-SiO 2 by the positron annihilation technique. (author)

  4. MCHANGO WA MWALIMU J.K. NYERERE KATIKA TAFSIRI NA ...

    African Journals Online (AJOL)

    Kwa kuzingatia tafsiri mbili za J.K. Nyerere, Julius Kaizer (1963) na Mabepari wa Venus (1969), makala inaeleza: (i) kwa nini Mwalimu Nyerere alitafsiri maandishi ya Shakespeare, (ii) ufanisi wa tafsiri zake, na (iii) mchango wa tafsiri hizo. Makala inaonyesha kuwa tafsiri hizo zinazingatia mbinu za kisemantiki zaidi kuliko ...

  5. QCD in e+e- annihilation

    International Nuclear Information System (INIS)

    Ali, A.

    1981-04-01

    The promise of e + e - annihilation as an ideal laboratory to test Quantum Chromodynamics, QCD, has been the dominating theme in elementary particle physics during the last several years. An attempt is made to partially survey the subject in deep perturbative region in e + e - annihilation where theoretical ambiguities are minimal. Topics discussed include a review of the renormalization group methods relevant for e + e - annihilation, total hadronic cross section, jets and large-psub(T) phenomena, non-perturbative quark and gluon fragmentation effects and analysis of the jet distributions measured at DORIS, SPEAR and PETRA. My hope is to review realistic tests of QCD in e + e - annihilation - as opposed to the ultimate tests, which abound in literature. (orig.)

  6. Characterization of lacunar defects by positrons annihilation

    International Nuclear Information System (INIS)

    Barthe, M.F.; Corbel, C.; Blondiaux, G.

    2003-01-01

    Among the nondestructive methods for the study of matter, the positrons annihilation method allows to sound the electronic structure of materials by measuring the annihilation characteristics. These characteristics depend on the electronic density as seen by the positon, and on the electron momentums distribution which annihilate with the positon. The positon is sensible to the coulombian potential variations inside a material and sounds preferentially the regions away from nuclei which represent potential wells. The lacunar-type defects (lack of nuclei) represent deep potential wells which can trap the positon up to temperatures close to the melting. This article describes the principles of this method and its application to the characterization of lacunar defects: 1 - positrons: matter probes (annihilation of electron-positon pairs, annihilation characteristics, positrons sources); 2 - positrons interactions in solids (implantation profiles, annihilation states, diffusion and trapping, positon lifetime spectrum: evolution with the concentration of defects); 3 - measurement of annihilation characteristics with two gamma photons (lifetime spectroscopy with the β + 22 Na isotope, spectroscopy of Doppler enlargement of the annihilation line); 4 - determination of the free volume of defects inside or at the surface of materials (annihilation signature in lacunar defects, lacuna, lacunar clusters and cavities, acceptors nature in semiconductors: ionic or lacunar, interface defects, precipitates in alloys); 5 - conclusions. (J.S.)

  7. The aesthetic interpretation on Wooden Drum Dancing of Wa people

    Directory of Open Access Journals (Sweden)

    Youfeng Wang

    2017-02-01

    Full Text Available The Wa nationality, a typical ethnic group in Yunnan province, is an ancient one lives across Yunnan. The main residences of it are border area beside northern Yunnan and the Wa States in Burma. Among all the Wa dances, Wooden Drum Dancing leads a vital position, and it is also a symbolic dancing in the culture of Wa people. The feature of Wooden Drum Dancing is that every action expending by the beats of wooden drum, namely, first the wooden drum, then the Wooden Drum Dancing. Dancing is an important content in the life of Wa people, and the aesthetics of life comes from dancing, so they present their value on worship by the form of dancing. This article is going to interpret the aesthetic standard on Wa people’s Wooden Drum Dancing by the view of aesthetics, and come into a conclude that the inspiration of such dancing came from practice and their worship to nature and ancestor. The Wooden Drum Dancing displays totally the tough air and solidarity of Wa people, which also presents the fair society of them. The Wooden Drum Dancing is an enriched art that Wa People took from particle life, so dancing of Wa is often classified into the aesthetic area of plain. The information of people’s living situation displayed by Wa dancing also conveys their rich emotions. The sense of beauty within Wooden Drum Dancing will give others a solemn feeling. The formal beauty is displayed by the rhythm of upper part of body, and the power beauty is displayed by the rhythm of the lower part of body.

  8. Simulation of the annihilation emission of galactic positrons; Modelisation de l'emission d'annihilation des positrons Galactiques

    Energy Technology Data Exchange (ETDEWEB)

    Gillard, W

    2008-01-15

    Positrons annihilate in the central region of our Galaxy. This has been known since the detection of a strong emission line centered on an energy of 511 keV in the direction of the Galactic center. This gamma-ray line is emitted during the annihilation of positrons with electrons from the interstellar medium. The spectrometer SPI, onboard the INTEGRAL observatory, performed spatial and spectral analyses of the positron annihilation emission. This thesis presents a study of the Galactic positron annihilation emission based on models of the different interactions undergone by positrons in the interstellar medium. The models are relied on our present knowledge of the properties of the interstellar medium in the Galactic bulge, where most of the positrons annihilate, and of the physics of positrons (production, propagation and annihilation processes). In order to obtain constraints on the positrons sources and physical characteristics of the annihilation medium, we compared the results of the models to measurements provided by the SPI spectrometer. (author)

  9. Pionic annihilation of antiprotons stopped on 3He

    International Nuclear Information System (INIS)

    Bendiscioli, G.; Filippini, V.; Rotondi, A.; Salvini, P.; Venaglioni, A.; Bossolasco, S.; Bussa, M.P.; Busso, L.; Fava, L.; Ferrero, L.; Maggiora, A.; Panzieri, D.; Piragino, G.; Piragino, R.; Tosello, F.; Batusov, Yu.A.; Falomkin, I.V.; Pontecorvo, G.B.; Rozhdestvensky, A.M.; Sapozhnikov, M.G.; Tretyak, V.I.; Guaraldo, C.; Haatuft, A.; Halsteinslid, A.; Myklebost, K.; Olsen, J.M.; Zenoni, A.

    1990-01-01

    The pionic annihilation of antiprotons stopped on 3 He nuclei in a self-shunted streamer chamber exposed to the antiproton beam of LEAR is studied. The data concern charged-particle multiplicity distributions, branching ratios for different final states, the probability of final-state interaction, π - , π + , p and d momentum spectra, like and unlike pion angular correlations, π and other charged-particle angular correlations. The comparison of the 3 He data with those obtained on 1 H, 2 H and 4 He does not reveal relevant effects due to the increase of the nucleon number; the small differences can be seen as due to a weak final-state interaction. (orig.)

  10. Is a weak violation of the Pauli principle possible?

    International Nuclear Information System (INIS)

    Ignat'ev, A.Y.; Kuz'min, V.A.

    1987-01-01

    We examine models in which there is a weak violation of the Pauli principle. A simple algebra of creation and annihilation operators is constructed which contains a parameter β and describes a weak violation of the Pauli principle (when β = 0 the Pauli principle is satisfied exactly). The commutation relations in this algebra turn out to be trilinear. A model based on this algebra is described. It allows transitions in which the Pauli principle is violated, but the probability of these transitions is suppressed by the quantity β 2 (even though the interaction Hamiltonian does not contain small parameters)

  11. SUSY-QCD corrections to the (co)annihilation of neutralino dark matter within the MSSM

    Energy Technology Data Exchange (ETDEWEB)

    Meinecke, Moritz

    2015-06-15

    Based on experimental observations, it is nowadays assumed that a large component of the matter content in the universe is comprised of so-called cold dark matter. Furthermore, latest measurements of the temperature fluctuations of the cosmic microwave background provided an estimation of the dark matter relic density at a measurement error of one percent (concerning the experimental 1σ-error). The lightest neutralino χ 0{sub 1}, a particle which subsumes under the phenomenologically interesting category of weakly interacting massive particles, is a viable dark matter candidate for many supersymmetric (SUSY) models whose relic density Ω{sub χ} {sub 0{sub 1}} happens to lie quite naturally within the experimentally favored ballpark of dark matter. The high experimental precision can be used to constrain the SUSY parameter space to its cosmologically favored regions and to pin down phenomenologically interesting scenarios. However, to actually benefit from this progress on the experimental side it is also mandatory to minimize the theoretical uncertainties. An important quantity within the calculation of the neutralino relic density is the thermally averaged sum over different annihilation and coannihilation cross sections of the neutralino and further supersymmetric particles. It is now assumed and also partly proven that these cross sections can be subject to large loop corrections which can even shift the associated Ω{sub χ} {sub 0{sub 1}} by a factor larger than the current experimental error. However, most of these corrections are yet unknown. In this thesis, we calculate higher-order corrections for some of the most important (co)annihilation channels both within the framework of the R-parity conserving Minimal Supersymmetric Standard Model (MSSM) and investigate their impact on the final neutralino relic density Ω{sub χ} {sub 0{sub 1}}. More precisely, this work provides the full O(α{sub s}) corrections of supersymmetric quantum chromodynamics (SUSY

  12. Characterization of lacunar defects by positrons annihilation

    CERN Document Server

    Barthe, M F; Blondiaux, G

    2003-01-01

    Among the nondestructive methods for the study of matter, the positrons annihilation method allows to sound the electronic structure of materials by measuring the annihilation characteristics. These characteristics depend on the electronic density as seen by the positon, and on the electron momentums distribution which annihilate with the positon. The positon is sensible to the coulombian potential variations inside a material and sounds preferentially the regions away from nuclei which represent potential wells. The lacunar-type defects (lack of nuclei) represent deep potential wells which can trap the positon up to temperatures close to the melting. This article describes the principles of this method and its application to the characterization of lacunar defects: 1 - positrons: matter probes (annihilation of electron-positon pairs, annihilation characteristics, positrons sources); 2 - positrons interactions in solids (implantation profiles, annihilation states, diffusion and trapping, positon lifetime spec...

  13. CERN: Antiprotons resist annihilation

    International Nuclear Information System (INIS)

    Anon.

    1992-01-01

    Ask any particle physicist what is the eventual fate of an antiproton in matter and he will likely tell you that It annihilates'. True as this answer is, it hides a number of fascinating questions about the actual 'route' followed by the antiproton into the nucleus where it finally stops before annihilating with a nuclear particle

  14. Dark matter annihilations into two light fermions and one gauge boson. General analysis and antiproton constraints

    International Nuclear Information System (INIS)

    Garny, Mathias; Ibarra, Alejandro; Vogl, Stefan

    2011-12-01

    We study in this paper the scenario where the dark matter is constituted by Majo- rana particles which couple to a light Standard Model fermion and an extra scalar via a Yukawa coupling. In this scenario, the annihilation rate into the light fermions with the mediation of the scalar particle is strongly suppressed by the mass of the fermion. Nevertheless, the helicity suppression is lifted by the associated emission of a gauge boson, yielding annihilation rates which could be large enough to allow the indirect detection of the dark matter particles. We perform a general analysis of this scenario, calculating the annihilation cross section of the processes χχ → f anti fV when the dark matter particle is a SU(2) L singlet or doublet, f is a lepton or a quark, and V is a photon, a weak gauge boson or a gluon. We point out that the annihilation rate is particularly enhanced when the dark matter particle is degenerate in mass to the intermediate scalar particle, which is a scenario barely constrained by collider searches of exotic charged or colored particles. Lastly, we derive upper limits on the relevant cross sections from the non-observation of an excess in the cosmic antiproton-to-proton ratio measured by PAMELA. (orig.)

  15. Dark matter annihilations into two light fermions and one gauge boson. General analysis and antiproton constraints

    Energy Technology Data Exchange (ETDEWEB)

    Garny, Mathias [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany); Ibarra, Alejandro; Vogl, Stefan [Technische Univ. Muenchen, Garching (Germany). Physik-Department

    2011-12-15

    We study in this paper the scenario where the dark matter is constituted by Majo- rana particles which couple to a light Standard Model fermion and an extra scalar via a Yukawa coupling. In this scenario, the annihilation rate into the light fermions with the mediation of the scalar particle is strongly suppressed by the mass of the fermion. Nevertheless, the helicity suppression is lifted by the associated emission of a gauge boson, yielding annihilation rates which could be large enough to allow the indirect detection of the dark matter particles. We perform a general analysis of this scenario, calculating the annihilation cross section of the processes {chi}{chi} {yields} f anti fV when the dark matter particle is a SU(2){sub L} singlet or doublet, f is a lepton or a quark, and V is a photon, a weak gauge boson or a gluon. We point out that the annihilation rate is particularly enhanced when the dark matter particle is degenerate in mass to the intermediate scalar particle, which is a scenario barely constrained by collider searches of exotic charged or colored particles. Lastly, we derive upper limits on the relevant cross sections from the non-observation of an excess in the cosmic antiproton-to-proton ratio measured by PAMELA. (orig.)

  16. Athari za uhamishaji wa sarufi ya Kiluo kwenye upatanisho wa sarufi ...

    African Journals Online (AJOL)

    Viambishi vya upatanishi hutumiwa tu kikundi nomino kinapoundwa na kiwakilishi. Athari ya uhamishaji wa sarufi ya Kiluo kwenye sarufi ya Kiswahili ilibainika katika viwango vitatu vya kisarufi: ngeli, nafsi na idadi. Utafiti uliongozwa na nadharia ya Umilikifu na Uhusisho (Chomsky, 1981). Nadharia hii huonesha hali ya ...

  17. Quasinuclear baryonium and annihilation

    International Nuclear Information System (INIS)

    Kerbikov, B.O.; Shapiro, I.S.

    1978-01-01

    The properties of the quasinuclear baryonium are considered in the framework of the dynamical coupled channel model. The main principles of the model are reviewed. The energy spectrum of the N anti N system and the problem of the baryonium radius are discussed. A detailed investigation of the problem of baryonium annihilation width and the low energy N anti N annihilation cross section is presented

  18. Positron annihilation spectroscopy in materials structure studies

    International Nuclear Information System (INIS)

    Grafutin, Viktor I; Prokop'ev, Evgenii P

    2002-01-01

    A relatively new method of materials structure analysis - positron annihilation spectroscopy (PAS) - is reviewed. Measurements of positron lifetimes, the determination of positron 3γ- and 2γ-annihilation probabilities, and an investigation of the effects of different external factors on the fundamental characteristics of annihilation constitute the basis for this promising method. The ways in which the positron annihilation process operates in ionic crystals, semiconductors, metals and some condensed matter systems are analyzed. The scope of PAS is described and its prospects for the study of the electronic and defect structures are discussed. The applications of positron annihilation spectroscopy in radiation physics and chemistry of various substances as well as in physics and chemistry of solutions are exemplified. (instruments and methods of investigation)

  19. Skyrmion creation and annihilation by spin waves

    International Nuclear Information System (INIS)

    Liu, Yizhou; Yin, Gen; Lake, Roger K.; Zang, Jiadong; Shi, Jing

    2015-01-01

    Single skyrmion creation and annihilation by spin waves in a crossbar geometry are theoretically analyzed. A critical spin-wave frequency is required both for the creation and the annihilation of a skyrmion. The minimum frequencies for creation and annihilation are similar, but the optimum frequency for creation is below the critical frequency for skyrmion annihilation. If a skyrmion already exists in the cross bar region, a spin wave below the critical frequency causes the skyrmion to circulate within the central region. A heat assisted creation process reduces the spin-wave frequency and amplitude required for creating a skyrmion. The effective field resulting from the Dzyaloshinskii-Moriya interaction and the emergent field of the skyrmion acting on the spin wave drive the creation and annihilation processes

  20. Neutral currents and the gauge group of weak and electromagnetic interactions

    International Nuclear Information System (INIS)

    Rajpoot, S.

    1977-12-01

    In considering the question of neutral current parity conversation, models of weak and electromagnetic interactions based on the gauge sub group SU(2)sub(L)xSU(2)sub(R)x(U) 1 are examined. The thesis is presented in the following sections: (1) Introduction. (2) Natural left-right symmetric theory and its neutral current phenomenology. (3) Effects of neutral weak currents in electron-positron annihilation. (4) Dilepton production in pp and anti pp collisions as a probe to the nature of the neutral current interaction. (U.K.)

  1. Search for Dark Matter Annihilation in the Galactic Halo using IceCube

    DEFF Research Database (Denmark)

    Medici, Morten Ankersen

    , and with the right properties of this hypothesized particle, it is possible to look for a signal from dark matter annihilation. In this work, the dark matter particle candidate of weakly interacting massive particles shall be presented, and the possibilities of observing it’s self-annihilation to neutrinos shall......The existence of dark matter has by now been demonstrated to such a de- gree that the next step is to understand what actually constitute this unknown gravitational mass. The total amount of matter in the universe cannot be explained without the introduction of a particle beyond the Standard Model...... detector for atmospheric muons it is possible to search for a neutrino signals form the center of the Milky Way located on the souther hemisphere. In this thesis, a complete analysis is carried out on data from 1004 days of IceCube data, looking for an excess of neutrinos consistent with the dark matter...

  2. Biological Effectiveness of Antiproton Annihilation

    DEFF Research Database (Denmark)

    Maggiore, C.; Agazaryan, N.; Bassler, N.

    2004-01-01

    from the annihilation of antiprotons produce an increase in ‘‘biological dose’’ in the vicinity of the narrow Bragg peak for antiprotons compared to protons. This experiment is the first direct measurement of the biological effects of antiproton annihilation. The background, description, and status...

  3. Simulation of the annihilation emission of galactic positrons

    International Nuclear Information System (INIS)

    Gillard, W.

    2008-01-01

    Positrons annihilate in the central region of our Galaxy. This has been known since the detection of a strong emission line centered on an energy of 511 keV in the direction of the Galactic center. This gamma-ray line is emitted during the annihilation of positrons with electrons from the interstellar medium. The spectrometer SPI, onboard the INTEGRAL observatory, performed spatial and spectral analyses of the positron annihilation emission. This thesis presents a study of the Galactic positron annihilation emission based on models of the different interactions undergone by positrons in the interstellar medium. The models are relied on our present knowledge of the properties of the interstellar medium in the Galactic bulge, where most of the positrons annihilate, and of the physics of positrons (production, propagation and annihilation processes). In order to obtain constraints on the positrons sources and physical characteristics of the annihilation medium, we compared the results of the models to measurements provided by the SPI spectrometer. (author)

  4. Positron annihilation characterization of nanostructured ferritic alloys

    International Nuclear Information System (INIS)

    Alinger, M.J.; Glade, S.C.; Wirth, B.D.; Odette, G.R.; Toyama, T.; Nagai, Y.; Hasegawa, M.

    2009-01-01

    Nanostructured ferritic alloys (NFAs) were produced by mechanically alloying Fe-14Cr-3W-0.4Ti and 0.25Y 2 O 3 (wt%) powders followed by hot isostatic pressing consolidation at 850, 1000 and 1150 deg. C. Positron annihilation lifetime and orbital momentum spectroscopy measurements are in qualitative agreement with small angle neutron scattering, transmission electron microscopy and atom probe tomography observations, indicating that up to 50% of the annihilations occur at high densities of Y-Ti-O enriched nm-scale features (NFs). Some annihilations may also occur in small cavities. In Y-free control alloys, that do not contain NFs, positrons primarily annihilate in the Fe-Cr matrix and at features such as dislocations, while a small fraction annihilate in large cavities or Ar bubbles.

  5. Antihydrogen annihilation reconstruction with the ALPHA silicon detector

    Energy Technology Data Exchange (ETDEWEB)

    Andresen, G.B. [Department of Physics and Astronomy, Aarhus University, DK-8000 Aarhus C (Denmark); Ashkezari, M.D. [Department of Physics, Simon Fraser University, Burnaby, BC, Canada V5A 1S6 (Canada); Bertsche, W. [Department of Physics, Swansea University, Swansea SA2 8PP (United Kingdom); Bowe, P.D. [Department of Physics and Astronomy, Aarhus University, DK-8000 Aarhus C (Denmark); Butler, E. [European Laboratory for Particle Physics, CERN, CH-1211 Geneva 23 (Switzerland); Cesar, C.L. [Instituto de Fisica, Universidade Federal do Rio de Janeiro, Rio de Janeiro 21941-972 (Brazil); Chapman, S. [Department of Physics, University of California, Berkeley, CA 94720-7300 (United States); Charlton, M.; Deller, A.; Eriksson, S. [Department of Physics, Swansea University, Swansea SA2 8PP (United Kingdom); Fajans, J. [Department of Physics, University of California, Berkeley, CA 94720-7300 (United States); Friesen, T. [Department of Physics and Astronomy, University of Calgary, Calgary, AB, Canada T2N 1N4 (Canada); Fujiwara, M.C. [TRIUMF, 4004 Wesbrook Mall, Vancouver, BC, Canada V6T 2A3 (Canada); Department of Physics and Astronomy, University of Calgary, Calgary, AB, Canada T2N 1N4 (Canada); Gill, D.R. [TRIUMF, 4004 Wesbrook Mall, Vancouver, BC, Canada V6T 2A3 (Canada); Gutierrez, A. [Department of Physics and Astronomy, University of British Columbia, Vancouver, BC, Canada V6T 1Z4 (Canada); Hangst, J.S. [Department of Physics and Astronomy, Aarhus University, DK-8000 Aarhus C (Denmark); Hardy, W.N. [Department of Physics and Astronomy, University of British Columbia, Vancouver, BC, Canada V6T 1Z4 (Canada); Hayden, M.E. [Department of Physics, Simon Fraser University, Burnaby, BC, Canada V5A 1S6 (Canada); Hayano, R.S. [Department of Physics, University of Tokyo, Tokyo 113-0033 (Japan); Humphries, A.J. [Department of Physics, Swansea University, Swansea SA2 8PP (United Kingdom); and others

    2012-08-21

    The ALPHA experiment has succeeded in trapping antihydrogen, a major milestone on the road to spectroscopic comparisons of antihydrogen with hydrogen. An annihilation vertex detector, which determines the time and position of antiproton annihilations, has been central to this achievement. This detector, an array of double-sided silicon microstrip detector modules arranged in three concentric cylindrical tiers, is sensitive to the passage of charged particles resulting from antiproton annihilation. This article describes the method used to reconstruct the annihilation location and to distinguish the annihilation signal from the cosmic ray background. Recent experimental results using this detector are outlined.

  6. Antihydrogen annihilation reconstruction with the ALPHA silicon detector

    CERN Document Server

    Andresen, G B; Bertsche, W; Bowe, P D; Butler, E; Cesar, C L; Chapman, S; Charlton, M; Deller, A; Eriksson, S; Fajans, J; Friesen, T; Fujiwara, M C; Gill, D.R; Gutierrez, A; Hangst, J S; Hardy, W N; Hayden, M E; Hayano, R S; Humphries, A J; Hydomako, R; Jonsell, S; Jorgensen, L V; Kurchaninov, L; Madsen, N; Menary, S; Nolan, P; Olchanski, K; Olin, A; Povilus, A; Pusa, P; Sarid, E; Seif el Nasr, S; Silveira, D M; So, C; Storey, J W; Thompson, R I; van der Werf, D P; Yamazaki, Y

    2012-01-01

    The ALPHA experiment has succeeded in trapping antihydrogen, a major milestone on the road to spectroscopic comparisons of antihydrogen with hydrogen. An annihilation vertex detector, which determines the time and position of antiproton annihilations, has been central to this achievement. This detector, an array of double-sided silicon microstrip detector modules arranged in three concentric cylindrical tiers, is sensitive to the passage of charged particles resulting from antiproton annihilation. This article describes the method used to reconstruct the annihilation location and to distinguish the annihilation signal from the cosmic ray background. Recent experimental results using this detector are outlined.

  7. Positron annihilation spectroscopy study of porous silicon

    International Nuclear Information System (INIS)

    Britkov, O.M.; Gavrilov, S.A.; Kalugin, V.V.; Timoshenkov, S.P.; Grafutin, V.I.; Ilyukhina, O.V.; Myasishcheva, G.G.; Prokop'ev, E.P.; Funtikov, Yu.V.

    2007-01-01

    Experimental studies of porous silicon by means of a standard positron annihilation technique based on measuring the angular distribution of annihilation photons, are reported. It was shown that the spectra of angular correlation of annihilation radiation in porous silicon are approximated well by a parabola (I p ) and two Gaussians (I g1 , I g2 ). The narrow Gaussian component I g1 is most likely due to the annihilation of localized para-positronium in pores. The full width at half maximum is on the order of 0.8 mrad, a value that corresponds to the kinetic energy of an annihilating positron-electron pair (0.079 ± 0.012 eV), and its intensity is about 1.5%. The total positronium yield in porous silicon reaches 6% in this case. The particle radius determined in the study is about 10-20 A [ru

  8. Dark Matter Annihilation at the Galactic Center

    Energy Technology Data Exchange (ETDEWEB)

    Linden, Timothy Ryan [Univ. of California, Santa Cruz, CA (United States)

    2013-06-01

    Observations by the WMAP and PLANCK satellites have provided extraordinarily accurate observations on the densities of baryonic matter, dark matter, and dark energy in the universe. These observations indicate that our universe is composed of approximately ve times as much dark matter as baryonic matter. However, e orts to detect a particle responsible for the energy density of dark matter have been unsuccessful. Theoretical models have indicated that a leading candidate for the dark matter is the lightest supersymmetric particle, which may be stable due to a conserved R-parity. This dark matter particle would still be capable of interacting with baryons via weak-force interactions in the early universe, a process which was found to naturally explain the observed relic abundance of dark matter today. These residual annihilations can persist, albeit at a much lower rate, in the present universe, providing a detectable signal from dark matter annihilation events which occur throughout the universe. Simulations calculating the distribution of dark matter in our galaxy almost universally predict the galactic center of the Milky Way Galaxy (GC) to provide the brightest signal from dark matter annihilation due to its relative proximity and large simulated dark matter density. Recent advances in telescope technology have allowed for the rst multiwavelength analysis of the GC, with suitable e ective exposure, angular resolution, and energy resolution in order to detect dark matter particles with properties similar to those predicted by the WIMP miracle. In this work, I describe ongoing e orts which have successfully detected an excess in -ray emission from the region immediately surrounding the GC, which is di cult to describe in terms of standard di use emission predicted in the GC region. While the jury is still out on any dark matter interpretation of this excess, I describe several related observations which may indicate a dark matter origin. Finally, I discuss the

  9. Asili na Chimbuko la Wazungumzaji wa Kimakunduchi: Hoja za ...

    African Journals Online (AJOL)

    Wakati tukiwa tunasherehekea mafanikio ya lugha ya Kiswahili katika nyanja mbalimbali, hatuna budi kujiuliza katika mijadala yetu ni kwa kiwango gani tumezishirikisha lahaja za Kiswahili katika kubaini mambo mbalimbali ikiwemo historia ya lugha hii. Tukumbuke kwamba wakati wa uteuzi wa lahaja ya Kiunguja kuwa ...

  10. Kuingiliana kwa Lugha ya Kiswahili na Kiingereza: Uswahilishaji wa ...

    African Journals Online (AJOL)

    Kuingiliana kwa lugha ni taaluma katika uwanja wa isimu inayohusu lugha zinazoingiliana na kuathiriana. Kuingiliana kwa lugha sio jambo jipya katika dunia. Watu ambao ndio watumiaji wa lugha wamesababisha lugha kuiingiliana waliposafiri au kuhama sehemu moja hadi nyingine kutokana na sababu za kiuchumi, ...

  11. ANTICOOL: Simulating positron cooling and annihilation in atomic gases

    Science.gov (United States)

    Green, D. G.

    2018-03-01

    The Fortran program ANTICOOL, developed to simulate positron cooling and annihilation in atomic gases for positron energies below the positronium-formation threshold, is presented. Given positron-atom elastic scattering phase shifts, normalised annihilation rates Zeff, and γ spectra as a function of momentum k, ANTICOOL enables the calculation of the positron momentum distribution f(k , t) as a function of time t, the time-varying normalised annihilation rate Z¯eff(t) , the lifetime spectrum and time-varying annihilation γ spectra. The capability and functionality of the program is demonstrated via a tutorial-style example for positron cooling and annihilation in room temperature helium gas, using accurate scattering and annihilation cross sections and γ spectra calculated using many-body theory as input.

  12. Electron-positron annihilation physics

    International Nuclear Information System (INIS)

    Foster, B.

    1990-01-01

    Electron-Positron Annihilation Physics is a detailed introduction to the main topics in e + e - annihilation, with particular emphasis on experimental work. Four main areas are covered, each in great detail, beginning with the Standard Model and its application to the production of lepton, quark and boson pairs. Secondly, the general features of fragmentation and different fragmentation models are explained. Chapter 3 is devoted to heavy quark and lepton physics, to which e + e - experiments have made an immense contribution. The final chapter, 'Where do we go from here?', looks for new phenomena beyond the Standard Model. Predictions of theory are compared with experimental results, highlighting shortcomings of some current theories. Details of instrumentation are included whenever possible. This ensures that the book is of maximum practical use to research workers. A comprehensive introduction to the major topics in the field, Electron-Positron Annihilation Physics is aimed at both graduate students studying high-energy physics and mature research workers. (author)

  13. Pionic annihilation of antiprotons stopped on sup 3 He

    Energy Technology Data Exchange (ETDEWEB)

    Bendiscioli, G.; Filippini, V.; Rotondi, A.; Salvini, P.; Venaglioni, A. (Pavia Univ. (Italy). Dipt. di Fisica Nucleare e Teorica Istituto Nazionale di Fisica Nucleare, Pavia (Italy)); Bossolasco, S.; Bussa, M.P.; Busso, L.; Fava, L.; Ferrero, L.; Maggiora, A.; Panzieri, D.; Piragino, G.; Piragino, R.; Tosello, F. (Turin Univ. (Italy). Ist. di Fisica Generale Istituto Nazionale di Fisica Nucleare, Turin (Italy)); Batusov, Yu.A.; Falomkin, I.V.; Pontecorvo, G.B.; Rozhdestvensky, A.M.; Sapozhnikov, M.G.; Tretyak, V.I. (Joint Inst. for Nuclear Research, Dubna (USSR)); Guaraldo, C. (Istituto Nazionale di Fisica Nucleare, Frascati (Italy). Lab. Nazionale di Frascati); Lodi Rizzini, E. (Brescia Univ. (Italy). Dipt. di Automazione Industriale Istituto Nazionale di Fisica Nucleare, Turin (Italy)); Haatuft, A.; Halsteinslid, A.; Myklebost, K.; Olsen, J.M. (Bergen Univ. (Norway). Dept. of Physics); Breivik, F.O.; Jacobsen, T.; Soerensen, S.O. (Oslo Univ. (Norway). Physics Dept.); Balestra

    1990-11-26

    The pionic annihilation of antiprotons stopped on {sup 3}He nuclei in a self-shunted streamer chamber exposed to the antiproton beam of LEAR is studied. The data concern charged-particle multiplicity distributions, branching ratios for different final states, the probability of final-state interaction, {pi}{sup -}, {pi}{sup +}, p and d momentum spectra, like and unlike pion angular correlations, {pi} and other charged-particle angular correlations. The comparison of the {sup 3}He data with those obtained on {sup 1}H, {sup 2}H and {sup 4}He does not reveal relevant effects due to the increase of the nucleon number; the small differences can be seen as due to a weak final-state interaction. (orig.).

  14. ATHENA: an actual antihydrogen annihilation

    CERN Multimedia

    2002-01-01

    This is an image of an actual matter-antimatter annihilation due to an atom of antihydrogen in the ATHENA experiment, located on the Antiproton Decelerator (AD) at CERN since 2001. The antiproton produces four charged pions (yellow) whose positions are given by silicon microstrips (pink) before depositing energy in CsI crystals (yellow cubes). The positron also annihilates to produce back-to-back gamma rays (red).

  15. Positron Transport and Annihilation in the Galactic Bulge

    Directory of Open Access Journals (Sweden)

    Fiona Helen Panther

    2018-03-01

    Full Text Available The annihilation of positrons in the Milky Way Galaxy has been observed for ∼50 years; however, the production sites of these positrons remains hard to identify. The observed morphology of positron annihilation gamma-rays provides information on the annihilation sites of these Galactic positrons. It is understood that the positrons responsible for the annihilation signal originate at MeV energies. The majority of sources of MeV positrons occupy the star-forming thin disk of the Milky Way. If positrons propagate far from their sources, we must develop accurate models of positron propagation through all interstellar medium (ISM phases in order to reveal the currently uncertain origin of these Galactic positrons. On the other hand, if positrons annihilate close to their sources, an alternative source of MeV positrons with a distribution that matches the annihilation morphology must be identified. In this work, I discuss the various models that have been developed to understand the origin of the 511 keV line from the direction of the Galactic bulge, and the propagation of positrons in the ISM.

  16. Positrons annihilation and the Galactic center

    International Nuclear Information System (INIS)

    Wallyn, Pierre

    1992-01-01

    The Galactic center has been observed in gamma rays, many times since more than two decades and we do not still have a full comprehensive picture of this region. It is fairly well established that the 511 keV annihilation line has two origins: a steady diffuse emission, which follows more or less the type I supernovae distribution along the Galactic plane and a variable emission coming from the positrons emitted by (at least) one compact object and annihilating in a nearby cold molecular cloud. We present here an analysis of the profiles and intensifies of the 511 keV annihilation line observed in the direction of the Galactic center. We find that a warm medium (temperature of 8000 K) can describe the annihilation of positrons from the diffuse component of the line. The high state observations of the 511 keV line can be explained if the time-variable component is coming from the annihilation of the positrons in a cold medium (temperature around 80 K). This constraint on the annihilation medium temperature supports the association with the molecular cloud G-0.86-0.08 in the direction of 1E1740.7-2942. On may 22, 1989, HEXAGONE detected a narrow 511 keV line and also a broad emission around 170 keV in the direction of the Galactic center. Two weeks before, EXITE observed in the same direction a new transient source EXS 1737.9-2952 which showed a bump around 102 keV. We propose a simple semi-quantitative model which can mimic the bumps as well as its time variations and emphasize the strong similarities between EXS1737.9-2952 and Nova Muscae. We study the behaviour of positron annihilation by charge exchange in the cold phase of the interstellar medium. We calculate formula for the slowing-down time before thermalization of positrons of a given initial energy, for different medium densities. Our scenario explains the lack of detection of the recombination lines from positronium and gives new constraints on their possible observation. (author) [fr

  17. Positron Annihilation in Insulating Materials

    International Nuclear Information System (INIS)

    Asoka-Kumar, P; Sterne, PA

    2002-01-01

    We describe positron results from a wide range of insulating materials. We have completed positron experiments on a range of zeolite-y samples, KDP crystals, alkali halides and laser damaged SiO 2 . Present theoretical understanding of positron behavior in insulators is incomplete and our combined theoretical and experimental approach is aimed at developing a predictive understanding of positrons and positronium annihilation characteristics in insulators. Results from alkali halides and alkaline-earth halides show that positrons annihilate with only the halide ions, with no apparent contribution from the alkali or alkaline-earth cations. This contradicts the results of our existing theory for metals, which predicts roughly equal annihilation contributions from cation and anion. We also present result obtained using Munich positron microprobe on laser damaged SiO 2 samples

  18. Positron annihilation in metallic glasses - a general survey

    International Nuclear Information System (INIS)

    Brauer, G.; Kajcsos, Zs.; Kemeny, T.

    1981-08-01

    This report presents a review of the literature on positron annihilation studies concerning metallic glasses. After some general information and overview on structural models of metallic glasses as well as a short description of the positron annihilation method itself are added. Conclusions regarding information on the structure of metallic glasses obtainable by positron annihilation are also given. (author)

  19. Event simulation for the WA80 experiment

    International Nuclear Information System (INIS)

    Sorensen, S.P.

    1986-01-01

    The HIJET and LUND event generators are compared. It is concluded that for detector construction and design of experimental setups, the differences between the two models are marginal. The coverage of the WA80 setup in pseudorapidity and energy is demonstrated. The performance of some of the WA80 detectors (zero-degree calorimeter, wall calorimeter, multiplicity array, and SAPHIR lead-glass detector) is evaluated based on calculations with the LUND or the HIJET codes combined with codes simulating the detector responses. 9 refs., 3 figs

  20. Initial angular momentum state in pp annihilation at rest

    CERN Document Server

    Bizzarri, R

    1972-01-01

    The author shows that no quantitative statement on the relative importance of initial P-states in pp annihilation can be made. Annihilations in flight indicate that P-wave annihilation into K/sub 1 //sup 0/K/sub 1//sup 0/ is inhibited while annihilation into pi pi is enhanced and might suggest a P-wave contamination approximately 10%. The observatory of the final state K/sub 1//sup 0/K/sub 1//sup 0/n from annihilations at rest indicates that the depression of the K/sub 1//sup 0/K/sub 1//sup 0/ final state is not so important and suggests a P-wave contamination smaller than 4%. Furthermore the successes obtained in the analysis of various final states on the assumption of S-wave annihilation are hard to reconcile with a P-wave contribution bigger than approximately 5%. (20 refs).

  1. Antimatter annihilation detection with AEgIS

    CERN Document Server

    Gligorova, Angela

    2015-01-01

    AE ̄ gIS (Antimatter Experiment: Gravity, Interferometry, Spectroscopy) is an antimatter exper- iment based at CERN, whose primary goal is to carry out the first direct measurement of the Earth’s gravitational acceleration on antimatter. A precise measurement of antimatter gravity would be the first precision test of the Weak Equivalence Principle for antimatter. The principle of the experiment is based on the formation of antihydrogen through a charge exchange reaction between laser excited (Rydberg) positronium and ultra-cold antiprotons. The antihydrogen atoms will be accelerated by an inhomogeneous electric field (Stark acceleration) to form a pulsed cold beam. The free fall of the antihydrogen due to Earth’s gravity will be measured using a moiré de- flectometer and a hybrid position detector. This detector is foreseen to consist of an active silicon part, where the annihilation of antihydrogen takes place, followed by an emulsion part coupled to a fiber time-of-flight detector. This overview prese...

  2. Metatheatricalizing Communal Exploitation in Ngugi wa Thiong’o and Ngugi wa Miriis’ I Will Marry When I want

    Directory of Open Access Journals (Sweden)

    Niyi Akingbe

    2014-01-01

    Full Text Available Metatheatre often refers to the capability of a stage text and performance to ostensibly establish a gamut of commentaries needed to repudiate a pervading social and political quagmire, tellingly obtainable in societies under siege. Metatheatre is a long established theatre tradition which has been sufficiently calibrated in William Shakespeare's A Midsummer Night's Dream, put into a utilitarian proclivity in Anton Chekhov's The Seagull, and fully aestheticized in Jean Genet's The Balcony and The Blacks. It is also a tradition which has been successfully exploited in Wole Soyinka's Madmen and Specialists; Athol Fugard's Sizwe Bansi is Dead; Femi Osofisan's The Chattering and the Song and Segun Oyekunle's Katakata for Sofahead. Ngugi wa Thiong'o and Ngugi wa Mirii steeped a metatheatre into the interface of politics and religion in I Will Marry When I Want, in order to foreground the hypocrisy of Christianity as underscored by the exploitation of the downtrodden masses, by the land grabbing Christian elite of the Kenyan society. This paper will be examining how Ngugi wa Thiong'o and Ngugi wa Miriis' I Will Marry When I Want builds on the harvest of the oral, mimetic and metaphoric signification of myth, history and song, to launch a barrage of criticism against a backdrop of land theft. This appropriation is poignantly accentuated by a language of equivocation, usually associated with the Christian elite in Kenya. The paper will among other things emphasize that, the rapacious gluttony for land grabbing is indubitably faith driven, as clearly demonstrated by the Kenyan Christian elite in the play.

  3. 2015 OLC Lidar: Wasco, WA

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — WSI collected Light Detection and Ranging (LiDAR) data for the Oregon LiDAR Consortium (OLC) Wasco County, WA, study area. The Oregon LiDAR Consortium's Wasco County...

  4. Preparing for WA34

    CERN Multimedia

    1977-01-01

    Following a proposal by a CERN-Florence-Genova Collaboration to study charmed particles photoproduced in emulsion plates tagged by the Omega apparatus triggers, WA34 was a test exposure to demonstrate the validity of the experimental method. Here (centre) Giordano Diambrini-Palazzi inside the Omega magnet. the validity of the experimental method.

  5. The annihilation spectrum of relatiVistic electron-positron plasma

    International Nuclear Information System (INIS)

    Aragonyan, F.A.; Atoyan, A.M.; Syunyaev, R.A.

    1980-01-01

    The annihilation spectrum of isotropically distributed monoenergetic electrons and positrons is obtained. The spectrum of the (e + e - ) plasma is analyzed in a large range of plasma temperatures. The comparison of transitions peratures. The comparison of transitions intensities of annihilation radiation and bremsstrahlung shows that for temperatures kT 2 (e + e - ) plasma is cooled mainly due to annihilation. The case of the fast positron annihilation on the rest electrons also considered. The possible astrophysical applications are discussed [ru

  6. Angular correlation in positron annihilation

    International Nuclear Information System (INIS)

    Arponen, J.; Pajanne, E.

    1978-01-01

    The angular correlation of the two gamma quanta emitted when a thermalized positron annihilates with metallic conduction electrons is investigated by applying the newly developed theory of electron gas as a system of interacting collective excitations. The method leads in a natural way to the appearance of high-momentum components (i.e. pair momentum p>psub(F) in the annihilation radiation already in the case of annihilation with conduction electrons only. The amount of these components is significant approximately (10 %) in a dilute electron gas (like alkali metals), but fairly irrelevant for higher densities. The momentum-dependence of the enhancement factor for a dense system (with rsub(s) approximately equal to 2) agrees well both with the earlier theories due to Kahana and others, and also with recent accurate experimental observations. As rsub(s) increases into the alkali-metal region, the enhancement factor for p< psub(F) becomes relatively more and more constant, in contrast with the trend in the Kahana theory. In this density regime the experimental results seem to vary widely, although most of them desagree with the present prediction. We discuss the possible discrepancy and try to account for the effects of the core annihilation by a simple model. (author)

  7. Simple picture of the annihilation process

    International Nuclear Information System (INIS)

    Gotsman, E.; Nussinov, S.

    1980-01-01

    We propose a simple geometrical picture for B-barB annihilations, which is motivated by the electric-flux-tube model and is consistent with the quark-rearrangement model, as well as the nonplanar multiperipheral quark-exchange model. Within its framework we are able to explain all the salient features of the experimental annihilation data

  8. Hadron production in e+e- annihilation

    International Nuclear Information System (INIS)

    Lueth, V.

    1977-01-01

    The lectures cover recent results on hadron production by e + e - annihilation. Included are total hadronic cross section and scale invariance as applied to e + e - annihilation, the present status of the psi spectroscopy by study of the decay modes of the narrow psi resonances, and the recent discovery of charmed mesons. 93 references

  9. Structure formation constraints on Sommerfeld-enhanced dark matter annihilation

    International Nuclear Information System (INIS)

    Armendariz-Picon, Cristian; Neelakanta, Jayanth T.

    2012-01-01

    We study the growth of cosmic structure in a ΛCDM universe under the assumption that dark matter self-annihilates with an averaged cross section times relative velocity that grows with the scale factor, an increase known as Sommerfeld-enhancement. Such an evolution is expected in models in which a light force carrier in the dark sector enhances the annihilation cross section of dark matter particles, and has been invoked, for instance, to explain anomalies in cosmic ray spectra reported in the past. In order to make our results as general as possible, we assume that dark matter annihilates into a relativistic species that only interacts gravitationally with the standard model. This assumption also allows us to test whether the additional relativistic species mildly favored by cosmic-microwave background data could originate from dark matter annihilation. We do not find evidence for Sommerfeld-enhanced dark matter annihilation and derive the corresponding upper limits on the annihilation cross-section

  10. Novel Pathway of Salicylate Degradation by Streptomyces sp. Strain WA46

    OpenAIRE

    Ishiyama, Daisuke; Vujaklija, Dusica; Davies, Julian

    2004-01-01

    A novel salicylate-degrading Streptomyces sp., strain WA46, was identified by UV fluorescence on solid minimal medium containing salicylate; trace amounts of gentisate were detected by high-pressure liquid chromatography when strain WA46 was grown with salicylate. PCR amplification of WA46 DNA with degenerate primers for gentisate 1,2-dioxygenase (GDO) genes produced an amplicon of the expected size. Sequential PCR with nested GDO primers was then used to identify a salicylate degradation gen...

  11. Thermal equilibrium defects in anthracene probed by positron annihilation

    International Nuclear Information System (INIS)

    Uedono, Akira; Tanigawa, Shoichiro; Tachibana, Masaru; Shimizu, Mikio; Satoh, Masaaki; Kojima, Kenichi; Ishibashi, Shoji; Kawano, Takao.

    1996-01-01

    Defects in anthracene were investigated by the positron annihilation technique. Doppler broadening profiles of the annihilation radiation and lifetime spectra of positrons were measured in the temperature range between 305 K and 516 K. The lifetime of positrons annihilated from the delocalized state was determined to be 0.306 ns around room temperature. Below the melting point, the observed temperature dependence of the line shape parameter S was explained assuming the formation energy of thermal equilibrium defects was 1 eV. Above the melting point, the pick-off annihilation of ortho-positronium in open spaces was observed, where the size of these spaces was estimated to be 0.2 nm 3 . The annihilation of positrons from the self-trapped state was also discussed. (author)

  12. Thermal equilibrium defects in anthracene probed by positron annihilation

    Energy Technology Data Exchange (ETDEWEB)

    Uedono, Akira; Tanigawa, Shoichiro [Tsukuba Univ., Ibaraki (Japan). Inst. of Materials Science; Tachibana, Masaru; Shimizu, Mikio; Satoh, Masaaki; Kojima, Kenichi; Ishibashi, Shoji; Kawano, Takao

    1996-06-01

    Defects in anthracene were investigated by the positron annihilation technique. Doppler broadening profiles of the annihilation radiation and lifetime spectra of positrons were measured in the temperature range between 305 K and 516 K. The lifetime of positrons annihilated from the delocalized state was determined to be 0.306 ns around room temperature. Below the melting point, the observed temperature dependence of the line shape parameter S was explained assuming the formation energy of thermal equilibrium defects was 1 eV. Above the melting point, the pick-off annihilation of ortho-positronium in open spaces was observed, where the size of these spaces was estimated to be 0.2 nm{sup 3}. The annihilation of positrons from the self-trapped state was also discussed. (author)

  13. Antiproton-helium annihilation around 45 MeV/c

    International Nuclear Information System (INIS)

    Balestra, F.; Bassolasco, S.; Bussa, M.P.; Busso, L.; Ferrero, L.; Panzieri, D.; Piragino, G.; Tosello, F.; Barbieri, R.; Bendiscioli, G.; Filippini, V.; Rotondi, A.; Salvini, P.; Zenoni, A.; Batusov, Yu.A.; Falomkin, I.V.; Pontecorvo, G.B.; Rozhdestvensky, A.M.; Sapozhnikov, M.G.; Tretyak, V.I.; Breivik, F.O.; Jacobsen, T.; Soerensen, S.O.

    1989-01-01

    The anti p 4 He annihilation cross section averaged over the interval 40-50 MeV/c has been measured using a streamer chamber in a magnetic field. The measured value is 1342±250 mb. It agrees with a behaviour like 1/p of the annihilation cross section. Our result has been obtained at the lowest momentum achieved till now in measurements of antiproton annihilation in flight. (orig.)

  14. Antiproton-helium annihilation around 45 MeV/c

    Energy Technology Data Exchange (ETDEWEB)

    Balestra, F.; Bassolasco, S.; Bussa, M.P.; Busso, L.; Ferrero, L.; Panzieri, D.; Piragino, G.; Tosello, F. (Turin Univ. (Italy). Ist. di Fisica Generale; Istituto Nazionale di Fisica Nucleare, Turin (Italy)); Barbieri, R.; Bendiscioli, G.; Filippini, V.; Rotondi, A.; Salvini, P.; Zenoni, A. (Pavia Univ. (Italy). Dipt. di Fisica Nucleare e Teorica; Istituto Nazionale di Fisica Nucleare, Pavia (Italy)); Batusov, Yu.A.; Falomkin, I.V.; Pontecorvo, G.B.; Rozhdestvensky, A.M.; Sapozhnikov, M.G.; Tretyak, V.I. (Joint Inst. for Nuclear Research, Dubna (USSR)); Breivik, F.O.; Jacobsen, T.; Soerensen, S.O. (Oslo Univ. (Norway). Fysisk Inst.); Guaraldo, C.; Maggiora, A. (Istituto Nazionale di Fisica Nucleare, Frascati (Italy). Lab. Nazionale di Frascati); Haatuft, A.; Halsteinslid, A.; Myklebost, K.; Olsen, J.M. (Bergen Univ. (Norway). Dept. of Physics); Lodi Rizzini, E. (Brescia Univ. (Italy). Dipt. di Automazione Industriale); Masala, M. (Brescia Univ. (Italy). Dipt. di Automazione Ind

    1989-10-26

    The anti p{sup 4}He annihilation cross section averaged over the interval 40-50 MeV/c has been measured using a streamer chamber in a magnetic field. The measured value is 1342+-250 mb. It agrees with a behaviour like 1/p of the annihilation cross section. Our result has been obtained at the lowest momentum achieved till now in measurements of antiproton annihilation in flight. (orig.).

  15. Results on charm hadroproduction from CERN experiment WA82

    Energy Technology Data Exchange (ETDEWEB)

    Antinori, F.; Barberis, D.; Beusch, W.; Davenport, M.; Dufey, J.P.; French, B.R.; Harrison, K.; Jacholkowski, A.; Kirk, A.; Lamanna, E.; Lassalle, J.C.; Muller, F.; Redaelli, N.; Roda, C.; Weymann, M. (CERN, Geneva (Switzerland)); Forino, A.; Gessaroli, R.; Mazzanti, P.; Quareni, A.; Viaggi, F. (Dipartimento di Fisica and INFN, Bologna (Italy)); Anselmi, R.; Casanova, V.; Dameri, M.; Hurst, R.; Novelli, P.; Osculati, B.; Rossi, L.; Tomasini, G. (Dipartimento di Fisica and INFN, Genova (Italy)); Buys, A.; Grard, F.; Legros, P. (Universite de Mons-Hainaut and IISN, Mons (Belgium)); Adamovich, M.; Alexandrov, Y.; Kharlamov, S.; Nechaeva, P.; Zavertyaev, M. (Lebedev Physical Institute, Moscow (Russian Federation))

    1992-02-01

    Experiment WA82 has collected data from 1987 to 1989 with the [Omega][prime] spectrometer at the CERN SPS. The aim of WA82 was a high statistics study of charm hadroproduction, using a silicon microstrip vertex detector and an impact parameter trigger. Latest results on the nuclear dependence of charm production and on the [ital x][sub [ital F

  16. Cosmic gamma-ray background from dark matter annihilation

    International Nuclear Information System (INIS)

    Ando, Shin'ichiro

    2007-01-01

    High-energy photons from pair annihilation of dark matter particles contribute to the cosmic gamma-ray background (CGB) observed in a wide energy range. The precise shape of the energy spectrum of CGB depends on the nature of dark matter particles. In order to discriminate between the signals from dark matter annihilation and other astrophysical sources, however, the information from the energy spectrum of CGB may not be sufficient. We show that dark matter annihilation not only contributes to the mean CGB intensity, but also produces a characteristic anisotropy, which provides a powerful tool for testing the origins of the observed CGB. We show that the expected sensitivity of future gamma-ray detectors such as GLAST should allow us to measure the angular power spectrum of CGB anisotropy, if dark matter particles are supersymmetric neutralinos and they account for most of the observed mean intensity. As the intensity of photons from annihilation is proportional to the density squared, we show that the predicted shape of the angular power spectrum of gamma rays from dark matter annihilation is different from that due to other astrophysical sources such as blazars, whose intensity is linearly proportional to density. Therefore, the angular power spectrum of the CGB provides a 'smoking-gun' signature of gamma rays from dark matter annihilation

  17. Dislocation dipole annihilation in diamond and silicon

    Energy Technology Data Exchange (ETDEWEB)

    Rabier, J; Pizzagalli, L, E-mail: jacques.rabier@univ-poitiers.fr [Institut PPRIMME, Departement de Physique et Mecanique des Materiaux - UPR 3346 CNRS, Universite de Poitiers, ENSMA - SP2MI, BP 30179, F-86962 Chasseneuil Futuroscope Cedex (France)

    2011-02-01

    The mechanism of dislocation dipole annihilation has been investigated in C and Si using atomistic calculations with the aim of studying their annihilation by-products. It is shown, in C as well as in Si, that dipole annihilation yields debris that can be depicted as a cluster of vacancies, or alternately by two internal free surfaces. These defects have no strain field and can hardly be seen using usual TEM techniques. This suggests that the brown colouration of diamond could be due to microstructures resulting from deformation mechanisms associated with dipole formation and their annihilation rather than to a climb mechanism and vacancy aggregation. In silicon where a number of dipoles have been evidenced by TEM when dislocation trails are found, such debris could be the missing link responsible for the observation of strong chemical reactivity and electrical activity in the wake of moving dislocations.

  18. Evidence of isospin effects in antiproton-nucleus annihilation

    International Nuclear Information System (INIS)

    Balestra, F.; Bossolasco, S.; Bussa, M.P.; Busso, L.; Ferrero, L.; Panzieri, D.; Piragino, G.; Tosello, F.; Barbieri, R.; Bendiscioli, G.; Rotondi, A.; Salvini, P.; Venaglioni, A.; Zenoni, A.; Batusov, Yu.A.; Falomkin, I.V.; Pontecorvo, G.B.; Rozhdestvensky, A.M.; Sapozhnikov, M.G.; Tretyak, V.I.; Guaraldo, C.; Maggiora, A.; Haatuft, A.; Halsteinslid, A.; Myklebost, K.; Olsen, J.M.; Breivik, F.O.; Jacobsen, T.; Soerensen, S.O.

    1989-01-01

    Antiproton- 3 He annihilation events at rest have been detected using a self-shunted streamer chamber. The ratio of the cross section for annihilation on neutrons and on protons has been measured (0.467±0.035). It is compared with other results from annihilation on free nucleons, deuterium, 3 He and 4 He. The low value of the ratio seems to indicate a strong isospin dependence of the antinucleon-nucleon P-wave amplitude. (orig.)

  19. Light dark matter through assisted annihilation

    International Nuclear Information System (INIS)

    Dey, Ujjal Kumar; Maity, Tarak Nath; Ray, Tirtha Sankar

    2017-01-01

    In this paper we investigate light dark matter scenarios where annihilation to Standard Model particles at tree-level is kinematically forbidden. In such cases annihilation can be aided by massive Standard Model-like species, called assisters , in the initial state that enhances the available phase space opening up novel tree-level processes. We investigate the feasibility of such non-standard assisted annihilation processes to reproduce the observed relic density of dark matter. We present a simple scalar dark matter-scalar assister model where this is realised. We find that if the dark matter and assister are relatively degenerate the required relic density can be achieved for a keV-MeV scale dark matter. We briefly discuss the cosmological constraints on such dark matter scenarios.

  20. Results on charm hadroproduction from CERN experiment WA82

    International Nuclear Information System (INIS)

    Antinori, F.; Barberis, D.; Beusch, W.; Davenport, M.; Dufey, J.P.; French, B.R.; Harrison, K.; Jacholkowski, A.; Kirk, A.; Lamanna, E.; Lassalle, J.C.; Muller, F.; Redaelli, N.; Roda, C.; Weymann, M.; Forino, A.; Gessaroli, R.; Mazzanti, P.; Quareni, A.; Viaggi, F.; Anselmi, R.; Casanova, V.; Dameri, M.; Hurst, R.; Novelli, P.; Osculati, B.; Rossi, L.; Tomasini, G.; Buys, A.; Grard, F.; Legros, P.; Adamovich, M.; Alexandrov, Y.; Kharlamov, S.; Nechaeva, P.; Zavertyaev, M.

    1992-01-01

    Experiment WA82 has collected data from 1987 to 1989 with the Ω' spectrometer at the CERN SPS. The aim of WA82 was a high statistics study of charm hadroproduction, using a silicon microstrip vertex detector and an impact parameter trigger. Latest results on the nuclear dependence of charm production and on the x F distributions of D + and D - mesons are presented and discussed

  1. Exclusive channels in bar pp annihilation at rest

    International Nuclear Information System (INIS)

    Bluem, P.

    1992-01-01

    Exclusive channels in bar pp annihilation at rest provide a powerful tool for studying the meson spectrum below the bar pp threshold. The mesons can be classified in SU(3) multiplets according to their quantum numbers. The states which do not fit into this classification are candidates for new forms of hadronic matter like glueballs, hybrids, and multi-quark states. Recent results on the search for exotic states in exclusive channels of bar pp annihilation at rest are discussed. No less important is the study of the annihilation mechanism. In particular, high-statistic measurements of bar pp annihilation at rest into two-meson final states are an excellent tool for studying quark dynamics. Examples of two-body reactions are presented. 24 refs., 9 figs., 3 tabs

  2. Quantum beats in positronium 3γ annihilation decay observed in an age dependent, magnetically perturbed angular distribution (ADPAD), experiment

    International Nuclear Information System (INIS)

    Ivanov, E.; Vata, I.; Dudu, D.; Rusen, I.; Stefan, N.; Catavencu, V.

    2005-01-01

    We have been able to observe experimentally quantum beat oscillations of Positronium 3γ annihilation decay at Positronium ages from 5 ns to 300 ns. We describe in some detail our equipment aiming at a consolidation of a new method of Positron Annihilation Spectroscopy. The equipment is dedicated to the study of hyperfine interactions of Positronium atoms in weak magnetic fields; four identical time spectrometers which have been used to measure simultaneously oscillations of positron life time spectra at privileged angles for the 3γ detectors. To overcome typical uncertainties in revealing small oscillation amplitudes the four life time spectra have been registered using a unique chronometer (TAC-ADC line) associated to a mixing - routing unit interfacing a PC memory. The present stage of performance is illustrated and further developments are suggested. (authors)

  3. Korean WA-DGNSS User Segment Software Design

    Directory of Open Access Journals (Sweden)

    Sayed Chhattan Shah

    2013-03-01

    Full Text Available Korean WA-DGNSS is a large scale research project funded by Ministry of Land, Transport and Maritime Affairs Korea. It aims to augment the Global Navigation Satellite System by broadcasting additional signals from geostationary satellites and providing differential correction messages and integrity data for the GNSS satellites. The project is being carried out by a consortium of universities and research institutes. The research team at Electronics and Telecommunications Research Institute is involved in design and development of data processing softwares for wide area reference station and user segment. This paper focuses on user segment software design. Korean WA-DGNSS user segment software is designed to perform several functions such as calculation of pseudorange, ionosphere and troposphere delays, application of fast and slow correction messages, and data verification. It is based on a layered architecture that provides a model to develop flexible and reusable software and is divided into several independent, interchangeable and reusable components to reduce complexity and maintenance cost. The current version is designed to collect and process GPS and WA-DGNSS data however it is flexible to accommodate future GNSS systems such as GLONASS and Galileo.

  4. Contribution from S and P waves in pp annihilation at rest

    CERN Document Server

    Bendiscioli, G; Fontana, A; Montagna, P; Rotondi, A; Salvini, P; Bertin, A; Bruschi, M; Capponi, M; De Castro, S; Donà, R; Galli, D; Giacobbe, B; Marconi, U; Massa, I; Piccinini, M; Cesari, N S; Spighi, R; Vecchi, S; Vagnoni, V M; Villa, M; Vitale, A; Zoccoli, A; Bianconi, A; Bonomi, G; Lodi-Rizzini, E; Venturelli, L; Zenoni, A; Cicalò, C; De Falco, A; Masoni, A; Puddu, G; Serci, S; Usai, G L; Gorchakov, O E; Prakhov, S N; Rozhdestvensky, A M; Tretyak, V I; Poli, M; Gianotti, P; Guaraldo, C; Lanaro, A; Lucherini, V; Petrascu, C; Kudryavtsev, A E; Balestra, F; Bussa, M P; Busso, L; Cerello, P G; Denisov, O Yu; Ferrero, L; Grasso, A; Maggiora, A; Panzarasa, A; Panzieri, D; Tosello, F; Botta, E; Bressani, Tullio; Calvo, D; Costa, S; D'Isep, D; Feliciello, A; Filippi, A; Marcello, S; Mirfakhraee, N; Agnello, M; Iazzi, F; Minetti, B; Tessaro, S

    2001-01-01

    The annihilation frequencies of 19 pp annihilation reactions at rest obtained in different target densities are analysed in order to determine the values of the P-wave annihilation percentage at each target density and the average hadronic branching ratios from P- and S-states. Both the assumptions of linear dependence of the annihilation frequencies on the P-wave annihilation percentage of the protonium state and the approach with the enhancement factors of Batty (1989) are considered. Furthermore the cases of incompatible measurements are discussed. (55 refs).

  5. Positron Annihilation Characteristics in Polymer Composites

    International Nuclear Information System (INIS)

    Ashry, A.; Hemdan, M.; Ismail, A.; Ismail, H.; Osman, H.

    2000-01-01

    The effect of incorporation of GPF-carbon black on the free volume properties as well as the Doppler broadening parameters has been investigated for Natural rubber/Styrene Butadiene rubber (NR/SBR) blends. It is seen that, the free volume decreases with increasing of the GPF-black. Besides, as the size of the free volume decreases, the W-parameter, which corresponds to high momentum region, decreases and the S-parameter, which corresponds to low momentum one, shows an opposite behaviour. Furthermore, the d.c.electrical conductivity, mechanical and swelling behavior have been also investigated. Positron Annihilation Lifetime (PAL) and Doppler Broadening of the Annihilation Radiation (DBAR) results are compared with the other physical parameters measured. The analysis of positron annihilation parameters introduces a trusted support for the interpretations of the other macroscopic physical properties

  6. Annihilation of antiproton on deuteron at rest

    International Nuclear Information System (INIS)

    Grach, I.; Shmatikov, M.

    1982-01-01

    The system of Faddeev equations for amplitudes of anti pD iteraction at rest accounting for higher partial anti NN waves is derived. From its solution the total and elastic anti pD cross sections are calculated. Predictions for the missing-mass spectrum in the anti pD annihilation are made. The P-wave anti NN states give small contribution to the anti pD cross section at rest, the theoretical value of the latter being less than the experimental cross section extrapolated to the threshold. Let us emphasize that the total anti pD cross section depending weakly on the radii of anti NN interactions is sensitive to the values of the anti NN scattering lengths. Experimental data for anti pD cross sections at rest can be obtained only by extrapolation procedure. Henceforth it is very important to investigate the anti pD interactions at low but non-zero momenta where the direct comparison to the experiment is possible [ru

  7. Defect characterization with positron annihilation

    International Nuclear Information System (INIS)

    Granatelli, L.; Lynn, K.G.

    1980-01-01

    Positron annihilation in metal crystals is reviewed. A brief introduction to the positron annihilation technique is presented first. Then the ability of the positron technique to perform microstructural characterization of four types of lattice defects (vacancies, voids, dislocations, grain boundaries) is discussed. It is frequently not possible to obtain samples that contain only one type of defect in nonnegligible concentrations. Such situations exist for some alloys and for fatigued metal samples. Finally, the current limitations and some future prospects of the technique are presented. 79 references, 14 figures, 1 table

  8. Majibu Kwa Makala “Mkanganyiko Wa Dhana Za Mzizi, Kiini Na ...

    African Journals Online (AJOL)

    Masuala yanayojadiliwa na Gambarage ni ya uwanja wa mofolojia au sarufimaumbo katika taaluma ya isimu. Uwanja huu unaochunguza maneno na muundo wake katika lugha unajihusisha na vipengele na michakato mingi ambayo, kwa hakika itabidi iendelee kuchunguzwa kwa namna mbalimbali. Mchunguzi wa ...

  9. Doppler-broadening of positron annihilation in a biological environment

    International Nuclear Information System (INIS)

    Torrisi, L.; La Mela, C.; Catania, Univ.

    1997-01-01

    The aim of this study was to investigate the Doppler effect of the 511 keV γ peak from positron annihilation in biological matter: The broadening of the annihilation peak is due to positron annihilation with electrons that have high momentum. In aqueous solutions annihilation depends on the temperature and it is linked positronium formation. Measurements in vivo, on human brain, were taken during the diagnosis of positron emission tomography (PET) on healthy patients by injecting them with the beta emitter of short lifetime 18F . The Doppler-broadening in biological tissues rich in water content decreased significantly compared to biological solutions and water

  10. Zadig: latest improvements to Bremsstrahlung treatment and in-flight annihilation scheme; Zadig: amelioration du traitement Bremsstrahlung et traitement de l'annihilation en vol

    Energy Technology Data Exchange (ETDEWEB)

    Menard, St

    2006-07-01

    Multigroup cross-section for the 3-dimensional Monte-Carlo transport code DIANE are produced by the ZADIG code. Although DIANE does not transport the electrons and positrons, the production of Bremsstrahlung photons induced by the electrons and positrons during their slowing down is taken into account in the ZADIG code because the electron-gamma cascade is an important process in high energy gamma ray transport. ZADIG does not distinguish positrons from electrons except for the positron annihilation. However, the user can turn on this direction. This report presents the latest improvements to the Bremsstrahlung model of ZADIG and to the positron annihilation algorithm implemented in the code. Positrons can annihilate either in flight or at rest in the latest release of ZADIG. As MCNP does not take into account the annihilation in flight, results of ZADIG-DIANE calculations are compared to the results of GEANT-4 in order to validate the annihilation scheme of ZADIG. The results with annihilation divided by the results without present similar trends between 0.6 and 10 MeV for the 2 codes (GEANT-4 and ZADIG-DIANE), in other words an influence of 5%, so the annihilation scheme programmed in ZADIG appears to be satisfying and can be considered as validated.

  11. Positron annihilation in solids: positronium diffusion; Annihilation du positon dans les solides diffusion du positonium

    Energy Technology Data Exchange (ETDEWEB)

    Paulin, R [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

    1969-04-01

    The existence of two slow components in life-time spectrum of positron annihilation in silicium, aluminium and alkaline-earth oxides powders is established. These two long mean-lives {approx_equal} 10{sup -9} s and {approx_equal} 10{sup -7} s result from annihilation, inside and outside the grains respectively, of ortho-positronium formed in defects present in ionic crystals investigated. Dynamic behaviour of Ps, so revealed, is analyzed in terms of diffusion in excellent agreement with experiment. Diffusion constants of the order of 10{sup -4} cm{sup 2} sec{sup -1} and mean path before annihilation from 50 to 300 Angstrom are measured. From 100 to 500 K the temperature influence upon diffusion process is effective only in SiO{sub 2} where activation energy is found about 10{sup -2} eV. The p-Ps zero point energy evaluated by angular correlation gives the order of magnitude for defects dimensions and diffusion mean-time. Finally, o-Ps behaviour in space between grains, where its interaction with atmospheric gases can be only detected, is analysed. (author) [French] Nous mettons en evidence l'existence de deux composantes lentes dans le spectre de temps de vie du positon avant annihilation dans des poudres d'oxydes alcalinoterreux d'alumine et de silice. Ces deux longues vies moyennes {approx_equal} 10{sup -9} s et {approx_equal} 10{sup -7} s resultent respectivement de l'annihilation a l'interieur et a l'exterieur des grains de l'ortho-positonium forme dans certains defauts presents dans les cristaux ioniques etudies. L'analyse des proprietes dynamiques du Ps ainsi revelees, est effectuee en termes de diffusion en excellent accord avec l'experience. Des constantes de diffusion de l'ordre de 10{sup -4} cm{sup 2} sec{sup -1} et des parcours moyens avant annihilation variant de 50 a 300 Angstrom sont ainsi mesures. Entre 100 et 500 K l'influence de la temperature sur le processus de diffusion n'est sensible que dans SiO{sub 2} ou l'energie d'activation est trouvee

  12. Determination and applications of enhancement factors for positron and ortho-positronium annihilations

    International Nuclear Information System (INIS)

    Mitroy, J.

    2005-01-01

    Electron-positron annihilation rates calculated directly from the electron and positron densities are known to underestimate the true annihilation rate. A correction factor, known as the enhancement factor, allows for the local increase of the electron density around the positron caused by the attractive electron-positron interaction. Enhancement factors are given for positrons annihilating with the 1s electron in H, He + , He, Li 2+ , and Li + . The enhancement factor for a free positron annihilating with He + and He is found to be close to that of ortho-positronium (i.e., Ps in its triplet state) annihilating with these atoms. The enhancement factor for Ps-He scattering is used in conjunction with the known annihilation rate for pickoff annihilation to derive a scattering length of 1.47a 0 for Ps-He scattering. Further, enhancement factors for e + -Ne and e + -Ar annihilation are used in conjunction with the pickoff annihilation rate to estimate scattering lengths of 1.46a 0 for Ps-Ne scattering and 1.75a 0 for Ps-Ar scattering

  13. New particles produced in electron--positron annihilation

    International Nuclear Information System (INIS)

    Perl, M.L.

    1975-01-01

    The main properties of the new particles produced in e + e - annihilation are reviewed. Included are properties of the continuum region, the 4.1-GeV enhancement, the psi and psi', radiative decays of the psi and psi', singly charmed particle searches in e + - e - annihilation, and the e/sub μ/ events

  14. 2015 OLC Lidar DEM: Wasco, WA

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — WSI collected Light Detection and Ranging (LiDAR) data for the Oregon LiDAR Consortium (OLC) Wasco County, WA, study area. The Oregon LiDAR Consortium's Wasco County...

  15. Ki wa ja loodus / Martin Rünkla

    Index Scriptorium Estoniae

    Rünk, Martin

    2010-01-01

    Ki wa näitus "Wildlife documentaries" ("Looduse valetõlked") Tallinnas Draakoni galeriis 23. jaanuarini 2010. Eksponeeritud mustvalged tekstimaalid. Kunstnik tõlgendab looduspilte ja helisid tekstina

  16. Surface investigations by means of positrons annihilation

    International Nuclear Information System (INIS)

    Dryzek, J.; Stegemann, T.; Cleff, B.

    1996-01-01

    The aim of the report is a presentation of the positron annihilation studies performed on the Cu samples that surface was exposed to the friction and wear processes. Using the measurement of Doppler broadening of annihilation line, we were able to detect the profile of vacancies in the top layers of the defected metals. It was established that one could describe the profile by a simple exponential function of the depth in all cases. The range of vacancies concentration depth depends on the load, time and the speed of the defects creation processes on the surface of a sample. The outline of the positron annihilation method is also given. (author). 10 refs, 16 figs, 5 tabs

  17. Reptiles and Amphibians of Fairchild Air Force Base, WA

    Science.gov (United States)

    2013-05-10

    Reptiles and Amphibians of Fairchild Air Force Base, WA C on st ru ct io n E n gi n ee ri n g R es ea rc...online library at http://acwc.sdp.sirsi.net/client/default. ERDC/CERL TR-13-5 May 2013 Reptiles and Amphibians of Fairchild Air Force Base, WA...Washington, DC 20314-1000 ERDC/CERL TR-13-5 ii Abstract Many reptile and amphibian (collectively termed “herpetofauna”) populations are declining at

  18. Comparison between photon annihilation-then-creation and photon creation-then-annihilation thermal states: Non-classical and non-Gaussian properties

    Science.gov (United States)

    Xu, Xue-Xiang; Yuan, Hong-Chun; Wang, Yan

    2014-07-01

    We investigate the nonclassical properties of arbitrary number photon annihilation-then-creation operation (AC) and creation-then-annihilation operation (CA) to the thermal state (TS), whose normalization factors are related to the polylogarithm function. Then we compare their quantum characters, such as photon number distribution, average photon number, Mandel Q-parameter, purity and the Wigner function. Because of the noncommutativity between the annihilation operator and the creation operator, the ACTS and the CATS have different nonclassical properties. It is found that nonclassical properties are exhibited more strongly after AC than after CA. In addition we also examine their non-Gaussianity. The result shows that the ACTS can present a slightly bigger non-Gaussianity than the CATS.

  19. Comparison between photon annihilation-then-creation and photon creation-then-annihilation thermal states: Non-classical and non-Gaussian properties

    International Nuclear Information System (INIS)

    Xu Xue-Xiang; Wang Yan; Yuan Hong-Chun

    2014-01-01

    We investigate the nonclassical properties of arbitrary number photon annihilation-then-creation operation (AC) and creation-then-annihilation operation (CA) to the thermal state (TS), whose normalization factors are related to the polylogarithm function. Then we compare their quantum characters, such as photon number distribution, average photon number, Mandel Q-parameter, purity and the Wigner function. Because of the noncommutativity between the annihilation operator and the creation operator, the ACTS and the CATS have different nonclassical properties. It is found that nonclassical properties are exhibited more strongly after AC than after CA. In addition we also examine their non-Gaussianity. The result shows that the ACTS can present a slightly bigger non-Gaussianity than the CATS. (general)

  20. Biological effectiveness of antiproton annihilation

    DEFF Research Database (Denmark)

    Holzscheiter, M.H.; Agazaryan, N.; Bassler, Niels

    2004-01-01

    We describe an experiment designed to determine whether or not the densely ionizing particles emanating from the annihilation of antiprotons produce an increase in ‘‘biological dose’’ in the vicinity of the narrow Bragg peak for antiprotons compared to protons. This experiment is the first direct...... measurement of the biological effects of antiproton annihilation. The experiment has been approved by the CERN Research Board for running at the CERN Antiproton Decelerator (AD) as AD-4/ACE (Antiproton Cell Experiment) and has begun data taking in June of 2003. The background, description and the current...

  1. Biological effectiveness of antiproton annihilation

    CERN Document Server

    Holzscheiter, Michael H.; Bassler, Niels; Beyer, Gerd; De Marco, John J.; Doser, Michael; Ichioka, Toshiyasu; Iwamoto, Keisuke S.; Knudsen, Helge V.; Landua, Rolf; Maggiore, Carl; McBride, William H.; Møller, Søren Pape; Petersen, Jorgen; Smathers, James B.; Skarsgard, Lloyd D.; Solberg, Timothy D.; Uggerhøj, Ulrik I.; Withers, H.Rodney; Vranjes, Sanja; Wong, Michelle; Wouters, Bradly G.

    2004-01-01

    We describe an experiment designed to determine whether or not the densely ionizing particles emanating from the annihilation of antiprotons produce an increase in “biological dose” in the vicinity of the narrow Bragg peak for antiprotons compared to protons. This experiment is the first direct measurement of the biological effects of antiproton annihilation. The experiment has been approved by the CERN Research Board for running at the CERN Antiproton Decelerator (AD) as AD-4/ACE (Antiproton Cell Experiment) and has begun data taking in June of 2003. The background, description and the current status of the experiment are given.

  2. 2012 USGS Lidar: Elwha River (WA)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — TASK NAME: Elwha River, WA LiDAR LiDAR Data Acquisition and Processing Production Task USGS Contract No. G10PC00057 Task Order No. G11PD01088 Woolpert Order No....

  3. Muziki wa Hip Hop na Haki Za Kijamii: Dhima, Changamoto na ...

    African Journals Online (AJOL)

    Ni dhahiri kuwa haki za kijamii zinaweza kuwasilishwa kwa jamii pana kupitia sanaa ya hip hop. Makala haya basi, yanabainisha dhima na mchango wa muziki wa hip hop katika masuala ya haki za kijamii, yanafafanua changamoto za muziki huu katika kuwasilisha haki za kijamii na kutoa mapendekezo kwa makundi ...

  4. The p-antip annihilation in the quark model

    International Nuclear Information System (INIS)

    Niskanen, J.A.

    1988-05-01

    After a concise review of the N-antiN annihilation in the quark rearrangement and 3 P 0 annihilation models, preliminary results are given for the case with an additional term where a q-antiq pair with the gluon quantum number 3 S 1

  5. Soliton annihilation in the perturbed sine-Gordon system

    DEFF Research Database (Denmark)

    Pedersen, Niels Falsig; Samuelsen, Mogens Rugholm; Welner, D.

    1984-01-01

    Fluxon-antifluxon annihilation in the perturbed sine-Gordon equation with loss and driving terms is investigated. For the infinite line we find a simple analytic expression for the threshold driving term corresponding to annihilation. With the application of the results to a Josephson junction...

  6. Production bias and cluster annihilation: Why necessary?

    DEFF Research Database (Denmark)

    Singh, B.N.; Trinkaus, H.; Woo, C.H.

    1994-01-01

    the primary cluster density is high. Therefore, a sustained high swelling rate driven by production bias must involve the annihilation of primary clusters at sinks. A number of experimental observations which are unexplainable in terms of the conventional dislocation bias for monointerstitials is considered......-field approach. The production bias approach, on the other hand, is based on the physical features of the cascade damage and is therefore considered to be more appropriate for describing the damage accumulation under cascade damage conditions. However, production bias can not produce high a swelling rate when....... It is found that the production bias and cluster annihilation are necessary to explain these observations, with, in many cases, the explicit consideration of the annihilation of the primary interstitial clusters....

  7. Peculiarities of annihilation of polarized positronium in polarized media

    International Nuclear Information System (INIS)

    Silenko, A.Ya.

    2005-01-01

    Features of positronium annihilation (PA) in polarized media are investigated. Strong exchange interaction with nonpaired electrons of paramagnetic atoms essentially accelerates the PA in comparison with annihilation of free positrons. The value of the spin projection on the direction of polarized nonpaired electrons has essential effect on the orthopositronium lifetime and on the width of the gamma spectrum annihilation line. It is shown that these features of PA permit to use it for studying the paramagnetic polarization [ru

  8. Positron annihilation in solids: positronium diffusion; Annihilation du positon dans les solides diffusion du positonium

    Energy Technology Data Exchange (ETDEWEB)

    Paulin, R. [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

    1969-04-01

    The existence of two slow components in life-time spectrum of positron annihilation in silicium, aluminium and alkaline-earth oxides powders is established. These two long mean-lives {approx_equal} 10{sup -9} s and {approx_equal} 10{sup -7} s result from annihilation, inside and outside the grains respectively, of ortho-positronium formed in defects present in ionic crystals investigated. Dynamic behaviour of Ps, so revealed, is analyzed in terms of diffusion in excellent agreement with experiment. Diffusion constants of the order of 10{sup -4} cm{sup 2} sec{sup -1} and mean path before annihilation from 50 to 300 Angstrom are measured. From 100 to 500 K the temperature influence upon diffusion process is effective only in SiO{sub 2} where activation energy is found about 10{sup -2} eV. The p-Ps zero point energy evaluated by angular correlation gives the order of magnitude for defects dimensions and diffusion mean-time. Finally, o-Ps behaviour in space between grains, where its interaction with atmospheric gases can be only detected, is analysed. (author) [French] Nous mettons en evidence l'existence de deux composantes lentes dans le spectre de temps de vie du positon avant annihilation dans des poudres d'oxydes alcalinoterreux d'alumine et de silice. Ces deux longues vies moyennes {approx_equal} 10{sup -9} s et {approx_equal} 10{sup -7} s resultent respectivement de l'annihilation a l'interieur et a l'exterieur des grains de l'ortho-positonium forme dans certains defauts presents dans les cristaux ioniques etudies. L'analyse des proprietes dynamiques du Ps ainsi revelees, est effectuee en termes de diffusion en excellent accord avec l'experience. Des constantes de diffusion de l'ordre de 10{sup -4} cm{sup 2} sec{sup -1} et des parcours moyens avant annihilation variant de 50 a 300 Angstrom sont ainsi mesures. Entre 100 et 500 K l'influence de la temperature sur le processus de diffusion n'est sensible

  9. The influence of antioxidant on positron annihilation in polypropylene

    International Nuclear Information System (INIS)

    Djourelov, N.; He, C.; Suzuki, T.; Ito, Y; Kondo, K.; Ito, Y.; Shantarovich, V.P.

    2003-01-01

    The purpose of this report is to check the influence of the carbonyl groups (CG), created by oxygen naturally dissolved in a polymer matrix and by the source irradiation, on annihilation characteristics of free positrons using the positron annihilation lifetime spectroscopy (PALS) and coincidence Doppler-broadening spectroscopy (CDBS). Positron annihilation in a pure polypropylene (PP) and in an antioxidant-containing polypropylene (PPA) sample at room and low temperatures has been studied by CDBS. PALS has been used as an o-Ps (orth-positronium) formation monitor. The momentum density distributions of electrons obtained by CDBS at the beginning of measurements have been compared to that at the o-Ps intensity saturation level. It has been shown that the initial concentration of carbonyl groups in a PP sample is high, while for an antioxidant-containing sample, PPA, carbonyl groups are not detected by CDBS. CDBS spectra for a PP can be explained by annihilation of free positrons with the oxygen contained in the carbonyl groups. For a PPA sample, no significant contribution of annihilation with oxygen core electrons can be concluded. (Y. Kazumata)

  10. Studies of glasses by positron annihilation

    International Nuclear Information System (INIS)

    Brauer, G.; Boden, G.

    1981-04-01

    Investigations of silica glasses, pyrocerams and metallic glasses by positron annihilation (lifetime, Doppler broadening) are presented. The measurements on silica glasses showed, that silica glass fused from naturally occuring quartz exhibits a higher order than that one produced from SiCl 4 . Furthermore it was found that the order of silica glasses increases after heat treatment above 900 0 C. Thus the X-amorphous state of silica glasses could be characterized by positron annihilation what is impossible at present by diffraction methods. (author)

  11. Higher-order nonclassical effects generated by multiple-photon annihilation-then-creation and creation-then-annihilation coherent states

    International Nuclear Information System (INIS)

    Yuan Hong-Chun; Xiao Jin; Xiong Chao; Zhu Xi-Fang; Xu Xue-Xiang

    2016-01-01

    We explore two observable nonclassical properties of quantum states generated by repeatedly operating annihilation-then-creation (AC) and creation-then-annihilation (CA) on the coherent state, respectively, such as higher-order sub-Poissonian statistics and higher-order squeezing-enhanced effect. The corresponding analytical expressions are derived in detail depending on m . By numerically comparing those quantum properties, it is found that these states above have very different nonclassical properties and nonclassicality is exhibited more strongly after AC operation than after CA operation. (paper)

  12. Experimentation at LEP: weak-electromagnetic interference, QED and two-photon physics

    International Nuclear Information System (INIS)

    Davier, M.

    1979-01-01

    The energy range opened by LEP will permit a clean and direct study of the weak interaction. Of particular importance are those effects resulting from the interference between the weak and the electromagnetic (EM) currents: it is shown that they give access to the basic couplings which can be measured unambiguously. The paper is in three parts. The first and major section deals with the weak interaction experiments. Most of the calculations and estimates rely on the Weinberg-Salam model as a realistic guide of what might happen. The second section is devoted to 2γ processes. On one hand they constitute an interesting physics study which has been assessed both from theory and experiment and appears promising. On the other hand, they can generate background to many annihilation channels and this aspect has been studied in detail. The last section presents a brief look at short distance tests of Quantum Electrodynamics (QED) - a restricted, but important area of research at LEP. (Auth.)

  13. Dark matter annihilation with s-channel internal Higgsstrahlung

    Energy Technology Data Exchange (ETDEWEB)

    Kumar, Jason; Liao, Jiajun, E-mail: liaoj@hawaii.edu; Marfatia, Danny

    2016-08-10

    We study the scenario of fermionic dark matter that annihilates to standard model fermions through an s-channel axial vector mediator. We point out that the well-known chirality suppression of the annihilation cross section can be alleviated by s-channel internal Higgsstrahlung. The shapes of the cosmic ray spectra are identical to that of t-channel internal Higgsstrahlung in the limit of a heavy mediating particle. Unlike the general case of t-channel bremsstrahlung, s-channel Higgsstrahlung can be the dominant annihilation process even for Dirac dark matter. Since the s-channel mediator can be a standard model singlet, collider searches for the mediator are easily circumvented.

  14. Dark matter annihilation with s-channel internal Higgsstrahlung

    International Nuclear Information System (INIS)

    Kumar, Jason; Liao, Jiajun; Marfatia, Danny

    2016-01-01

    We study the scenario of fermionic dark matter that annihilates to standard model fermions through an s-channel axial vector mediator. We point out that the well-known chirality suppression of the annihilation cross section can be alleviated by s-channel internal Higgsstrahlung. The shapes of the cosmic ray spectra are identical to that of t-channel internal Higgsstrahlung in the limit of a heavy mediating particle. Unlike the general case of t-channel bremsstrahlung, s-channel Higgsstrahlung can be the dominant annihilation process even for Dirac dark matter. Since the s-channel mediator can be a standard model singlet, collider searches for the mediator are easily circumvented.

  15. Quest Trial Q348: Evaluation of WaMoS II Data

    Science.gov (United States)

    2013-04-01

    and slam warning.” Quest Sea Trial Q348 page 7 “In July of 2011, as part of the 11gi project, DRDC acquired and installed a new WaMoS...Fourier series expansion was originally implemented to compare WaMoS II data to reference data of an airborne LIDAR scanner, which yielded very good

  16. Positron Annihilation Ratio Spectroscopy (PsARS) Applied to Positronium Formation Studies

    Science.gov (United States)

    2010-03-01

    Positron Annihilation Ratio Spectroscopy (PsARS). These experimental techniques have been used for a variety of military and civilian applications ... POSITRON ANNIHILATION RATIO SPECTROSCOPY (PsARS) APPLIED TO POSITRONIUM FORMATION STUDIES THESIS...of Defense, or the United States Government. AFIT/GNE/ENP/10-M07 POSITRON ANNIHILATION RATIO SPECTROSCOPY

  17. The Isotropic Radio Background and Annihilating Dark Matter

    Energy Technology Data Exchange (ETDEWEB)

    Hooper, Dan [Fermi National Accelerator Laboratory (FNAL), Batavia, IL (United States); Belikov, Alexander V. [Institut d' Astrophysique (France); Jeltema, Tesla E. [Univ. of California, Santa Cruz, CA (United States); Linden, Tim [Univ. of California, Santa Cruz, CA (United States); Profumo, Stefano [Univ. of California, Santa Cruz, CA (United States); Slatyer, Tracy R. [Princeton Univ., Princeton, NJ (United States)

    2012-11-01

    Observations by ARCADE-2 and other telescopes sensitive to low frequency radiation have revealed the presence of an isotropic radio background with a hard spectral index. The intensity of this observed background is found to exceed the flux predicted from astrophysical sources by a factor of approximately 5-6. In this article, we consider the possibility that annihilating dark matter particles provide the primary contribution to the observed isotropic radio background through the emission of synchrotron radiation from electron and positron annihilation products. For reasonable estimates of the magnetic fields present in clusters and galaxies, we find that dark matter could potentially account for the observed radio excess, but only if it annihilates mostly to electrons and/or muons, and only if it possesses a mass in the range of approximately 5-50 GeV. For such models, the annihilation cross section required to normalize the synchrotron signal to the observed excess is sigma v ~ (0.4-30) x 10^-26 cm^3/s, similar to the value predicted for a simple thermal relic (sigma v ~ 3 x 10^-26 cm^3/s). We find that in any scenario in which dark matter annihilations are responsible for the observed excess radio emission, a significant fraction of the isotropic gamma ray background observed by Fermi must result from dark matter as well.

  18. Positron annihilation microprobe

    Energy Technology Data Exchange (ETDEWEB)

    Canter, K F [Brandeis Univ., Waltham, MA (United States)

    1997-03-01

    Advances in positron annihilation microprobe development are reviewed. The present resolution achievable is 3 {mu}m. The ultimate resolution is expected to be 0.1 {mu}m which will enable the positron microprobe to be a valuable tool in the development of 0.1 {mu}m scale electronic devices in the future. (author)

  19. Origin and annihilation physics of positrons in the Galaxy

    International Nuclear Information System (INIS)

    Alexis, Anthony

    2014-01-01

    A gamma radiation at 511 keV is observed since the early 1970's toward the Galactic bulge region. This emission is the signature of a large number of electron-positron annihilations, the positron being the electron's antiparticle. Unfortunately, the origin of the positrons responsible for this emission is still a mystery. Many positron-source candidates have been suggested but none of them can account for the galactic annihilation emission. The spatial distribution of this emission is indeed very atypical. Since 2002, the SPI spectrometer onboard the INTEGRAL space laboratory revealed an emission strongly concentrated toward the galactic bulge and a weaker emission from the galactic disk. This morphology is unusual because it does not correspond to any of the known galactic astrophysical-object or interstellar-matter distributions. The assumption that positrons annihilate close to their sources (i.e. the spatial distribution of the annihilation emission reflects the spatial distribution of the sources) has consequently been called into question. Recent studies suggest that positrons could propagate far away from their sources before annihilating. This physical aspect could be the key point to solve the riddle of the galactic positron origin. This thesis is devoted to the modelling of the propagation and annihilation of positrons in the Galaxy, in order to compare simulated spatial models of the annihilation emission with recent measurements provided by SPI/INTEGRAL. This method allows to put constraints on the origin of galactic positrons. We therefore developed a propagation Monte-Carlo code of positrons within the Galaxy in which we implemented all the theoretical and observational knowledge about positron physics (sources, transport modes, energy losses, annihilation modes) and the interstellar medium of our Galaxy (interstellar gas distributions, galactic magnetic fields, structures of the gaseous phases). Due to uncertainties in several physical parameters

  20. Propagation and attenuation of sound waves as well as spectrally resolved Rayleigh scattering in weakly ionized plasmas

    International Nuclear Information System (INIS)

    Kopainsky, J.

    1975-01-01

    In weakly ionized plasmas the scattering of electromagnetic waves on free electrons (Thompson scattering) can be neglected as compared with the scattering on bound electrons (Rayleigh scattering). If the scattering process can be described by a fluid dynamical model it is caused by sound waves which are generated or annihilated by the incident electromagnetic wave. The propagation of sound waves results in a shift of the scattered line whereas their absorption within the plasma produces the broadening of the scattered line. The theory of propagation of sound in weakly ionized plasmas is developed and extended to Rayleigh scattering. The results are applied to laser scattering in a weakly ionized hydrogen plasma. (Auth.)

  1. Radiation damage analysis by positron annihilation spectroscopy

    International Nuclear Information System (INIS)

    Siegel, R.W.

    1979-01-01

    The application of positron annihilation spectroscopy (PAS) to the characterization and study of defects in metals produced by radiation damage is discussed. The physical basis for the positron annihilation techniques (lifetime, Doppler broadening, angular correlation) is introduced and the techniques briefly described. Some examples of the application of PAS to radiation damage analysis are presented with a view toward elucidating the particular advantages of PAS over more traditional defect characterization techniques

  2. Substructure boosts to dark matter annihilation from Sommerfeld enhancement

    International Nuclear Information System (INIS)

    Bovy, Jo

    2009-01-01

    The recently introduced Sommerfeld enhancement of the dark matter annihilation cross section has important implications for the detection of dark matter annihilation in subhalos in the Galactic halo. In addition to the boost to the dark matter annihilation cross section from the high densities of these subhalos with respect to the main halo, an additional boost caused by the Sommerfeld enhancement results from the fact that they are kinematically colder than the Galactic halo. If we further believe the generic prediction of the cold dark matter paradigm that in each subhalo there is an abundance of substructure which is approximately self-similar to that of the Galactic halo, then I show that additional boosts coming from the density enhancements of these small substructures and their small velocity dispersions enhance the dark matter annihilation cross section even further. I find that very large boost factors (10 5 to 10 9 ) are obtained in a large class of models. The implications of these boost factors for the detection of dark matter annihilation from dwarf spheroidal galaxies in the Galactic halo are such that, generically, they outshine the background gamma-ray flux and are detectable by the Fermi Gamma-ray Space Telescope.

  3. Porous silicon investigated by positron annihilation

    International Nuclear Information System (INIS)

    Cruz, R.M. de la; Pareja, R.

    1989-01-01

    The effect of the anodic conversion in silicon single crystals is investigated by positron lifetime measurements. Anodization at constant current induces changes in the positron lifetime spectrum of monocrystalline silicon samples. It is found that theses changes are primarily dependent on the silicon resistivity. The annihilation parameter behaviour of anodized samples, treated at high temperature under reducing conditions, is also investigated. The results reveal that positron annihilation can be a useful technique to characterize porous silicon formed by anodizing as well as to investigate its thermal behaviour. (author)

  4. To the measurement of 3γ/2γ ratio for positron annihilation in matter using annihilation energy spectrum

    International Nuclear Information System (INIS)

    Andrukhovich, S.K.; Berestov, A.V.; Antovich, N.M.; Metelitsa, O.N.

    2001-01-01

    Processes of the summation of cascade γ-quanta usually neglected, when registering the annihilation energy spectrum for the determination of the three-photon annihilation probability P 3γ of positronium in samples, are studied. The deviations of the actual P 3γ value from that determined without allowance made for the summation processes are 56% and 25% for Na(Tl) and Ge detectors placed at the distance of 3 cm from a positron source respectively. (author)

  5. Positron two-photon annihilation coincidence technique: difference mode

    Energy Technology Data Exchange (ETDEWEB)

    Karol, P J; Klobuchar, R L [Carnegie-Mellon Univ., Pittsburgh, Pa. (USA). Dept. of Chemistry

    1978-05-01

    A difference (or comparative) mode in the measurement of two-photon coincidences from positron or positronium annihilation has been developed. The method can be used to advantage, particularly in gases, in determining annihilation parameters such as quenching cross sections for low concentration strongly quenching chemical species in a reference medium which is relatively non-quenching.

  6. Positron annihilation studies on high temperature superconductors

    International Nuclear Information System (INIS)

    Sundar, C.S.; Bharathi, A.

    1991-01-01

    The results of positron annihilation measurements as a function of temperature, across Tc, in a variety of high temperature superconductors such as Y-Ba-Cu-O (Y1237), Y-Ba-Cu-O (Y1248), Bi-Sr-Ca-Cu-O, Tl-Ba-Ca-Cu-O, Ba-K-Bi-O and Nd-Ce-Cu-O are presented. It is shown that the variation of annihilation parameters in the superconducting state is correlated with the diposition of the positron density distribution with respect to the superconducting CuO planes. An increase in positron lifetime is observed below Tc when the positrons probe the CuO planes whereas a decrease in lifetime is observed when the positron density overlaps predominantly with the apical oxygen atom. With this correlation, the different temperature variation of annihilation parameters, seen in the various high temperature superconductors, is understood in terms of a local charge transfer from the planar oxygen atom to the apical oxygen atom. The significance of these results in the context of various theoretical models of high temperature superconductivity is discussed. In addition, the application of positron annihilation spectroscopy to the study of oxygen defects in the Y-Ba-Cu-O, Bi-Sr-Ca-Cu-O and Nd-Ce-Cu-O is presented. (author). 53 refs., 17 figs., 2 tabs

  7. Radiation damage analysis by positron annihilation spectroscopy

    International Nuclear Information System (INIS)

    Siegel, R.W.

    1982-01-01

    Positron annihilation spectroscopy (PAS) has in recent years become a valuable new tool for investigating defects in metals. The ability of the positron to localize in a trapped state at various defect sites, in which the positron annihilates with unique characteristics, has enabled the positron to be used as a localized probe of these defect sites. Several reviews of the application of PAS to the study of defects in metals have been published, as have more general treatises on the applications of positron annihilation to the study of solids. PAS has made, and has considerably greater potential for, a significant contribution to radiation damage analysis in two areas of importance: (1) the determination of atomic-defect properties, a knowledge of which is necessary for the modeling required to couple the results of model experiments using electron and ion irradiation with the expected irradiation conditions of reactor systems, and (2) the monitoring and characterization of irradiation-induced microstructure development. A unique aspect of PAS for radiation damage analysis is the defect specificity of the annihilation characteristics of a trapped positron. In addition to its value as an independent analytical tool, PAS can be a useful complement to more traditional techniques for defect studies

  8. Results from CERN experiment WA80

    International Nuclear Information System (INIS)

    Gutbrod, H.H.; Plasil, F.; Albrecht, R.

    1988-01-01

    As in the case of most of the experiments discussed at this conference, the primary goal of WA80 is a search for evidence that a quark-gluon plasma (QGP) has been formed, or that some similar phase transition has taken place. A number of signatures for QGP formation have been suggested, and most experiments have been designed so as to obtain data that pertain to one or more of these signatures. In the case of WA80, the primary probe for the investigation of the QGP is the measurement of photons that may be emitted from the plasma phase. An understanding of the various QGP signatures, however, requires an understanding of the background created by reaction products that do not relate directly to QGP production and thus requires a thorough understanding of the reaction mechanism governing nucleus-nucleus collisions at these extreme energies. Consequently, another important goal of WA80 is to survey nucleus-nucleus collisions at 60 and 200 GeV/nucleon and to compare the results to those obtained from proton-nucleus interactions. We have pursued this second goal by measuring forward and transverse energies, by studying the multiplicities of produced charged particles over a large range of pseudorapidity, by investigating transverse momentum spectra of neutral products, and by examining target fragmentation products. In this paper we review all of our results obtained with 60- and 200-GeV/nucleon /sup 16/O projectiles, with the exception of charged-particle multiplicity data, which are discussed in a separate presentation at this conference. We also present the first preliminary calorimeter results from /sup 32/S bombardments at 6.4 TeV. 22 refs., 13 figs., 2 tabs

  9. Uses and Gratifications Theory dalam Media Sosial WA (WhatsApp)

    OpenAIRE

    Suparmo, Ludwiq

    2017-01-01

    It has been known for decades that the conventional mass communications have been eroded and transformed due to the information technology into advanced means of communication. One of these has become viral as the social media through WA (whatsApp) application, which surely has brought a phenomenal effect on the uses and gratifications theory that was more applied on mass communications. The research based on a qualitative methodology exploring to several WA Groups has revealed the rank of us...

  10. Effect of Voids on Angular Correlation of Positron Annihilation Photons in Molybdenum

    DEFF Research Database (Denmark)

    Mogensen, O. E.; Petersen, K.; Cotterill, R. M. J.

    1972-01-01

    POSITRON annihilation investigations of defects in crystals have shown that for sufficiently high defect concentrations (typically above about 10−6) all positrons become trapped in the defects before annihilation, thus changing the characteristics of the annihilation process. For example, trappin...

  11. Positron annihilation and pressure-induced electronic s-d transition

    International Nuclear Information System (INIS)

    McMahan, A.K.; Skriver, H.L.

    1985-06-01

    The polycrystalline, partial annihilation rates for positrons in compressed cesium have been calculated using the linear muffin-tin orbitals method. These results suggest that the pressure-induced electronic s-d transition in Cs should be directly observable by momentum sensitive positron annihilation experiments

  12. Positron annihilation in solids: positronium diffusion

    International Nuclear Information System (INIS)

    Paulin, R.

    1969-04-01

    The existence of two slow components in life-time spectrum of positron annihilation in silicium, aluminium and alkaline-earth oxides powders is established. These two long mean-lives ≅ 10 -9 s and ≅ 10 -7 s result from annihilation, inside and outside the grains respectively, of ortho-positronium formed in defects present in ionic crystals investigated. Dynamic behaviour of Ps, so revealed, is analyzed in terms of diffusion in excellent agreement with experiment. Diffusion constants of the order of 10 -4 cm 2 sec -1 and mean path before annihilation from 50 to 300 Angstrom are measured. From 100 to 500 K the temperature influence upon diffusion process is effective only in SiO 2 where activation energy is found about 10 -2 eV. The p-Ps zero point energy evaluated by angular correlation gives the order of magnitude for defects dimensions and diffusion mean-time. Finally, o-Ps behaviour in space between grains, where its interaction with atmospheric gases can be only detected, is analysed. (author) [fr

  13. High statistics study of $\\bar{p}p$ annihilation physics at the EHS

    CERN Multimedia

    2002-01-01

    We propose to perform an experiment to study antiproton-proton annihilations at 50 GeV/c, using the EHS facility.\\\\ \\\\ We will study in detail annihilation processes in terms of the underlying quark structure, and to compare our results with the predictions of the three principal models: quark fusion, fragmentation and recombination.\\\\ \\\\ These models achieved satisfactory results for pion and non-strange resonance production but failed for strange particle production. In fact a study of the production of strange particles could lead to valuable dues in understanding the annihilation mechanisms. A possible explanation of their production is that fast gluons materialize as strange quark pairs in the annihilation process. \\\\ \\\\ We expect to obtain 35 K, well identified, annihilation events.

  14. Revisiting big-bang nucleosynthesis constraints on dark-matter annihilation

    Energy Technology Data Exchange (ETDEWEB)

    Kawasaki, Masahiro [Institute for Cosmic Ray Research, The University of Tokyo, Kashiwa 277-8582 (Japan); Kavli IPMU (WPI), UTIAS, The University of Tokyo, Kashiwa 277-8583 (Japan); Kohri, Kazunori [Theory Center, IPNS, KEK, Tsukuba 305-0801 (Japan); Sokendai, Tsukuba 305-0801 (Japan); Moroi, Takeo [Kavli IPMU (WPI), UTIAS, The University of Tokyo, Kashiwa 277-8583 (Japan); Department of Physics, University of Tokyo, Tokyo 113-0033 (Japan); Takaesu, Yoshitaro, E-mail: takaesu@hep-th.phys.s.u-tokyo.ac.jp [Department of Physics, University of Tokyo, Tokyo 113-0033 (Japan)

    2015-12-17

    We study the effects of dark-matter annihilation during the epoch of big-bang nucleosynthesis on the primordial abundances of light elements. We improve the calculation of the light-element abundances by taking into account the effects of anti-nucleons emitted by the annihilation of dark matter and the interconversion reactions of neutron and proton at inelastic scatterings of energetic nucleons. Comparing the theoretical prediction of the primordial light-element abundances with the latest observational constraints, we derive upper bounds on the dark-matter pair-annihilation cross section. Implication to some of particle-physics models are also discussed.

  15. Revisiting big-bang nucleosynthesis constraints on dark-matter annihilation

    Directory of Open Access Journals (Sweden)

    Masahiro Kawasaki

    2015-12-01

    Full Text Available We study the effects of dark-matter annihilation during the epoch of big-bang nucleosynthesis on the primordial abundances of light elements. We improve the calculation of the light-element abundances by taking into account the effects of anti-nucleons emitted by the annihilation of dark matter and the interconversion reactions of neutron and proton at inelastic scatterings of energetic nucleons. Comparing the theoretical prediction of the primordial light-element abundances with the latest observational constraints, we derive upper bounds on the dark-matter pair-annihilation cross section. Implication to some of particle-physics models are also discussed.

  16. Positron annihilation in superconductive metals

    Energy Technology Data Exchange (ETDEWEB)

    Dekhtjar, I.J.

    1969-03-10

    A correlation is shown between the parameters of superconductive metals and those of positron annihilation. Particular attention is paid to the density states obtained from the electron specific heat.

  17. On the Role of the Annihilation Channel in Front Form Positronium

    OpenAIRE

    Trittmann, Uwe

    1997-01-01

    The annihilation channel is implemented into the front form calculations of the positronium spectrum presented in a previous publication. The effective Hamiltonian is calculated analytically. Its eigensolutions are obtained numerically. A complete separation of the dynamical and instantaneous part of the annihilation interaction is observed. We find the remarkable effect that the annihilation channel stabilizes the cutoff behavior of the spectrum.

  18. Search for new physics in energetic single photon production in $e^+ e^-$ annihilation at the Z resonance

    CERN Document Server

    Acciarri, M; Aguilar-Benítez, M; Ahlen, S P; Alcaraz, J; Alemanni, G; Allaby, James V; Aloisio, A; Alverson, G; Alviggi, M G; Ambrosi, G; Anderhub, H; Andreev, V P; Angelescu, T; Anselmo, F; Arefev, A; Azemoon, T; Aziz, T; Bagnaia, P; Baksay, L; Banerjee, S; Banerjee, Sw; Banicz, K; Barczyk, A; Barillère, R; Barone, L; Bartalini, P; Baschirotto, A; Basile, M; Battiston, R; Bay, A; Becattini, F; Becker, U; Behner, F; Berdugo, J; Berges, P; Bertucci, B; Betev, B L; Bhattacharya, S; Biasini, M; Biland, A; Bilei, G M; Blaising, J J; Blyth, S C; Bobbink, Gerjan J; Böck, R K; Böhm, A; Boldizsar, L; Borgia, B; Bourilkov, D; Bourquin, Maurice; Boutigny, D; Braccini, S; Branson, J G; Brigljevic, V; Brock, I C; Buffini, A; Buijs, A; Burger, J D; Burger, W J; Busenitz, J K; Cai, X D; Campanelli, M; Capell, M; Cara Romeo, G; Carlino, G; Cartacci, A M; Casaus, J; Castellini, G; Cavallari, F; Cavallo, N; Cecchi, C; Cerrada-Canales, M; Cesaroni, F; Chamizo-Llatas, M; Chang, Y H; Chaturvedi, U K; Chekanov, S V; Chemarin, M; Chen, A; Chen, G; Chen, G M; Chen, H F; Chen, H S; Chen, M; Chiefari, G; Chien, C Y; Cifarelli, Luisa; Cindolo, F; Civinini, C; Clare, I; Clare, R; Cohn, H O; Coignet, G; Colijn, A P; Colino, N; Commichau, V; Costantini, S; Cotorobai, F; de la Cruz, B; Csilling, Akos; Dai, T S; D'Alessandro, R; De Asmundis, R; Degré, A; Deiters, K; Denes, P; De Notaristefani, F; DiBitonto, Daryl; Diemoz, M; Van Dierendonck, D N; Di Lodovico, F; Dionisi, C; Dittmar, Michael; Dominguez, A; Doria, A; Dova, M T; Drago, E; Duchesneau, D; Duinker, P; Durán, I; Dutta, S; Easo, S; Efremenko, Yu V; El-Mamouni, H; Engler, A; Eppling, F J; Erné, F C; Ernenwein, J P; Extermann, Pierre; Fabre, M; Faccini, R; Falciano, S; Favara, A; Fay, J; Fedin, O; Felcini, Marta; Fenyi, B; Ferguson, T; Ferroni, F; Fesefeldt, H S; Fiandrini, E; Field, J H; Filthaut, Frank; Fisher, P H; Fisk, I; Forconi, G; Fredj, L; Freudenreich, Klaus; Furetta, C; Galaktionov, Yu; Ganguli, S N; García-Abia, P; Gau, S S; Gentile, S; Gerald, J; Gheordanescu, N; Giagu, S; Goldfarb, S; Goldstein, J; Gong, Z F; Gougas, Andreas; Gratta, Giorgio; Grünewald, M W; Gupta, V K; Gurtu, A; Gutay, L J; Hartmann, B; Hasan, A; Hatzifotiadou, D; Hebbeker, T; Hervé, A; Van Hoek, W C; Hofer, H; Hong, S J; Hoorani, H; Hou, S R; Hu, G; Innocente, Vincenzo; Jenkes, K; Jin, B N; Jones, L W; de Jong, P; Josa-Mutuberria, I; Kasser, A; Khan, R A; Kamrad, D; Kamyshkov, Yu A; Kapustinsky, J S; Karyotakis, Yu; Kaur, M; Kienzle-Focacci, M N; Kim, D; Kim, D H; Kim, J K; Kim, S C; Kim, Y G; Kinnison, W W; Kirkby, A; Kirkby, D; Kirkby, Jasper; Kiss, D; Kittel, E W; Klimentov, A; König, A C; Kopp, A; Korolko, I; Koutsenko, V F; Krämer, R W; Krenz, W; Kunin, A; Ladrón de Guevara, P; Laktineh, I; Landi, G; Lapoint, C; Lassila-Perini, K M; Laurikainen, P; Lebeau, M; Lebedev, A; Lebrun, P; Lecomte, P; Lecoq, P; Le Coultre, P; Lee, H J; Leggett, C; Le Goff, J M; Leiste, R; Leonardi, E; Levchenko, P M; Li Chuan; Lin, C H; Lin, W T; Linde, Frank L; Lista, L; Liu, Z A; Lohmann, W; Longo, E; Lu, W; Lü, Y S; Lübelsmeyer, K; Luci, C; Luckey, D; Luminari, L; Lustermann, W; Ma Wen Gan; Maity, M; Majumder, G; Malgeri, L; Malinin, A; Maña, C; Mangeol, D J J; Mangla, S; Marchesini, P A; Marin, A; Martin, J P; Marzano, F; Massaro, G G G; McNally, D; Mele, S; Merola, L; Meschini, M; Metzger, W J; Von der Mey, M; Mi, Y; Mihul, A; Van Mil, A J W; Mirabelli, G; Mnich, J; Molnár, P; Monteleoni, B; Moore, R; Morganti, S; Moulik, T; Mount, R; Müller, S; Muheim, F; Muijs, A J M; Nahn, S; Napolitano, M; Nessi-Tedaldi, F; Newman, H; Niessen, T; Nippe, A; Nisati, A; Nowak, H; Oh, Yu D; Opitz, H; Organtini, G; Ostonen, R; Palomares, C; Pandoulas, D; Paoletti, S; Paolucci, P; Park, H K; Park, I H; Pascale, G; Passaleva, G; Patricelli, S; Paul, T; Pauluzzi, M; Paus, C; Pauss, Felicitas; Peach, D; Pei, Y J; Pensotti, S; Perret-Gallix, D; Petersen, B; Petrak, S; Pevsner, A; Piccolo, D; Pieri, M; Piroué, P A; Pistolesi, E; Plyaskin, V; Pohl, M; Pozhidaev, V; Postema, H; Produit, N; Prokofev, D; Prokofiev, D O; Rahal-Callot, G; Raja, N; Rancoita, P G; Rattaggi, M; Raven, G; Razis, P A; Read, K; Ren, D; Rescigno, M; Reucroft, S; Van Rhee, T; Riemann, S; Riles, K; Rind, O; Robohm, A; Rodin, J; Roe, B P; Romero, L; Rosier-Lees, S; Rosselet, P; Van Rossum, W; Roth, S; Rubio, Juan Antonio; Ruschmeier, D; Rykaczewski, H; Salicio, J; Sánchez, E; Sanders, M P; Sarakinos, M E; Sarkar, S; Sassowsky, M; Sauvage, G; Schäfer, C; Shchegelskii, V; Schmidt-Kärst, S; Schmitz, D; Schmitz, P; Schneegans, M; Scholz, N; Schopper, Herwig Franz; Schotanus, D J; Schwenke, J; Schwering, G; Sciacca, C; Sciarrino, D; Servoli, L; Shevchenko, S; Shivarov, N; Shoutko, V; Shukla, J; Shumilov, E; Shvorob, A V; Siedenburg, T; Son, D; Sopczak, André; Soulimov, V; Smith, B; Spillantini, P; Steuer, M; Stickland, D P; Stone, H; Stoyanov, B; Strässner, A; Strauch, K; Sudhakar, K; Sultanov, G G; Sun, L Z; Susinno, G F; Suter, H; Swain, J D; Tang, X W; Tauscher, Ludwig; Taylor, L; Ting, Samuel C C; Ting, S M; Tonutti, M; Tonwar, S C; Tóth, J; Tully, C; Tuchscherer, H; Tung, K L; Uchida, Y; Ulbricht, J; Uwer, U; Valente, E; Van de Walle, R T; Vesztergombi, G; Vetlitskii, I; Viertel, Gert M; Vivargent, M; Völkert, R; Vogel, H; Vogt, H; Vorobev, I; Vorobyov, A A; Vorvolakos, A; Wadhwa, M; Wallraff, W; Wang, J C; Wang, X L; Wang, Z M; Weber, A; Wittgenstein, F; Wu, S X; Wynhoff, S; Xu, J; Xu, Z Z; Yang, B Z; Yang, C G; Yao, X Y; Ye, J B; Yeh, S C; You, J M; Zalite, A; Zalite, Yu; Zemp, P; Zeng, Y; Zhang, Z; Zhang, Z P; Zhou, B; Zhou, Y; Zhu, G Y; Zhu, R Y; Zichichi, Antonino; Ziegler, F

    1997-01-01

    Using a sample of $\\mathrm{e^{+}e^{-}}$ annihilation events collected with the L3 detector at the Z resonance corresponding to an integrated luminosity of 137 pb$^{-1}$, we have searched for anomalous production of $\\gamma \\mathrm{X}$ final states where $\\mathrm{X}$ represents stable, weakly interacting particles and the photon energy is greater than 15 GeV. The sample of events found is consistent with Standard Model expectations. Upper limits are set on $\\Z \\gamma$ couplings, the $\\tau$ neutrino magnetic moment, and the branching ratio for $\\mathrm{Z} \\rightarrow \\gamma \\mathrm{X}$.

  19. Molecular model for annihilation rates in positron complexes

    Energy Technology Data Exchange (ETDEWEB)

    Assafrao, Denise [Laboratorio de Atomos e Moleculas Especiais, Departamento de Fisica, ICEx, Universidade Federal de Minas Gerais, P.O. Box 702, 30123-970 Belo Horizonte, MG (Brazil); Department of Applied Mathematics and Theoretical Physics, Queen' s University of Belfast, Belfast BT7 1NN, Northern Ireland (United Kingdom); Walters, H.R. James [Department of Applied Mathematics and Theoretical Physics, Queen' s University of Belfast, Belfast BT7 1NN, Northern Ireland (United Kingdom); Mohallem, Jose R. [Laboratorio de Atomos e Moleculas Especiais, Departamento de Fisica, ICEx, Universidade Federal de Minas Gerais, P.O. Box 702, 30123-970 Belo Horizonte, MG (Brazil); Department of Applied Mathematics and Theoretical Physics, Queen' s University of Belfast, Belfast BT7 1NN, Northern Ireland (United Kingdom)], E-mail: rachid@fisica.ufmg.br

    2008-02-15

    The molecular approach for positron interaction with atoms is developed further. Potential energy curves for positron motion are obtained. Two procedures accounting for the nonadiabatic effective positron mass are introduced for calculating annihilation rate constants. The first one takes the bound-state energy eigenvalue as an input parameter. The second is a self-contained and self-consistent procedure. The methods are tested with quite different states of the small complexes HPs, e{sup +}He (electronic triplet) and e{sup +}Be (electronic singlet and triplet). For states yielding the positronium cluster, the annihilation rates are quite stable, irrespective of the accuracy in binding energies. For the e{sup +}Be states, annihilation rates are larger and more consistent with qualitative predictions than previously reported ones.

  20. Molecular model for annihilation rates in positron complexes

    International Nuclear Information System (INIS)

    Assafrao, Denise; Walters, H.R. James; Mohallem, Jose R.

    2008-01-01

    The molecular approach for positron interaction with atoms is developed further. Potential energy curves for positron motion are obtained. Two procedures accounting for the nonadiabatic effective positron mass are introduced for calculating annihilation rate constants. The first one takes the bound-state energy eigenvalue as an input parameter. The second is a self-contained and self-consistent procedure. The methods are tested with quite different states of the small complexes HPs, e + He (electronic triplet) and e + Be (electronic singlet and triplet). For states yielding the positronium cluster, the annihilation rates are quite stable, irrespective of the accuracy in binding energies. For the e + Be states, annihilation rates are larger and more consistent with qualitative predictions than previously reported ones

  1. Direct photons in WA98

    CERN Document Server

    Aggarwal, M M; Ahammed, Z; Angelis, Aris L S; Antonenko, V G; Arefev, V; Astakhov, V A; Avdeichikov, V; Awes, T C; Baba, P V K S; Badyal, S K; Barlag, C; Bathe, S; Batyunya, B; Bernier, T; Bhalla, K B; Bhatia, V S; Blume, C; Bock, R; Bohne, E M; Böröcz, Z K; Bucher, D; Buijs, A; Büsching, H; Carlén, L; Chalyshev, V; Chattopadhyay, S; Cherbachev, R; Chujo, T; Claussen, A; Das, A C; Decowski, M P; Delagrange, H; Dzhordzhadze, V; Dönni, P; Dubovik, I; Dutt, S; Dutta-Majumdar, M R; El-Chenawi, K F; Eliseev, S; Enosawa, K; Foka, P Y; Fokin, S L; Ganti, M S; Garpman, S; Gavrishchuk, O P; Geurts, F J M; Ghosh, T K; Glasow, R; Gupta, S K; Guskov, B; Gustafsson, Hans Åke; Gutbrod, H H; Higuchi, R; Hrivnacova, I; Ippolitov, M S; Kalechofsky, H; Kamermans, R; Kampert, K H; Karadzhev, K; Karpio, K; Kato, S; Kees, S; Klein-Bösing, C; Knoche, S; Kolb, B W; Kosarev, I G; Kucheryaev, I; Krümpel, T; Kugler, A; Kulinich, P A; Kurata, M; Kurita, K; Kuzmin, N A; Langbein, I; Lee, Y Y; Löhner, H; Luquin, Lionel; Mahapatra, D P; Man'ko, V I; Martin, M; Martínez, G; Maksimov, A; Mgebrishvili, G; Miake, Y; Mir, M F; Mishra, G C; Miyamoto, Y; Mohanty, B; Morrison, D; Mukhopadhyay, D S; Naef, H; Nandi, B K; Nayak, S K; Nayak, T K; Neumaier, S; Nyanin, A; Nikitin, V A; Nikolaev, S; Nilsson, P O; Nishimura, S; Nomokonov, V P; Nystrand, J; Obenshain, F E; Oskarsson, A; Otterlund, I; Pachr, M; Pavlyuk, S; Peitzmann, Thomas; Petracek, V; Pinganaud, W; Plasil, F; Von Poblotzki, U; Purschke, M L; Rak, J; Raniwala, R; Raniwala, S; Ramamurthy, V S; Rao, N K; Retière, F; Reygers, K; Roland, G; Rosselet, L; Rufanov, I A; Roy, C; Rubio, J M; Sako, H; Sambyal, S S; Santo, R; Sato, S; Schlagheck, H; Schmidt, H R; Schutz, Y; Shabratova, G; Shah, T H; Sibiryak, Yu; Siemiarczuk, T; Silvermyr, D; Sinha, B C; Slavin, N V; Söderström, K; Solomey, Nickolas; Sood, G; Sørensen, S P; Stankus, P; Stefanek, G; Steinberg, P; Stenlund, E; Stüken, D; Sumbera, M; Svensson, S; Trivedi, M D; Tsvetkov, A A; Tykarski, L; Urbahn, J; Van den Pijll, E C; van Eijndhoven, N; van Nieuwenhuizen, G J; Vinogradov, A; Viyogi, Y P; Vodopyanov, A S; Vörös, S; Wyslouch, B; Yagi, K; Yokota, Y; Young, G R

    2002-01-01

    A measurement of direct photon production in /sup 208/Pb+/sup 208/Pb collisions at 158 A GeV has been carried out in the CERN WA98 experiment. The invariant yield of direct photons was extracted as a function of transverse momentum in the interval 0.51.5 GeV/c. the result constitutes the first observation of direct photons in ultrarelativistic heavy-ion collisions. (19 refs).

  2. Evaluation of nonuniformity of polymeric membrane materials by positron annihilation technique

    International Nuclear Information System (INIS)

    Shantarovich, V.P.; Kevdina, I.B.; Yampol'skij, Yu.P.

    2000-01-01

    Time distribution of annihilation radiation of positrons in some glass-like polymers including polymer membrane materials in the air and in nitrogen atmosphere was studied experimentally. Main attention is paid to long-lived component of distribution, i.e. ortho-positronium annihilation (positron-electron bound system). Influence of atmospheric oxygen on positronium annihilation characteristics was detected. The conceived notions on the mechanisms of positronium formation, localization and annihilation in the polymers suggest irregularity of distribution of free volumes of different size in the polymer matrix. The concentration and size of the elementary free volumes, as well as sizes of micro heterogeneities containing the volumes are evaluated [ru

  3. Effect of the element substitutions in Cu position on positron annihilation spectra

    International Nuclear Information System (INIS)

    Zhou Xianyi

    1991-01-01

    The effect of the element substitutions in Cu position on positron annihilation spectra was studied systematically by the measurement of one-dimensional angular correlation spectra of positron annihilation radiation for YBa 2 Cu 3-x M x O y (M = Sn, Al) samples. The results show that 1D ACPAR of YBaCuO superconductor is constituted by two Gaussian parts, corresponding to annihilation position sampled in the Cu-O plane and Cu-O chain respectively. The parabola like the positron annihilation with Fermi electron gas in metals and alloys is not found out. Positron annihilation spectra are sensitive to the element substitution in Cu positions, especially in Cu-chains, and could be used to probe the substituting positions in Y-Ba-Cu-O superconductors

  4. INSTRUMENTS AND METHODS OF INVESTIGATION: Positron annihilation spectroscopy in materials structure studies

    Science.gov (United States)

    Grafutin, Viktor I.; Prokop'ev, Evgenii P.

    2002-01-01

    A relatively new method of materials structure analysis — positron annihilation spectroscopy (PAS) — is reviewed. Measurements of positron lifetimes, the determination of positron 3γ- and 2γ-annihilation probabilities, and an investigation of the effects of different external factors on the fundamental characteristics of annihilation constitute the basis for this promising method. The ways in which the positron annihilation process operates in ionic crystals, semiconductors, metals and some condensed matter systems are analyzed. The scope of PAS is described and its prospects for the study of the electronic and defect structures are discussed. The applications of positron annihilation spectroscopy in radiation physics and chemistry of various substances as well as in physics and chemistry of solutions are exemplified.

  5. Study of double scattering effect in antiproton--deuteron annihilation

    International Nuclear Information System (INIS)

    Zemany, P.D.

    1975-01-01

    The double scattering process in the deuteron is investigated for the reaction anti pd → p/sub s/ + mesons. About 30 percent of the apparent anti pn annihilations are involved in double scattering. A model which describes the properties of protons emerging from apparent anti pn annihilations is presented

  6. Positron annihilation and perturbed angular correlation studies of radiation damage

    International Nuclear Information System (INIS)

    Zhu Jiazheng; Li Anli; Xu Yongjun; Wang Zhiqiang; Zhou Dongmei; Zheng Yongnan; Zhu Shengyun; Iwata, T.

    2002-01-01

    The positron annihilation and perturbed angular correlation techniques have been employed to study radiation damage in Si and Nb. The results obtained by the positron annihilation are consistent with those given by the perturbed angular correlation

  7. Production of Higgs bosons and hyperions in e+e- annihilation

    International Nuclear Information System (INIS)

    Ali, A.

    1980-10-01

    The production of hyperions - low lying pseudo-Goldstone modes of the hypercolor scenario - in e + e - annihilation is studied and contrasted with the production of elementary Higgs of the canonical methodology. 1. The possibility of implementing the Higgs mechanism in a dynamical way, without the use of elementary spin-0 fields, has lately been the subject of much discussion. In several recent communications it has been pointed out that the most popular dynamical scheme, the so-called hypercolor scenario, may be experimentally distinguishable from the canonical Weinberg-Salam scheme via experiments at relatively low (10-100 GeV) energies. [There is, of course, an a priori expectation that differences between the two schemes will be manifest in experiments at TeV energies; this energy regime, however is not likely to be accessible in the near future.] The considerations of refs.(2-4) hinge in a crucial way on one's ability to (a) produce spin-O particles, of mass approx. 10 GeV, coupled semi-weakly to ordinary quarks and leptons and (b) distinguish Higgs particles, phi's, from the low-lying bosons of the hypercolor scenario, generically called π's, exploiting mainly the difference in parity. Our purpose in this note is to point out that the pseudosclar nature of π''s introduces a fundamental difference in the production mechanism of phi's and π''s in a large class of reactions. In particular, we calculate the production rates of phi's and π''s in e + e - annihilation and in the decays of the spin-1 bosons Z and toponium, Jsub(T). (orig.)

  8. Annihilation of antiprotons at rest in 3He and 4He

    International Nuclear Information System (INIS)

    Balestra, F.; Bossolasco, S.; Bussa, M.P.; Busso, L.; Fava, L.; Ferrero, L.; Panzieri, D.; Piragino, G.; Tosello, F.; Bendiscioli, G.; Rotondi, A.; Salvini, P.; Zenoni, A.; Batusov, Yu.A.; Bunyatov, S.A.; Falomkin, I.V.; Nichitiu, F.; Pontecorvo, G.B.; Sapozhnikov, M.G.; Tretyak, V.I.; Guaraldo, C.; Maggiora, A.; Haatuft, A.; Halsteinslid, A.; Myklebost, K.; Olsen, J.M.; Breivik, F.O.; Jacobsen, T.; Soerensen, S.O.

    1987-01-01

    At LEAR of CERN the annihilation of antiprotons, stopping in 3 He and 4 He filling a self-shunted streamer chamber in a magnetic field, has been studied. The charged-particle multiplicities have been measured and the relative probabilities of π - production in anti p 3 He and anti p 4 He annihilation events have been obtained. The ratio between the anti p annihilation probability on the neutron and the proton for 3 He and 4 He has been deduced to be about half the value obtained for 2 H in bubble chamber experiments. The analysis of the results shows that this difference cannot be due only to the pion final-state interaction or to the shadow effect of the nucleons of the nuclei. The probability of anti p annihilation at rest on a proton bound in the nucleus results to be twice as high as that on a bound neutron, showing the dominance of annihilation in the I=0 isospin states. (orig.)

  9. Characterization of the melting process of PTFE using positron annihilation spectroscopy

    International Nuclear Information System (INIS)

    Honda, Y; Nishijima, S

    2015-01-01

    Poly(tetrafluoroethylene) (PTFE) is a semi-crystalline polymer and the lifetime of ortho-positronium(o-Ps) is known to be able to be separated into two components due to annihilation in the crystal region and in the amorphous region. The melting process of PTFE was investigated using positron annihilation spectroscopy and X-ray diffraction. The results indicated that volume expansion with an increase of temperature is dominantly due to the expansion of the amorphous region and a Ps bubble is formed at melting in both regions. The o-Ps relating to the crystal region definitely remains on the surface of crystal at the time of annihilation. The production of lower energy electrons at melting was deduced by the analysis of the Doppler broadened annihilation photopeak, and the increase in the number of such electrons was found to have great influence on the formation of the o-Ps and annihilation processes of positron and o-Ps. (paper)

  10. Application of positron annihilation to the characterization of polymer structure

    International Nuclear Information System (INIS)

    Suzuki, T.; Yu, R.S.; Ito, Y.; Kondo, K.; Shantarovich, V.

    2005-01-01

    Positron annihilation has been applied to study characteristics of polymers last many years. Positron behaves as a nano-meter probe and brings out information of chemical structures, geometric structures, and momentum of electrons through the annihilation gamma-rays. Positrons injected in polymers tends to form positronium, which is similar structure to hydrogen atom and consists of electron and positron. Positronium diffuses through polymer structures and preferentially trapped by intermolecular spaces, if there is not any strong polar group in the chemical structure. Inside the spaces positronium annihilates through pick-off annihilation with electrons constituting walls of the spaces. Thus the pick-off annihilation brings out information about the interaction with electrons on the walls forming the spaces. These information can be measured by the positron annihilation lifetime spectroscopy (PALS) and Doppler broadening spectroscopy: from the former lifetimes and intensities of positronium can be measured and from the latter energy spectrum of the positron annihilation gamma-rays. The lifetimes are connected with the nano-meter size of the spaces and, using an empirical formula, the pore size can be estimated quantitatively. However the intensities bring out many kinds of information. Knowing the sample chemical structures, the values can be simply connected with the amount of spaces and often reflect the polar effect and temperature effect. In the positron annihilation technique, the energy distribution of-positron annihilation gamma-rays plays important role in the investigation of positron interaction with atoms constituting polymer chemical structures. The energy distribution can be measured using a high pure Ge detector. Although the spectrum obtained by one Ge detector has a large peak to back-ground ratio, using a coincidence technique of two Ge detectors, the coincidence Doppler broadening spectrum (CDBS) can improve the ratio from the order of 10-2 to 10

  11. THE EFFECTS OF DARK MATTER ANNIHILATION ON COSMIC REIONIZATION

    Energy Technology Data Exchange (ETDEWEB)

    Kaurov, Alexander A.; Hooper, Dan; Gnedin, Nickolay Y., E-mail: kaurov@uchicago.edu [Department of Astronomy and Astrophysics, The University of Chicago, Chicago, IL 60637 (United States)

    2016-12-20

    We revisit the possibility of constraining the properties of dark matter (DM) by studying the epoch of cosmic reionization. Previous studies have shown that DM annihilation was unlikely to have provided a large fraction of the photons which ionized the universe, but instead played a subdominant role relative to stars and quasars. The DM might, however, have begun to efficiently annihilate with the formation of primordial microhalos at z  ∼ 100–200, much earlier than the formation of the first stars. Therefore, if DM annihilation ionized the universe at even the percent level over the interval z  ∼ 20–100, it could leave a significant imprint on the global optical depth, τ . Moreover, we show that cosmic microwave background polarization data and future 21 cm measurements will enable us to more directly probe the DM contribution to the optical depth. In order to compute the annihilation rate throughout the epoch of reionization, we adopt the latest results from structure formation studies and explore the impact of various free parameters on our results. We show that future measurements could make it possible to place constraints on the DM’s annihilation cross-sections, which are at a level comparable to those obtained from the observations of dwarf galaxies, cosmic-ray measurements, and studies of recombination.

  12. Light-Baryon Production in Binary $pd$ Annihilation Reactions at Rest

    CERN Document Server

    Denisov, O Yu; Balestra, F; Botta, E; Bressani, Tullio; Bussa, M P; Busso, L; Calvo, D; Cerello, P G; Costa, S; D'Isep, D; Fava, L; Feliciello, A; Ferrero, L; Filippi, A; Garfagnini, R; Grasso, A; Iazzi, F; Maggiora, A; Marcello, S; Minetti, B; Mirfakhraee, N; Panzarasa, A; Panzieri, D; Piragino, G; Tosello, F; Zosi, G; Alberico, V; Bertin, A; Bruschi, M; Capponi, M; D'Antone, I; De Castro, S; Ferretti, A; Galli, D; Giacobbe, B; Marconi, U; Piccinini, M; Poli, M; Semprini-Cesari, N; Spighi, R; Vecchi, S; Vagnoni, V M; Vigotti, F; Villa, M; Vitale, A; Zoccoli, A; Bianconi, A; Corradini, M; Lodi-Rizzini, E; Venturelli, L; Zenoni, A; Cicalò, C; Masoni, A; Mauro, S; Puddu, G; Serci, S; Temnikov, P P; Usai, G L; Gortchakov, O E; Prakhov, S N; Rozhdestvensky, A M; Sapozhnikov, M G; Tretyak, V I; Gianotti, P; Guaraldo, C; Lanaro, A; Lucherini, V; Nichitiu, F; Petrascu, C; Ableev, V G; Cavion, C; Gastaldi, Ugo; Lombardi, M; Maron, G; Vannucci, Luigi; Vedovato, G; Bendiscioli, G; Filippini, V; Fontana, A; Montagna, P; Rotondi, A; Salvini, P; Pauli, G; Tessaro, S; Santi, L

    1999-01-01

    We report the study of light baryon production in two-prong annihilation reactions due to antiprotons stopping in gaseous deuterium and detected by the OBELIX spectrometer (LEAR, CERN). A clear signal of the Delta (1232) production in binary reactions was found in both annihilation channels: pd to pi /sup -/ Delta /sup +/( Delta /sup +/ to pi /sup 0/p) and pd to pi /sup 0/ Delta /sup 0/( Delta /sup 0/ to pi /sup -/p). The annihilation probabilities for these reactions turned out to be Y=(1.01+or-0.08)*10/sup -5/ and Y= (1.12+or-0.20)*10/sup -5/, respectively. In addition, the annihilation probability for the prototype Pontecorvo reaction pd to pi /sup -/p was measured with the best world statistics: Y= (1.46+or-0.08)*10/sup -5/. (16 refs).

  13. Experimental analysis of the double Cabibbo-suppressed weak decay D+ -> φ K+

    International Nuclear Information System (INIS)

    Lima, Jose Guilherme Rocha de.

    1991-03-01

    A phenomenological estimate of the branching fraction of the weak decay D + -> θ K + is made, which cannot be explained only through spectator processes and which is a rare process because it is a doubly Cabibbo suppressed decay. After describing the Charm Photoproduction Experiment E691, we present the results obtained in the search for this decay in the data collected by E691. These results suggest a significant contribution from W annihilation processes for the decays of the charmed meson D + . (author). 41 refs, 37 figs, 17 tabs

  14. View of the WA10 set-up

    CERN Multimedia

    CERN PhotoLab

    1977-01-01

    The WA10 experiment by the Geneva-Lausanne Collaboration was set-up in the H5 beam (unseparated, up to 50 GeV/c) to study K+-p --> K0pi+-p and other reactions of similar topology, and the energy dependence of resonance production.

  15. Studies of defects and defect agglomerates by positron annihilation spectroscopy

    DEFF Research Database (Denmark)

    Eldrup, Morten Mostgaard; Singh, B.N.

    1997-01-01

    A brief introduction to positron annihilation spectroscopy (PAS), and in particular lo its use for defect studies in metals is given. Positrons injected into a metal may become trapped in defects such as vacancies, vacancy clusters, voids, bubbles and dislocations and subsequently annihilate from...... the trapped state iri the defect. The annihilation characteristics (e.g., the lifetime of the positron) can be measured and provide information about the nature of the defect (e.g., size, density, morphology). The technique is sensitive to both defect size (in the range from monovacancies up to cavities...

  16. Flavoured co-annihilation

    Indian Academy of Sciences (India)

    2012-10-06

    Oct 6, 2012 ... (2) one can see that increasing δRR will decrease the stau mass or in other words the co-annihilation will occur at a lower neutralino mass for the fixed universal scalar mass parameter (m0). But having large flavour violating entry in the ˜μR–˜τR sectors of the sleptonic mass matrix will also give rise to rare ...

  17. Significant gamma-ray lines from dark matter annihilation

    Energy Technology Data Exchange (ETDEWEB)

    Duerr, Michael [DESY, Notkestrasse 85, 22607 Hamburg (Germany); Fileviez Perez, Pavel; Smirnov, Juri [Max-Planck-Institut fuer Kernphysik, Saupfercheckweg 1, 69117 Heidelberg (Germany)

    2016-07-01

    Gamma-ray lines from dark matter annihilation are commonly seen as a ''smoking gun'' for the particle nature of dark matter. However, in many dark matter models the continuum background from tree-level annihilations makes such a line invisible. I present two simple extensions of the Standard Model where the continuum contributions are suppressed and the gamma-ray lines are easily visible over the continuum background.

  18. Applications of positron annihilation to dermatology and skin cancer

    International Nuclear Information System (INIS)

    Liu, Guang; Chen, Hongmin; Chakka, Lakshmi; Gadzia, Joseph E.; Jean, Y.C.

    2007-01-01

    Positronium annihilation lifetime experiments have been performed to investigate the interaction between skin cancer and positronium for human skin samples. Positronium annihilation lifetime is found to be shorter and intensity is found to be less for the samples with basal cell carcinoma and squamous cell carcinoma than the normal skin samples. These results indicate a reduction of free volume in the molecular level for the skin with cancer with respect to the skin without cancer. Positron annihilation spectroscopy may be potentially developed as a new noninvasive and external method for dermatology clinics, early detection of cancer, and nano-PET technology in the future. (copyright 2007 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  19. Applications of positron annihilation to dermatology and skin cancer

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Guang; Chen, Hongmin; Chakka, Lakshmi [Department of Chemistry, University of Missouri-Kansas City, Kansas City, MO 64110 (United States); Gadzia, Joseph E. [Dermatology, Department of Internal Medicine, University of Kansas Medical Center, Kansas City, KS 66103 and Kansas Medical Clinic, Topeka, KS 66614 (United States); Jean, Y.C. [Department of Chemistry, University of Missouri-Kansas City, Kansas City, MO 64110 (United States); R and D Center for Membrane Technology, Chung Yuan Christian University, Chung-Li (China)

    2007-07-01

    Positronium annihilation lifetime experiments have been performed to investigate the interaction between skin cancer and positronium for human skin samples. Positronium annihilation lifetime is found to be shorter and intensity is found to be less for the samples with basal cell carcinoma and squamous cell carcinoma than the normal skin samples. These results indicate a reduction of free volume in the molecular level for the skin with cancer with respect to the skin without cancer. Positron annihilation spectroscopy may be potentially developed as a new noninvasive and external method for dermatology clinics, early detection of cancer, and nano-PET technology in the future. (copyright 2007 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  20. Study of radiation damage in metals by positron annihilation

    International Nuclear Information System (INIS)

    Gauster, W.B.

    1977-01-01

    Positron annihilation is a sensitive technique for probing defects in metals and it has recently been shown to be a valuable tool for the study of radiation damage. After an introduction to the three basic experimental methods (angular correlation, Doppler broadening, and lifetime measurements), the interaction of positrons with lattice defects is reviewed. Results for the annealing of damage after low temperature irradiation are used to show that positron annihilation has provided new information on annealing kinetics. The role of positron techniques in characterizing complex defect structures resulting from high-temperature neutron irradiation is reviewed and the possible utility of positron annihilation as a nondestructive monitor of property changes is pointed out

  1. Dynamics of an exclusion process with creation and annihilation

    International Nuclear Information System (INIS)

    Juhasz, Robert; Santen, Ludger

    2004-01-01

    We examine the dynamical properties of an exclusion process with creation and annihilation of particles in the framework of a phenomenological domain-wall theory, by scaling arguments and by numerical simulation. We find that the length and the time scales are finite in the maximum current phase for finite creation and annihilation rates as opposed to the algebraically decaying correlations of the totally asymmetric simple exclusion process (TASEP). Critical exponents of the transition to the TASEP are determined. The case where bulk creation and annihilation rates vanish faster than the inverse of the system size N is also analysed. We point out that shock localization is possible even for rates proportional to N -a , 1 < a < 2

  2. Detection of the weak γ activities from new neutron-rich nuclei

    International Nuclear Information System (INIS)

    Zhang Li; Wang Jicheng; Zhao Jinhua; Yang Yongfeng; Zheng Jiwen; Hu Qingyuan; Guo Tianrui

    2003-01-01

    Energic signals of γ rays detected by a HPGe γ detector were coincided with γ-ray, energy-loss signals detected by a 4πΔEβ detector. Then the coinciding β-ray spectra was anticoincided with timing logical signals of 511 keV γ ray created in positron annihilate, detected by a large BGO detector. This special coincidence-anticoincidence system has played an important role in the first observation of the new neutron-rich nuclide 209 Hg. It is shown that this is an effective method to detecting very weak γ-ray activities of neutron-rich isotope in an element-separation sample

  3. Sensitivity of orthopositronium annihilation to density fluctuations in ethane gas

    International Nuclear Information System (INIS)

    Eftekhari, A.

    1982-01-01

    The annihilation rates of orthopositronium (o-Ps) and free positrons and positronium formation fractions have been measured in gaseous ethane at seven temperatures between 295 and 377 K for densities in the range 1.2-286 amagat. The pick off quenching rate of o-Ps is observed to vary with temperature at low densities of ethane. The observed behavior of the o-Ps annihilation rates with density and temperature is interpreted in terms of density fluctuations in ethane gas. A simple theoretical model is developed which explains the observed annihilation behavior reasonably well at those temperatures and densities where density fluctuations are small. The annihilation rates of flow-energy positrons indicate the formation of positron-ethane collision complexes and self-trapping of positrons in clusters of ethane molecules. The o-Ps yields appear to be independent of temperature and show a strong dependence on the density of the gas

  4. Counter support for WA35

    CERN Multimedia

    CERN PhotoLab

    1977-01-01

    This assembly was equipped with 78 counters, each consisting of a lucite cone, to produce Cerenkov light, and a CsI scintillator plate of 3 mm thickness glued on the face of the cone. The experiment WA35 was set-up in the s1 beam (West Hall) by the Darmstadt-Heidelberg-Virginia-Warsaw Collaboration to measure angular distributions and multiplicities of pions and recoil protons produced by hadrons interacting in nuclei. (See Annual Report 1976 p. 39)

  5. Defect Characterization in Semiconductors with Positron Annihilation Spectroscopy

    Science.gov (United States)

    Tuomisto, Filip

    Positron annihilation spectroscopy is an experimental technique that allows the selective detection of vacancy defects in semiconductors, providing a means to both identify and quantify them. This chapter gives an introduction to the principles of the positron annihilation techniques and then discusses the physics of some interesting observations on vacancy defects related to growth and doping of semiconductors. Illustrative examples are selected from studies performed in silicon, III-nitrides, and ZnO.

  6. Asymmetric dark matter annihilation as a test of non-standard cosmologies

    International Nuclear Information System (INIS)

    Gelmini, Graciela B.; Huh, Ji-Haeng; Rehagen, Thomas

    2013-01-01

    We show that the relic abundance of the minority component of asymmetric dark matter can be very sensitive to the expansion rate of the Universe and the temperature of transition between a non-standard pre-Big Bang Nucleosynthesis cosmological phase and the standard radiation dominated phase, if chemical decoupling happens before this transition. In particular, because the annihilation cross section of asymmetric dark matter is typically larger than that of symmetric dark matter in the standard cosmology, the decrease in relic density of the minority component in non-standard cosmologies with respect to the majority component may be compensated by the increase in annihilation cross section, so that the annihilation rate at present of asymmetric dark matter, contrary to general belief, could be larger than that of symmetric dark matter in the standard cosmology. Thus, if the annihilation cross section of the asymmetric dark matter candidate is known, the annihilation rate at present, if detectable, could be used to test the Universe before Big Bang Nucleosynthesis, an epoch from which we do not yet have any data

  7. Light mesons and separated J(PC) sources in N-antiN annihilations at rest

    International Nuclear Information System (INIS)

    Lucaci-Timoce, Angela; Lazanu, I.

    2002-01-01

    N-antiN annihilations at rest and in flight are the most productive physics tools to investigate the spectroscopy of light mesons. The annihilations proceed from more sources of initial states, with different J (PC) quantum numbers. This makes the interpretation of the experimental data much more difficult than in the case of other annihilation process, as for example the e + e - annihilations, and introduces ambiguities in the results. In this talk, the possibilities to separate the N-antiN contributions of initial quantum states in different annihilation channels, are analyzed. The interference phenomena that appear are also discussed. (authors)

  8. A systematic effective operator analysis of semi-annihilating dark matter

    International Nuclear Information System (INIS)

    Cai, Yi; Spray, Andrew

    2017-01-01

    Semi-annihilation is a generic feature of dark matter theories stabilized by symmetries larger than a ℤ 2 . It contributes to thermal freeze out, but is irrelevant for direct and collider searches. This allows semi-annihilating dark matter to avoid those limits in a natural way. We use an effective operator approach to make the first model-independent study of the associated phenomenology. We enumerate all possible operators that contribute to 2→2 semi-annihilation up to dimension 6, plus leading terms at dimension 7. We find that when the only light states charged under the dark symmetry are dark matter, the model space is highly constrained. Only fifteen operators exist, and just two for single-component dark sectors. If there can be additional light, unstable “dark partner” states the possible phenomenology greatly increases, at the cost of additional model dependence in the dark partner decay modes. We also derive the irreducible constraints on models with single-component dark matter from cosmic ray searches and astrophysical observations. We find that for semi-annihilation to electrons and light quarks, the thermal relic cross sections can be excluded for dark matter masses up to 100 GeV. However, significant model space for semi-annihilating dark matter remains.

  9. Constraints on dark matter annihilation from CMB observations before Planck

    Energy Technology Data Exchange (ETDEWEB)

    Lopez-Honorez, Laura [Theoretische Natuurkunde, Vrije Universiteit Brussel and The International Solvay Institutes, Pleinlaan 2, B-1050 Brussels (Belgium); Mena, Olga; Palomares-Ruiz, Sergio; Vincent, Aaron C., E-mail: llopezho@vub.ac.be, E-mail: omena@ific.uv.es, E-mail: sergio.palomares.ruiz@ist.utl.pt, E-mail: vincent@ific.uv.es [Instituto de Física Corpuscular (IFIC), CSIC-Universitat de València, Apartado de Correos 22085, E-46071 Valencia (Spain)

    2013-07-01

    We compute the bounds on the dark matter (DM) annihilation cross section using the most recent Cosmic Microwave Background measurements from WMAP9, SPT'11 and ACT'10. We consider DM with mass in the MeV–TeV range annihilating 100% into either an e{sup +}e{sup −} or a μ{sup +}μ{sup −} pair. We consider a realistic energy deposition model, which includes the dependence on the redshift, DM mass and annihilation channel. We exclude the canonical thermal relic abundance cross section ((σv) = 3 × 10{sup −26}cm{sup 3}s{sup −1}) for DM masses below 30 GeV and 15 GeV for the e{sup +}e{sup −} and μ{sup +}μ{sup −} channels, respectively. A priori, DM annihilating in halos could also modify the reionization history of the Universe at late times. We implement a realistic halo model taken from results of state-of-the-art N-body simulations and consider a mixed reionization mechanism, consisting on reionization from DM as well as from first stars. We find that the constraints on DM annihilation remain unchanged, even when large uncertainties on the halo model parameters are considered.

  10. Positron life time and annihilation Doppler broadening measurements on transition metal complexes

    International Nuclear Information System (INIS)

    Levay, B.; Burger, K.

    1982-01-01

    Positron life time and annihilation Doppler broadening measurements have been carried out on 44 solid coordination compounds. Several correlations have been found between the annihilation life time (tau 1 ) and line shape parameters (L) and the chemical structure of the compounds. Halide ligands were the most active towards positrons. This fact supports the assumption on the possible formation of [e + X - ] positron-halide bound state. The life time was decreasing and the annihilation energy spectra were broadening with the increasing negative character of the halides. The aromatic base ligands affected the positron-halide interaction according to their basicity and space requirement and thus they indirectly affected the annihilation parameters, too. In the planar and tetrahedral complexes the electron density on the central met--al ion affected directly the annihilation parameters, while in the octahedral mixed complexes it had only an ind--irect effect through the polarization of the halide ligands. (author)

  11. Benchmarking triplet-triplet annihilation photon upconversion schemes.

    Science.gov (United States)

    Gertsen, Anders S; Koerstz, Mads; Mikkelsen, Kurt V

    2018-05-07

    Photon upconversion facilitated by triplet-triplet annihilation in molecular systems is a promising path toward utilization of sub bandgap photons in photovoltaic devices. Prior to the challenging synthesis of new molecules, quantum chemical computations can aid the design process and provide suggestions for new and optimal systems. Here, we benchmark time-dependent density functional methods by their ability to describe relevant photophysical quantities of a range of different types of sensitizer/annihilator pairs to provide guidelines for future computational studies of potential new pairs. Using meta-GGA, hybrid, and range-separated hybrid functionals, we find that the hybrid functionals B3LYP and PBE0 (incorporating low to medium fractions of exact exchange of 20% and 25%, respectively) describe singlet absorptions the best, while triplet energetics are best described by the meta-GGA functionals M06-L and M11-L (incorporating no exact exchange), respectively. Furthermore, we find that the Tamm-Dancoff approximation of time-dependent density functional theory in general does not improve the description of neither singlet nor triplet energies of sensitizer/annihilator pairs.

  12. Study of $\\eta$ and $\\eta'$ Production in $\\overline{n}p$ Annihilations

    CERN Document Server

    Filippi, A; Botta, E; Bressani, Tullio; Calvo, D; Costa, S; D'Isep, F; Feliciello, A; Iazzi, F; Marcello, S; Minetti, B; Mirfakhraee, N; Balestra, F; Bussa, M P; Busso, L; Cerello, P G; Denisov, O Yu; Garfagnini, R; Grasso, A; Maggiora, A; Panzarasa, A; Panzieri, D; Tosello, F; Bertin, A; Bruschi, M; Capponi, M; De Castro, S; Donà, R; Galli, D; Giacobbe, B; Marconi, U; Massa, I; Piccinini, M; Poli, M; Semprini-Cesari, N; Spighi, R; Vagnoni, V M; Vecchi, S; Villa, M; Vitale, A; Zoccoli, A; Bianconi, A; Bonomi, G; Lodi-Rizzini, E; Venturelli, L; Zenoni, A; Cicalò, C; Masoni, A; Mauro, S; Puddu, G; Serci, S; Usai, G L; Gorchakov, O E; Prakhov, S N; Rozhdestvensky, A M; Sapozhnikov, M G; Tretyak, V I; Gianotti, P; Guaraldo, C; Lanaro, A; Lucherini, V; Petrascu, C; Ableev, V G; Vannucci, Luigi; Vedovato, G; Bendiscioli, G; Filippini, V; Fontana, A; Montagna, P; Rotondi, A; Salvini, P; Tessaro, S

    1999-01-01

    The annihilation fractions and cross sections for the np annihilation reaction in flight (~50-400 MeV/c) into eta pi /sup +/ and eta ' pi /sup +/ final states have been measured. The first ones follow the trend expected for P wave annihilations. From the ratios of the yields an evaluation of the pseudoscalar mixing angle in the standard form is possible. The value found shows that for pseudoscalar meson production from P wave the quark line rule is not grossly violated. (22 refs).

  13. Impact of dark matter decays and annihilations on structure formation

    NARCIS (Netherlands)

    Mapelli, M.; Ripamonti, E.

    2007-01-01

    Abstract: We derived the evolution of the energy deposition in the intergalactic medium (IGM) by different decaying (or annihilating) dark matter (DM) candidates. Heavy annihilating DM particles (with mass larger than a few GeV) have no influence on reionization and heating, even if we assume that

  14. KONSELING PERNIKAHAN BERBASIS ASMARA ( As-Sakinah, Mawaddah, Wa Rahmah

    Directory of Open Access Journals (Sweden)

    Nur Ahmad

    2017-02-01

    Full Text Available Keluarga merupakan sistem sosial yang alamiah dan keluarga berfungsi membentuk aturan-aturan, komunikasi serta negosiasi diantara para anggota keluarga. Ketiga fungsi keluarga ini mempunyai sejumlah implikasi terhadap perkembangan dan keberadaan para anggota keluarga. Keluarga melakukan suatu pola interaksi yang diulang-ulang melalui partisipasi seluruh anggota keluarga. Sehingga strategi konseling pernikahan yang dibangun akan membantu terpeliharanya hubungan-hubungan keluarga harmonis As-Sakinah, Mawaddah, Wa Rahmah juga dituntut untuk memodifikasi pola-pola transaksi dalam memenuhi kebutuhan keluarga yang mengalami perubahan yang didambakan. Membangun Keluarga bahagia melalui pendekatan konseling pernikahan pada dasarnya merupakan upaya untuk memperoleh kebahagiaan dan kesejahteraan hidup baik lahir maupun batin. Keluarga dibentuk untuk memadukan rasa kasih dan sayang diantara dua makhluk berlainan jenis, yang berlanjut untuk menyebarkan rasa kasih dan sayang keibuan dan keayahan terhadap seluruh anggota keluarga. Namun apa yang didambakan, apa yang diidealkan serta apa yang seharusnya dalam kenyataan tidak senantiasa berjalan mulus sebagaimana mestinya. Kebahagiaan yang diharapkan semoga dapat diraih dari bahtera kehidupan berumah tangga dan bukan sebaliknya yang kerapkali dirasakan justru kesedihan. Kata kunci : konseling pernikahan, sakinah mawaddah wa rahmah   MARRIAGE COUNSELING BASED ON AS-SAKINAH MAWADDAH WA RAHMAH. The family is the natural and social system functioning family formed the rules, communication and negotiations between members of the family. The three functions of this family has a number of implications for the development and the existence of the family members. Perform a family interaction patterns that are repeated through the participation of all members of the family. So the marriage counselling strategy built will help the nurturing harmonious family relationships, As-Sakinah, Mawaddah Wa Rahmah is also required

  15. Recent developments in weak interactions and e+e- annihilation. An elementary introduction to 'charm'

    International Nuclear Information System (INIS)

    Pham, Xuan-Yem.

    1976-01-01

    The recent developments about 'charm', a new quantum number postulated in the framework of models unifying electromagnetic and weak interactions are briefly reviewed. Many experimental facts seem to support this hypothesis. A proliferation of quarks, and their right-handed currents are also discussed in the light of some new experimental data on anti-neutrino scattering [fr

  16. Polarization of photons in matter–antimatter annihilation

    Energy Technology Data Exchange (ETDEWEB)

    Moskaliuk, S.S. [Bogolyubov Institute for Theoretical Physics, Metrolohichna Street, 14-b, Kyiv-143, Ukraine, UA-03143 e-mail: mss@bitp.kiev.ua (Ukraine)

    2015-03-10

    In this work we demonstrate the possibility of generation of linear polarization of the electromagnetic field (EMF) due to the quantum effects in matter-antimatter annihilation process for anisotropic space of the I type according to Bianchi. We study the dynamics of this process to estimate the degree of polarisation of the EMF in the external gravitational field of the anisotropic Bianchi I model. It has been established that the quantum effects in matter-antimatter annihilation process in the external gravitational field of the anisotropic Bianchi I model provide contribution to the degree of polarisation of the EMF in quadrupole harmonics.

  17. Examination of minor actinide annihilation by BWR core

    International Nuclear Information System (INIS)

    Hida, Kazuki

    1995-01-01

    From the viewpoint of reducing burden for disposing high level waste generated from spent fuel, the examination of recycling minor actinide (MA) to reactors and reducing its accumulation has been advanced. In this study, the possibility of annihilation in the case of recycling it to a BWR was examined. The main MAs are 237 Np, 241 Am, 243 Am, 242 Cm, and 244 Cm. However, as for Cm isotopes, the half life is short, the amount of generation is small, and the rate of neutron emission is high, therefore, those are disposed as waste, and 237 Np, 241 Am and 243 Am were taken as the objects of recycling. In order to grasp the basic characteristics in the case of recycling MAs to a BWR, MAs were added to UO 2 fuel, MOX fuel and HCR fuel and burned, and the nuclear conversion characteristics were examined. As the result, it was found that they were converted to short half life nuclides, and as the neutron spectra were softer, the rate of annihilation was higher. In the case of recycling MAs by concentrating to a specific reactor, reactivity loss, the degree of uranium enrichment required for compensating reactivity, and the rate of MA annihilation were calculated. Based on these data, the MA recycling system was set up, and the rate of MA annihilation was evaluated. This is reported. (K.I.)

  18. A positron annihilation lifetime spectroscopy study of porous silicon using a continuous lifetime fitting algorithm

    International Nuclear Information System (INIS)

    Derlet, P.M.; Choy, T.C.

    1996-01-01

    In the present work we report on a positron annihilation lifetime spectroscopy (PALS) investigation of porous silicon using a continuous lifetime fitting algorithm. Our motivation lies in the underlying disadvantage in discrete lifetime fitting algorithms where the number of components must initially be assumed since in general a realistic spectrum does not uniquely determine this number. This becomes particularly apparent when looking at highly disordered systems where the notion of a discrete spectrum may be invalid and indeed crucial to an understanding of the optical absorption and photo-luminescence properties. Using the PALS data collected from different porous silicon samples in conjunction with other methods of characterisation, we have extended the findings of previous work. In particular we resolve three rather than two ortho-positronium components, suggesting that there may be an additional intermediary scale of porosity in which ortho-positronium annihilates. We also establish the existence of a very weak ortho-positronium component in the pre-anodised wafers at a time scale approximately equal to the longest time ortho-positronium component seen in porous silicon, suggesting that irregularities of a particular magnitude exist before anodisation and that these may, in part, be the catalyst for the initial pore formation process

  19. Fusion Reactions and Matter-Antimatter Annihilation for Space Propulsion

    Science.gov (United States)

    2005-07-13

    FUSION REACTIONS AND MATTER- ANTIMATTER ANNIHILATION FOR SPACE PROPULSION Claude DEUTSCH LPGP (UMR-CNRS 8578), Bât. 210, UPS, 91405 Orsay...REPORT TYPE N/A 3. DATES COVERED - 4. TITLE AND SUBTITLE šFusion Reactions And Matter- Antimatter Annihilation For Space Propulsion 5a...which is possible with successful MCF or ICF. Appropriate vessel designs will be presented for fusion as well as for antimatter propulsion. In

  20. 78 FR 26249 - Drawbridge Operation Regulation; Lake Washington Ship Canal, Seattle, WA

    Science.gov (United States)

    2013-05-06

    ...The Coast Guard has issued a temporary deviation from the operating schedule that governs the Montlake Bridge across the Lake Washington Ship Canal, mile 5.2, at Seattle, WA, and the University Bridge across the Lake Washington Ship Canal, mile 4.3, at Seattle, WA. This deviation is necessary to accommodate the ``Beat the Bridge'' foot race. This deviation allows the bridges to remain in the closed position to allow safe movement of event participants.

  1. Alternative method for reconstruction of antihydrogen annihilation vertices

    Energy Technology Data Exchange (ETDEWEB)

    Amole, C., E-mail: chanpreet.amole@cern.ch [York University, Department of Physics and Astronomy (Canada); Ashkezari, M. D. [Simon Fraser University, Department of Physics (Canada); Andresen, G. B. [Aarhus University, Department of Physics and Astronomy (Denmark); Baquero-Ruiz, M. [University of California, Department of Physics (United States); Bertsche, W. [Swansea University, Department of Physics (United Kingdom); Bowe, P. D. [Aarhus University, Department of Physics and Astronomy (Denmark); Butler, E. [CERN, Physics Department (Switzerland); Cesar, C. L. [Universidade Federal do Rio de Janeiro, Instituto de Fisica (Brazil); Chapman, S. [University of California, Department of Physics (United States); Charlton, M.; Deller, A.; Eriksson, S. [Swansea University, Department of Physics (United Kingdom); Fajans, J. [University of California, Department of Physics (United States); Friesen, T.; Fujiwara, M. C. [University of Calgary, Department of Physics and Astronomy (Canada); Gill, D. R. [TRIUMF (Canada); Gutierrez, A. [University of British Columbia, Department of Physics and Astronomy (Canada); Hangst, J. S. [Aarhus University, Department of Physics and Astronomy (Denmark); Hardy, W. N. [University of British Columbia, Department of Physics and Astronomy (Canada); Hayano, R. S. [University of Tokyo, Department of Physics (Japan); Collaboration: ALPHA Collaboration; and others

    2012-12-15

    The ALPHA experiment, located at CERN, aims to compare the properties of antihydrogen atoms with those of hydrogen atoms. The neutral antihydrogen atoms are trapped using an octupole magnetic trap. The trap region is surrounded by a three layered silicon detector used to reconstruct the antiproton annihilation vertices. This paper describes a method we have devised that can be used for reconstructing annihilation vertices with a good resolution and is more efficient than the standard method currently used for the same purpose.

  2. Alternative method for reconstruction of antihydrogen annihilation vertices

    CERN Document Server

    Amole, C; Andresen , G B; Baquero-Ruiz, M; Bertsche, W; Bowe, P D; Butler, E; Cesar, C L; Chapman, S; Charlton, M; Deller, A; Eriksson, S; Fajans, J; Friesen, T; Fujiwara, M C; Gill, D R; Gutierrez, A; Hangst, J S; Hardy, W N; Hayano, R S; Hayden, M E; Humphries, A J; Hydomako, R; Jonsell, S; Kurchaninov, L; Madsen, N; Menary, S; Nolan, P; Olchanski, K; Olin, A; Povilus, A; Pusa, P; Robicheaux, F; Sarid, E; Silveira, D M; So, C; Storey, J W; Thompson, R I; van der Werf, D P; Wurtele, J S; Yamazaki,Y

    2012-01-01

    The ALPHA experiment, located at CERN, aims to compare the properties of antihydrogen atoms with those of hydrogen atoms. The neutral antihydrogen atoms are trapped using an octupole magnetic trap. The trap region is surrounded by a three layered silicon detector used to reconstruct the antiproton annihilation vertices. This paper describes a method we have devised that can be used for reconstructing annihilation vertices with a good resolution and is more efficient than the standard method currently used for the same purpose.

  3. Knock-on electrons in WA98 silicon drift detector

    International Nuclear Information System (INIS)

    Eliseev, S.

    1997-01-01

    Silicon Drift Detector is used to estimate production of knock-on electrons created by passage of 158 GeV /u fully stripped Pb ion through thick lead target. Analysed data were collected in 1995 during Pb+Pb run in WA98 heavy ion experiment at CERN SPS. Information from WA98 Cherenkov beam counter makes it possible to classify events according to number of additional Pb ions which have during detector's read-out time passed through the target without nuclear interaction. Events with one and none pile-up ion are used for statistical separation of knock-on electrons from all detected charged particles. Resulting inclusive spectra of knock-on electrons are compared with GRANT simulations and good agreement is found. (author)

  4. Positron and positronium annihilation in silica-based thin films studied by a pulsed positron beam

    International Nuclear Information System (INIS)

    Suzuki, R.; Ohdaira, T.; Kobayashi, Y.; Ito, K.; Shioya, Y.; Ishimaru, T.

    2003-01-01

    Positron and positronium annihilation in silica-based thin films has been investigated by means of measurement techniques with a monoenergetic pulsed positron beam. The age-momentum correlation study revealed that positron annihilation in thermally grown SiO 2 is basically the same as that in bulk amorphous SiO 2 while o-Ps in the PECVD grown SiCOH film predominantly annihilate with electrons of C and H at the microvoid surfaces. We also discuss time-dependent three-gamma annihilation in porous low-k films by two-dimensional positron annihilation lifetime spectroscopy

  5. Applications of positron annihilation spectroscopy to study microstructural properties of polymers

    International Nuclear Information System (INIS)

    Jean, Y.C.

    1992-01-01

    Positron annihilation spectroscopy (PAS) has been applied to characterize the free-volume properties of polymers. Positron annihilation lifetime measurements give direct information about the dimension, content, and hole-size distributions of free-volume in amorphous materials. The angular correlation of positron annihilation radiation measurements give additional information about the shape of the free-volume holes in oriented polymeric materials. The unique capability of PAS to probe free-volume properties is from the fact that positronium atom is preferentially trapped in the atomic-scale holes which have a size ranging from 1 to 10 A. (author)

  6. Positron-electron annihilation in a field of a fixed electric dipole

    International Nuclear Information System (INIS)

    Butkevich, E.R.; Sabirov, R.Kh.

    1989-01-01

    Positron annihilation from dipole Ps state conditioned by simultaneous localization of positron and electron in the field of fixed electric dipole is considered. Calculation of annihilation γ-quantum angular correlation curve is performed. For the fixed value of the dipole moment the correlation curve half-width is reduced with the reduction of dipole charges. Correlation curve narrowing takes place with the growth of dipole moment. It is stressed that when interpreting the narrow component one should be careful when choosing the appropriate annihilation mechanism. Experimental result analysis is given

  7. Notes on symmetric and exterior depth and annihilator numbers

    Directory of Open Access Journals (Sweden)

    Gesa Kampf

    2008-11-01

    Full Text Available We survey and compare invariants of modules over the polynomial ring and the exterior algebra. In our considerations, we focus on the depth. The exterior analogue of depth was first introduced by Aramova, Avramov and Herzog. We state similarities between the two notion of depth and exhibit their relation in the case of squarefree modules. Work of Conca, Herzog and Hibi and Trung, respectively, shows that annihilator numbers are a meaningful generalization of depth over the polynomial ring. We introduce and study annihilator numbers over the exterior algebra. Despite some minor differences in the definition, those invariants show common behavior. In both situations a positive linear combination of the annihilator numbers can be used to bound the symmetric and exterior graded Betti numbers, respectively, from above.

  8. pbarp, pbarD, pbar sup 4 He annihilation cross sections at low energy

    CERN Document Server

    Tessaro, S; Capponi, M; Cereda, B; De Castro, S; Ferretti, A; Galli, D; Giacobbe, B; Marconi, U; Piccinini, M; Semprini-Cesari, N; Spighi, R; Vecchi, S; Vezzani, A; Vigotti, F; Villa, M; Vitale, A; Zoccoli, A; Belli, G; Corradini, M; Donzella, A; Lodi-Rizzini, E; Venturelli, L; Zenoni, A; Cicalò, C; Masoni, A; Puddu, G; Serci, S; Temnikov, P P; Usai, G L; Ableev, V G; Denisov, O Yu; Gorchakov, O E; Prakhov, S N; Rozhdestvensky, A M; Sapozhnikov, M G; Tretyak, V I; Poli, M; Gianotti, P; Guaraldo, C; Lanaro, A; Lucherini, V; Nichitiu, F; Petrascu, C; Rosca, A; Cavion, C; Gastaldi, Ugo; Lombardi, M; Vannucci, Luigi; Vedovato, G; Andrighetto, A; Morando, M; Ricci, R A; Bendiscioli, G; Filippini, V; Fontana, A; Montagna, P; Rotondi, A; Saino, A; Salvini, P; Filippi, A; Balestra, F; Botta, E; Bressani, Tullio; Bussa, M P; Busso, L; Calvo, D; Cerello, P G; Costa, S; D'Isep, F; Fava, L; Feliciello, A; Ferrero, L; Garfagnini, R; Grasso, A; Maggiora, A; Marcello, S; Mirfakhraee, N; Panzieri, D; Parena, D; Rossetto, E; Tosello, F; Zosi, G; Agnello, M; Iazzi, F; Minetti, B; Pauli, G; Tessaro, S; Santi, L

    1999-01-01

    New measurements of the pbarp annihilation cross section have been performed with the OBELIX apparatus between 37 and 70 MeV/c. From previous samples of data it was already clear that the 1/p behaviour for the annihilation cross section is drastically modified at very low momenta, due to the Coulomb interaction. However, at the lowest measured momentum (43.6 MeV/c), the annihilation cross section was unexpectedly high; this evidence suggested a more accurate investigation of this region. Furthermore, measurements of annihilation cross section have been performed with pbar impinging on D sub 2 and sup 4 He targets.

  9. 76 FR 73664 - Notice of Inventory Completion: Washington State University, Museum of Anthropology, Pullman, WA

    Science.gov (United States)

    2011-11-29

    ...: Washington State University, Museum of Anthropology, Pullman, WA AGENCY: National Park Service, Interior. ACTION: Notice. SUMMARY: The Washington State University, Museum of Anthropology (WSU) has completed an... University, Museum of Anthropology, Pullman, WA 99164-4910, telephone (509) 335-4314. SUPPLEMENTARY...

  10. 75 FR 14463 - Notice of Inventory Completion: University of Washington, Department of Anthropology, Seattle, WA

    Science.gov (United States)

    2010-03-25

    ... Washington, Department of Anthropology, Seattle, WA AGENCY: National Park Service, Interior. ACTION: Notice... University of Washington, Department of Anthropology, Seattle, WA. The human remains were removed from... University of Washington, Department of Anthropology and Burke Museum staff in consultation with...

  11. Experiment WA1 (CDHS Neutrino Experiment)

    CERN Multimedia

    CERN PhotoLab

    1977-01-01

    Experiment WA1, also known under CDHS (CERN, Dortmund, Heidelberg, Saclay; spokesman Jack Steinberger), was the first neutrino experiment on the SPS, in its West Area. Magnetized iron (with a toroidal field) forms the core of the detector. On its outside we see drift chambers and photomultipliers (detecting the light from the plastic scintillators further in). Peter Schilly is wearing a white coat. See also CERN Annual Report 1976, p.57.

  12. Weak-scale hidden sector and energy transport in fireball models of gamma-ray bursts

    International Nuclear Information System (INIS)

    Demir, Durmus A.; Mosquera Cuesta, Herman J.

    2000-12-01

    The annihilation of pairs of very weakly interacting particles in the neighborhood of gamma-ray sources is introduced here as a plausible mechanism to overcome the baryon load problem. This way we can explain how these very high energy gamma-ray bursts can be powered at the onset of very energetic events like supernovae (collapsars) explosions or coalescences of binary neutron stars. Our approach uses the weak-scale hidden sector models in which the Higgs sector of the standard model is extended to include a gauge singlet that only interacts with the Higgs particle. These particles would be produced either during the implosion of the red supergiant star core or at the aftermath of a neutron star binary merger. The whole energetics and timescales of the relativistic blast wave, the fireball, are reproduced. (author)

  13. Applications of Positron Annihilation Spectroscopy

    OpenAIRE

    Asoka-Kumar , P.; Lynn , K.

    1995-01-01

    We describe the application of Positron Annihilation Spectroscopy (PAS) to some selected technologically important systems. The method involves a nondestructive probe to detect low levels of open-volume defects. The discussion shows the application of PAS to a wide range of advanced material systems.

  14. The annihilation diagram in three-body D-meson decay

    International Nuclear Information System (INIS)

    Donoghue, J.F.; Holstein, B.R.

    1981-01-01

    We discuss some features of three-body decays of the D meson cohich are puzzling from the standpoint of the annihilation diagram. As a result, we (1) provide an upper bound on the lifetime ratio of D's, tau + sub(D)/tau 0 sub(D) smaller than 2.5 +- 3.4 and (2) argue that the puzzles are resolved, even if somewhat inelegantly, if final state interactions generate the annihilation diagram. (orig.)

  15. A NOVEL APPROACH IN THE WEAKLY INTERACTING MASSIVE PARTICLE QUEST: CROSS-CORRELATION OF GAMMA-RAY ANISOTROPIES AND COSMIC SHEAR

    International Nuclear Information System (INIS)

    Camera, Stefano; Fornasa, Mattia; Fornengo, Nicolao; Regis, Marco

    2013-01-01

    Both cosmic shear and cosmological gamma-ray emission stem from the presence of dark matter (DM) in the universe: DM structures are responsible for the bending of light in the weak-lensing regime and those same objects can emit gamma rays, either because they host astrophysical sources (active galactic nuclei or star-forming galaxies) or directly by DM annihilations (or decays, depending on the properties of the DM particle). Such gamma rays should therefore exhibit strong correlation with the cosmic shear signal. In this Letter, we compute the cross-correlation angular power spectrum of cosmic shear and gamma rays produced by the annihilation/decay of weakly interacting massive particle DM, as well as by astrophysical sources. We show that this observable provides novel information on the composition of the extragalactic gamma-ray background (EGB), since the amplitude and shape of the cross-correlation signal strongly depend on which class of sources is responsible for the gamma-ray emission. If the DM contribution to the EGB is significant (at least in a definite energy range), although compatible with current observational bounds, its strong correlation with the cosmic shear makes such signal potentially detectable by combining Fermi Large Area Telescope data with forthcoming galaxy surveys, like the Dark Energy Survey and Euclid. At the same time, the same signal would demonstrate that the weak-lensing observables are indeed due to particle DM matter and not to possible modifications of general relativity.

  16. A Novel Approach in the Weakly Interacting Massive Particle Quest: Cross-correlation of Gamma-Ray Anisotropies and Cosmic Shear

    Science.gov (United States)

    Camera, Stefano; Fornasa, Mattia; Fornengo, Nicolao; Regis, Marco

    2013-07-01

    Both cosmic shear and cosmological gamma-ray emission stem from the presence of dark matter (DM) in the universe: DM structures are responsible for the bending of light in the weak-lensing regime and those same objects can emit gamma rays, either because they host astrophysical sources (active galactic nuclei or star-forming galaxies) or directly by DM annihilations (or decays, depending on the properties of the DM particle). Such gamma rays should therefore exhibit strong correlation with the cosmic shear signal. In this Letter, we compute the cross-correlation angular power spectrum of cosmic shear and gamma rays produced by the annihilation/decay of weakly interacting massive particle DM, as well as by astrophysical sources. We show that this observable provides novel information on the composition of the extragalactic gamma-ray background (EGB), since the amplitude and shape of the cross-correlation signal strongly depend on which class of sources is responsible for the gamma-ray emission. If the DM contribution to the EGB is significant (at least in a definite energy range), although compatible with current observational bounds, its strong correlation with the cosmic shear makes such signal potentially detectable by combining Fermi Large Area Telescope data with forthcoming galaxy surveys, like the Dark Energy Survey and Euclid. At the same time, the same signal would demonstrate that the weak-lensing observables are indeed due to particle DM matter and not to possible modifications of general relativity.

  17. A NOVEL APPROACH IN THE WEAKLY INTERACTING MASSIVE PARTICLE QUEST: CROSS-CORRELATION OF GAMMA-RAY ANISOTROPIES AND COSMIC SHEAR

    Energy Technology Data Exchange (ETDEWEB)

    Camera, Stefano [CENTRA, Instituto Superior Tecnico, Universidade Tecnica de Lisboa, Lisboa (Portugal); Fornasa, Mattia [School of Physics and Astronomy, University of Nottingham, Nottingham (United Kingdom); Fornengo, Nicolao; Regis, Marco [Dipartimento di Fisica, Universita di Torino and INFN, Torino (Italy)

    2013-07-01

    Both cosmic shear and cosmological gamma-ray emission stem from the presence of dark matter (DM) in the universe: DM structures are responsible for the bending of light in the weak-lensing regime and those same objects can emit gamma rays, either because they host astrophysical sources (active galactic nuclei or star-forming galaxies) or directly by DM annihilations (or decays, depending on the properties of the DM particle). Such gamma rays should therefore exhibit strong correlation with the cosmic shear signal. In this Letter, we compute the cross-correlation angular power spectrum of cosmic shear and gamma rays produced by the annihilation/decay of weakly interacting massive particle DM, as well as by astrophysical sources. We show that this observable provides novel information on the composition of the extragalactic gamma-ray background (EGB), since the amplitude and shape of the cross-correlation signal strongly depend on which class of sources is responsible for the gamma-ray emission. If the DM contribution to the EGB is significant (at least in a definite energy range), although compatible with current observational bounds, its strong correlation with the cosmic shear makes such signal potentially detectable by combining Fermi Large Area Telescope data with forthcoming galaxy surveys, like the Dark Energy Survey and Euclid. At the same time, the same signal would demonstrate that the weak-lensing observables are indeed due to particle DM matter and not to possible modifications of general relativity.

  18. 78 FR 44594 - Notice of Inventory Completion: Washington State Parks and Recreation Commission, Olympia, WA

    Science.gov (United States)

    2013-07-24

    ..., 2013. ADDRESSES: Alicia Woods, Washington State Parks and Recreation Commission, PO Box 42650, Olympia, WA 98504-2650, telephone (360) 902- 0939, email Alicia[email protected] . SUPPLEMENTARY INFORMATION... to Alicia Woods, Washington State Parks and Recreation Commission, PO Box 42650, Olympia, WA 98504...

  19. SiO 2/SiC interface proved by positron annihilation

    Science.gov (United States)

    Maekawa, M.; Kawasuso, A.; Yoshikawa, M.; Itoh, H.

    2003-06-01

    We have studied positron annihilation in a Silicon carbide (SiC)-metal/oxide/semiconductor (MOS) structure using a monoenergetic positron beam. The Doppler broadening of annihilation quanta were measured as functions of the incident positron energy and the gate bias. Applying negative gate bias, significant increases in S-parameters were observed. This indicates the migration of implanted positrons towards SiO 2/SiC interface and annihilation at open-volume type defects. The behavior of S-parameters depending on the bias voltage was well correlated with the capacitance-voltage ( C- V) characteristics. We observed higher S-parameters and the interfacial trap density in MOS structures fabricated using the dry oxidation method as compared to those by pyrogenic oxidation method.

  20. SiO2/SiC interface proved by positron annihilation

    International Nuclear Information System (INIS)

    Maekawa, M.; Kawasuso, A.; Yoshikawa, M.; Itoh, H.

    2003-01-01

    We have studied positron annihilation in a Silicon carbide (SiC)-metal/oxide/semiconductor (MOS) structure using a monoenergetic positron beam. The Doppler broadening of annihilation quanta were measured as functions of the incident positron energy and the gate bias. Applying negative gate bias, significant increases in S-parameters were observed. This indicates the migration of implanted positrons towards SiO 2 /SiC interface and annihilation at open-volume type defects. The behavior of S-parameters depending on the bias voltage was well correlated with the capacitance-voltage (C-V) characteristics. We observed higher S-parameters and the interfacial trap density in MOS structures fabricated using the dry oxidation method as compared to those by pyrogenic oxidation method

  1. Study of high-k gate dielectrics by means of positron annihilation

    International Nuclear Information System (INIS)

    Uedono, A.; Naito, T.; Otsuka, T.; Ito, K.; Shiraishi, K.; Yamabe, K.; Miyazaki, S.; Watanabe, H.; Umezawa, N.; Hamid, A.; Chikyow, T.; Ohdaira, T.; Suzuki, R.; Ishibashi, S.; Inumiya, S.; Kamiyama, S.; Akasaka, Y.; Nara, Y.; Yamada, K.

    2007-01-01

    High-dielectric constant (high-k) gate materials, such as HfSiO x and HfAlO x , fabricated by atomic-layer-deposition techniques were characterized using monoenergetic positron beams. Measurements of the Doppler broadening spectra of annihilation radiation and the lifetime spectra of positrons indicated that positrons annihilated from the trapped state by open volumes that exist intrinsically in amorphous structures of the films. The size distributions of the open volumes and the local atomic configurations around such volumes can be discussed using positron annihilation parameters, and they were found to correlate with the electrical properties of the films. We confirmed that the positron annihilation is useful technique to characterize the matrix structure of amorphous high-k materials, and can be used to determine process parameters for the fabrication of high-k gate dielectrics. (copyright 2007 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  2. Radiative corrections to neutralino annihilation. Recent developments

    International Nuclear Information System (INIS)

    Herrmann, Bjoern

    2010-11-01

    Evaluating the relic density of dark matter is an interesting possibility to constrain the parameter space of new physics models. However, this calculation is affected by several sources of uncertainty. On the particle physics side, considerable progress has been made in the recent years concerning the calculation of the annihilation cross-section of dark matter, which is needed in this context. In particular, within the Minimal Supersymmetric Standard Model, the theoretical uncertainty has been reduced through the calculation of loop corrections. The present contribution gives an overview over the achievements that have been made in QCD corrections to neutralino pair annihilation. The numerical impact is illustrated for a few examples. (orig.)

  3. Depth-dependent positron annihilation in different polymers

    Energy Technology Data Exchange (ETDEWEB)

    Yang, J.; Zhang, P.; Cheng, G.D.; Li, D.X.; Wu, H.B.; Li, Z.X.; Cao, X.Z. [Key Laboratory of Nuclear Analysis Techniques, Institute of High Energy Physics, Chinese Academy of Sciences, No. 19 Yuquan Lu, Beijing 100049 (China); Jia, Q.J. [Beijing Synchrotron Radiation Facility, Institute of High Energy Physics, Chinese Academy of Sciences, No. 19 Yuquan Lu, Beijing 100049 (China); Yu, R.S. [Key Laboratory of Nuclear Analysis Techniques, Institute of High Energy Physics, Chinese Academy of Sciences, No. 19 Yuquan Lu, Beijing 100049 (China); Wang, B.Y., E-mail: wangboy@ihep.ac.cn [Key Laboratory of Nuclear Analysis Techniques, Institute of High Energy Physics, Chinese Academy of Sciences, No. 19 Yuquan Lu, Beijing 100049 (China)

    2013-09-01

    Depth-dependent positron annihilation Doppler broadening measurements were conducted for polymers with different chemical compositions. Variations of the S parameter with respect to incident positron energy were observed. For pure hydrocarbons PP, HDPE and oxygen-containing polymer PC, S parameter rises with increasing positron implantation depth. While for PI and fluoropolymers like PTFE, ETFE and PVF, S parameter decreases with higher positron energy. For chlorine-containing polymer PVDC, S parameter remains nearly constant at all incident positron energies. It is suggested that these three variation trends are resulted from a competitive effect between the depth-dependent positronium formation and the influence of highly electronegative atoms on positron annihilation characteristics.

  4. Peculiarities occurrence and microstrip gas chambers studied through experiment WA97; La production d`etrangete et les chambres gazeuses a micropistes dans le cadre de l`experience WA97

    Energy Technology Data Exchange (ETDEWEB)

    Kachelhoffer, T.

    1995-04-01

    This paper presents the studies on development of a Monte-Carlo type generator used for inclusive production of odd baryons and antibaryons through proton- proton and proton- nucleus collisions. Experiment WA97 consisted in designing simulation software for MSGCs (Micro-strips Gas Chambers) as well as the redefining of particle paths with the help of these chambers. This work made it possible to design the MSGC detector for experiment WA97. (TEC). 71 refs., 88 figs.

  5. Isospin effects in anti p3He annihilation at rest

    International Nuclear Information System (INIS)

    Balestra, F.; Barbieri, R.; Batusov, Yu.A.; Bendiscioli, G.; Breivik, F.O.; Bossolasco, S.; Bussa, M.P.; Busso, L.; Falomkin, I.V.; Ferrero, L.; Guaraldo, C.; Haatuft, A.; Halsteinslid, A.; Jacobsen, T.; Lodi Rizzini, E.; Maggiora, A.; Myklebost, K.; Olsen, J.M.; Panzieri, D.; Piragino, G.; Pontecorvo, G.B.; Rozhdestvensky, A.M.; Rotondi, A.; Salvini, P.; Sapozhnikov, M.G.; Soerensen, S.O.; Tosello, F.; Tretyak, V.I.; Venaglioni, A.; Zenoni, A.

    1989-01-01

    The analysis of anti p 3 He annihilation events at rest (from the PS 179 experiment at LEAR) gives the value 0.467±0.035 for the ratio between the annihilation cross sections on n and on p. This low value indicates a strong isospin dependence of the anti NN amplitude in P wave. (orig.)

  6. Simplified models of dark matter with a long-lived co-annihilation partner

    Science.gov (United States)

    Khoze, Valentin V.; Plascencia, Alexis D.; Sakurai, Kazuki

    2017-06-01

    We introduce a new set of simplified models to address the effects of 3-point interactions between the dark matter particle, its dark co-annihilation partner, and the Standard Model degree of freedom, which we take to be the tau lepton. The contributions from dark matter co-annihilation channels are highly relevant for a determination of the correct relic abundance. We investigate these effects as well as the discovery potential for dark matter co-annihilation partners at the LHC. A small mass splitting between the dark matter and its partner is preferred by the co-annihilation mechanism and suggests that the co-annihilation partners may be long-lived (stable or meta-stable) at collider scales. It is argued that such long-lived electrically charged particles can be looked for at the LHC in searches of anomalous charged tracks. This approach and the underlying models provide an alternative/complementarity to the mono-jet and multi-jet based dark matter searches widely used in the context of simplified models with s-channel mediators. We consider four types of simplified models with different particle spins and coupling structures. Some of these models are manifestly gauge invariant and renormalizable, others would ultimately require a UV completion. These can be realised in terms of supersymmetric models in the neutralino-stau co-annihilation regime, as well as models with extra dimensions or composite models.

  7. Bremsstrahlung Based Positron Annihilation Spectroscopy for Material Defect Analysis

    International Nuclear Information System (INIS)

    Selim, F.A.; Wells, D.P.; Harmon, F.; Kwofie, J.; Lancaster, G.; Jones, J.L.

    2003-01-01

    The Idaho Accelerator Center (IAC) has developed new techniques for Positron Annihilation Spectroscopy (PAS) using highly penetrating γ-rays to create positrons inside the material via pair production. γ-Ray induced positron annihilation spectroscopy can provide highly penetrating probes for material characterization and defect analysis. Bremsstrahlung beams from small, pulsed electron Linacs (6 MeV) have been used to bombard the materials to generate positrons, which annihilate with the material electrons emitting 511 keV radiation. We have also synchronized bremsstrahlung pulses with laser irradiation pulses to study dynamic structural changes in material. In addition, we have developed another method using (p,γ) reactions from a 2 MeV proton beam, which induce coincident γ-rays to perform positron life-time spectroscopy. We have showed the feasibility of extending PAS into thick samples and a wide variety of materials and industrial applications

  8. Fractal studies on the positron annihilation in metals

    International Nuclear Information System (INIS)

    Lung, C.W.

    1994-06-01

    Traditionally, the Euclidean lines, circles and spheres have served as the basis of the intuitive understanding of the geometry of nature. Recently, the concept of fractals has caught the imagination of scientists in many fields. This paper is to continue our previous work on position annihilation near fractal surfaces to demonstrate that the concept of fractals provides a powerful tool for understanding the structure and properties of defects and rough surfaces in relation to positron annihilation studies. Some problems on Berry geometrical phase have also been discussed. (author). 15 refs, fig., 1 tab

  9. Modeling of positron states and annihilation in solids

    International Nuclear Information System (INIS)

    Puska, M.J.

    2003-01-01

    Theoretical models and computational aspects to describe positron states and to predict positron annihilation characteristics in solids are discussed. The comparison of the calculated positron lifetimes, core annihilation lineshapes, and two-dimensional angular correlation maps with experimental results are used in identifying the structure (including the chemical composition) of vacancy-type defects and their development e.g. during thermal annealing. The basis of the modeling is the two-component density-functional theory. The ensuing approximations and the state-of-the-art electronic-structure computation methods enable practical schemes with a quantitative predicting power. (author)

  10. Relativistic hydrodynamics, heavy ion reactions and antiproton annihilation

    International Nuclear Information System (INIS)

    Strottman, D.

    1985-01-01

    The application of relativistic hydrodynamics to relativistic heavy ions and antiproton annihilation is summarized. Conditions for validity of hydrodynamics are presented. Theoretical results for inclusive particle spectra, pion production and flow analysis are given for medium energy heavy ions. The two-fluid model is introduced and results presented for reactions from 800 MeV per nucleon to 15 GeV on 15 GeV per nucleon. Temperatures and densities attained in antiproton annihilation are given. Finally, signals which might indicate the presence of a quark-gluon plasma are briefly surveyed

  11. Oxygen vacancies in oxides studied by annihilation of mono-energetic positrons

    Energy Technology Data Exchange (ETDEWEB)

    Hugenschmidt, Christoph; Pikart, Philip [ZWE FRM II, Technische Universitaet Muenchen, Lichtenbergstrasse 1, 85747 Garching (Germany); Physik-Department E21, Technische Universitaet Muenchen, James-Franck-Strasse, 85748 Garching (Germany); Schreckenbach, Klaus [Physik-Department E21, Technische Universitaet Muenchen, James-Franck-Strasse, 85748 Garching (Germany)

    2009-07-01

    Oxygen vacancies play a fundamental role for the material properties of various oxides, e.g. charge carrier density in high-Tc superconductors, magnetic properties of diluted magnetic semiconductors or paramagnetic properties of SiO{sub 2}. In this study, open volume defects in (metal) oxides are investigated by Doppler-broadening spectroscopy (DBS) of the positron annihilation. More detailed information about the chemical surrounding at the positron annihilation site is gained by additional coincident DBS experiments, where a signature of positrons annihilating with electrons from oxygen is observed. The mono-energetic positron beam at NEPOMUC was used which allows depth dependent measurements, and hence the investigation of thin oxide layers. Recent results for metallic oxides such as ZnO are presented and compared with various non-metallic oxides such as amorphous and crystalline SiO{sub 2}, oxygen terminated Si-surface, and ice. The role of neutral and charged oxygen vacancies and the application of the positron annihilation technique to study oxygen vacancies will be discussed.

  12. Radiative annihilation and isospin mixing in protonium

    International Nuclear Information System (INIS)

    Gutsche, T.; Faessler, A.; Vinh Mau, R.

    1999-01-01

    In recent experiments by the Crystal Barrel collaboration at CERN, a systematic study of reactions of the type p-bar p → γX where X γ,π 0 ,η , ω and η' were performed and the branching ratios are measured. Thereby, a sensitive test for different NN interaction models in the p-bar p atom can be performed. We evaluate the branching ratio for radiative proton-antiproton annihilation in the framework of the constituent quark model. In setting up the annihilation mechanism we adopt a two-step process where the p-bar p system first annihilates into two mesons π 0 ρ, π 0 ω, ωω, ρ 0 ρ 0 , ωρ 0 , ηρ, ηω and where the produced vector meson converts into a photon analogous to the vector dominance model (VDM). Both steps can be derived from the underlying quark mechanism. Amplitudes for the strong annihilation of p-bar p into two mesons are calculated in the framework of the so-called A 2 quark model. Radiative decay channels, in contrast to nonstrange mesonic decay channels, couple to the isospin I = 0 and I = 1 components of the atomic p-bar p initial states. The resulting transition amplitudes interfere in the predictions for the branching ratios. Combining experimental inputs with the outlined theoretical derivation we are able to extract the interference terms from the data, which are sizable and depend strongly on the initial atomic state considered. The interference terms are used to determine the isospin mixing effects in the p-bar p atomic wave functions. Radiative decays offer a unique window to study isospin mixing effects in the p-bar p system, which are strongly dependent on the NN-bar initial state interaction model. (authors)

  13. Doppler Broadening of In-Flight Positron Annihilation Radiation due to Electron Momentum

    International Nuclear Information System (INIS)

    Hunt, A. W.; Cassidy, D. B.; Sterne, P. A.; Cowan, T. E.; Howell, R. H.; Lynn, K. G.; Golevchenko, J. A.

    2001-01-01

    We report the first observation of electron momentum contributions to the Doppler broadening of radiation produced by in-flight two-photon annihilation in solids. In these experiments an approximately 2.5 MeV positron beam impinged on thin polyethylene, aluminum, and gold targets. Since energetic positrons easily penetrate the nuclear Coulomb potential and do not cause a strong charge polarization, the experimental annihilation line shapes agree well with calculations based on a simple independent-particle model. Moreover, annihilations with the deepest core electrons are greatly enhanced

  14. Search for Dark Matter Annihilation in Galaxy Groups.

    Science.gov (United States)

    Lisanti, Mariangela; Mishra-Sharma, Siddharth; Rodd, Nicholas L; Safdi, Benjamin R

    2018-03-09

    We use 413 weeks of publicly available Fermi Pass 8 gamma-ray data combined with recently developed galaxy group catalogs to search for evidence of dark matter annihilation in extragalactic halos. In our study, we use luminosity-based mass estimates and mass-to-concentration relations to infer the J factors and associated uncertainties for hundreds of galaxy groups within a redshift range z≲0.03. We employ a conservative substructure boost factor model, which only enhances the sensitivity by an O(1) factor. No significant evidence for dark matter annihilation is found, and we exclude thermal relic cross sections for dark matter masses below ∼30  GeV to 95% confidence in the bb[over ¯] annihilation channel. These bounds are comparable to those from Milky Way dwarf spheroidal satellite galaxies. The results of our analysis increase the tension but do not rule out the dark matter interpretation of the Galactic Center excess. We provide a catalog of the galaxy groups used in this study and their inferred properties, which can be broadly applied to searches for extragalactic dark matter.

  15. Search for Dark Matter Annihilation in Galaxy Groups

    Science.gov (United States)

    Lisanti, Mariangela; Mishra-Sharma, Siddharth; Rodd, Nicholas L.; Safdi, Benjamin R.

    2018-03-01

    We use 413 weeks of publicly available Fermi Pass 8 gamma-ray data combined with recently developed galaxy group catalogs to search for evidence of dark matter annihilation in extragalactic halos. In our study, we use luminosity-based mass estimates and mass-to-concentration relations to infer the J factors and associated uncertainties for hundreds of galaxy groups within a redshift range z ≲0.03 . We employ a conservative substructure boost factor model, which only enhances the sensitivity by an O (1 ) factor. No significant evidence for dark matter annihilation is found, and we exclude thermal relic cross sections for dark matter masses below ˜30 GeV to 95% confidence in the b b ¯ annihilation channel. These bounds are comparable to those from Milky Way dwarf spheroidal satellite galaxies. The results of our analysis increase the tension but do not rule out the dark matter interpretation of the Galactic Center excess. We provide a catalog of the galaxy groups used in this study and their inferred properties, which can be broadly applied to searches for extragalactic dark matter.

  16. Positron-Electron Annihilation Process in (2,2)-Difluoropropane Molecule

    Science.gov (United States)

    Liu, Yang; Ma, Xiao-Guang; Zhu, Ying-Hao

    2016-04-01

    The positron-electron annihilation process in (2,2)-difluoropropane molecule and the corresponding gamma-ray spectra are studied by quantum chemistry method. The positrophilic electrons in (2,2)-difluoropropane molecule are found for the first time. The theoretical predictions show that the outermost 2s electrons of fluoride atoms play an important role in positron-electron annihilation process of (2,2)-difiuoropropane. In the present scheme, the correlation coefficient between the theoretical gamma-ray spectra and the experiments can be 99%. The present study gives an alternative annihilation model for positron-electron pair in larger molecules. Supported by the National Natural Science Foundation of China under Grant No. 11347011 and the Natural Science Foundation Project of Shandong Province under Grant No. ZR2011AM010 and 2014 Technology Innovation Fund of Ludong University under Grant Nos. 1d151007 and ld15l016

  17. High nuclear temperatures by antimatter-matter annihilation

    International Nuclear Information System (INIS)

    Gibbs, W.R.; Strottman, D.

    1985-01-01

    It is suggested that the quark-gluon phase be created through the use of antiproton or antideuteron beams. The first advantage to this method, using higher energy antiprotons than 1.5 GeV/c, is that the higher momenta antiprotons penetrate more deeply so that mesons produced are more nearly contained within the nucleus. Another advantage is that the annihilation products are very forward-peaked and tend to form a beam of mesons so that the energy density does not disperse very rapidly. Calculations were performed using the intranuclear cascade to try to follow the process of annihilation in some detail. The intranuclear cascade type calculation method is compared to the hydrodynamic approach. 8 refs., 8 figs

  18. Increased Elemental Specificity of Positron Annihilation Spectra

    International Nuclear Information System (INIS)

    Asoka-Kumar, P.; Alatalo, M.; Ghosh, V.J.; Kruseman, A.C.; Nielsen, B.; Lynn, K.G.

    1996-01-01

    Positron annihilation spectroscopy (PAS) is a sensitive probe for studying the electronic structure of defects in solids. We show that the high-momentum part of the Doppler-broadened annihilation spectra can be used to distinguish different elements. This is achieved by using a new two-detector coincidence system to examine the line shape variations originating from high-momentum core electrons. Because the core electrons retain their atomic character even when atoms form a solid, these results can be directly compared to simple theoretical predictions. The new approach adds increased elemental specificity to the PAS technique, and is useful in studying the elemental variations around a defect site. copyright 1996 The American Physical Society

  19. Hybrid mesons (Q anti Qg) in N anti N annihilation

    International Nuclear Information System (INIS)

    Dover, C.B.; Gutsche, T.; Faessler, A.

    1993-09-01

    N anti N annihilation reactions provide exciting possibilities to study mesonic resonances beyond the usual Q anti Q spectrum. Particularly the search for Q anti Qg mesons containing an explicit dynamical excitation of the gluon field is not promising, since hybrids are predicted to display unique features: exotic quantum numbers (J πC ) and dynamical selection rules for their decay modes. The authors have investigated the possibility of producing hybrids from p anti p atomic states in reactions of the type N anti N(L= 0,1) → π + Q anti Qg. Production rates for hybrid mesons are found to display a strong dependence on the quantum numbers and kinematical factors associated with the transition. The dependence on the orbital angular momentum L of the p anti p atomic state, accessible in p anti p annihilation at rest, would provide a striking signature for the production of hybrids. In estimating branching ratios for the formation of Q anti Qg hybrid mesons in N anti N annihilation reactions at rest, the authors have employed a microscopic model with constituent quarks and gluons in analogy to the annihilation model for the production of Q anti Q mesons

  20. Positron annihilation spectroscopy in condensed matter

    International Nuclear Information System (INIS)

    Brauer, G.

    1982-09-01

    The topic of positron annihilation spectroscopy (PAS) is the investigation of all aspects connected with the annihilation of slow positrons. This work deals with the application of PAS to different problems of materials science. The first chapter is an introduction to fundamental aspects of positron annihilation, as far as they are important to the different experimental techniques of PAS. Chapter 2 is concerned with the information obtainable by PAS. The three main experimental techniques of PAS (2γ-angular correlation, positron lifetime and Doppler broadening) are explained and problems in the application of these methods are discussed. Chapter 3 contains experimental results. According to the different fields of application it was subgrouped into: 1. Investigations of crystalline solids. Detection of structural defects in Cu, estimation of defect concentrations, study of the sintering of Cu powders as well as lattice defects in V 3 Si. 2. Chemical investigations. Structure of mixed solvents, selective solvation of mixed solvents by electrolytes as well as the micellization of sodium dodecylsulphate in aqueous solutions. 3. Investigations of glasses. Influence of heat treatment and production technology on the preorder of X-amorphous silica glass as well as preliminary measurements of pyrocerams. 4. Investigations of metallic glasses. Demonstration of the influence of production technology on parameters measurable by PAS. Chapter 4 contains a summary as well as an outlook of further applications of PAS to surface physics, medicine, biology and astrophysics. (author)

  1. Beam current transformer (BCT) for experiment WA1/2

    CERN Multimedia

    CERN PhotoLab

    1978-01-01

    In experiment WA1/2, a 400 GeV proton beam from the SPS was directed at a target, downstream of which a hadron line selected, in several narrow momentum bands, a beam of either pi+ and K+ or pi- and K-. These neutrino-parent particles, before entering a 292 m long decay tunnel, passed through a set of 2 BCTs of a design seen here. They measured the hadron intensity (10^10 to 10^11 particles/pulse) with a precision of the order of 1%. There were 2 of them, for enhanced precision and confidence. After the discovery of neutral currents in the Gargamelle-experiment, WA1/2 was the first follow-up, high-precision experiment (Z.Phys.C35, 443-452, 1987 and Z.Phys.C45, 361-379, 1990). See also 7706516X.

  2. Gigafida and slWaC: topic comparison

    Directory of Open Access Journals (Sweden)

    Nataša Logar Berginc

    2013-05-01

    Full Text Available In the article, the following two issues are analyzed: (a incorporation of texts from the Internet into existing reference corpora and comparison with the existence of web corpora, and (b the latest two corpora of Slovenian language texts: the Gigafida corpus consisting mainly of printed texts and to a lesser extent also web texts, and the slWaC corpus which is entirely compiled from web texts. First, similarities and differences between the two corpora are identified using the topic modelling method, and then the same method is applied to the individual taxonomic categories of the Gigafida corpus. The first part of the analysis showed that the work of reference corpus compilers is currently still incoherent with regard to the incorporation of Internet texts into corpora which should reveal the overall picture of a certain language. In case compilers decide to incorporate web texts, the range of included genres is generally broad. The second part of the analysis showed a significant thematic variation between the Gigafida and slWaC corpora, and pointed out the most typical themes covered by each of the six Gigafida corpus parts.

  3. Glass transition and relaxation processes of polymers studied by positron annihilation

    Energy Technology Data Exchange (ETDEWEB)

    Uedono, Akira; Tanigawa, Shoichiro [Tsukuba Univ., Ibaraki (Japan). Inst. of Materials Science

    1996-10-01

    The glass transition and relaxation processes of polymers were studied by the positron annihilation technique. A positron implanted into polymers might annihilate from positronium (Ps) states in open spaces. Ps is a bound state between a positron and an electron, and its nonrelativistic quantum mechanics is practically identical to that of a hydrogen atom. The lifetime of Ps can be associated with the size of the open spaces, and the formation probability of Ps provides information of motions of molecules. Since the glass transition or relaxation processes affect behavior of open spaces, one can study these phenomena through the detection of the open spaces using the positron annihilation technique. In the present paper, we report studies of the glass transition and relaxation processes in polyethylene, polypropylene, and polystyrene by measurements of lifetime spectra of positrons and those of Doppler broadening profiles of the annihilation radiation. For these specimens, by measurements of the lifetime of Ps, {tau}{sub 3}, as a function of temperature, the glass transition temperature, T{sub g}, was determined as an onset temperature of the increase in the temperature coefficient of {tau}{sub 3}. Below T{sub g}, local motions of molecules were detected by measurements of the formation probability of Ps. The positron annihilation as a tool for the characterization of polymers was discussed. (author). 51 refs.

  4. Real-time Detection of Antihydrogen Annihilations and Applications to Spectroscopy

    Directory of Open Access Journals (Sweden)

    Stracka Simone

    2014-04-01

    Full Text Available A detection scheme based on real-time measurement of antihydrogen annihilations during radiation injection is presented, which allows an efficient use of the trapped atoms for laser and microwave spectroscopy. The application of real-time detection of H¯$\\bar H$ annihilations to microwave spectroscopy, which yielded the first evidence of microwave induced spin-flip transitions in trapped antihydrogen [1], is reported.

  5. Positron Annihilation Spectroscopy as a Novel Interfacial Probe for Thin Polymeric Films and Nano-Composites

    Science.gov (United States)

    Awad, Somia; Chen, Hongmin; Maina, Grace; Lee, L. James; Gu, Xiaohong; Jean, Y. C.

    2010-03-01

    Positron annihilation spectroscopy (PAS) has been developed as a novel probe to characterize the sub-nanometer defect, free volume, profile from the surface, interfaces, and to the bulk in polymeric materials when a variable mono-energy slow positron beam is used. Free-volume hole sizes, fractions, and distributions are measurable as a function of depth at the high precision. PAS has been successfully used to study the interfacial properties of polymeric nanocomposites at different chemical bonding. In nano-scale thin polymeric films, such as in PS/SiO2, and PU/ZnO, significant variations of Tg as a function of depth and of wt% oxide are observed. Variations of Tg are dependent on strong or weak interactions between polymers and nano-scale oxides surfaces.

  6. Characterization of advanced semiconductor materials by positron annihilation

    International Nuclear Information System (INIS)

    Uedono, Akira; Suzuki, Ryoichi; Ohdaira, Toshiyuki; Ishibashi, Shoji

    2005-01-01

    Positron annihilation is an established technique for investigating vacancy-type defects near surfaces or interfaces. Using this technique, one can identify defect species in a nondestructive manner. Because there is no restriction of sample conductivity or temperature, this technique can be applied to a various materials, such as semiconductors, metals, metal oxides, and polymers. The positron annihilation has been applied to the studies of Si-technology related materials, which show that it can provide useful information for the development of semiconductor devices. In this article, we report the results obtained for electroplated Cu, strained Si and high-k materials. (author)

  7. Microemulsion systems studied by positron annihilation techniques. II

    International Nuclear Information System (INIS)

    Lopez, R.; Olea, O.; Fucugauchi, L.A.

    1982-01-01

    The positron annihilation technique was applied to assess the effect of the double bond of the surfactant molecule on the microemulsion formation mechanism by replacing sodium stearate by sodium oleate in surfactant-cosurfactant-solvent-water systems. Diameters of microemulsions were measured by dynamic laser light scattering, and the obtained values concur with the present positron annihilation data. Structures of these microemulsions have been assessed by considering the available conformation and shapes of the surfactant-cosurfactant-solvent-assemblies. Volumes of the same aggregates have been calculated by taking into consideration the packing constraint imposed upon kink formation. (Auth.)

  8. Positron annihilation near fractal surfaces

    International Nuclear Information System (INIS)

    Lung, C.W.; Deng, K.M.; Xiong, L.Y.

    1991-07-01

    A model for positron annihilation in the sub-surface region near a fractal surface is proposed. It is found that the power law relationship between the mean positron implantation depth and incident positron energy can be used to measure the fractal dimension of the fractal surface in materials. (author). 10 refs, 2 figs

  9. A Study of the Vacancy-Impurity Interaction in Dilute Nickel Alloys by Core Electron Annihilation

    Science.gov (United States)

    Arbuzov, V. L.; Danilov, S. E.; Druzhkov, A. P.

    1997-08-01

    It is shown that the angular correlation of annihilation radiation can be used to identify vacancy-impurity complexes in dilute alloys. Annihilation of trapped positrons with core electrons bears information about the chemical environment of a vacancy defect. The method is especially effective for d-matrices doped with sp-impurities since annihilation parameters of positrons with d- and sp-shell electrons differ considerably. The potentialities of the method of core-electron annihilation of positrons are demonstrated taking electron-irradiated dilute Ni-P and Ni-Si alloys as an example. It is shown that the interaction between the vacancies, which migrate at the III stage of annealing, and P atoms in Ni-P causes a considerable change in the annihilation parameters of positrons with core electrons compared to pure Ni. In Ni-Si alloys the annihilation parameters of trapped positrons with core electrons do not differ from those in Ni. This fact is an evidence that Si atoms do not interact with vacancies in Ni.

  10. Raimo Pullat kohtus Lech Wałesaga / Harda Roosna

    Index Scriptorium Estoniae

    Roosna, Harda, 1956-

    2014-01-01

    Tallinna Ülikooli emeriitprofessor Raimo Pullat kohtus Poola ekspresidendi Lech Wałesaga Gdanski tehnikakõrgkooli 110. aastapäeva pidustustel, kuhu ta oli kutsutud kui peatselt valmiva teose "Värav tulevikku. Ganzigi Tehnikakõrgkool Eesti haritlaskonna kujunemisloos 1904-1939" autor

  11. Positron annihilation in germanium in thermal equilibrium at high temperature

    Energy Technology Data Exchange (ETDEWEB)

    Uedono, Akira; Moriya, Tsuyoshi; Komuro, Naoyuki; Tanigawa, Shoichiro [Tsukuba Univ., Ibaraki (Japan). Inst. of Materials Science; Kawano, Takao; Ikari, Atsushi

    1996-09-01

    Annihilation characteristics of positrons in Ge in thermal equilibrium at high temperature were studied using a monoenergetic positron beam. Precise measurements of Doppler broadening profiles of annihilation radiation were performed in the temperature range between 300 K and 1211 K. The line shape parameters of Doppler broadening profiles were found to be almost constant at 300-600 K. The changes in these parameters were observed to start above 600 K. This was attributed to both the decrease in the fraction of positrons annihilating with core electrons and the lowering of the crystal symmetry around the region detected by positron-electron pairs. This suggests that behaviors of positrons are dominated by some form of positron-lattice coupling in Ge at high temperatures. The temperature dependence of the diffusion length of positrons was also discussed. (author)

  12. Members of the WA9 team celebrate

    CERN Multimedia

    CERN PhotoLab

    1976-01-01

    WA9 was an experiment set up by the Clermont Ferrand-Leningrad-Lyon-Uppsala Collaboration to study with high precision elastic scattering in the Coulomb interference region. Here: A.A. Vorobyov, M. Querrou, A.P. Kashchuk, I.I. Tkach, J.P. Martin, T. Ekelöf, G.A. Korolev, (?), V.A. Schegelsky, A.S. Denisov, S. Kullander, M. Chemarin, P. Grafström, S. Maury, E. Hagberg

  13. Antiproton annihilation in very low-energy antihydrogen scattering by simple atoms and molecules

    International Nuclear Information System (INIS)

    Armour, E.A.G.; Gregory, M.R.; Liu, Y.

    2006-01-01

    The aim of experimentalists currently working on the preparation of antihydrogen is to trap it at very low temperatures so that its properties can be studied. Of concern to experimentalists are processes that lead to a loss of antihydrogen through annihilation. The dominant annihilation process that leads to the loss of antihydrogen is the annihilation of the antiproton with nuclei through the strong interaction. A recent scattering calculation of antihydrogen with hydrogen at very low energy, using the complex strong interaction potential of Kohno and Weise, has found an average annihilation cross-section of 0.13E -1/2 a 0 -2 , where E is the energy of relative motion. The antihydrogen-helium system is of particular interest to experimentalists as helium may be present as an impurity in the trap. Also there is interest in the possibility of using it to cool antihydrogen. We present a treatment of antihydrogen scattering with helium at very low temperatures. The annihilation cross-sections obtained are much larger than antihydrogen-hydrogen scattering cross-section, making it very unlikely that helium can be used to cool antihydrogen

  14. Probing dark matter annihilation in the Galaxy with antiprotons and gamma rays

    Energy Technology Data Exchange (ETDEWEB)

    Cuoco, Alessandro; Heisig, Jan; Korsmeier, Michael; Krämer, Michael, E-mail: cuoco@physik.rwth-aachen.de, E-mail: heisig@physik.rwth-aachen.de, E-mail: korsmeier@physik.rwth-aachen.de, E-mail: mkraemer@physik.rwth-aachen.de [Institute for Theoretical Particle Physics and Cosmology, RWTH Aachen University, 52056 Aachen (Germany)

    2017-10-01

    A possible hint of dark matter annihilation has been found in Cuoco, Korsmeier and Krämer (2017) from an analysis of recent cosmic-ray antiproton data from AMS-02 and taking into account cosmic-ray propagation uncertainties by fitting at the same time dark matter and propagation parameters. Here, we extend this analysis to a wider class of annihilation channels. We find consistent hints of a dark matter signal with an annihilation cross-section close to the thermal value and with masses in range between 40 and 130 GeV depending on the annihilation channel. Furthermore, we investigate in how far the possible signal is compatible with the Galactic center gamma-ray excess and recent observation of dwarf satellite galaxies by performing a joint global fit including uncertainties in the dark matter density profile. As an example, we interpret our results in the framework of the Higgs portal model.

  15. Annihilation gamma ray background characterization and rejection for a positron camera

    International Nuclear Information System (INIS)

    Levin, C.S.; Tornai, M.P.; MacDonald, L.R.

    1996-01-01

    We have developed a miniature (1.2 cm 2 ) beta-ray camera prototype to assist a surgeon in locating and removing the margins of a resected tumor. When imaging positron emitting radiopharmaceuticals, annihilation gamma ray interactions in the detector can mimic those of the betas. The extent of the background contamination depends on the detector, geometry and tumor specificity of the radiopharmaceutical. We have characterized the effects that annihilation gamma rays have on positron imaging with the camera. We studied beta and gamma ray detection rates and imaging using small positron or electron sources directly exposed to the detector to simulate hot tumor remnants and a cylinder filled with 18 F to simulate annihilation background from the brain. For various ratios of phantom brain/tumor activity, a annihilation gamma rate of 1.8 cts/sec/gCi was measured in the CaF 2 (Eu) detector. We present two gamma-ray background rejection schemes that use a β-γ coincidence. Results show that the coincidence methods works with ∼99% gamma ray rejection efficiency

  16. Heating of galactic gas by dark matter annihilation in ultracompact minihalos

    Energy Technology Data Exchange (ETDEWEB)

    Clark, Hamish A.; Iwanus, Nikolas; Lewis, Geraint F. [Sydney Institute for Astronomy, School of Physics A28, The University of Sydney, NSW 2006 (Australia); Elahi, Pascal J. [International Centre for Radio Astronomy Research, University of Western Australia, 35 Stirling Highway, Crawley, WA 6009 (Australia); Scott, Pat, E-mail: hamish.clark@sydney.edu.au, E-mail: nikolas.iwanus@sydney.edu.au, E-mail: pascal.elahi@uwa.edu.au, E-mail: geraint.lewis@sydney.edu.au, E-mail: p.scott@imperial.ac.uk [Department of Physics, Imperial College London, Blackett Laboratory, Prince Consort Road, London SW7 2AZ (United Kingdom)

    2017-05-01

    The existence of substructure in halos of annihilating dark matter would be expected to substantially boost the rate at which annihilation occurs. Ultracompact minihalos of dark matter (UCMHs) are one of the more extreme examples of this. The boosted annihilation can inject significant amounts of energy into the gas of a galaxy over its lifetime. Here we determine the impact of the boost factor from UCMH substructure on the heating of galactic gas in a Milky Way-type galaxy, by means of N-body simulation. If 1% of the dark matter exists as UCMHs, the corresponding boost factor can be of order 10{sup 5}. For reasonable values of the relevant parameters (annihilation cross section 3×10{sup −26} cm{sup 3} s{sup −1}, dark matter mass 100 GeV, 10% heating efficiency), we show that the presence of UCMHs at the 0.1% level would inject enough energy to eject significant amounts of gas from the halo, potentially preventing star formation within ∼1 kpc of the halo centre.

  17. New techniques of positron annihilation

    International Nuclear Information System (INIS)

    1983-02-01

    Studies on new techniques of positron annihilation and its application to various fields are presented. First, production of slow positron and its characteristic features are described. The slow positron can be obtained from radioisotopes by using a positron moderator, proton beam bombardment on a boron target, and pair production by using an electron linear accelerator. Bright enhancement of the slow positron beam is studied. Polarized positron beam can be used for the study of the momentum distribution of an electron in ferromagnetic substances. Production of polarized positrons and measurements of polarization are discussed. Various phases of interaction between slow positrons and atoms (or molecules) are described. A comparative study of electron scavenging effects on luminescence and on positronium formation in cyclohexane is presented. The positron annihilation phenomena are applicable for the surface study. The microscopic information on the surface of porous material may be obtained. The slow positrons are also useful for the surface study. Production and application of slow muon (positive and negative) are presented in this report. (Kato, T.)

  18. Annihilation diagrams in two-body nonleptonic decays of charmed mesons

    International Nuclear Information System (INIS)

    Bedaque, P.; Das, A.; Mathur, V.S.

    1994-06-01

    In the pole-dominance model for the two-body nonleptonic decays of charmed mesons D → PV and D → VV, it is shown that the contributions of the intermediate pseudoscalar and the axial-vector meson poles cancel each other in the annihilation diagrams in the chiral limit. In the same limit, the annihilation diagrams for the D → PP decays vanish independently. (author). 6 refs, 3 figs

  19. Annihilation of antiprotons at rest in 3He and 4He

    International Nuclear Information System (INIS)

    Balestra, F.; Bossolasco, S.; Bussa, M.P.; Busso, L.; Fava, L.; Ferrero, L.; Panzieri, D.; Piragino, G.; Tosello, F.; Bendiscioli, G.; Rotondi, R.; Salvini, P.; Zenoni, A.; Batusov, Y.A.; Bunyatov, S.A.; Falomkin, I.V.; Nichitiu, F.; Pontecorvo, G.B.; Sapozhnikov, M.G.; Tretyak, V.I.; Guaraldo, C.; Maggiora, A.; Haatuft, A.; Halsteinslid, A.; Myklebost, K.; Olsen, J.M.; Breivik, F.O.; Jacobsen, T.; Sorensen, S.O.

    1987-01-01

    At LEAR of CERN the annihilation of antiprotons stopping in 3 He and 4 He filling a self shunted streamer chamber in magnetic field has been studied. The relative probabilities of π - production in anti p 3 He and anti p 4 He annihilation events have been obtained. The ratio between the anti p annihilation probability on the neutron and on the proton for 3 He and 4 He has been deduced to be about half the value obtained for 2 H in bubble chamber experiments. The analysis of the results shows this difference cannot be ascribed only to the pion final state interaction or to the shadow effect of the nucleons in the nuclei. 9 refs.; 2 figs

  20. Can annihilating dark matter be lighter than a few GeVs?

    International Nuclear Information System (INIS)

    Boehm, C; Ensslin, T A; Silk, J

    2004-01-01

    We estimate the gamma-ray fluxes from the residual annihilations of dark matter (DM) particles having a mass m dm from [MeV, O(10) GeV] (a possible solution to the DM issue provided they have a new kind of interactions and no significant coupling to the Z) and compare them to observations. We find that particles lighter than O(100 MeV) can be viable DM candidates provided their dominant annihilation cross section is S-wave suppressed so as to satisfy the gamma-ray constraints. A similar conclusion is obtained for particles lighter than O(10) GeV from the study of radio fluxes, assuming a NFW profile and that they mainly annihilate into electrons

  1. Positron scattering and annihilation from hydrogenlike ions

    International Nuclear Information System (INIS)

    Novikov, S.A.; Bromley, M.W.J.; Mitroy, J.

    2004-01-01

    The Kohn variational method is used with a configuration-interaction-type wave function to determine the J=0 and J=1 phase shifts and annihilation parameter Z eff for positron-hydrogenic ion scattering. The phase shifts are within 1-2% of the best previous calculations. The values of Z eff are small and do not exceed unity for any of the momenta considered. At thermal energies Z eff is minute with a value of order 10 -50 occurring for He + at k=0.05a 0 -1 . In addition to the variational calculations, analytic expressions for the phase shift and annihilation parameters within the Coulomb wave Born approximation are derived and used to help elucidate the dynamics of positron collisions with positive ions

  2. Association of vWA and TPOX Polymorphisms with Venous Thrombosis in Mexican Mestizos

    Science.gov (United States)

    Meraz-Ríos, Marco Antonio; Majluf-Cruz, Abraham; Santana, Carla; Noris, Gino; Camacho-Mejorado, Rafael; Acosta-Saavedra, Leonor C.; Calderón-Aranda, Emma S.; Hernández-Juárez, Jesús; Magaña, Jonathan J.; Gómez, Rocío

    2014-01-01

    Objective. Venous thromboembolism (VTE) is a multifactorial disorder and, worldwide, the most important cause of morbidity and mortality. Genetic factors play a critical role in its aetiology. Microsatellites are the most important source of human genetic variation having more phenotypic effect than many single nucleotide polymorphisms. Hence, we evaluate a possible relationship between VTE and the genetic variants in von Willebrand factor, human alpha fibrinogen, and human thyroid peroxidase microsatellites to identify possible diagnostic markers. Methods. Genotypes were obtained from 177 patients with VTE and 531 nonrelated individuals using validated genotyping methods. The allelic frequencies were compared; Bayesian methods were used to correct population stratification to avoid spurious associations. Results. The vWA-18, TPOX-9, and TPOX-12 alleles were significantly associated with VTE. Moreover, subjects bearing the combination vWA-18/TPOX-12 loci exhibited doubled risk for VTE (95% CI = 1.02–3.64), whereas the combination vWA-18/TPOX-9 showed an OR = 10 (95% CI = 4.93–21.49). Conclusions. The vWA and TPOX microsatellites are good candidate biomarkers in venous thromboembolism diseases and could help to elucidate their origins. Additionally, these polymorphisms could become useful markers for genetic studies of VTE in the Mexican population; however, further studies should be done owing that this data only show preliminary evidence. PMID:25250329

  3. Positron annihilation at the Si/SiO2 interface

    International Nuclear Information System (INIS)

    Leung, T.C.; Weinberg, Z.A.; Asoka-Kumar, P.; Nielsen, B.; Rubloff, G.W.; Lynn, K.G.

    1992-01-01

    Variable-energy positron annihilation depth-profiling has been applied to the study of the Si/SiO 2 interface in Al-gate metal-oxide-semiconductor (MOS) structures. For both n- and p-type silicon under conditions of negative gate bias, the positron annihilation S-factor characteristic of the interface (S int ) is substantially modified. Temperature and annealing behavior, combined with known MOS physics, suggest strongly that S int depends directly on holes at interface states or traps at the Si/SiO 2 interface

  4. Positron annihilation in disordered regions in neutron-irradiated Ge and Si

    International Nuclear Information System (INIS)

    Pustovoit, A.K.; Konopleva, R.F.; Kupchishin, A.I.; Mukashev, K.M.

    1989-01-01

    The method of angular distribution of annihilation photons was used to investigate the formation and annealing of radiation defects in Ge and Si irradiated with reactor neutrons. These effects were studied as a function of the type of conduction of the dopant concentration. The nature of annealing demonstrated positron annihilation at multivacancy complexes located within disordered regions

  5. Positron-annihilation studies on the YBa2Cu4O8 superconductor

    International Nuclear Information System (INIS)

    Sundar, C.S.; Bharathi, A.; Jean, Y.C.; Hor, P.H.; Meng, R.L.; Xue, Y.Y.; Huang, Z.J.; Chu, C.W.

    1990-01-01

    Positron-lifetime and Doppler-broadened annihilation-radiation line-shape parameter S in YBa 2 Cu 4 O 8 are observed to decrease with temperature below T c . The calculation of the positron-density distribution shows that the maximum of the positron density is in the region between the Cu-O double chains. The correlation between the temperature dependence of annihilation parameters and the positron-density distribution is discussed. The decrease in annihilation parameters below T c is understood in terms of a local electron transfer from the CuO 2 layers to the Cu-O chains in the superconducting state

  6. Development of a pico-second life-time spectrometer for positron annihilation studies

    International Nuclear Information System (INIS)

    Pujari, P.K.; Datta, T.; Tomar, B.S.; Das, S.K.

    1992-01-01

    Positron annihilation technique is a sensitive probe to investigate various physico-chemical phenomena due to the ability to provide information about the electron momentum and density in any medium. While measurements on the Doppler broadening and angular correlation of annihilation photons provide information about the electron momentum, the electron density at the annihilation site is obtained, by the positron life-time measurement. This report describes the development, optimization and calibration of a high resolution life-time spectrometer (FWHM=230 ps), based on fast-fast coincidence technique, a relatively new concept in nuclear timing spectroscopy. (author). 4 refs., 9 figs., 1 tab

  7. 75 FR 14467 - Notice of Inventory Completion: Pierce College District, Lakewood, WA, and Thomas Burke Memorial...

    Science.gov (United States)

    2010-03-25

    ... DEPARTMENT OF THE INTERIOR National Park Service Notice of Inventory Completion: Pierce College... completion of an inventory of human remains in the control of the Pierce College District, Lakewood, WA, and...), University of Washington, Seattle, WA. The human remains were most likely removed from Gig Harbor, Pierce...

  8. Asymmetric thermal-relic dark matter. Sommerfeld-enhanced freeze-out, annihilation signals and unitarity bounds

    International Nuclear Information System (INIS)

    Baldes, Iason; Petraki, Kalliopi

    2017-03-01

    Dark matter that possesses a particle-antiparticle asymmetry and has thermalised in the early universe, requires a larger annihilation cross-section compared to symmetric dark matter, in order to deplete the dark antiparticles and account for the observed dark matter density. The annihilation cross-section determines the residual symmetric component of dark matter, which may give rise to annihilation signals during CMB and inside haloes today. We consider dark matter with long-range interactions, in particular dark matter coupled to a light vector or scalar force mediator. We compute the couplings required to attain a final antiparticle-to-particle ratio after the thermal freeze-out of the annihilation processes in the early universe, and then estimate the late-time annihilation signals. We show that, due to the Sommerfeld enhancement, highly asymmetric dark matter with long-range interactions can have a significant annihilation rate, potentially larger than symmetric dark matter of the same mass with contact interactions. We discuss caveats in this estimation, relating to the formation of stable bound states. Finally, we consider the non-relativistic partial-wave unitarity bound on the inelastic cross-section, we discuss why it can be realised only by long-range interactions, and showcase the importance of higher partial waves in this regime of large inelasticity. We derive upper bounds on the mass of symmetric and asymmetric thermal-relic dark matter for s-wave and p-wave annihilation, and exhibit how these bounds strengthen as the dark asymmetry increases.

  9. Asymmetric thermal-relic dark matter: Sommerfeld-enhanced freeze-out, annihilation signals and unitarity bounds

    Energy Technology Data Exchange (ETDEWEB)

    Baldes, Iason [DESY, Notkestraße 85, Hamburg, D-22607 Germany (Germany); Petraki, Kalliopi, E-mail: iason.baldes@desy.de, E-mail: kpetraki@lpthe.jussieu.fr [Laboratoire de Physique Théorique et Hautes Energies (LPTHE), UMR 7589 CNRS and UPMC, 4 Place Jussieu, Paris, F-75252 France (France)

    2017-09-01

    Dark matter that possesses a particle-antiparticle asymmetry and has thermalised in the early universe, requires a larger annihilation cross-section compared to symmetric dark matter, in order to deplete the dark antiparticles and account for the observed dark matter density. The annihilation cross-section determines the residual symmetric component of dark matter, which may give rise to annihilation signals during CMB and inside haloes today. We consider dark matter with long-range interactions, in particular dark matter coupled to a light vector or scalar force mediator. We compute the couplings required to attain a final antiparticle-to-particle ratio after the thermal freeze-out of the annihilation processes in the early universe, and then estimate the late-time annihilation signals. We show that, due to the Sommerfeld enhancement, highly asymmetric dark matter with long-range interactions can have a significant annihilation rate, potentially larger than symmetric dark matter of the same mass with contact interactions. We discuss caveats in this estimation, relating to the formation of stable bound states. Finally, we consider the non-relativistic partial-wave unitarity bound on the inelastic cross-section, we discuss why it can be realised only by long-range interactions, and showcase the importance of higher partial waves in this regime of large inelasticity. We derive upper bounds on the mass of symmetric and asymmetric thermal-relic dark matter for s -wave and p -wave annihilation, and exhibit how these bounds strengthen as the dark asymmetry increases.

  10. Asymmetric thermal-relic dark matter. Sommerfeld-enhanced freeze-out, annihilation signals and unitarity bounds

    Energy Technology Data Exchange (ETDEWEB)

    Baldes, Iason [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany); Petraki, Kalliopi [Nationaal Instuut voor Kernfysica en Hoge-Energiefysica (NIKHEF), Amsterdam (Netherlands); UMR 7589 CNRS et UPMC, Paris (France). Laboratoire de Physique Theorique et Hautes Energies (LPTHE)

    2017-03-15

    Dark matter that possesses a particle-antiparticle asymmetry and has thermalised in the early universe, requires a larger annihilation cross-section compared to symmetric dark matter, in order to deplete the dark antiparticles and account for the observed dark matter density. The annihilation cross-section determines the residual symmetric component of dark matter, which may give rise to annihilation signals during CMB and inside haloes today. We consider dark matter with long-range interactions, in particular dark matter coupled to a light vector or scalar force mediator. We compute the couplings required to attain a final antiparticle-to-particle ratio after the thermal freeze-out of the annihilation processes in the early universe, and then estimate the late-time annihilation signals. We show that, due to the Sommerfeld enhancement, highly asymmetric dark matter with long-range interactions can have a significant annihilation rate, potentially larger than symmetric dark matter of the same mass with contact interactions. We discuss caveats in this estimation, relating to the formation of stable bound states. Finally, we consider the non-relativistic partial-wave unitarity bound on the inelastic cross-section, we discuss why it can be realised only by long-range interactions, and showcase the importance of higher partial waves in this regime of large inelasticity. We derive upper bounds on the mass of symmetric and asymmetric thermal-relic dark matter for s-wave and p-wave annihilation, and exhibit how these bounds strengthen as the dark asymmetry increases.

  11. Asymmetric thermal-relic dark matter: Sommerfeld-enhanced freeze-out, annihilation signals and unitarity bounds

    International Nuclear Information System (INIS)

    Baldes, Iason; Petraki, Kalliopi

    2017-01-01

    Dark matter that possesses a particle-antiparticle asymmetry and has thermalised in the early universe, requires a larger annihilation cross-section compared to symmetric dark matter, in order to deplete the dark antiparticles and account for the observed dark matter density. The annihilation cross-section determines the residual symmetric component of dark matter, which may give rise to annihilation signals during CMB and inside haloes today. We consider dark matter with long-range interactions, in particular dark matter coupled to a light vector or scalar force mediator. We compute the couplings required to attain a final antiparticle-to-particle ratio after the thermal freeze-out of the annihilation processes in the early universe, and then estimate the late-time annihilation signals. We show that, due to the Sommerfeld enhancement, highly asymmetric dark matter with long-range interactions can have a significant annihilation rate, potentially larger than symmetric dark matter of the same mass with contact interactions. We discuss caveats in this estimation, relating to the formation of stable bound states. Finally, we consider the non-relativistic partial-wave unitarity bound on the inelastic cross-section, we discuss why it can be realised only by long-range interactions, and showcase the importance of higher partial waves in this regime of large inelasticity. We derive upper bounds on the mass of symmetric and asymmetric thermal-relic dark matter for s -wave and p -wave annihilation, and exhibit how these bounds strengthen as the dark asymmetry increases.

  12. Weapon system simulation in flight (WaSiF)

    Science.gov (United States)

    Bartoldus, Klaus H.

    2005-05-01

    The research and technology demonstration program was co-funded by the Ministries of Defence of five European countries under the framework of the "EUropean Cooperation for the Long term in Defence" (EUCLID) MoU to include Germany, Italy, The Netherlands, Portugal and Turkey with considerable financial contribution from the industrial entities. EADS Military Aircraft Munich has led a team of seven industries and research centers, including Aermacchi of Italy, DutchSpace and NLR of The Netherlands, OGMA and INETI of Portugal and Marmara Research Center of Turkey. The purpose of the project was the design, realization and demonstration of an embedded real time simulation system allowing the combat training of operational aircrew in a virtual air defence scenario and threat environment against computer generated forces in the air and on the ground while flying on a real aircraft. The simulated scenario is focused on air-to-air beyond visual range engagements of fighter aircraft. WaSiF represents one of the first demonstrations of an advanced embedded real time training system onboard a fighter/training aircraft. The system is integrated onboard the MB339CX aircraft. The overall flight test activity covered a wide variety of test conditions for a total of 21 test flights; the operational airborne time of the WaSiF amounted to nearly 18 hours. The demonstration and evaluation were quite positive; the five-nation aircrew was very fond of their first encounter with the virtual world in the military flight training. A common view and approach towards Network Centric Warfare is but emerging. WaSiF in a future networked configuration holds lots of promise to serve the needs of Integrated Air Defence: Common training in a virtual environment.

  13. Use of Mobile Phones to Support Coursework: Evidence from Wa ...

    African Journals Online (AJOL)

    Department of Information and Communication Technology. Wa Polytechnic .... A smartphone is a mobile phone with more advanced computing capability and ..... Use of mobile phones for project based learning by undergraduate students of ...

  14. Annihilation decays of bottomonium

    International Nuclear Information System (INIS)

    Monteiro, Antony Prakash; Bhat, Manjunath; D'Souza, Praveen P.; Vijaya Kumar, K.B.

    2016-01-01

    The bound state of a bottom quark b and its anti quark b-bar known as bottomonium was first seen in the spectrum of μμ"- pairs produced in 400 GeV proton-nucleus collisions at Fermilab. It was discovered as spin triplet states ϒ(1S), ϒ(2S) and ϒ(3S) by E288 collaboration at Fermilab. We have calculated annihilation decay widths of bottomonium states. The calculated decay widths are presented

  15. Bubble chamber: antiproton annihilation

    CERN Multimedia

    1971-01-01

    These images show real particle tracks from the annihilation of an antiproton in the 80 cm Saclay liquid hydrogen bubble chamber. A negative kaon and a neutral kaon are produced in this process, as well as a positive pion. The invention of bubble chambers in 1952 revolutionized the field of particle physics, allowing real tracks left by particles to be seen and photographed by expanding liquid that had been heated to boiling point.

  16. SMM detection of diffuse Galactic 511 keV annihilation radiation

    Science.gov (United States)

    Share, G. H.; Kinzer, R. L.; Kurfess, J. D.; Messina, D. C.; Purcell, W. R.

    1988-01-01

    Observations of the 511 keV annihilation line from the vicinity of the Galactic center from October to February for 1980/1981, 1981/1982, 1982/1983, 1984/1985, and 1985/1986 are presented. The measurements were made with the gamma-ray spectrometer on the SMM. The design of the instrument and some of its properties used in the analysis are described, and the methods used for accumulating, fitting, and analyzing the data are outlined. It is shown how the Galactic 511 keV line was separated from the intense and variable background observed in orbit. The SMM observations are compared with previous measurements of annihilation radiation from the Galactic center region, and the astrophysical implications are discussed. It is argued that most of the measurements made to date suggest the presence of an extended Galactic source of annihilation radiation.

  17. The Distribution and Annihilation of Dark Matter Around Black Holes

    Science.gov (United States)

    Schnittman, Jeremy D.

    2015-01-01

    We use a Monte Carlo code to calculate the geodesic orbits of test particles around Kerr black holes, generating a distribution function of both bound and unbound populations of dark matter (DM) particles. From this distribution function, we calculate annihilation rates and observable gamma-ray spectra for a few simple DM models. The features of these spectra are sensitive to the black hole spin, observer inclination, and detailed properties of the DM annihilation cross-section and density profile. Confirming earlier analytic work, we find that for rapidly spinning black holes, the collisional Penrose process can reach efficiencies exceeding 600%, leading to a high-energy tail in the annihilation spectrum. The high particle density and large proper volume of the region immediately surrounding the horizon ensures that the observed flux from these extreme events is non-negligible.

  18. V-FOR-WaTer - a new virtual research environment for environmental research

    Science.gov (United States)

    Strobl, Marcus; Azmi, Elnaz; Hassler, Sibylle; Mälicke, Mirko; Meyer, Jörg; Zehe, Erwin

    2017-04-01

    The preparation of heterogeneous datasets for scientific analysis is still a demanding task. Data preprocessing for hydrological models typically involves gathering datasets from different sources, extensive work within geoinformation systems, data transformation, the generation of computational grids and the definition of initial and boundary conditions. V-FOR-WaTer, a standardized and scalable data hub with compatible analysis tools, will ease comprehensive studies and significantly reduce data preparation time. The idea behind V-FOR-WaTer is to bring together various datasets (e.g. point measurements, 2D/3D data, time series data) from different sources (e.g. gathered in research projects, or as part of regular monitoring of state offices) and to provide common as well as innovative scaling tools in space and time to generate a coherent data grid. Each dataset holds detailed standardized metadata to ensure usability of the data, offer a comprehensive search function and provide reference information for appropriate citation of the dataset creators. V-FOR-WaTer includes a basis of data and tools, but its purpose is to grow by users who extend the virtual research environment with their own tools and research data. Researchers who upload new data or tools can receive a digital object identifier, or protect their data and tools from others until publication. Access to data and tools provided from V-FOR-WaTer happens via an easy-to-use web portal. Due to its modular architecture the portal is ready to be extended with new tools and features and also offers interfaces to Matlab, Python and R.

  19. Positron Annihilation Ratio Spectroscopy Study of Electric Fields Applied to Positronium at Material Interfaces

    Science.gov (United States)

    2011-03-01

    from 142 ns to a few ns [3:3]. Through the application of positron annihilation lifetime spectroscopy (PALS) on a material, the o-Ps lifetime can be...Force Base, Ohio APPROVED FOR PUBLIC RELEASE; DISTRIBUTION UNLIMITED. POSITRON ANNIHILATION RATIO SPECTROSCOPY STUDY OF ELECTRIC FIELDS APPLIED TO...protection in the United States. AFIT/GNE/ENP/11-M19 POSITRON ANNIHILATION RATIO SPECTROSCOPY STUDY OF ELECTRIC FIELDS APPLIED TO POSITRONIUM AT

  20. Annihilation vs. Decay: Constraining dark matter properties from a gamma-ray detection

    CERN Document Server

    Palomares-Ruiz, Sergio

    2010-01-01

    Most proposed dark matter candidates are stable and are produced thermally in the early Universe. However, there is also the possibility of unstable (but long-lived) dark matter, produced thermally or otherwise. We propose a strategy to distinguish between dark matter annihilation and/or decay in the case that a clear signal is detected in gamma-ray observations of Milky Way dwarf spheroidal galaxies with current or future gamma-ray experiments. The sole measurement of the energy spectrum of an indirect signal would render the discrimination between these cases impossible. We show that by examining the dependence of the intensity and energy spectrum on the angular distribution of the emission, the origin could be identified as decay, annihilation, or both. In addition, once the type of signal is established, we show how these measurements could help to extract information about the dark matter properties, including mass, annihilation cross section, lifetime, dominant annihilation and decay channels, and the p...

  1. Measurement of antiproton annihilation on Cu, Ag and Au with emulsion films

    International Nuclear Information System (INIS)

    Aghion, S.; Consolati, G.; Evans, C.; Ferragut, R.; Amsler, C.; Ariga, A.; Ariga, T.; Ereditato, A.; Bonomi, G.; Bräunig, P.; Demetrio, A.; Brusa, R.S.; Cabaret, L.; Comparat, D.; Caccia, M.; Castelli, F.; Caravita, R.; Noto, L. Di; Cerchiari, G.; Doser, M.

    2017-01-01

    The characteristics of low energy antiproton annihilations on nuclei (e.g. hadronization and product multiplicities) are not well known, and Monte Carlo simulation packages that use different models provide different descriptions of the annihilation events. In this study, we measured the particle multiplicities resulting from antiproton annihilations on nuclei. The results were compared with predictions obtained using different models in the simulation tools GEANT4 and FLUKA. For this study, we exposed thin targets (Cu, Ag and Au) to a very low energy antiproton beam from CERN's Antiproton Decelerator, exploiting the secondary beamline available in the AEgIS experimental zone. The antiproton annihilation products were detected using emulsion films developed at the Laboratory of High Energy Physics in Bern, where they were analysed at the automatic microscope facility. The fragment multiplicity measured in this study is in good agreement with results obtained with FLUKA simulations for both minimally and heavily ionizing particles.

  2. Measurement of antiproton annihilation on Cu, Ag and Au with emulsion films

    Science.gov (United States)

    Aghion, S.; Amsler, C.; Ariga, A.; Ariga, T.; Bonomi, G.; Bräunig, P.; Brusa, R. S.; Cabaret, L.; Caccia, M.; Caravita, R.; Castelli, F.; Cerchiari, G.; Comparat, D.; Consolati, G.; Demetrio, A.; Di Noto, L.; Doser, M.; Ereditato, A.; Evans, C.; Ferragut, R.; Fesel, J.; Fontana, A.; Gerber, S.; Giammarchi, M.; Gligorova, A.; Guatieri, F.; Haider, S.; Hinterberger, A.; Holmestad, H.; Huse, T.; Kawada, J.; Kellerbauer, A.; Kimura, M.; Krasnický, D.; Lagomarsino, V.; Lansonneur, P.; Lebrun, P.; Malbrunot, C.; Mariazzi, S.; Matveev, V.; Mazzotta, Z.; Müller, S. R.; Nebbia, G.; Nedelec, P.; Oberthaler, M.; Pacifico, N.; Pagano, D.; Penasa, L.; Petracek, V.; Pistillo, C.; Prelz, F.; Prevedelli, M.; Ravelli, L.; Rienaecker, B.; RØhne, O. M.; Rotondi, A.; Sacerdoti, M.; Sandaker, H.; Santoro, R.; Scampoli, P.; Simon, M.; Smestad, L.; Sorrentino, F.; Testera, G.; Tietje, I. C.; Vamosi, S.; Vladymyrov, M.; Widmann, E.; Yzombard, P.; Zimmer, C.; Zmeskal, J.; Zurlo, N.

    2017-04-01

    The characteristics of low energy antiproton annihilations on nuclei (e.g. hadronization and product multiplicities) are not well known, and Monte Carlo simulation packages that use different models provide different descriptions of the annihilation events. In this study, we measured the particle multiplicities resulting from antiproton annihilations on nuclei. The results were compared with predictions obtained using different models in the simulation tools GEANT4 and FLUKA. For this study, we exposed thin targets (Cu, Ag and Au) to a very low energy antiproton beam from CERN's Antiproton Decelerator, exploiting the secondary beamline available in the AEgIS experimental zone. The antiproton annihilation products were detected using emulsion films developed at the Laboratory of High Energy Physics in Bern, where they were analysed at the automatic microscope facility. The fragment multiplicity measured in this study is in good agreement with results obtained with FLUKA simulations for both minimally and heavily ionizing particles.

  3. Results from the WA92 experiment

    International Nuclear Information System (INIS)

    Malferrari, L.

    1995-01-01

    We report on a search for beauty particles produced in π - -nucleon interactions at √(s)≅26 GeV at the CERN Ω' spectrometer. Data were collected using the WA92 apparatus, which included a high-resolution imaging detector and a system for triggering on secondary vertices. The search for beauty decays using conventional analysis procedures is described and a new event-selection method, based on neural-network techniques, is presented. Results obtained with the new and the conventional methods are compared. (orig.)

  4. Investigation of vanadium oxide bronzes of phase β by means of annihilation of positrons

    International Nuclear Information System (INIS)

    Dryzek, E.

    1992-01-01

    The vanadium bronzes with general composition M x V 2 O 5 (where M means the donor element Li, Na, K, Cu, Na) have been the object of the investigation. The positron annihilation method as well as the broadening of the annihilation line in Doppler spectra have been the basing methods for the study of material structure. The donor lattice vacancies have been investigated as a positron traps being responsible for the shape of annihilation spectra. The model of clustering of donor ions has been constructed. On that base and temperature dependence of the positron annihilation spectra the thermodynamical parameters of donor ion vacancies in vanadium bronzes have been calculated. 112 refs, 33 figs, 11 tabs

  5. Isotopes - Recolonization of the Cedar River, WA by Pacific salmon

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The objective of this study is to quantify population, community, and ecosystem level changes as a result of salmon recolonization of the Cedar River, WA above...

  6. Diet - Recolonization of the Cedar River, WA by Pacific salmon

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The objective of this study is to quantify population, community, and ecosystem level changes as a result of salmon recolonization of the Cedar River, WA above...

  7. Bounds on Dark Matter annihilations from 21 cm data arXiv

    CERN Document Server

    D'Amico, Guido; Strumia, Alessandro

    The observation of an absorption feature in the 21 cm spectrum at redshift $z\\approx 17$ implies bounds on Dark Matter annihilations for a broad range of masses, given that significant heating of the intergalactic medium would have erased such feature. The resulting bounds on the DM annihilation cross sections are comparable to the strongest ones from all other observables.

  8. Cosmological constraints on dark matter annihilation and decay. Cross-correlation analysis of the extragalactic γ-ray background and cosmic shear

    Energy Technology Data Exchange (ETDEWEB)

    Shirasaki, Masato [National Astronomical Observatory of Japan, Mitaka, Tokyo (Japan); Macias, Oscar; Horiuchi, Shunsaku [Virginia Tech, Blacksburg, VA (United States). Center for Neutrino Physics; Shirai, Satoshi [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany); Yoshida, Naoki [Tokyo Univ. (Japan). Dept. of Physics; Tokyo Univ., Chiba (Japan). Kavli Inst. for the Physics and Mathematics of the Universe (WPI); Japan Science and Technology Agency, Saitama (Japan). CREST

    2016-07-15

    We derive constraints on dark matter (DM) annihilation cross section and decay lifetime from cross-correlation analyses of the data from Fermi-LAT and weak lensing surveys that cover a wide area of ∝660 squared degrees in total. We improve upon our previous analyses by using an updated extragalactic γ-ray background data reprocessed with the Fermi Pass 8 pipeline, and by using well-calibrated shape measurements of about twelve million galaxies in the Canada-France-Hawaii Lensing Survey (CFHTLenS) and Red-Cluster-Sequence Lensing Survey (RCSLenS). We generate a large set of full-sky mock catalogs from cosmological N-body simulations and use them to estimate statistical errors accurately. The measured cross correlation is consistent with null detection, which is then used to place strong cosmological constraints on annihilating and decaying DM. For leptophilic DM, the constraints are improved by a factor of ∝ 100 in the mass range of O(1) TeV when including contributions from secondary γ rays due to the inverse-Compton upscattering of background photons. Annihilation cross-sections of left angle σν right angle ∝ 10{sup -23} cm{sup 3}/s are excluded for TeV-scale DM depending on channel. Lifetimes of ∝10{sup 25} sec are also excluded for the decaying TeV-scale DM. Finally, we apply this analysis to wino DM and exclude the wino mass around 200 GeV. These constraints will be further tightened, and all the interesting wino DM parameter region can be tested, by using data from future wide-field cosmology surveys.

  9. Cosmological constraints on dark matter annihilation and decay. Cross-correlation analysis of the extragalactic γ-ray background and cosmic shear

    International Nuclear Information System (INIS)

    Shirasaki, Masato; Macias, Oscar; Horiuchi, Shunsaku; Yoshida, Naoki; Tokyo Univ., Chiba; Japan Science and Technology Agency, Saitama

    2016-07-01

    We derive constraints on dark matter (DM) annihilation cross section and decay lifetime from cross-correlation analyses of the data from Fermi-LAT and weak lensing surveys that cover a wide area of ∝660 squared degrees in total. We improve upon our previous analyses by using an updated extragalactic γ-ray background data reprocessed with the Fermi Pass 8 pipeline, and by using well-calibrated shape measurements of about twelve million galaxies in the Canada-France-Hawaii Lensing Survey (CFHTLenS) and Red-Cluster-Sequence Lensing Survey (RCSLenS). We generate a large set of full-sky mock catalogs from cosmological N-body simulations and use them to estimate statistical errors accurately. The measured cross correlation is consistent with null detection, which is then used to place strong cosmological constraints on annihilating and decaying DM. For leptophilic DM, the constraints are improved by a factor of ∝ 100 in the mass range of O(1) TeV when including contributions from secondary γ rays due to the inverse-Compton upscattering of background photons. Annihilation cross-sections of left angle σν right angle ∝ 10"-"2"3 cm"3/s are excluded for TeV-scale DM depending on channel. Lifetimes of ∝10"2"5 sec are also excluded for the decaying TeV-scale DM. Finally, we apply this analysis to wino DM and exclude the wino mass around 200 GeV. These constraints will be further tightened, and all the interesting wino DM parameter region can be tested, by using data from future wide-field cosmology surveys.

  10. Antiproton annihilation in very low-energy antihydrogen scattering by simple atoms and molecules

    Energy Technology Data Exchange (ETDEWEB)

    Armour, E.A.G. [School of Mathematical Sciences, University of Nottingham, Nottingham NG7 2RD (United Kingdom); Gregory, M.R. [School of Mathematical Sciences, University of Nottingham, Nottingham NG7 2RD (United Kingdom)]. E-mail: mark.gregory@maths.nottingham.ac.uk; Liu, Y. [School of Mathematical Sciences, University of Nottingham, Nottingham NG7 2RD (United Kingdom)

    2006-06-15

    The aim of experimentalists currently working on the preparation of antihydrogen is to trap it at very low temperatures so that its properties can be studied. Of concern to experimentalists are processes that lead to a loss of antihydrogen through annihilation. The dominant annihilation process that leads to the loss of antihydrogen is the annihilation of the antiproton with nuclei through the strong interaction. A recent scattering calculation of antihydrogen with hydrogen at very low energy, using the complex strong interaction potential of Kohno and Weise, has found an average annihilation cross-section of 0.13E{sup -1/2}a{sub 0}{sup -2}, where E is the energy of relative motion. The antihydrogen-helium system is of particular interest to experimentalists as helium may be present as an impurity in the trap. Also there is interest in the possibility of using it to cool antihydrogen. We present a treatment of antihydrogen scattering with helium at very low temperatures. The annihilation cross-sections obtained are much larger than antihydrogen-hydrogen scattering cross-section, making it very unlikely that helium can be used to cool antihydrogen.

  11. Positron annihilation study of structural subnanovoids and irradiation damages in silica-based glasses

    International Nuclear Information System (INIS)

    Inoue, K.

    2004-01-01

    Structural subnanovoids in glass solidified with radioactive waste disposal were studied by positron annihilation 2-dimensional angular correlation and positron life time measurements. Positroniums in crystalline SiO 2 were in a delocalized state, but in glass SiO 2 were in a localized state. Pick-off annihilation (pair annihilation between an ortho-positroniums and a spin antiparallel electron) rate was shortened with decreasing molarity of glass network formers and consequently radii of structural subnanovoids were reduced. The sizes of structural subnanovoids determined from the pick-off annihilation were good agreement with those measured by momentum distribution of para-positroniums. In waste disposal model glass, no presence of positronims indicated that radioactive substances occupied almost all subnanovoids, and therefore voids with large size enough to localize positroniums (above 0.1 nm radius) could not be present. (Y. Kazumata)

  12. Vector dark matter annihilation with internal bremsstrahlung

    Energy Technology Data Exchange (ETDEWEB)

    Bambhaniya, Gulab, E-mail: gulab@prl.res.in [Physical Research Laboratory, Ahmedabad 380009 (India); Kumar, Jason, E-mail: jkumar@hawaii.edu [Department of Physics & Astronomy, University of Hawaii, Honolulu, HI 96822 (United States); Marfatia, Danny, E-mail: dmarf8@hawaii.edu [Department of Physics & Astronomy, University of Hawaii, Honolulu, HI 96822 (United States); Nayak, Alekha C., E-mail: acnayak@iitk.ac.in [Department of Physics, Indian Institute of Technology, Kanpur 208016 (India); Tomar, Gaurav, E-mail: tomar@prl.res.in [Physical Research Laboratory, Ahmedabad 380009 (India)

    2017-03-10

    We consider scenarios in which the annihilation of self-conjugate spin-1 dark matter to a Standard Model fermion–antifermion final state is chirality suppressed, but where this suppression can be lifted by the emission of an additional photon via internal bremsstrahlung. We find that this scenario can only arise if the initial dark matter state is polarized, which can occur in the context of self-interacting dark matter. In particular, this is possible if the dark matter pair forms a bound state that decays to its ground state before the constituents annihilate. We show that the shape of the resulting photon spectrum is the same as for self-conjugate spin-0 and spin-1/2 dark matter, but the normalization is less heavily suppressed in the limit of heavy mediators.

  13. Antinucleon-nucleon annihilation dynamics

    International Nuclear Information System (INIS)

    Myhrer, F.; Massachusetts Inst. of Tech., Cambridge

    1989-01-01

    The antinucleon-nucleon annihilation is predominantly described by a hot-fireball process where the many final quantum numbers are distributed in a statistical fashion. It is argued that caution must be used in employing the long-range meson-exchange forces to describe the protonium atomic states. The simplest processes of two final mesons do show puzzling behavior which might be a reflection of quark dynamics, but no guiding principles for these quark calculations have been established yet. (orig.)

  14. Exciplex-exciplex energy transfer and annihilation in solid films of porphyrin-fullerene dyads.

    Science.gov (United States)

    Lehtivuori, Heli; Lemmetyinen, Helge; Tkachenko, Nikolai V

    2006-12-20

    Exciplex-exciplex annihilation was observed for the first time in porphyrin-fullerene molecular films. The films were prepared using Langmuir-Blodgett and drop casting methods. The exciplex-exciplex interactions were studied using femtosecond pump-probe method. The exciplex-exciplex annihilation can be seen as a fast (within few picoseconds) decay of the transient absorption at excitation densities higher than 0.4 mJ/cm2. Analysis of the excitation density dependences indicates that in average four dyads are involved in the exciplex-exciplex interaction, suggesting that an exciplex-exciplex energy transfer may precede the annihilation.

  15. Searching for Dark Matter Annihilation in the Smith High-Velocity Cloud

    Science.gov (United States)

    Drlica-Wagner, Alex; Gomez-Vargas, German A.; Hewitt, John W.; Linden, Tim; Tibaldo, Luigi

    2014-01-01

    Recent observations suggest that some high-velocity clouds may be confined by massive dark matter halos. In particular, the proximity and proposed dark matter content of the Smith Cloud make it a tempting target for the indirect detection of dark matter annihilation. We argue that the Smith Cloud may be a better target than some Milky Way dwarf spheroidal satellite galaxies and use gamma-ray observations from the Fermi Large Area Telescope to search for a dark matter annihilation signal. No significant gamma-ray excess is found coincident with the Smith Cloud, and we set strong limits on the dark matter annihilation cross section assuming a spatially extended dark matter profile consistent with dynamical modeling of the Smith Cloud. Notably, these limits exclude the canonical thermal relic cross section (approximately 3 x 10 (sup -26) cubic centimeters per second) for dark matter masses less than or approximately 30 gigaelectronvolts annihilating via the B/B- bar oscillation or tau/antitau channels for certain assumptions of the dark matter density profile; however, uncertainties in the dark matter content of the Smith Cloud may significantly weaken these constraints.

  16. Power spectrum tomography of dark matter annihilation with local galaxy distribution

    Energy Technology Data Exchange (ETDEWEB)

    Ando, Shin' ichiro, E-mail: s.ando@uva.nl [GRAPPA Institute, University of Amsterdam, 1098 XH Amsterdam (Netherlands)

    2014-10-01

    Cross-correlating the gamma-ray background with local galaxy catalogs potentially gives stringent constraints on dark matter annihilation. We provide updated theoretical estimates of sensitivities to the annihilation cross section from gamma-ray data with Fermi telescope and 2MASS galaxy catalogs, by elaborating the galaxy power spectrum and astrophysical backgrounds, and adopting the Markov-Chain Monte Carlo simulations. In particular, we show that taking tomographic approach by dividing the galaxy catalogs into more than one redshift slice will improve the sensitivity by a factor of a few to several. If dark matter halos contain lots of bright substructures, yielding a large annihilation boost (e.g., a factor of ∼100 for galaxy-size halos), then one may be able to probe the canonical annihilation cross section for thermal production mechanism up to masses of ∼700 GeV. Even with modest substructure boost (e.g., a factor of ∼10 for galaxy-size halos), on the other hand, the sensitivities could still reach a factor of three larger than the canonical cross section for dark matter masses of tens to a few hundreds of GeV.

  17. Searching for dark matter annihilation in the Smith high-velocity cloud

    International Nuclear Information System (INIS)

    Drlica-Wagner, Alex; Gómez-Vargas, Germán A.; Hewitt, John W.; Linden, Tim; Tibaldo, Luigi

    2014-01-01

    Recent observations suggest that some high-velocity clouds may be confined by massive dark matter halos. In particular, the proximity and proposed dark matter content of the Smith Cloud make it a tempting target for the indirect detection of dark matter annihilation. We argue that the Smith Cloud may be a better target than some Milky Way dwarf spheroidal satellite galaxies and use γ-ray observations from the Fermi Large Area Telescope to search for a dark matter annihilation signal. No significant γ-ray excess is found coincident with the Smith Cloud, and we set strong limits on the dark matter annihilation cross section assuming a spatially extended dark matter profile consistent with dynamical modeling of the Smith Cloud. Notably, these limits exclude the canonical thermal relic cross section (∼ 3 × 10 –26 cm 3 s –1 ) for dark matter masses ≲ 30 GeV annihilating via the b b-bar or τ + τ – channels for certain assumptions of the dark matter density profile; however, uncertainties in the dark matter content of the Smith Cloud may significantly weaken these constraints.

  18. Solvable single-species aggregation-annihilation model for chain-shaped cluster growth

    International Nuclear Information System (INIS)

    Ke Jianhong; Lin Zhenquan; Zheng Yizhuang; Chen Xiaoshuang; Lu Wei

    2007-01-01

    We propose a single-species aggregation-annihilation model, in which an aggregation reaction between two clusters produces an active cluster and an annihilation reaction produces an inert one. By means of the mean-field rate equation, we respectively investigate the kinetic scaling behaviours of three distinct systems. The results exhibit that: (i) for the general aggregation-annihilation system, the size distribution of active clusters consistently approaches the conventional scaling form; (ii) for the system with the self-degeneration of the cluster's activities, it takes the modified scaling form; and (iii) for the system with the self-closing of active clusters, it does not scale. Moreover, the size distribution of inert clusters with small size takes a power-law form, while that of large inert clusters obeys the scaling law. The results also show that all active clusters will eventually transform into inert ones and the inert clusters of any size can be produced by such an aggregation-annihilation process. This model can be used to mimic the chain-shaped cluster growth and can provide some useful predictions for the kinetic behaviour of the system

  19. Searching for dark matter annihilation in the Smith high-velocity cloud

    Energy Technology Data Exchange (ETDEWEB)

    Drlica-Wagner, Alex [Center for Particle Astrophysics, Fermi National Accelerator Laboratory, Batavia, IL 60510 (United States); Gómez-Vargas, Germán A. [Departamento de Fisíca, Pontificia Universidad Católica de Chile, Avenida Vicuña Mackenna 4860, Santiago (Chile); Hewitt, John W. [CRESST, University of Maryland, Baltimore County, Baltimore, MD 21250 (United States); Linden, Tim [The Kavli Institute for Cosmological Physics, University of Chicago, Chicago, IL 60637 (United States); Tibaldo, Luigi [W. W. Hansen Experimental Physics Laboratory, Kavli Institute for Particle Astrophysics and Cosmology, Department of Physics and SLAC National Accelerator Laboratory, Stanford University, Stanford, CA 94305 (United States)

    2014-07-20

    Recent observations suggest that some high-velocity clouds may be confined by massive dark matter halos. In particular, the proximity and proposed dark matter content of the Smith Cloud make it a tempting target for the indirect detection of dark matter annihilation. We argue that the Smith Cloud may be a better target than some Milky Way dwarf spheroidal satellite galaxies and use γ-ray observations from the Fermi Large Area Telescope to search for a dark matter annihilation signal. No significant γ-ray excess is found coincident with the Smith Cloud, and we set strong limits on the dark matter annihilation cross section assuming a spatially extended dark matter profile consistent with dynamical modeling of the Smith Cloud. Notably, these limits exclude the canonical thermal relic cross section (∼ 3 × 10{sup –26} cm{sup 3} s{sup –1}) for dark matter masses ≲ 30 GeV annihilating via the b b-bar or τ{sup +}τ{sup –} channels for certain assumptions of the dark matter density profile; however, uncertainties in the dark matter content of the Smith Cloud may significantly weaken these constraints.

  20. Theory of triplet-triplet annihilation in optically detected magnetic resonance

    Science.gov (United States)

    Keevers, T. L.; McCamey, D. R.

    2016-01-01

    Triplet-triplet annihilation allows two low-energy photons to be upconverted into a single high-energy photon. By essentially engineering the solar spectrum, this allows solar cells to be made more efficient and even exceed the Shockley-Quiesser limit. Unfortunately, optimizing the reaction pathway is difficult, especially with limited access to the microscopic time scales and states involved in the process. Optical measurements can provide detailed information: triplet-triplet annihilation is intrinsically spin dependent and exhibits substantial magnetoluminescence in the presence of a static magnetic field. Pulsed optically detected magnetic resonance is especially suitable, since it combines high spin sensitivity with coherent manipulation. In this paper, we develop a time-domain theory of triplet-triplet annihilation for complexes with arbitrary spin-spin coupling. We identify unique "Rabi fingerprints" for each coupling regime and show that this can be used to characterize the microscopic Hamiltonian.

  1. Positron annihilation probing for the hydratation rate of cement paste

    International Nuclear Information System (INIS)

    Myllylae, R.; Karras, M.

    1975-01-01

    Positron annihilation has been found to be a possible probe for the exponential hydratation of cement paste. Both lifetime and Doppler line broadening measurements revealed the hydratation rate. With the aid of increased stability in the lifetime spectrometer it has been possible to extend the measuring sensitivity over a period of several weeks. Two main lifetimes, tau 1 = 480 +- 20 psec and tau 2 = 2.1 +- 0.1 nsec, were observed to be constant during the hydratation. The intensity of the 2.1 nsec component changed from 4 to 8% after 47 days, and simultaneously the annihilation line narrowed from 2.6 to 2.4 keV. This behaviour has been interpreted as an increase in positronium formation. The possible practical applications of positron annihilation radiation as a hydratation probe has been evaluated for use in a concrete laboratory and even for regular construction work. (orig.) [de

  2. Application of positron annihilation to the characterization of zeolites

    International Nuclear Information System (INIS)

    Nakanishi, H.; Ujihira, Y.

    1982-01-01

    Positron annihilation lifetime and Doppler-broadening measurements were carried out for synthetic zeolite 13X, SK-40, NH 4 -X, and NH 4 -Y by varying the evacuation temperature in order to study the character of the zeolite cages. Four components of the positron annihilation, derived from the lifetime spectra, were interpreted from the results of the authors' measurements and other studies on zeolites. The o-Ps lifetimes in the cages became longer as the desorption of water molecules proceeded. It was found that some active groups in zeolites interacted with o-Ps and reduced the o-Ps lifetime after all the water molecules had detected. Bronsted acid in the zeolite acted not only as an oxidizer but also as an inhibitor of Ps formation. An attempt was made to estimate the amount of Bronsted acids by the positron lifetime technique. The longest lifetime of 50 ns indicates o-Ps annihilation in a pore with 60 A free diameter, which seems to exist irregularly in the faujasite zeolites. It was found that o-Ps was oxidized in this large cavity

  3. Positron annihilation lifetime study of oxide dispersion strengthened steels

    International Nuclear Information System (INIS)

    Krsjak, V.; Szaraz, Z.; Hähner, P.

    2012-01-01

    A comparative positron annihilation lifetime study has been performed on various commercial ferritic and ferritic/martensitic oxide dispersion strengthened (ODS) steels. Both as-extruded and recrystallized materials were investigated. In the materials with recrystallized coarse-grained microstructures, only the positron trapping at small vacancy clusters and yttria nanofeatures was observed. Materials which had not undergone recrystallization treatment clearly showed additional positron trapping which is associated with dislocations. Dislocation densities were calculated from a two-component decomposition of the positron lifetime spectra by assuming the first component to be a superposition of the bulk controlled annihilation rate and the dislocation controlled trapping rate. The second component (which translates into lifetimes of 240–260 ps) was found to be well separated in all those ODS materials. This paper presents the potentialities and limitations of the positron annihilation lifetime spectroscopy, and discusses the results of the experimental determination of the defect concentrations and sensitivity of this technique to the material degradation due to thermally induced precipitation of chromium-rich α′ phases.

  4. Exciplex-exciplex energy transfer and annihilation in solid films of porphyrin-fullerene dyads

    NARCIS (Netherlands)

    Lehtivuori, Heli; Lemmetyinen, Helge; Tkachenko, Nikolai V.

    2006-01-01

    Exciplex-exciplex annihilation was observed for the first time in porphyrin-fullerene molecular films. The films were prepared using Langmuir-Blodgett and drop casting methods. The exciplex-exciplex interactions were studied using femtosecond pump-probe method. The exciplex-exciplex annihilation can

  5. Direct Detection Phenomenology in Models Where the Products of Dark Matter Annihilation Interact with Nuclei

    DEFF Research Database (Denmark)

    Cherry, John F.; Frandsen, Mads T.; Shoemaker, Ian M.

    2015-01-01

    We investigate the direct detection phenomenology of a class of dark matter (DM) models in which DM does not directly interact with nuclei, {but rather} the products of its annihilation do. When these annihilation products are very light compared to the DM mass, the scattering in direct detection...... to nuclei, the limit from annihilation to relativistic particles in the Sun can be stronger than that of conventional non-relativistic direct detection by more than three orders of magnitude for masses in a 2-7 GeV window.......We investigate the direct detection phenomenology of a class of dark matter (DM) models in which DM does not directly interact with nuclei, {but rather} the products of its annihilation do. When these annihilation products are very light compared to the DM mass, the scattering in direct detection...... experiments is controlled by relativistic kinematics. This results in a distinctive recoil spectrum, a non-standard and or even absent annual modulation, and the ability to probe DM masses as low as a $\\sim$10 MeV. We use current LUX data to show that experimental sensitivity to thermal relic annihilation...

  6. Seroepidemiologic Survey for Human Sparganosis in Mto wa Mbu ...

    African Journals Online (AJOL)

    Seroepidemiologic Survey for Human Sparganosis in Mto wa Mbu Division, Monduli District, Tanzania. ... Data for the questionnaire for all 116 ELISA positive inhabitants revealed that had history of eating game meat and drinking water from running springs. The data revealed that ELISA would be useful to find infected ...

  7. Crystallization and preliminary X-ray analysis of the vWA domain of human anthrax toxin receptor 1

    International Nuclear Information System (INIS)

    Cai, Chenguang; Zhao, Ying; Tong, Xiaohang; Fu, Sheng; Li, Yuanyuan; Wu, Yang; Li, Xumei; Lou, Zhiyong

    2010-01-01

    The vWA domain of human anthrax toxin receptor 1 was overexpressed in E. coli, purified and crystallized. Diffraction data were collected to 1.8 Å resolution. The Gram-positive spore-forming bacterium Bacillus anthracis causes anthrax by secreting anthrax toxin, which consists of protective antigen (PA), lethal factor and oedema factor. Binding of PA to receptors triggers the multi-step process of anthrax toxin entry into target cells. Two distinct cellular receptors, ANTXR1 (also known as tumour endothelial marker 8; TEM8) and ANTXR2 (also known as capillary morphogenesis protein 2; CMG2), for anthrax toxin have been identified. Although the crystal structure of the extracellular von Willebrand factor A (vWA) domain of CMG2 has been reported, the difference between the vWA domains of TEM8 and CMG2 remains unclear because there are no structural data for the TEM8 vWA domain. In this report, the TEM8 vWA domain was expressed, purified and crystallized. X-ray diffraction data were collected to 1.8 Å resolution from a single crystal, which belonged to space group P1 with unit-cell parameters a = 65.9, b = 66.1, c = 74.4 Å, α = 63.7, β = 88.2, γ = 59.9°

  8. Application of positron annihilation lifetime technique for {gamma}-irradiation stresses study in chalcogenide vitreous semiconductors

    Energy Technology Data Exchange (ETDEWEB)

    Shpotyuk, O.; Golovchak, R.; Kovalskiy, A. [Scientific Research Company ' ' Carat' ' , Stryjska str. 20279031 Lviv (Ukraine); Filipecki, J.; Hyla, M. [Physics Institute, Pedagogical University, Al. Armii Krajowej 13/1542201 Czestochowa (Poland)

    2002-08-01

    The influence of {gamma}-irradiation on the positron annihilation lifetime spectra in chalcogenide vitreous semiconductors of As-Ge-S system has been analysed. The correlations between lifetime data, structural features and chemical compositions of glasses have been discussed. The observed lifetime components are connected with bulk positron annihilation and positron annihilation on various native and {gamma}-induced open volume defects. It is concluded that after {gamma}-irradiation of investigated materials the {gamma}-induced microvoids based on S{sub 1}{sup -}, As{sub 2}{sup -}, and Ge{sub 3}{sup -} coordination defects play the major role in positron annihilation processes. (Abstract Copyright[2002], Wiley Periodicals, Inc.)

  9. Positron-annihilation-radiation transmission gauge

    International Nuclear Information System (INIS)

    Padawer, G.M.

    1984-01-01

    A radiographic method and apparatus for nondestructively monitoring a specimen for density variations are disclosed. A positron-annihilation-radiation-emitting point source is situated approximately midway along the axis separating two detectors sensitive to positron-annihilation (0.511-MeV photon) radiation. The outputs of the two detectors are fed to an electronic circuit that reckons only time-coincident events that are sensed simultaneously in the two detectors. The specimen to be measured is positioned between the source and one of the detectors such that the cone of detected, i.e., coincident, photons intercepts the region of interest. The number of coincidences that are counted in a preset time interval are recorded, or, alternatively, the coincidence count rate is monitored directly with a ratemeter. A linear scan of the region of interest is performed by the sequential displacing of the source/detectors axis with respect to the measured specimen, or the specimen with respect to the source/detectors axis. The number of coincidence counts accumulated within a preset time interval are recorded for each displacement. The spatial variation of density within the specimen is inferred from corresponding variations in the coincidence count rate

  10. Monochromatic neutrinos from massive fourth generation neutrino annihilation in the Sun and Earth

    International Nuclear Information System (INIS)

    Belotskij, K.M.; Khlopov, M.Yu.; Shibaev, K.I.

    2001-01-01

    Accumulation inside the Earth and Sun of heavy (with the mass of 50 GeV) primordial neutrinos and antineutrinos of the fourth generation and their successive annihilation is considered. The minimal estimations of annihilational fluxes of monochromatic e, μ, τ neutrinos (neutrinos and antineutrinos) with the energy of 50 GeV are 4.1·10 -6 cm -2 ·s -1 from the Earth core and 1.1·10 -7 cm -2 ·s -1 from the Sun core. That makes the analysis of underground neutrino observatory data the additional source of information on the existence of massive stable 4th generation neutrino. It is shown that due to the kinetic equilibrium between the influx of the neutrinos and their annihilation the existence of new U(1)-gauge interaction of the 4th generation neutrino does not virtually influence the estimations of annihilational e-, μ-, τ-neutrino fluxes

  11. 22 Na positron source for annihilation positron spectroscopy

    International Nuclear Information System (INIS)

    Cimpeanu, Catalina; Craciun, L.; Dragulescu, E.; Dudu, D.; Racolta, P.M.; Voiculescu, Dana; Miron, N.

    2002-01-01

    To extend the nuclear physics applications and to perform the study of vacancy - type defects in metals, semiconductors, polymers etc., we decided to promote positron annihilation techniques. In order to achieve this goal we started a project of dedicated positron sources produced at the IFIN-HH U-120 Cyclotron. We have used the nuclear reaction 24 Mg(d,α) 22 Na and deuterons of 13 MeV energy. The paper presents the main steps of this procedure like: general conditions required for 22 NaCl sources, reactive chamber and characteristics of Mg target, parameters for the irradiation, radiochemical procedures to separate Na from Mg after the irradiation and geometrical or mechanical requirements for dedicated NaCl source for positron annihilation spectrometry. In the e + lifetime measurements the e + 'death - stop' signals are always provided by γ - quanta generated by the e + e - annihilation and the 'birth - start' signals may be obtained from 'prompt' γ - quanta emitted from the NaCl source (the 1.275 MeV photons). The 22 NaCl stock solution obtained by radiochemical separation will be kept in the sealed quartz vials in dry places and will be dropped between the studied materials before use in positron spectrometry. (authors)

  12. Annihilation of unthermalized positrons in a silicon single crystal at 770K

    International Nuclear Information System (INIS)

    Zaitsev, Yu.E.; Mungir, L.; Ue'pe, L.R.

    1984-01-01

    A model is considered for the annihilation of nonrelativistic positrons from quantized states in lattice channels. Annihilation gamma rays of energy over 511 keV have been observed when the positrons from an Na 22 source strike a silicon single crystal at 77 0 K. The experimental results agree well with the proposed model

  13. Positron annihilation spectroscopy in doped p-type ZnO

    Science.gov (United States)

    Majumdar, Sayanee; Sanyal, D.

    2011-07-01

    Positron annihilation lifetime (PAL) spectroscopy has been used to investigate the vacancy type defect of the Li and N doped ZnO. The mono-vacancies, shallow -vacancies and open volume defects have been found in both the Li and N doped ZnO. The mono-vacancies, shallow-vacancies and open volume defects increase in N-doped ZnO as the size of N is quite high compared to Li. Positron annihilation study showed that the doping above 1-3% Li and 3-4% N in ZnO are not required in order to achieve low resistivity, high hole concentration and good mobility.

  14. Applications of slow positrons to cancer research: Search for selectivity of positron annihilation to skin cancer

    International Nuclear Information System (INIS)

    Jean, Y.C.; Li Ying; Liu Gaung; Chen, Hongmin; Zhang Junjie; Gadzia, Joseph E.

    2006-01-01

    Slow positrons and positron annihilation spectroscopy (PAS) have been applied to medical research in searching for positron annihilation selectivity to cancer cells. We report the results of positron lifetime and Doppler broadening energy spectroscopies in human skin samples with and without cancer as a function of positron incident energy (up to 8 μm depth) and found that the positronium annihilates at a significantly lower rate and forms at a lower probability in the samples having either basal cell carcinoma (BCC) or squamous cell carcinoma (SCC) than in the normal skin. The significant selectivity of positron annihilation to skin cancer may open a new research area of developing positron annihilation spectroscopy as a novel medical tool to detect cancer formation externally and non-invasively at the early stages

  15. Applications of slow positrons to cancer research: Search for selectivity of positron annihilation to skin cancer

    Energy Technology Data Exchange (ETDEWEB)

    Jean, Y.C. [Department of Chemistry, University of Missouri-Kansas City, 205 Spenscer Chemistry Building, 5009 Rockhill Road, Kansas City, MO 64110 (United States)]. E-mail: jeany@umkc.edu; Li Ying [Department of Chemistry, University of Missouri-Kansas City, 205 Spenscer Chemistry Building, 5009 Rockhill Road, Kansas City, MO 64110 (United States); Liu Gaung [Department of Chemistry, University of Missouri-Kansas City, 205 Spenscer Chemistry Building, 5009 Rockhill Road, Kansas City, MO 64110 (United States); Chen, Hongmin [Department of Chemistry, University of Missouri-Kansas City, 205 Spenscer Chemistry Building, 5009 Rockhill Road, Kansas City, MO 64110 (United States); Zhang Junjie [Department of Chemistry, University of Missouri-Kansas City, 205 Spenscer Chemistry Building, 5009 Rockhill Road, Kansas City, MO 64110 (United States); Gadzia, Joseph E. [Dermatology, Department of Internal Medicine, University of Kansas Medical Center, Kansas City, KS 66103 (United States); Kansas Medical Clinic, Topeka, KS 66614 (United States)

    2006-02-28

    Slow positrons and positron annihilation spectroscopy (PAS) have been applied to medical research in searching for positron annihilation selectivity to cancer cells. We report the results of positron lifetime and Doppler broadening energy spectroscopies in human skin samples with and without cancer as a function of positron incident energy (up to 8 {mu}m depth) and found that the positronium annihilates at a significantly lower rate and forms at a lower probability in the samples having either basal cell carcinoma (BCC) or squamous cell carcinoma (SCC) than in the normal skin. The significant selectivity of positron annihilation to skin cancer may open a new research area of developing positron annihilation spectroscopy as a novel medical tool to detect cancer formation externally and non-invasively at the early stages.

  16. The 21 cm signal and the interplay between dark matter annihilations and astrophysical processes

    Energy Technology Data Exchange (ETDEWEB)

    Lopez-Honorez, Laura [Theoretische Natuurkunde, Vrije Universiteit Brussel and The International Solvay Institutes, Pleinlaan 2, B-1050 Brussels (Belgium); Mena, Olga; Moliné, Ángeles; Palomares-Ruiz, Sergio [Instituto de Física Corpuscular (IFIC), CSIC-Universitat de València, Apartado de Correos 22085, E-46071 Valencia (Spain); Vincent, Aaron C., E-mail: llopezho@vub.ac.be, E-mail: omena@ific.uv.es, E-mail: maria.moline@ist.utl.pt, E-mail: sergio.Palomares.Ruiz@ific.uv.es, E-mail: aaron.vincent@durham.ac.uk [Institute for Particle Physics Phenomenology (IPPP), Department of Physics, Durham University, Durham DH1 3LE (United Kingdom)

    2016-08-01

    Future dedicated radio interferometers, including HERA and SKA, are very promising tools that aim to study the epoch of reionization and beyond via measurements of the 21 cm signal from neutral hydrogen. Dark matter (DM) annihilations into charged particles change the thermal history of the Universe and, as a consequence, affect the 21 cm signal. Accurately predicting the effect of DM strongly relies on the modeling of annihilations inside halos. In this work, we use up-to-date computations of the energy deposition rates by the products from DM annihilations, a proper treatment of the contribution from DM annihilations in halos, as well as values of the annihilation cross section allowed by the most recent cosmological measurements from the Planck satellite. Given current uncertainties on the description of the astrophysical processes driving the epochs of reionization, X-ray heating and Lyman-α pumping, we find that disentangling DM signatures from purely astrophysical effects, related to early-time star formation processes or late-time galaxy X-ray emissions, will be a challenging task. We conclude that only annihilations of DM particles with masses of ∼100 MeV, could leave an unambiguous imprint on the 21 cm signal and, in particular, on the 21 cm power spectrum. This is in contrast to previous, more optimistic results in the literature, which have claimed that strong signatures might also be present even for much higher DM masses. Additional measurements of the 21 cm signal at different cosmic epochs will be crucial in order to break the strong parameter degeneracies between DM annihilations and astrophysical effects and undoubtedly single out a DM imprint for masses different from ∼100 MeV.

  17. Relic density and CMB constraints on dark matter annihilation with Sommerfeld enhancement

    International Nuclear Information System (INIS)

    Zavala, Jesus; White, Simon D. M.; Vogelsberger, Mark

    2010-01-01

    We calculate how the relic density of dark matter particles is altered when their annihilation is enhanced by the Sommerfeld mechanism due to a Yukawa interaction between the annihilating particles. Maintaining a dark matter abundance consistent with current observational bounds requires the normalization of the s-wave annihilation cross section to be decreased compared to a model without enhancement. The level of suppression depends on the specific parameters of the particle model, with the kinetic decoupling temperature having the most effect. We find that the cross section can be reduced by as much as an order of magnitude for extreme cases. We also compute the μ-type distortion of the CMB energy spectrum caused by energy injection from such Sommerfeld-enhanced annihilation. Our results indicate that in the vicinity of resonances, associated with bound states, distortions can be large enough to be excluded by the upper limit |μ|≤9.0x10 -5 found by the FIRAS (Far Infrared Absolute Spectrophotometer) instrument on the COBE (Cosmic Background Explorer) satellite.

  18. WaLIDD score, a new tool to diagnose dysmenorrhea and predict medical leave in university students

    Science.gov (United States)

    Teherán, Aníbal A; Piñeros, Luis Gabriel; Pulido, Fabián; Mejía Guatibonza, María Camila

    2018-01-01

    Background Dysmenorrhea is a frequent and misdiagnosed symptom affecting the quality of life in young women. A working ability, location, intensity, days of pain, dysmenorrhea (WaLIDD) score was designed to diagnose dysmenorrhea and to predict medical leave. Methods This cross-sectional design included young medical students, who completed a self-administered questionnaire that contained the verbal rating score (VRS; pain and drug subscales) and WaLIDD scales. The correlation between scales was established through Spearman test. The area under the receiver operating characteristic (ROC) curve, sensitivity, specificity, and likelihood ratio (LR +/−) were evaluated to diagnose students availing medical leave due to dysmenorrhea; moreover, to predict medical leave in students with dysmenorrhea, a binary logistic regression was performed. Results In all, 585 students, with a mean age of 21 years and menarche at 12 years, participated. Most of them had regular cycles, 5 days of menstrual blood flow and 1–2 days of lower abdominal pain. The WaLIDD scale presented an adequate internal consistency and strong correlation with VRS subscales. With a cutoff of >6 for WaLIDD and 2 for VRS subscales (drug subscale and pain subscale) to identify students with dysmenorrhea, these scales presented an area under the curve (AUC) ROC of 0.82, 0.62, and 0.67, respectively. To identify students taking medical leave due to dysmenorrhea, WaLIDD (cutoff >9) and VRS subscales (cutoff >2) presented an AUC ROC of 0.97, 0.68, and 0.81; moreover, the WaLIDD scale showed a good LR +14.2 (95% CI, 13.5–14.9), LR −0.00 (95% CI, undefined), and predictive risk (OR 5.38; 95% CI, 1.78–16.2). Conclusion This research allowed a comparison between two multidimensional scales regarding their capabilities, one previously validated and a new one, to discriminate among the general population of medical students, among those with dysmenorrhea or those availing medical leave secondary to dysmenorrhea

  19. Inclusive quarkonium production in e+e- annihilation

    International Nuclear Information System (INIS)

    Bayer, V.N.; Grozin, A.G.

    1981-03-01

    The inclusive production of S-wave state mesons composed of identical heavy quarks in e + e - annihilation at an energy high as compared with the meson mass, is considered. Exclusive production of meson pairs is also considered. (orig.)

  20. Application of positron annihilation in materials science

    International Nuclear Information System (INIS)

    Siegel, R.W.; Fluss, M.J.; Smedskjaer, L.C.

    1984-05-01

    Owing to the ability of the positron to annihilate from a variety of defect-trapped states, positron annihilation spectroscopy (PAS) has been applied increasingly to the characterization and study of defects in materials in recent years. In metals particularly, it has been demonstrated that PAS can yield defect-specific information which, by itself or in conjunction with more traditional experimental techniques, has already made a significant impact upon the determination of atomic-defect properties and the monitoring and characterization of vacancy-like microstructure development, as occurs during post-irradiation annealing. The applications of PAS are now actively expanding to the study of more complex defect-related phenomena in irradiated or deformed metals and alloys, phase transformations and structural disorder, surfaces and near-surface defect characterization. A number of these applications in materials science are reviewed and discussed with respect to profitable future directions

  1. On the inclusive annihilation of polarized e+e--pair with two observed hadrons

    International Nuclear Information System (INIS)

    Khachatryan, G.N.; Shakhnazaryan, Yu.G.

    1976-01-01

    The general consideration of the inclusive annihilation of polarized e + e - -pair with two observed hadrons in final state (e + e - →h 1 h 2 X) is carried out. The annihilation cross section is expressed in terms of five structure functions describing the transition γ*→h 1 h 2 X. The partial widths of the corresponding decay of a virtual photon for different polarizations of the photon are also introduced and the annihilation cross section is written through these widths. The density matrix of the virtual photon and its polarizational multipole moments are given as well

  2. Creation and annihilation operators for SU(3) in an SO(6,2) model

    International Nuclear Information System (INIS)

    Bracken, A.J.; MacGibbon, J.H.

    1984-01-01

    Creation and annihilation operators are defined which are Wigner operators (tensor shift operators) for SU(3). While the annihilation operators are simply boson operators, the creation operators are cubic polynomials in boson operators. Together they generate under commutation the Lie algebra of SO(6,2). A model for SU(3) is defined. The different SU(3) irreducible representations appear explicitly as manifestly covariant, irreducible tensors, whose orthogonality and normalisation properties are examined. Other Wigner operators for SU(3) can be constructed simply as products of the new creation and annihilation operators, or sums of such products. (author)

  3. Quantitative positron annihilation studies in citrates, halides and oxyhalides chemisorbed on γ-alumina catalyst

    International Nuclear Information System (INIS)

    Luo, X.H.; Jean, Y.C.; Cheng, K.L.

    1987-01-01

    A quantitative study of the γ-alumina catalyst chemisorbed by nitrates, halides, and oxyhalides has been conducted with the positron annihilation spectroscopy (PAS). Catalysts containing Fe, Co, or Ni have been extensively used in chemical industry and petroleum refining. The positron or Ps annihilation can provide a profile information about the bulk, near surface, and void. It is an in-situ surface technique. The PAS technique has shown its capability to determine the nitrate or chloride in γ-alumina as low as 0.02% in solids. It is interesting to note that the PAS may offer the oxidation state information in solids. This is not surprising because the positron annihilation is sensitive to the electron density variation in environments. Positron annihilation models for halides and oxyhalides are proposed

  4. Recent results from the WA98 experiment

    International Nuclear Information System (INIS)

    Peitzmann, T.; Aggarwal, M.M.; Agnihotri, A.; Ahammed, Z.; Angelis, A.L.S.; Antonenko, V.; Arefiev, V.; Astakhov, V.; Avdeitchikov, V.; Awes, T.C.; Baba, P.V.K.S.; Badyal, S.K.; Baldine, A.; Barabach, L.; Barlag, C.; Bathe, S.; Batiounia, B.; Bernier, T.; Bhalla, K.B.; Bhatia, V.S.; Blume, C.; Bohne, E.-M.; Bucher, D.; Buijs, A.; Buesching, H.; Carlen, L.; Chalyshev, V.; Chattopadhyay, S.; Cherbatchev, R.; Chujo, T.; Claussen, A.; Das, A.C.; Decowski, M.P.; Delagrange, H.; Djordjadze, V.; Donni, P.; Doubovik, I.; Dutt, S.; Dutta Majumdar, M.R.; El Chenawi, K.; Eliseev, S.; Enosawa, K.; Foka, P.; Fokin, S.; Frolov, V.; Ganti, M.S.; Garpman, S.; Gavrishchuk, O.; Geurts, F.J.M.; Ghosh, T.K.; Glasow, R.; Gupta, S.K.; Guskov, B.; Gustafsson, H.A.; Gutbrod, H.H.; Higuchi, R.; Hrivnacova, I.; Ippolitov, M.; Kalechofsky, H.; Kamermans, R.; Kampert, K.-H.; Karadjev, K.; Karpio, K.; Kato, S.; Kim, H.; Kolb, B.W.; Kosarev, I.; Koutcheryaev, I.; Kugler, A.; Kulinich, P.; Kurata, M.; Kurita, K.; Kuzmin, N.; Langbein, I.; Lebedev, A.; Lee, Y.Y.; Loehner, H.; Luquin, L.; Mahapatra, D.P.; Manko, V.; Martin, M.; Martinez, G.; Maximov, A.; Mehdiyev, R.; Mgebrichvili, G.; Miake, Y.; Mikhalev, D.; Mir, Md.F.; Mishra, G.C.; Miyamoto, Y.; Mohanty, B.; Morrison, D.; Mukhopadhyay, D.S.; Myalkovski, V.; Naef, H.; Nandi, B.K.; Nayak, S.K.; Nayak, T.K.; Neumaier, S.; Nianine, A.; Nikitine, V.; Nikolaev, S.; Nilsson, P.; Nishimura, S.; Nomokonov, P.; Nystrand, J.; Obenshain, F.E.; Oskarsson, A.; Otterlund, I.; Pachr, M.; Parfenov, A.; Pavliouk, S.; Petracek, V.; Plasil, F.; Pinganaud, W.; Purschke, M.L.; Raeven, B.; Rak, J.; Raniwala, R.; Raniwala, S.; Ramamurthy, V.S.; Rao, N.K.; Retiere, F.; Reygers, K.; Roland, G.; Rosselet, L.; Roufanov, I.; Roy, C.; Rubio, J.M.; Sako, H.; Sambyal, S.S.; Santo, R.; Sato, S.; Schlagheck, H.; Schmidt, H.-R.; Schutz, Y.; Shabratova, G.; Shah, T.H.; Sibiriak, I.; Siemiarczuk, T.; Silvermyr, D.; Sinha, B.C.; Slavine, N.; Soederstroem, K.; Solomey, N.; Soerensen, S.P.; Stankus, P.; Stefanek, G.; Steinberg, P.; Stenlund, E.; Sumbera, M.; Svensson, T.; Trivedi, M.D.; Tsvetkov, A.; Tykarski, L.; Urbahn, J.; Pijll, E.C.V.D.; Eijndhoven, N.V.; Nieuwenhuizen, G.J.V.; Vinogradov, A.; Viyogi, Y.P.; Vodopianov, A.; Voeroes, S.; Wyslouch, B.; Yagi, K.; Yokota, Y.; Young, G.R.

    1999-01-01

    Recent results of the WA98 experiment with Pb induced reactions at 158. A GeV are presented. The scaling properties of the transverse energy and the charged particle multiplicity at midrapidity with the number of participants is studied. Neutral pion spectra are compared to hydrodynamical parameterizations. The analysis of collective flow at target rapidity and at midrapidity is presented. The status of the study of direct photons and the search for isospin fluctuations is discussed

  5. 76 FR 3014 - Security Zone; Protection of Military Cargo, Captain of the Port Zone Puget Sound, WA

    Science.gov (United States)

    2011-01-19

    ... Coast Guard will enforce the Blair Waterway security zone in Commencement Bay, WA for protection of... DEPARTMENT OF HOMELAND SECURITY Coast Guard 33 CFR Part 165 [Docket No. USCG-2011-0015] Security Zone; Protection of Military Cargo, Captain of the Port Zone Puget Sound, WA AGENCY: Coast Guard, DHS...

  6. Pseudoscalar boson production in e+e- annihilation

    International Nuclear Information System (INIS)

    Grigoryan, S.G.; Chatrchyan, S.A.

    1987-01-01

    A mechanism of pseudoscalar boson production by the heavy quark-antiquark pair via one-photon exchange in e + e - annihilation is studied. The total cross sections of this reaction and energy distributions of produced p 0 -boson are obtained

  7. Electron-positron annihilation: unitarity, scaling and electrodynamics at high energies

    Energy Technology Data Exchange (ETDEWEB)

    Karl, G [Guelph Univ., Ontario (Canada); European Organization for Nuclear Research, Geneva (Switzerland))

    1974-01-01

    The work on e/sup +/e/sup -/ annihilation by Cabibbo, Wolfenstein and the author is reviewed. The restrictions of unitarity are analyzed and the connection between the cross sections sigmasub(h) (into hadrons) and sigmasub(..mu..) (into muons) is derived. The possibility of non-scaling in e/sup +/e/sup -/ annihilation is studied and it is pointed out that it leads to no contradiction with presently available information. It is further pointed out that non-scaling could provide a cut-off mechanism for quantum electrodynamics.

  8. Pore annihilation in a single-crystal nickel-base superalloy during hot isostatic pressing: Experiment and modelling

    International Nuclear Information System (INIS)

    Epishin, Alexander; Fedelich, Bernard; Link, Thomas; Feldmann, Titus; Svetlov, Igor L.

    2013-01-01

    Pore annihilation during hot isostatic pressing (HIP) was investigated in the single-crystal nickel-base superalloy CMSX-4 experimentally by interrupted HIP tests at 1288 °C/103 MPa. The kinetics of pore annihilation was determined by density measurement and quantitative metallography. Transmission electron microscopy of a HIPed specimen showed that the pores shrink via dislocation movement on octahedral glide planes. Theoretically pore closure under HIP condition was modelled by the finite element method using crystal plasticity and large strain theories. The modelling gives a similar kinetics of pore annihilation as observed experimentally, however somewhat higher annihilation rate

  9. Nanometer cavities studied by positron annihilation

    International Nuclear Information System (INIS)

    Mogensen, O.E.

    1992-01-01

    Positronium (Ps) is trapped in cavities in insulating solids, and the lifetime of ortho Ps is determined by the size of the cavity. The information on the properties of the cavities obtained by use of the standard slow positron beam and the 'normal' positron annihilation techniques is compared for several selected cases. (author)

  10. Solar atmospheric neutrinos and the sensitivity floor for solar dark matter annihilation searches

    Energy Technology Data Exchange (ETDEWEB)

    Argüelles, C.A. [Massachusetts Institute of Technology, 77 Massachusetts Ave., Cambridge MA (United States); De Wasseige, G. [Vrije Universiteit Brussel, Pleinlaan 2, 1050 Elsene, Brussels (Belgium); Fedynitch, A. [Karlsruhe Institute of Technology, 76021 Karlsruhe (Germany); Jones, B.J.P., E-mail: caad@mit.edu, E-mail: gdewasse@vub.ac.be, E-mail: anatoli.fedynitch@desy.de, E-mail: ben.jones@uta.edu [University of Texas at Arlington, 108 Science Hall, 502 Yates St, Arlington TX (United States)

    2017-07-01

    Cosmic rays interacting in the solar atmosphere produce showers that result in a flux of high-energy neutrinos from the Sun. These form an irreducible background to indirect solar WIMP self-annihilation searches, which look for heavy dark matter particles annihilating into final states containing neutrinos in the Solar core. This background will eventually create a sensitivity floor for indirect WIMP self-annihilation searches analogous to that imposed by low-energy solar neutrino interactions for direct dark matter detection experiments. We present a new calculation of the flux of solar atmospheric neutrinos with a detailed treatment of systematic uncertainties inherent in solar atmospheric shower evolution, and we use this to derive the sensitivity floor for indirect solar WIMP annihilation analyses. We find that the floor lies less than one order of magnitude beyond the present experimental limits on spin-dependent WIMP-proton cross sections for some mass points, and that the high-energy solar atmospheric neutrino flux may be observable with running and future neutrino telescopes.

  11. PAES: Positron annihilation induced Auger electron spectrometer

    OpenAIRE

    Hugenschmidt, Christoph

    2015-01-01

    Positron annihilation induced Auger electron spectroscopy (PAES) is a newly developed application for surface studies with high elemental selectivity and exceptional surface sensitivity. The instrument is operated by the Technische Universität München and is located at NEPOMUC.

  12. Data from SILAC-based quantitative analysis of lysates from mouse microglial cells treated with Withaferin A (WA).

    Science.gov (United States)

    Narayan, Malathi; Seeley, Kent W; Jinwal, Umesh K

    2016-06-01

    Mass spectrometry data collected in a study analyzing the effect of withaferin A (WA) on a mouse microglial (N9) cell line is presented in this article. Data was collected from SILAC-based quantitative analysis of lysates from mouse microglial cells treated with either WA or DMSO vehicle control. This article reports all the proteins that were identified in this analysis. The data presented here is related to the published research article on the effect of WA on the differential regulation of proteins in mouse microglial cells [1]. Mass spectrometry data has also been deposited in the ProteomeXchange with the identifier PXD003032.

  13. Positron Annihilation Induced Auger and Gamma Spectroscopy of Catalytically Important Surfaces

    Science.gov (United States)

    Weiss, A. H.; Nadesalingam, M. P.; Sundaramoorthy, R.; Mukherjee, S.; Fazleev, N. G.

    2006-10-01

    The annihilation of positrons with core electrons results in unique signatures in the spectra of Auger-electron and annihilation-gamma rays that can be used to make clear chemical identification of atoms at the surface. Because positrons implanted at low energies are trapped with high efficiency in the image-correlation well where they are localized just outside the surface it is possible to use annihilation induced Auger and Gamma signals to probe the surfaces of solids with single atomic layer depth resolution. In this talk we will report recent applications of Positron Annihilation Induced Auger Electron Spectroscopy (PAES) and Auger-Gamma Coincidence Spectroscopy (AGCS) to the study of surface structure and surface chemistry. Our research has demonstrated that PAES spectra can provide new information regarding the composition of the top-most atomic layer. Applications of PAES to the study of catalytically important surfaces of oxides and wide band-gap semiconductors including TiO2, SiO2,Cu2O, and SiC will be presented. We conclude with a discussion of the use of Auger-Gamma and Gamma-Gamma coincidence spectroscopy for the study of surfaces at pressures closer to those found in practical chemical reactors. Research supported by the Welch Foundation Grant Number Y-1100.

  14. A cross-sectional observational study of helmet use among motorcyclists in Wa, Ghana.

    Science.gov (United States)

    Akaateba, Millicent Awialie; Amoh-Gyimah, Richard; Yakubu, Ibrahim

    2014-03-01

    Motorcyclists' injuries and fatalities are a major public health concern in many developing countries including Ghana. This study therefore aimed to investigate the prevalence of helmet use among motorcyclists in Wa, Ghana. The method used involved a cross-sectional roadside observation at 12 randomly selected sites within and outside the CBD of Wa. A total of 14,467 motorcyclists made up of 11,360 riders and 3107 pillion riders were observed during the study period. Most observed riders (86.5%) and pillion riders (61.7%) were males. The overall prevalence of helmet use among the observed motorcyclists was 36.9% (95% CI: 36.1-37.7). Helmet use for riders was 45.8% (95% CI: 44.8-46.7) whilst that for pillion riders was 3.7% (95 CI: 3.0-4.4). Based on logistic regression analysis, higher helmet wearing rates were found to be significantly associated with female gender, weekdays, morning periods and at locations within the CBD. Riders at locations outside the CBD were about 7 times less likely to wear a helmet than riders within the CBD (48.9% compared to 42.3%; χ(2)(1)=49.526; plegislation that mandates the use of helmets by both riders and pillion riders on all roads in Ghana, helmet use is generally low in Wa. This suggests that all stakeholders in road safety should jointly intensify education on helmet use and pursue rigorous enforcement on all road types especially at locations outside the CBD to improve helmet use in Wa. Copyright © 2013 Elsevier Ltd. All rights reserved.

  15. Investigation of silicon sensors for their use as antiproton annihilation detectors

    Energy Technology Data Exchange (ETDEWEB)

    Pacifico, N., E-mail: nicola.pacifico@cern.ch [University of Bergen, Institute of Physics and Technology, Allégaten 55, 5007 Bergen (Norway); Aghion, S. [Politecnico di Milano, Piazza Leonardo da Vinci 32, 20133 Milano (Italy); Istituto Nazionale di Fisica Nucleare, Sez. di Milano, Via Celoria 16, 20133 Milano (Italy); Ahlén, O. [European Organisation for Nuclear Research, Physics Department, 1211 Geneva 23 (Switzerland); Belov, A.S. [Institute for Nuclear Research of the Russian Academy of Sciences, Moscow 117312 (Russian Federation); Bonomi, G. [University of Brescia, Department of Mechanical and Industrial Engineering, Via Branze 38, 25133 Brescia (Italy); Istituto Nazionale di Fisica Nucleare, Sez. di Pavia, Via Agostino Bassi 6, 27100 Pavia (Italy); Bräunig, P. [Kirchhoff Institute for Physics, Im Neuenheimer Feld 227, 69120 Heidelberg (Germany); Bremer, J. [European Organisation for Nuclear Research, Physics Department, 1211 Geneva 23 (Switzerland); Brusa, R.S. [Department of Physics, University of Trento, via Sommarive 14, 38123 Povo, Trento (Italy); INFN-TIFPA, via Sommarive 14, 38123 Povo, Trento (Italy); Burghart, G. [European Organisation for Nuclear Research, Physics Department, 1211 Geneva 23 (Switzerland); Cabaret, L. [Laboratoire Aimé Cotton, CNRS, Université Paris Sud, ENS Cachan, Bâtiment 505, Campus d' Orsay, 91405 Orsay Cedex (France); Caccia, M. [University of Insubria, Dipartimento di Scienza ed Alta Tecnologia, via Valleggio 11, Como (Italy); Canali, C. [University of Zurich, Physics Institute, Winterthurerstrasse 190, 8057 Zurich (Switzerland); Caravita, R. [Istituto Nazionale di Fisica Nucleare, Sez. di Genova, Via Dodecaneso 33, 16146 Genova (Italy); University of Genoa, Department of Physics, Via Dodecaneso 33, 16146 Genova (Italy); Castelli, F. [University of Milano, Department of Physics, Via Celoria 16, 20133 Milano (Italy); and others

    2014-11-21

    We present here a new application of silicon sensors aimed at the direct detection of antinucleons annihilations taking place inside the sensor's volume. Such detectors are interesting particularly for the measurement of antimatter properties and will be used as part of the gravity measurement module in the AEg{sup ¯}IS experiment at the CERN Antiproton Decelerator. One of the goals of the AEg{sup ¯}IS experiment is to measure the gravitational acceleration of antihydrogen with 1% precision. Three different silicon sensor geometries have been tested with an antiproton beam to investigate their properties as annihilation detection devices: strip planar, 3D pixels and monolithic pixel planar. In all cases we were successfully detecting annihilations taking place in the sensor and we were able to make a first characterization of the clusters and tracks.

  16. Evidence of mesoniums in anti pn annihilations and γγ reactions

    International Nuclear Information System (INIS)

    Liu, K.F.; Li, B.A.

    1987-01-01

    A new resonance at 1480 MeV with a width of 110 MeV is found in anti pn annihilations in the channel anti pn → π - X 0 (1480) → π - ρ 0 ρ 0 . Its mass, width and spin-parity are shown to be consistent with the ρ 0 ρ 0 enhancement observed in γγ reactions. Together with the suppression in the γγ → ρ + ρ - data which requires the admixture of an isotensor structure, this ρ 0 ρ 0 resonance in anti pn annihilation and γγ reactions and their small ππ branching ratios represent the best evidence yet for the Q 2 Q-bar 2 nature of the mesoniums. A ρ - ρ - resonance in anti pn annihilations which would betray the exotic isotensor nature of the resonance is predicted. (author)

  17. Challenges and Opportunities for Mainstreaming Climate Change Adaptation into WaSH Development Planning in Ghana

    Directory of Open Access Journals (Sweden)

    Salley Alhassan

    2017-07-01

    Full Text Available Climate change threatens water, sanitation and hygiene (WaSH facilities and services, as these are intimately linked to the water cycle and are vulnerable to changes in the quantity and quality of available water resources. Floods and droughts, which pollute and reduce water delivery respectively, have now become a perennial issue to deal with in the northern regions of Ghana. This study aimed to assess the degree to which climate change adaptation measures are mainstreamed into the water, sanitation and hygiene (WaSH development planning process in Ghana. Stakeholders from government and non-government agencies were interviewed to gain perspectives on the threat of climate change, the inclusion of climate change in WaSH planning and the barriers preventing mainstreaming. Despite awareness of climate change, adaptation measures have not been considered, and the immediate WaSH needs remain the priority. Overall, stakeholders felt the adaptive capacity of the Municipality was low and that mainstreaming has not yet occurred. Despite the lack of progress, there are great opportunities for mainstreaming climate change adaptation into planning through increasing awareness and capacity, legislative and institutional changes and the development of participatory systems to provide early warning systems and disaster risk analyses that will inform future planning.

  18. Challenges and Opportunities for Mainstreaming Climate Change Adaptation into WaSH Development Planning in Ghana.

    Science.gov (United States)

    Alhassan, Salley; Hadwen, Wade L

    2017-07-10

    Climate change threatens water, sanitation and hygiene (WaSH) facilities and services, as these are intimately linked to the water cycle and are vulnerable to changes in the quantity and quality of available water resources. Floods and droughts, which pollute and reduce water delivery respectively, have now become a perennial issue to deal with in the northern regions of Ghana. This study aimed to assess the degree to which climate change adaptation measures are mainstreamed into the water, sanitation and hygiene (WaSH) development planning process in Ghana. Stakeholders from government and non-government agencies were interviewed to gain perspectives on the threat of climate change, the inclusion of climate change in WaSH planning and the barriers preventing mainstreaming. Despite awareness of climate change, adaptation measures have not been considered, and the immediate WaSH needs remain the priority. Overall, stakeholders felt the adaptive capacity of the Municipality was low and that mainstreaming has not yet occurred. Despite the lack of progress, there are great opportunities for mainstreaming climate change adaptation into planning through increasing awareness and capacity, legislative and institutional changes and the development of participatory systems to provide early warning systems and disaster risk analyses that will inform future planning.

  19. Searches for dark matter self-annihilation signals from dwarf spheroidal galaxies and the Fornax galaxy cluster with imaging air Cherenkov telescopes

    International Nuclear Information System (INIS)

    Opitz, Bjoern Helmut Bastian

    2014-06-01

    Many astronomical observations indicate that dark matter pervades the universe and dominates the formation and dynamics of cosmic structures. Weakly interacting massive particles (WIMPs) with masses in the GeV to TeV range form a popular class of dark matter candidates. WIMP self-annihilation may lead to the production of γ-rays in the very high energy regime above 100 GeV, which is observable with imaging air Cherenkov telescopes (IACTs). For this thesis, observations of dwarf spheroidal galaxies (dSph) and the Fornax galaxy cluster with the Cherenkov telescope systems H.E.S.S., MAGIC and VERITAS were used to search for γ-ray signals of dark matter annihilations. The work consists of two parts: First, a likelihood-based statistical technique was introduced to combine published results of dSph observations with the different IACTs. The technique also accounts for uncertainties on the ''J factors'', which quantify the dark matter content of the dwarf galaxies. Secondly, H.E.S.S. observations of the Fornax cluster were analyzed. In this case, a collection of dark matter halo models was used for the J factor computation. In addition, possible signal enhancements from halo substructures were considered. None of the searches yielded a significant γ-ray signal. Therefore, the results were used to place upper limits on the thermally averaged dark matter self-annihilation cross-section left angle σν right angle. Different models for the final state of the annihilation process were considered. The cross-section limits range from left angle σν right angle UL ∝10 -19 cm 3 s -1 to left angle σν right angle UL ∝10 -25 cm 3 s -1 for dark matter particles masses between 100 GeV and 100 TeV. Some of the diverse model uncertainties causing this wide range of left angle σν right angle UL values were analyzed.

  20. Cross-correlation of weak lensing and gamma rays: implications for the nature of dark matter

    Science.gov (United States)

    Tröster, Tilman; Camera, Stefano; Fornasa, Mattia; Regis, Marco; van Waerbeke, Ludovic; Harnois-Déraps, Joachim; Ando, Shin'ichiro; Bilicki, Maciej; Erben, Thomas; Fornengo, Nicolao; Heymans, Catherine; Hildebrandt, Hendrik; Hoekstra, Henk; Kuijken, Konrad; Viola, Massimo

    2017-05-01

    We measure the cross-correlation between Fermi gamma-ray photons and over 1000 deg2 of weak lensing data from the Canada-France-Hawaii Telescope Lensing Survey (CFHTLenS), the Red Cluster Sequence Lensing Survey (RCSLenS), and the Kilo Degree Survey (KiDS). We present the first measurement of tomographic weak lensing cross-correlations and the first application of spectral binning to cross-correlations between gamma rays and weak lensing. The measurements are performed using an angular power spectrum estimator while the covariance is estimated using an analytical prescription. We verify the accuracy of our covariance estimate by comparing it to two internal covariance estimators. Based on the non-detection of a cross-correlation signal, we derive constraints on weakly interacting massive particle (WIMP) dark matter. We compute exclusion limits on the dark matter annihilation cross-section , decay rate Γdec and particle mass mDM. We find that in the absence of a cross-correlation signal, tomography does not significantly improve the constraining power of the analysis. Assuming a strong contribution to the gamma-ray flux due to small-scale clustering of dark matter and accounting for known astrophysical sources of gamma rays, we exclude the thermal relic cross-section for particle masses of mDM ≲ 20 GeV.

  1. Positron annihilation study of the CoFe2O4 ferrofluid

    International Nuclear Information System (INIS)

    Zhao Baogang; Ma Zhongping; Liu Cunye; Li Jian; Lin Yueqiang

    2000-01-01

    The CoFe 2 O 4 ferro fluid was studied by positron annihilation technique. The experimental results showed that there were three kinds of life-time state τ 1 = 151.0 ps, τ 2 = 457.9 ps and τ 3 = 2325.6 ps in the positron annihilation spectrum. It indicated that there were a large number of vacancy and vacancy cluster in the surface layer of the CoFe 2 O 4 nanoparticles

  2. PAES: Positron annihilation induced Auger electron spectrometer

    Directory of Open Access Journals (Sweden)

    Christoph Hugenschmidt

    2015-08-01

    Full Text Available Positron annihilation induced Auger electron spectroscopy (PAES is a newly developed application for surface studies with high elemental selectivity and exceptional surface sensitivity. The instrument is operated by the Technische Universität München and is located at NEPOMUC.

  3. Positron annihilation studies on BeO powders

    International Nuclear Information System (INIS)

    Brauer, G.; Kerbe, F.; Kajcsos, Z.; Ashry, A.

    1984-01-01

    The sintering behaviour of two differently produced BeO powders is studied by positron annihilation. The positron lifetime in dislocations is found to be tau/sub d/ = (185 +- 2) ps, whereas for the perfect lattice tau/sub c/ = (130 +- 2) ps. (author)

  4. Short gamma ray bursts triggered by neutrino-antineutrino annihilation

    Energy Technology Data Exchange (ETDEWEB)

    Yasin, Hannah; Perego, Albino [Institut fuer Kernphysik, TU Darmstadt (Germany); Arcones, Almudena [Institut fuer Kernphysik, TU Darmstadt (Germany); GSI Helmholtzzentrum fuer Schwerionenforschung GmbH, Darmstadt (Germany)

    2016-07-01

    Gamma ray bursts (GRB) are one of the most energetic events in the universe. Neutron star mergers are the most favourable candidate for the subclass of GRBs that last less than two seconds. It has been suggested that the annihilation of neutrino-antineutrino pairs emitted by the hot and dense merger remnant could be enough to launch a relativistic jet, producing such a burst. We calculate the energy deposition by neutrino-antineutrino annihilation based on the results of a Newtonian simulation of the aftermath of a binary neutron star merger. In addition, we investigate the necessary requirements for launching a GRB and compare with our numerical results.

  5. Positron annihilation studies on nasicon analogues containing cation vacancies

    International Nuclear Information System (INIS)

    Sreeramalu, V.; Sreepad, H.R.; Chandrashekara, A.; Ravindrachary, V.; Gopal, S.

    1990-01-01

    Positron annihilation studies were carried out on the Nasicon analogue Na 2 (La, Al)Zr(PO 4 ) 3 compound for three different concentrations (2.2, 2.8 and 5.2 by wt.%) of ZrO 2 in the nutrient. Angular correlation study of annihilated photons reveals that the defect concentration is maximum for 2.8(wt.%) of ZrO 2 . Further, positron lifetime studies indicate that the positrons are trapped at cation vacancies. Application of a two state trapping model to this system made it possible to evaluate the lifetime of positrons in the Bloch state and of positrons trapped at cation vacancies. (author). 16 refs., 4 figs

  6. Positron-annihilation-induced ion desorption from TiO2(110)

    Science.gov (United States)

    Tachibana, T.; Hirayama, T.; Nagashima, Y.

    2014-05-01

    We have investigated the positron-stimulated desorption of ions from a TiO2(110) surface. Desorbed O+ ions were detected in coincidence with the emission of annihilation γ rays. The energy dependence of the ion yields shows that the O+ ions were detected at energies much lower than the previously reported threshold for electron impact desorption corresponding to the excitation energy of Ti(3p) core electrons. These results provide evidence that core-hole creation by positron annihilation with electrons in the core levels leads to ion desorption.

  7. Application of positron annihilation technique to reverse osmosis membrane materials

    International Nuclear Information System (INIS)

    Shimazu, A.; Ikeda, K.; Miyazaki, T.; Ito, Y.

    2000-01-01

    Positron annihilation lifetime spectroscopy has been adopted as a new approach for studying vacancies of reverse osmosis membrane materials composed of cellulose acetate films and aromatic polyamide resins. The intensity of the ortho-positronium (o-Ps) lifetime increased with the amount of vacancies determined using N 2 isotherm at -195 deg. C. Changes of vacancy profiles induced by heat treatment in the cellulose acetate films were detected using o-Ps. It was found that the positron annihilation technique is applicable to the study of vacancy profiles associated with salt selectivity in typical reverse osmosis membranes.

  8. Experimental streams - Recolonization of the Cedar River, WA by Pacific salmon

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The objective of this study is to quantify population, community, and ecosystem level changes as a result of salmon recolonization of the Cedar River, WA above...

  9. Quantum efficiency harmonic analysis of exciton annihilation in organic light emitting diodes

    Energy Technology Data Exchange (ETDEWEB)

    Price, J. S.; Giebink, N. C., E-mail: ncg2@psu.edu [Department of Electrical Engineering, The Pennsylvania State University, University Park, Pennsylvania 16802 (United States)

    2015-06-29

    Various exciton annihilation processes are known to impact the efficiency roll-off of organic light emitting diodes (OLEDs); however, isolating and quantifying their contribution in the presence of other factors such as changing charge balance continue to be a challenge for routine device characterization. Here, we analyze OLED electroluminescence resulting from a sinusoidal dither superimposed on the device bias and show that nonlinearity between recombination current and light output arising from annihilation mixes the quantum efficiency measured at different dither harmonics in a manner that depends uniquely on the type and magnitude of the annihilation process. We derive a series of analytical relations involving the DC and first harmonic external quantum efficiency that enable annihilation rates to be quantified through linear regression independent of changing charge balance and evaluate them for prototypical fluorescent and phosphorescent OLEDs based on the emitters 4-(dicyanomethylene)-2-methyl-6-(4-dimethylaminostyryl)-4H-pyran and platinum octaethylporphyrin, respectively. We go on to show that, in most cases, it is sufficient to calculate the needed quantum efficiency harmonics directly from derivatives of the DC light versus current curve, thus enabling this analysis to be conducted solely from standard light-current-voltage measurement data.

  10. Search for right-handed neutrinos from dark matter annihilation with gamma-rays

    Energy Technology Data Exchange (ETDEWEB)

    Campos, Miguel D.; Queiroz, Farinaldo S.; Yaguna, Carlos E. [Max-Planck-Institut für Kernphysik, Saupfercheckweg 1, 69117 Heidelberg (Germany); Weniger, Christoph, E-mail: miguel.campos@mpi-hd.mpg.de, E-mail: farinaldo.queiroz@mpi-hd.mpg.de, E-mail: carlos.yaguna@uptc.edu.co, E-mail: c.weniger@uva.nl [GRAPPA, Institute of Physics, University of Amsterdam, Science Park 904, 1090 GL Amsterdam (Netherlands)

    2017-07-01

    Several extensions of the Standard Model contain right-handed (sterile) neutrinos in the GeV-TeV mass range. Due to their mixing with the active neutrinos, they may give rise to novel effects in cosmology, neutrino physics, and collider searches. In addition, right-handed neutrinos can also appear as final states from dark matter annihilations, with important implications for dark matter indirect detection searches. In this paper, we use current data from the Fermi Large Area Telescope (6-year observation of dwarf spheroidal galaxies) and H.E.S.S. (10-year observation of the Galactic center) to constrain the annihilation of dark matter into right-handed neutrinos. We consider right-handed neutrino with masses between 10 GeV and 1 TeV, including both two-body and three-body decays, to derive bounds on the dark matter annihilation rate, ( σ v ), as a function of the dark matter mass. Our results show, in particular, that the thermal dark matter annihilation cross section, 3× 10{sup −26} cm{sup 3} s {sup −1} , into right-handed neutrinos is excluded for dark matter masses smaller than 200 GeV.

  11. Search for right-handed neutrinos from dark matter annihilation with gamma-rays

    International Nuclear Information System (INIS)

    Campos, Miguel D.; Queiroz, Farinaldo S.; Yaguna, Carlos E.; Weniger, Christoph

    2017-01-01

    Several extensions of the Standard Model contain right-handed (sterile) neutrinos in the GeV-TeV mass range. Due to their mixing with the active neutrinos, they may give rise to novel effects in cosmology, neutrino physics, and collider searches. In addition, right-handed neutrinos can also appear as final states from dark matter annihilations, with important implications for dark matter indirect detection searches. In this paper, we use current data from the Fermi Large Area Telescope (6-year observation of dwarf spheroidal galaxies) and H.E.S.S. (10-year observation of the Galactic center) to constrain the annihilation of dark matter into right-handed neutrinos. We consider right-handed neutrino with masses between 10 GeV and 1 TeV, including both two-body and three-body decays, to derive bounds on the dark matter annihilation rate, ( σ v ), as a function of the dark matter mass. Our results show, in particular, that the thermal dark matter annihilation cross section, 3× 10 −26 cm 3 s −1 , into right-handed neutrinos is excluded for dark matter masses smaller than 200 GeV.

  12. The Emergence of Organizational Fit: Applying Configuration Theory to the Snohomish County (WA) Emergency Operations Center

    Science.gov (United States)

    2016-03-01

    Oaks, CA: Sage, 2001), 2. 30 Donaldson, “The Contingency Theory of Organizational Design,” 22. 18 theory emphasizes the necessity of fit,31 but it...ORGANIZATIONAL FIT: APPLYING CONFIGURATION THEORY TO THE SNOHOMISH COUNTY (WA) EMERGENCY OPERATIONS CENTER by Jason M. Biermann March 2016...CONFIGURATION THEORY TO THE SNOHOMISH COUNTY (WA) EMERGENCY OPERATIONS CENTER 5. FUNDING NUMBERS 6. AUTHOR(S) Jason M. Biermann 7. PERFORMING

  13. Measurement of the antiproton-nucleus annihilation cross-section at low energy

    Science.gov (United States)

    Aghai-Khozani, H.; Bianconi, A.; Corradini, M.; Hayano, R.; Hori, M.; Leali, M.; Lodi Rizzini, E.; Mascagna, V.; Murakami, Y.; Prest, M.; Vallazza, E.; Venturelli, L.; Yamada, H.

    2018-02-01

    Systematic measurements of the annihilation cross sections of low energy antinucleons were performed at CERN in the 80's and 90's. However the antiproton data on medium-heavy and heavy nuclear targets are scarce. The ASACUSA Collaboration at CERN has measured the antiproton annihilation cross section on carbon at 5.3 MeV: the value is (1.73 ± 0.25) barn. The result is compared with the antineutron experimental data and with the theoretical previsions.

  14. Bubble detector measurements of a mixed radiation field from antiproton annihilation

    International Nuclear Information System (INIS)

    Bassler, Niels; Knudsen, Helge; Moller, Soren Pape; Petersen, Jorgen B.; Rahbek, Dennis; Uggerhoj, Ulrik I.

    2006-01-01

    In the light of recent progress in the study of the biological potential of antiproton tumour treatment it is important to be able to characterize the neutron intensity arising from antiproton annihilation using simple, compact and reliable detectors. The intensity of fast neutrons from antiproton annihilation on polystyrene has been measured with bubble detectors and a multiplicity has been derived as well as an estimated neutron equivalent dose. Additionally the sensitivity of bubble detectors towards protons was measured

  15. Positron annihilation spectroscopy study on annealing effect of CuO nanoparticles

    International Nuclear Information System (INIS)

    Shi, Jianjian; Wang, Jiaheng; Yang, Wei; Zhu, Zhejie; Wu, Yichu

    2016-01-01

    The microstructure and defects of CuO nanoparticles under isochronal annealing were investigated by positron annihilation spectroscopy (PAS), X-ray diffraction (XRD) and scanning electron microscope (SEM). XRD and SEM results indicated that the average grain sizes of CuO nanoparticles grew slowly below 800 °C, and then increased rapidly with the annealing temperature from 800 to 1000 °C. Positron lifetime analysis exhibited that positrons were mainly annihilated in mono-vacancies (V Cu , V O ) and vacancy clusters when annealing from 200 to 800 °C. Furthermore, W-S plot of Doppler broadening spectra at different annealing temperatures found that the (W, S) points distributed on two different defect species, which suggested that V − Cu - V + O complexes were produced when the grains grew to bigger size after annealing above 800 °C, and positrons might annihilate at these complexes. (author)

  16. Positron annihilation spectroscopy study on annealing effect of CuO nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Shi, Jianjian; Wang, Jiaheng; Yang, Wei; Zhu, Zhejie; Wu, Yichu, E-mail: ycwu@whu.edu.cn [School of Physics and Technology, Hubei Key Laboratory of Nuclear Solid State Physics, Wuhan University (WHU), Wuhan (China)

    2016-03-15

    The microstructure and defects of CuO nanoparticles under isochronal annealing were investigated by positron annihilation spectroscopy (PAS), X-ray diffraction (XRD) and scanning electron microscope (SEM). XRD and SEM results indicated that the average grain sizes of CuO nanoparticles grew slowly below 800 °C, and then increased rapidly with the annealing temperature from 800 to 1000 °C. Positron lifetime analysis exhibited that positrons were mainly annihilated in mono-vacancies (V{sub Cu}, V{sub O}) and vacancy clusters when annealing from 200 to 800 °C. Furthermore, W-S plot of Doppler broadening spectra at different annealing temperatures found that the (W, S) points distributed on two different defect species, which suggested that V{sup −}{sub Cu} - V{sup +}{sub O} complexes were produced when the grains grew to bigger size after annealing above 800 °C, and positrons might annihilate at these complexes. (author)

  17. Data from SILAC-based quantitative analysis of lysates from mouse microglial cells treated with Withaferin A (WA

    Directory of Open Access Journals (Sweden)

    Malathi Narayan

    2016-06-01

    Full Text Available Mass spectrometry data collected in a study analyzing the effect of withaferin A (WA on a mouse microglial (N9 cell line is presented in this article. Data was collected from SILAC-based quantitative analysis of lysates from mouse microglial cells treated with either WA or DMSO vehicle control. This article reports all the proteins that were identified in this analysis. The data presented here is related to the published research article on the effect of WA on the differential regulation of proteins in mouse microglial cells [1]. Mass spectrometry data has also been deposited in the ProteomeXchange with the identifier http://www.ebi.ac.uk/pride/archive/projects/PXD003032.

  18. Prospects for discovering a neutrino line induced by dark matter annihilation

    Energy Technology Data Exchange (ETDEWEB)

    Aisati, Chaimae El; Garcia-Cely, Camilo; Hambye, Thomas; Vanderheyden, Laurent, E-mail: Chaimae.El.Aisati@ulb.ac.be, E-mail: Camilo.Alfredo.Garcia.Cely@ulb.ac.be, E-mail: thambye@ulb.ac.be, E-mail: laurent.vanderheyden@ulb.ac.be [Service de Physique Théorique—Université Libre de Bruxelles, Boulevard du Triomphe, CP225, 1050 Brussels (Belgium)

    2017-10-01

    In the near future, neutrino telescopes are expected to improve their sensitivity to the flux of monochromatic neutrinos produced by dark matter (DM) in our galaxy. This is illustrated by a new limit on the corresponding cross section that we derive from public IceCube data. In this context, we study which DM models could produce an observable flux of monochromatic neutrinos from DM annihilations. To this end, we proceed in two steps. First, within a set of simple and minimal assumptions concerning the properties of the DM particle, we determine the models that could give rise to a significant annihilation into monochromatic neutrinos at the freeze-out epoch. The list of models turns out to be very limited as a result of various constraints, in particular direct detection and neutrino masses at loop level. Given the fact that, even if largely improved, the sensitivities will be far from reaching the thermal annihilation cross section soon, a signal could only be observed if the annihilation into neutrinos today is boosted with respect to the freeze-out epoch. This is why, in a second step, we analyze the possibility of having such a large enhancement from the Sommerfeld effect. For each scenario, we also compute the cross sections into other annihilation products and confront our results with experimental constraints. We find that, within our simple and minimal assumptions, the expectation to observe monochromatic neutrinos is only possible in very specific scenarios. Some will be confirmed or excluded in the near future because they predict signals slightly below the current experimental sensitivities. We also discuss how these prospects change by relaxing our assumptions as well as by considering other types of sharp spectral features. For the latter, we consider boxed-shaped and bremsstrahlung spectra and provide the corresponding limits from IceCube data.

  19. 78 FR 67027 - Drawbridge Operation Regulation; Lake Washington, Seattle, WA

    Science.gov (United States)

    2013-11-08

    ... at Seattle, WA. The deviation is necessary to accommodate vehicular traffic attending football games... closed to vessel traffic to facilitate rapid movement of pre-game and post game football traffic... draw span will be required to open, if needed, for vessels engaged in emergency response operations...

  20. Application of positron annihilation line-shape analysis to fatigue damage for nuclear plant materials

    International Nuclear Information System (INIS)

    Maeda, N.; Uchida, M.; Ohta, Y.; Yoshida, K.

    1996-01-01

    Positron annihilation line-shape analysis is sufficiently sensitive to detect microstructural defects such as vacancies and dislocations. We are developing a portable positron annihilation system and applying this technique to fatigue damage in type 316 stainless steel and SA508 low alloy steel. The positron annihilation technique was found to be sensitive in the early fatigue life, i.e. up to 10% of the fatigue life, but showed little sensitivity in later stages of the fatigue life in type 316 stainless steel and SA508 low alloy steel. Type 316 stainless steel a higher positron annihilation sensitivity than that of SA508. It was considered that the amount of dislocation density change in the stainless steel was greater than that in the low alloy steel, because the initial microstructure contained a low dislocation density because of the solution heat treatment for the type 316 stainless steel. (orig.)

  1. [Study on malnutrition status among Wa ethnicity children and adolescents in Lingcang prefecture, Yunnan province].

    Science.gov (United States)

    Yang, Yunjuan; Chang, Litao; Chen, Lu; Wei, Xijing

    2015-12-01

    To analyze the malnutrition status among children and adolescents of Wa ethnicity in Lincang prefecture, Yunnan province from 2005 to 2014, and to provide evidence for the improvement of the situation. From 2005 to 2014, children and adolescents aged 7 to 18, from 19 primary and secondary schools in Cangyuan county of Lincang prefecture, Yunnan province, were chosen, using the multistage-stratified-random cluster sampling method, to receive physic examination. WHO-2006 standard was used. Situation related to the rate of growth retardation and malnutrition among students was analyzed, from 2005 to 2014. Data was from the National Student Physical Health Research Project. From 2000 to 2014, trends on nutrition development among these students were also studied. The rates related to growth retardation among 7-18 years-old Wa boys in 2005, 2010 and 2014 were 45.61%, 52.36% and 35.85%, with the rates of thinness as 1.44%, 0.76% and 1.36% , respectively. Rates on malnutrition were 52.35% , 56.01% and 41.13% , respectively. Rates related to growth retardation among 7-18 years-old Wa girls were 42.03%, 47.41% and 33.06%, respectively, with rates of thinness as 0.91%, 0.68% and 0.83%, respectively. The rates on malnutrition were 46.13%, 49.77% and 35.56%, respectively. From year 2005 to 2014, spurt on height growth of boys and girls were among the 13-14 years-old and 9-10 years-old, respectively. Girls were 4 years earlier, entering the sudden increase in the peak age than boys. Sex difference on height among the 18 years-old Wa youngsters were 11.99, 9.34 and 11.38 cm in 2005, 2010 and 2014, respectively. Malnutrition status of retardation on growth among Wa children and adolescents remained quite serious.

  2. Multi-messenger constraints and pressure from dark matter annihilation into e--e+ pairs

    International Nuclear Information System (INIS)

    Wechakama, Maneenate

    2013-01-01

    Despite striking evidence for the existence of dark matter from astrophysical observations, dark matter has still escaped any direct or indirect detection until today. Therefore a proof for its existence and the revelation of its nature belongs to one of the most intriguing challenges of nowadays cosmology and particle physics. The present work tries to investigate the nature of dark matter through indirect signatures from dark matter annihilation into electron-positron pairs in two different ways, pressure from dark matter annihilation and multi-messenger constraints on the dark matter annihilation cross-section. We focus on dark matter annihilation into electron-positron pairs and adopt a model-independent approach, where all the electrons and positrons are injected with the same initial energy E 0 ∝m dm c 2 . The propagation of these particles is determined by solving the diffusion-loss equation, considering inverse Compton scattering, synchrotron radiation, Coulomb collisions, bremsstrahlung, and ionization. The first part of this work, focusing on pressure from dark matter annihilation, demonstrates that dark matter annihilation into electron-positron pairs may affect the observed rotation curve by a significant amount. The injection rate of this calculation is constrained by INTEGRAL, Fermi, and H.E.S.S. data. The pressure of the relativistic electron-positron gas is computed from the energy spectrum predicted by the diffusion-loss equation. For values of the gas density and magnetic field that are representative of the Milky Way, it is estimated that the pressure gradients are strong enough to balance gravity in the central parts if E 0 0 . By comparing the predicted rotation curves with observations of dwarf and low surface brightness galaxies, we show that the pressure from dark matter annihilation may improve the agreement between theory and observations in some cases, but it also imposes severe constraints on the model parameters (most notably, the

  3. Application of positron annihilation techniques for semiconductor studies

    International Nuclear Information System (INIS)

    Karwasz, G.P.; Zecca, A.; Brusa, R.S.; Pliszka, D.

    2004-01-01

    Positron annihilation techniques, being non-destructive, allowing depth profiling down to a few micrometers and detecting open-volume defects (vacancies, dislocations etc.) at single ppm concentrations constitute a valuable and complementary method, compared to other solid-state-physics studies. We give examples of investigation in the field of semiconductors with different techniques, both with and without use of positron low-energy beams. The Doppler broadening of the 511 keV annihilation line method and the slow positron beam were used to study helium-implanted silicon and the surface reduction processes in semiconducting glasses. The positron lifetime technique and coincidence spectra of the Doppler broadening were used for systematic studies of metals and semiconductors. Doppler-coincidence method was then used to identify the kinetics of oxygen precipitates in Czochralski-grown silicon

  4. Positron annihilation studies of zirconia doped with metal cations of different valence

    Science.gov (United States)

    Prochazka, I.; Cizek, J.; Melikhova, O.; Konstantinova, T. E.; Danilenko, I. A.; Yashchishyn, I. A.; Anwand, W.; Brauer, G.

    2013-06-01

    New results obtained by applying positron annihilation spectroscopy to the investigation of zirconia-based nanomaterials doped with metal cations of different valence are reported. The slow-positron implantation spectroscopy combined with Doppler broadening measurements was employed to study the sintering of pressure-compacted nanopowders of tetragonal yttria-stabilised zirconia (t-YSZ) and t-YSZ with chromia additive. Positronium (Ps) formation in t-YSZ was proven by detecting 3γ-annihilations of ortho-Ps and was found to gradually decrease with increasing sintering temperature. A subsurface layer with enhanced 3γ-annihilations, compared to the deeper regions, could be identified. Addition of chromia was found to inhibit Ps formation. In addition, first results of positron lifetime measurements on nanopowders of zirconia phase-stabilised with MgO and CeO2 are presented.

  5. Opportunities for Increased Physical Activity in the Workplace: the Walking Meeting (WaM) Pilot Study, Miami, 2015.

    Science.gov (United States)

    Kling, Hannah E; Yang, Xuan; Messiah, Sarah E; Arheart, Kristopher L; Brannan, Debi; Caban-Martinez, Alberto J

    2016-06-23

    Despite the positive impact walking has on human health, few opportunities exist for workers with largely sedentary jobs to increase physical activity while at work. The objective of this pilot study was to examine the implementation, feasibility, and acceptability of using a Walking Meeting (WaM) protocol to increase the level of work-related physical activity among a group of sedentary white-collar workers. White-collar workers at a large university were invited to participate in a newly developed WaM protocol. Workers who conducted weekly meetings in groups of 2 or 3 individuals were recruited for the pilot study (n = 18) that took place from January 2015 to August 2015. Seventeen participants wore an accelerometer to measure physical activity levels during 3 consecutive weeks (first week baseline, followed by 2 weeks of organized WaMs) and participated in focus groups conducted during week 3 to document experiences with the WaM protocol. The WaM protocol met study criteria on feasibility, implementation, and acceptability among study participants. The average number of minutes (standard deviation) participants engaged in combined work-related moderate/vigorous physical activity per week during the 3 weeks increased from an average of 107 (55) minutes during the baseline week to 114 (67) minutes at week 2 and to 117 (65) minutes at week 3. White- collar workers were supportive of transforming regular seated meetings into walking meetings and increased their work-related physical activity levels.

  6. Characterisation of Ion Implantation-induced Defects in Certain Technologically Important Materials by Positron Annihilation (Review Paper)

    OpenAIRE

    P.M.G. Nambissan

    2009-01-01

    The application of positron annihilation spectroscopy for the studies of defects produced by different types of charged particles and ions in a variety of materials is discussed with specific examples. The ability to detect and quantify the information through the characteristic parameters of the annihilation radiation in a totally non-destructive method has made the fundamental process of electron-positron annihilation a powerful spectroscopic probe for investigating the structure and proper...

  7. Toward a minimum branching fraction for dark matter annihilation into electromagnetic final states

    International Nuclear Information System (INIS)

    Dent, James B.; Scherrer, Robert J.; Weiler, Thomas J.

    2008-01-01

    Observational limits on the high-energy neutrino background have been used to place general constraints on dark matter that annihilates only into standard model particles. Dark matter particles that annihilate into neutrinos will also inevitably branch into electromagnetic final states through higher-order tree and loop diagrams that give rise to charged leptons, and these charged particles can transfer their energy into photons via synchrotron radiation or inverse Compton scattering. In the context of effective field theory, we calculate the loop-induced branching ratio to charged leptons and show that it is generally quite large, typically > or approx. 1%, when the scale of the dark matter mass exceeds the electroweak scale, M W . For a branching fraction >or approx. 3%, the synchrotron radiation bounds on dark matter annihilation are currently stronger than the corresponding neutrino bounds in the interesting mass range from 100 GeV to 1 TeV. For dark matter masses below M W , our work provides a plausible framework for the construction of a model for 'neutrinos-only' dark matter annihilations.

  8. Dark matter annihilation into right-handed neutrinos and the galactic center gamma-ray excess

    Energy Technology Data Exchange (ETDEWEB)

    Tang, Yi-Lei [Center for High Energy Physics, Peking University,Beijing 100871 (China); Zhu, Shou-hua [Center for High Energy Physics, Peking University,Beijing 100871 (China); Institute of Theoretical Physics State Key Laboratory of Nuclear Physics and Technology,Peking University, Beijing 100871 (China); Collaborative Innovation Center of Quantum Matter,Beijing 100871 (China)

    2016-03-08

    In this paper, we will discuss a specific case that the dark matter particles annihilate into right-handed neutrinos. We calculate the predicted gamma-ray excess from the galactic center and compare our results with the data from the Fermi-LAT. An approximately 10–60 GeV right-handed neutrino with heavier dark matter particle can perfectly explain the observed spectrum. The annihilation cross section 〈σv〉 falls within the range 0.5–4×10{sup −26} cm{sup 3}/s, which is roughly compatible with the WIMP annihilation cross section.

  9. Surface investigations by means of positrons annihilation; Badania warstwy wierzchniej metoda anihilacji pozytonow

    Energy Technology Data Exchange (ETDEWEB)

    Dryzek, J. [Institute of Nuclear Physics, Cracow (Poland); Stegemann, T.; Cleff, B. [Muenster Univ. (Germany). Inst. fuer Kernphysik

    1996-12-31

    The aim of the report is a presentation of the positron annihilation studies performed on the Cu samples that surface was exposed to the friction and wear processes. Using the measurement of Doppler broadening of annihilation line, we were able to detect the profile of vacancies in the top layers of the defected metals. It was established that one could describe the profile by a simple exponential function of the depth in all cases. The range of vacancies concentration depth depends on the load, time and the speed of the defects creation processes on the surface of a sample. The outline of the positron annihilation method is also given. (author). 10 refs, 16 figs, 5 tabs.

  10. Element specificity of ortho-positronium annihilation for alkali-metal loaded SiO2 glasses.

    Science.gov (United States)

    Sato, K; Hatta, T

    2015-03-07

    Momentum distributions associated with ortho-positronium (o-Ps) pick-off annihilation photon are often influenced by light elements, as, e.g., carbon, oxygen, and fluorine. This phenomenon, so-called element specificity of o-Ps pick-off annihilation, has been utilized for studying the elemental environment around the open spaces. To gain an insight into the element specificity of o-Ps pick-off annihilation, the chemical shift of oxygen 1s binding energy and the momentum distributions associated with o-Ps pick-off annihilation were systematically investigated for alkali-metal loaded SiO2 glasses by means of X-ray photoelectron spectroscopy and positron-age-momentum correlation spectroscopy, respectively. Alkali metals introduced into the open spaces surrounded by oxygen atoms cause charge transfer from alkali metals to oxygen atoms, leading to the lower chemical shift for the oxygen 1s binding energy. The momentum distribution of o-Ps localized into the open spaces is found to be closely correlated with the oxygen 1s chemical shift. This correlation with the deepest 1s energy level evidences that the element specificity of o-Ps originates from pick-off annihilation with orbital electrons, i.e., dominantly with oxygen 2p valence electrons and s electrons with lower probability.

  11. Positron annihilation and Wheeler complexes in semiconductors

    International Nuclear Information System (INIS)

    Prokob'ev, E.P.

    1995-01-01

    The Wheeler complexes Ps-Ex (positronium-exciton) were studied. These complexes are formed during irradiation of semiconductors and ionic crystals with positrons at low temperatures under optical excitation by excitons. The binding energy of these and more complex entities preventing dissociation into Ps and Ex and/or Ex ± is at least 0.1 eV, and the lifetime for the two-photon self-annihilation is τ 2γ ∼ 5.02 x 10 -10 x c 3 s (x c is the phenomenological parameter of the effective-mass method). The estimation of lifetimes τ 2γ and τ 2γ t (the total lifetime of Ps-Ex complexes with account for positron annihilation on valence electrons) led to the conclusion that Ps-Ex complexes can be observed in a number of oxide semiconductors, in zinc sulfide, and in alkali halide crystals; however, it was difficult to observe such complexes in silicon, gallium arsenide, and other A 3 B 5 and A 2 B 6 semiconductors

  12. 77 FR 54805 - Revocation of Jet Route J-528; WA

    Science.gov (United States)

    2012-09-06

    ...-0749; Airspace Docket No. 11-ANM-29] RIN 2120-AA66 Revocation of Jet Route J-528; WA AGENCY: Federal Aviation Administration (FAA), DOT. ACTION: Final rule. SUMMARY: This action removes Jet Route J-528... 20591; telephone: (202) 267-8783. SUPPLEMENTARY INFORMATION: Background Jet Route J-528 is currently...

  13. Analysis of sub-nano spaces by positron annihilation spectroscopy

    International Nuclear Information System (INIS)

    Jean, Y.C.; Liu, J.; Huang, C.M.; Dai, G.H.; Yuan, J.P.

    1994-01-01

    Positron annihilation spectroscopy (PAS) has been realized to be a novel and potentially powerful tool to evolve the open spaces in the range 1-20 angstrom in molecular systems. Due to the repulsive force between the positron (the anti-particle of the electron) and the cores, annihilation signals are solely contributed from the open spaces, such as vacancies, holes, and voids in the molecular subtracts under study. By further developing two PAS techniques, positron lifetime (PAL), and angular correlation (ACAR), the authors are able to obtain useful and important information of: hole sizes, distributions, hole fractions, and anisotropic structures at sub-nano scales. Applications of PAS to chemical analysis, surface chemistry of inner pores, and polymer sciences are discussed

  14. Positron annihilation spectroscopy for chemical analysis (PASCA). Chapter 9

    International Nuclear Information System (INIS)

    Cheng, K.L.; Jean, Y.C.

    1988-01-01

    This chapter gives an up to date overview of positron annihilation spectroscopy for chemical analysis (PASCA). As an in situ technique PASCA is especially suitable for studying processes occurring at surfaces. The in situ characteristics of PASCA are treated. The principes of positron annihilation life time spectroscopy (PAL) are discussed and some important analytical applications such as, in determining of total surface areas and cavity volumes in chemical reactions, in the study of chemisorption and catalytic reactions on porous surfaces, in the analysis of bulk materials, in determining molecular association constants in biological systems, in proton and neutron activation analysis, in thin layer chromatography and in tracer technology. 28 refs.; 15 figs.; 8 tabs

  15. Atomic ionization at positron-electron annihilation at β+-decay

    International Nuclear Information System (INIS)

    Fedotkin, S.N.

    2012-01-01

    The role of the nuclear charge screening and corrections to the Born approximation for the flying from atom electron in a process of atomic ionization at annihilation of positron with another electron of daughter's atom at β + - decay is studied. It was considered the processes of ionization of different atomic shells (n = 1, 2, 3, 4) at annihilation of positron, emitted at β'+ - decay with K- electron of daughter's atom. It is shown that the screening effect is important only for shell with n = 4. While corrections to the Born approximation plays the essential role for all shells. It is shown that the most probable process is related with emission of the another K- electron

  16. D-brane anti-brane annihilation in an expanding universe

    International Nuclear Information System (INIS)

    Majumdar, Mahbub; Davis, Anne-Christine

    2003-01-01

    The time-varying density of D-branes and anti-D-branes in an expanding universe is calculated. The D-brane anti-brane annihilation rate is shown to be too small to compete with the expansion rate of a FRW type universe and the branes over-close the universe. This brane problem is analogous to the old monopole problem. Interestingly however, it is shown that small dimension D-branes annihilate more slowly than high dimension branes. Hence, an initially brany universe may be filled with only low dimension branes at late times. When combined with an appropriate late inflationary theory this leads to an attractive dynamical way to create a realistic braneworld scenario. (author)

  17. Applications of positron annihilation spectroscopy to polymeric and biological systems

    International Nuclear Information System (INIS)

    Jean, Y.C.; Chen, Hongmin; Liu, Guang; Chakka, Lakshmi; Gadzia, Joseph E.

    2007-01-01

    Positron annihilation spectroscopy (PAS) is a novel radio-analytical technique which uses the positron (anti-electron) and is capable of probing the atomic and molecular scale (0.2-2 nm) free-volume and hole properties in polymeric and biological materials. Recently, we developed positron annihilation lifetime and Doppler broadening of energy spectroscopies coupled with a variable mono-energetic positron beam to measure the free-volume depth profile from the surface, interfaces, and to the bulk. This paper presents applications of PAS to determine multi-layer structures, glass transition temperatures in nano-scale polymeric films and to detect cancer in the human skin. (author)

  18. Water Accounting Plus (WA+) - a water accounting procedure for complex river basins based on satellite measurements

    Science.gov (United States)

    Karimi, P.; Bastiaanssen, W. G. M.; Molden, D.

    2012-11-01

    Coping with the issue of water scarcity and growing competition for water among different sectors requires proper water management strategies and decision processes. A pre-requisite is a clear understanding of the basin hydrological processes, manageable and unmanageable water flows, the interaction with land use and opportunities to mitigate the negative effects and increase the benefits of water depletion on society. Currently, water professionals do not have a common framework that links hydrological flows to user groups of water and their benefits. The absence of a standard hydrological and water management summary is causing confusion and wrong decisions. The non-availability of water flow data is one of the underpinning reasons for not having operational water accounting systems for river basins in place. In this paper we introduce Water Accounting Plus (WA+), which is a new framework designed to provide explicit spatial information on water depletion and net withdrawal processes in complex river basins. The influence of land use on the water cycle is described explicitly by defining land use groups with common characteristics. Analogous to financial accounting, WA+ presents four sheets including (i) a resource base sheet, (ii) a consumption sheet, (iii) a productivity sheet, and (iv) a withdrawal sheet. Every sheet encompasses a set of indicators that summarize the overall water resources situation. The impact of external (e.g. climate change) and internal influences (e.g. infrastructure building) can be estimated by studying the changes in these WA+ indicators. Satellite measurements can be used for 3 out of the 4 sheets, but is not a precondition for implementing WA+ framework. Data from hydrological models and water allocation models can also be used as inputs to WA+.

  19. Positron annihilation studies of high dose Sb implanted silicon

    International Nuclear Information System (INIS)

    Schut, H.; Eijt, S.W.H.; Beling, C.D.; Ho, K.; Takamura, Y.

    2005-01-01

    The formation and evolution of vacancies and precipitates created by implantation of 60 keV, 2 x 10 16 cm -2 Sb + in pre-amorphized (0 0 1) Cz-Si is studied using the Doppler broadening (DB) and two-dimensional angular correlation of annihilation radiation (2D-ACAR) positron beam techniques. After implantation, samples were laser annealed (LTA) and subsequently thermal annealed at temperatures ranging from 400 to 1000 deg. C. Implantation-induced vacancy-type defects were detected up to a depth of 280 nm. After LTA, positron annihilation related to both Sb and remaining defects is observed in the first 100 nm below the surface. The deeper region only shows positron trapping at vacancy-type defects with strong reduced concentration. Complete removal is obtained after 600 deg. C anneal. At this temperature, the positron data for the upper region reveals trapping at Sb and Si sites only. With increasing annealing time (at 600 deg. C) or increasing temperature (up to 1000 deg. C) positron annihilation at Sb-sites associated with neighboring vacancies becomes apparent. Results are correlated with the observed Sb electrical deactivation above 600 deg. C, the shift from small Sb aggregates to precipitates and out-diffusion of Sb from the implantation region at higher temperatures

  20. Characterization of defects in metals by positron-annihilation spectroscopy

    International Nuclear Information System (INIS)

    Siegel, R.W.

    1981-10-01

    The application of positron-annihilation spectroscopy (PAS) to the characterization and study of defects in metals has grown rapidly and increasingly useful in recent years. Owing to the ability of the positron to annihilate from a variety of defect-trapped states in metals, PAS can yield defect-specific information which, by itself or in conjunction with more traditional experimental techniques, has already made a significant impact upon our knowledge regarding lattice defect properties in metals. This has been especially true for vacancy defets, as a result of the positron's affinity for lower-than-average electron-density regions in the metal. The physical basis for the positron annihilation techniques is presented in this paper; and the experimental techniques, lifetime, Doppler broadening, and angular correlation, are briefly described and compared with respect to the information that can be obtained from each of them. A number of examples of the application of PAS to the characterization of atomic defects and their agglomerates are presented. The particular examples, chosen from the areas of equilibrium vacancy formation and atomic-defect recovery, were selected with a view toward elucidating the particular advantages of PAS over more traditional defect-characterization techniques. Limitations of PAS are also pointed out. 98 references

  1. Baryon production in e+e--annihilation at PETRA

    International Nuclear Information System (INIS)

    Bartel, W.; Cords, D.; Dittmann, P.; Eichler, R.; Felst, R.; Krehbiel, H.; Meier, K.; Naroska, B.; O'Neill, L.H.

    1981-06-01

    Data on anti p and anti Λ production by e + e - -annihilation at CM energies between 30 and 36 GeV are presented. Indication for an angular anticorrelation in events with baryon antibaryon pairs is seen. (orig.)

  2. A positron annihilation study of hydrated DNA

    DEFF Research Database (Denmark)

    Warman, J. M.; Eldrup, Morten Mostgaard

    1986-01-01

    Positron annihilation measurements are reported for hydrated DNA as a function of water content and as a function of temperature (20 to -180.degree. C) for samples containing 10 and 50% wt of water. The ortho-positronium mean lifetime and its intensity show distinct variations with the degree...

  3. 33 CFR 165.1302 - Bangor Naval Submarine Base, Bangor, WA.

    Science.gov (United States)

    2010-07-01

    ... 33 Navigation and Navigable Waters 2 2010-07-01 2010-07-01 false Bangor Naval Submarine Base... Bangor Naval Submarine Base, Bangor, WA. (a) Location. The following is a security zone: The waters of... States Naval vessels. (ii) Vessels that are performing work at Naval Submarine Base Bangor pursuant to a...

  4. Annihilation vs. decay: constraining dark matter properties from a gamma-ray detection

    International Nuclear Information System (INIS)

    Palomares-Ruiz, Sergio; Siegal-Gaskins, Jennifer M.

    2010-01-01

    Most proposed dark matter candidates are stable and are produced thermally in the early Universe. However, there is also the possibility of unstable (but long-lived) dark matter, produced thermally or otherwise. We propose a strategy to distinguish between dark matter annihilation and/or decay in the case that a clear signal is detected in gamma-ray observations of Milky Way dwarf spheroidal galaxies with gamma-ray experiments. The sole measurement of the energy spectrum of an indirect signal would render the discrimination between these cases impossible. We show that by examining the dependence of the intensity and energy spectrum on the angular distribution of the emission, the origin could be identified as decay, annihilation, or both. In addition, once the type of signal is established, we show how these measurements could help to extract information about the dark matter properties, including mass, annihilation cross section, lifetime, dominant annihilation and decay channels, and the presence of substructure. Although an application of the approach presented here would likely be feasible with current experiments only for very optimistic dark matter scenarios, the improved sensitivity of upcoming experiments could enable this technique to be used to study a wider range of dark matter models

  5. Annihilation vs. decay: constraining dark matter properties from a gamma-ray detection

    Energy Technology Data Exchange (ETDEWEB)

    Palomares-Ruiz, Sergio [Centro de Física Teórica de Partículas, Instituto Superior Técnico, Av. Rovisco Pais 1, 1049-001 Lisboa (Portugal); Siegal-Gaskins, Jennifer M., E-mail: sergio.palomares.ruiz@ist.utl.pt, E-mail: jsg@mps.ohio-state.edu [Center for Cosmology and AstroParticle Physics, The Ohio State University, 191 W. Woodruff Ave., Columbus OH 43210 (United States)

    2010-07-01

    Most proposed dark matter candidates are stable and are produced thermally in the early Universe. However, there is also the possibility of unstable (but long-lived) dark matter, produced thermally or otherwise. We propose a strategy to distinguish between dark matter annihilation and/or decay in the case that a clear signal is detected in gamma-ray observations of Milky Way dwarf spheroidal galaxies with gamma-ray experiments. The sole measurement of the energy spectrum of an indirect signal would render the discrimination between these cases impossible. We show that by examining the dependence of the intensity and energy spectrum on the angular distribution of the emission, the origin could be identified as decay, annihilation, or both. In addition, once the type of signal is established, we show how these measurements could help to extract information about the dark matter properties, including mass, annihilation cross section, lifetime, dominant annihilation and decay channels, and the presence of substructure. Although an application of the approach presented here would likely be feasible with current experiments only for very optimistic dark matter scenarios, the improved sensitivity of upcoming experiments could enable this technique to be used to study a wider range of dark matter models.

  6. The non-destructive examination of reactor pressure vessel steels by positron annihilation

    International Nuclear Information System (INIS)

    Highton, J.P.

    1983-01-01

    The rapid radiation hardening of copper bearing reactor pressure vessel steels has been linked with microvoids that are associated with copper based complexes in the metal lattice. These microvoids are active in the sense that their size appears to be related to the temperature of irradiation, which thus determines their influence on dislocation mobility. These sites appear to grow by vacancy condensation which causes a reduction in the local lattice energy. Thus prolonged exposure to PWR temperatures, even in the absence of a neutron flux, may also cause embrittlement. It has been found that these sites, which represent a local negative charge, act as traps to positrons. The size of each site dictates its positron trapping potential. As the trapping potential increases so too does the probability that the positrons will annihilate with low momentum conduction electrons. The momentum of the annihilating electrons will determine the degree of Doppler broadening of the 511 keV annihilation gamma peak. Thus careful analysis of this peak can yield useful information on the degree of embrittlement caused by these active defect complexes. In this way positron annihilation offers a powerful non-destructive alternative to current methods of assessing the integrity of nuclear reactor pressure vessels. (author)

  7. Antiproton-neon annihilation at rest and at 607 MeV/c

    International Nuclear Information System (INIS)

    Balestra, F.; Bossolasco, S.; Bussa, M.P.; Busso, L.; Ferrero, L.; Panzieri, D.; Piragino, G.; Tosello, F.; Barbieri, R.; Bendiscioli, G.; Rotondi, A.; Salvini, P.; Zenoni, A.; Batusov, Yu.A.; Falomkin, I.V.; Pontecorvo, G.B.; Sapozhnikov, M.G.; Tretyak, V.I.; Guaraldo, C.; Maggiora, A.; Haatuft, A.; Halsteinslid, A.; Myklebost, K.; Olsen, J.M.; Breivik, F.O.; Jacobsen, T.; Soerensen, S.O.

    1989-01-01

    The analysis is based upon anti pNe annihilation events at rest and at 607 MeV/c detected with a self-shunted streamer chamber exposed to the LEAR beams. The main measured quantities are the following: charged-prong multiplicity, negative pion multiplicity; momentum, angular and rapidity distributions. General distributions are given as well as distributions as functions of charged prong multiplicity. A correlation is found between high multiplicity and depth of the annihilation point. The data are compared with recent theoretical analyses. (orig.)

  8. Correlations between TD annihilation and oxygen precipitation in Czochralski-grown silicon

    International Nuclear Information System (INIS)

    Reiche, M.

    1989-01-01

    Results of two-stage annealing experiments are presented including preannealing at T o C (TD formation) and a second annealing step at T=550 to 850 o C in order to study the annihilation of TD's and their influence on the oxygen precipitation. The investigations show that (1) TD's cannot act as nuclei for oxide precipitates and that (2) their annihilation, connected with the increased formation of Si I induced defects (RLD's), proves TD's to consist also of self-interstitials. (author) 11 refs., 4 figs

  9. Diffuse gamma ray constraints on annihilating or decaying Dark Matter after Fermi

    International Nuclear Information System (INIS)

    Cirelli, Marco; Panci, Paolo; Serpico, Pasquale D.

    2010-01-01

    We consider the diffuse gamma ray data from Fermi first year observations and compare them to the gamma ray fluxes predicted by Dark Matter annihilation or decay (both from prompt emission and from Inverse Compton Scattering), for different observation regions of the sky and a range of Dark Matter masses, annihilation/decay channels and Dark Matter galactic profiles. We find that the data exclude large regions of the Dark Matter parameter space not constrained otherwise and discuss possible directions for future improvements. Also, we further constrain Dark Matter interpretations of the e ± PAMELA/Fermi spectral anomalies, both for the annihilating and the decaying Dark Matter case: under very conservative assumptions, only models producing dominantly μ ± and assuming a cored Dark Matter galactic profile can fit the lepton data with masses around ∼2 TeV.

  10. Annihilation characteristics of positrons in oxide powders in relation to catalytic activities

    International Nuclear Information System (INIS)

    Ito, K.; Ohtsu, Y.; Tanigawa, S.; Enomura, A.; Tsuda, N.

    1982-01-01

    The annihilation chaaracteristics in magnesium oxide powders were studied by the measurements of Doppler broadening of annihilation radiations. MgO powders are well known as a solid base and are utilized as a catalyst for the reactions which start by extracting protons from molecules such as decomposition of alcohol. The isochronal annealing behavior of annihilation characteristics in the process Mg(OH) 2 → MgO was found to correspond just to the change in the number of basic points, specific surface area and catalytic activities in some reactions. From the results of the thermal equilibrium measurements of MgO powders after dehydration, the temperature dependence of S parameter can be considered as the thermal activation process of the escape of positrons from trapped states at surface to form positroniums. The derived value of this activation energy was 0.187 eV. (Auth.)

  11. Creation and annihilation operators for Nielsen-Olesen vortices in the coherent state approximation

    International Nuclear Information System (INIS)

    Pottinger, D.E.L.

    1978-01-01

    Using the standard techniques of canonical quantization, the author constructs approximate expressions for the creation and annihilation operators for Nielsen-Olesen vortices. The forms for the creation and annihilation operators are appropriate to situations where large-scale vortex condensation takes place. In particular, a phenomenon such as this is basic in the quark confinement schemes of Mandelstam and 't Hooft. (Auth.)

  12. Development of positron annihilation spectroscopy to test accelerated weathering of protective polymer coatings

    CERN Document Server

    Zhang, R; Chen, H M; Mallon, P; Sandreczki, T C; Richardson, J R; Jean, Y C; Nielsen, B; Suzuki, R; Ohdaira, T

    2000-01-01

    A variable mono-energetic positron beam with a computer-controlled system has recently been constructed at the University of Missouri-Kansas City for weathering studies of polymeric coatings. The beam is designed to measure the S-parameter from Doppler-broadening energy spectra and the sub-nanometer defect properties from positron annihilation lifetimes (PAL). Significant variations of S-parameter and ortho-positronium intensity in coatings, as obtained from the newly built beam and from the Electrotechnical Laboratory's beam, respectively, are observed as a function of depth and exposure time due to the Xe-light irradiation. A high sensitivity of positron annihilation signal response to the early stage of degradation is observed. Development of positron annihilation spectroscopy to test accelerated weathering of polymeric coatings is discussed.

  13. Correlates and Barriers Associated with Motorcycle Helmet Use in Wa, Ghana.

    Science.gov (United States)

    Akaateba, Millicent Awialie; Yakubu, Ibrahim; Akanbang, Bernard Afiik Akanpabadai

    2015-01-01

    This study was conducted to investigate the correlates and barriers to helmet use among motorcycle riders in Wa, a motorcycle-predominant town in Ghana. An additional objective was to determine the association between helmet use and riders' knowledge, attitudes, and beliefs toward helmets. Cross-sectional surveys including both observation of helmet use and interviews were conducted among motorcycle riders at 6 randomly selected fuel stations and 4 motorcycle service centers within and outside the Central Business District of Wa. Questions covered riders' sociodemographic and riding characteristics, helmet use, reasons for use or nonuse of helmets, and knowledge, attitudes, and beliefs about helmets. Analyses were based on frequencies and testing of strength of association using adjusted odds ratios (with 95% confidence intervals) in binary logistic regression. The prevalence of helmet use among the 271 sampled riders was 46% (95% confidence interval [CI], 40.2-52.0). Gender, age, marital status, and occupation were significant sociodemographic correlates of helmet use in Wa. Compared to currently married riders, unmarried riders were 5 times less likely to use a helmet. No significant association existed between riders' educational attainment and helmet use. Helmet use was also positively correlated with helmet ownership and license holding. The leading reasons stated for helmet nonuse among nonusers were not traveling a long distance and helmets block vision and hearing. Protection from injury, legal requirement, and coping with the police for fear of being accosted for helmet nonuse were identified as common reasons for helmet use. Positive attitudes and beliefs were also significantly correlated with helmet use. Despite the existence of a legislation mandating the use of helmets on all roads as well as the high level of awareness among riders on this legislation and the benefits of helmets, the incidence of helmet use among motorists continue to be low in Wa

  14. Development of accelerator-based γ-ray-induced positron annihilation spectroscopy technique

    International Nuclear Information System (INIS)

    Selim, F.A.; Wells, D.P.; Harmon, J. F.; Williams, J.

    2005-01-01

    Accelerator-based γ-ray-induced positron annihilation spectroscopy performs positron annihilation spectroscopy by utilizing MeV bremsstrahlung radiation generated from an accelerator (We have named the technique 'accelerator-based γ-ray-induced PAS', even though 'bremsstrahlung' is more correct here than 'γ rays'. The reason for that is to make the name of the technique more general, since PAS may be performed by utilizing MeV γ rays emitted from nuclei through the use of accelerators as described later in this article and as in the case of positron lifetime spectroscopy [F.A. Selim, D.P. Wells, and J.F. Harmon, Rev. Sci. Instrum. 76, 033905 (2005)].) instead of using positrons from radioactive sources or positron beams. MeV γ rays create positrons inside the materials by pair production. The induced positrons annihilate with the material electrons emitting a 511-keV annihilation radiation. Doppler broadening spectroscopy of the 511-keV radiation provides information about open-volume defects and plastic deformation in solids. The high penetration of MeV γ rays allows probing of defects at high depths in thick materials up to several centimeters, which is not possible with most of the current nondestructive techniques. In this article, a detailed description of the technique will be presented, including its benefits and limitations relative to the other nondestructive methods. Its application on the investigation of plastic deformation in thick steel alloys will be shown

  15. 77 FR 37317 - Drawbridge Operation Regulation; Lake Washington, Seattle, WA

    Science.gov (United States)

    2012-06-21

    ..., 2012. The deviation allows the floating draw span of the SR 520 Lake Washington Bridge to remain in the... schedule that governs the State Route 520 (SR 520) Bridge across Lake Washington at Seattle, WA. This... allows the bridge to remain in the closed position to allow safe movement of event participants. DATES...

  16. Automation of low temperature positron annihilation spectroscopy system

    International Nuclear Information System (INIS)

    Chaturvedi, T.P.; Venkiteswaran, S.; Pujari, P.K.

    1997-01-01

    This paper describes the automation implemented in the low temperature measurements in positron annihilation spectroscopic studies. This has not only widened the scope of the positron research, but also helps achieve result with better precision. (author). 3 refs., 1 fig

  17. Study of the process of positron annihilation in GaAs disturbed surface layers

    International Nuclear Information System (INIS)

    Vorob'ev, A.A.; Aref'ev, K.P.; Vorob'ev, S.A.; Karetnikov, A.S.; Prokop'ev, E.P.; Kuznetsov, Yu.N.; Khashimov, F.R.; Markova, T.I.

    1977-01-01

    The effect was investigated of single-crystal semiconductor surface treatment types on positron annihilation characteristics. CaAs single-crystal specimens were investigated with the following surface treatment types: (a) polishing with Al 2 O 3 abrasive powder water suspension; (b) mechanical polishing with diamond paste; (c) mechanical chemical polishing with Al 2 O 3 or ZrO 2 suspensions; (d) chemical polishing with the 1HF:3HNO 3 :2H 2 O mixture. The investigation of annihilation was performed by the method of distinguishing the narrow component Isub(N) from correlation curves in 14.5 kOc statical magnetic field and by that of measuring the relative value of friquantuum annihilation Psub(3γ). The maximum Isub(N) and Psub(3γ) values are shown to occur in GaAs specimens with the (d) type of treatment. The experimental data provided a conclusion about the presence of a maximum thickness oxide layer of complex composition on the surface of the specimens compared with oxide layer thicknesses on the surface of specimens with (a), (b), and (c) treatmens. It is concluded that the positron annihilation method may be successfully used for the study of semiconductor material oxide layers

  18. Strong CMB constraint on P-wave annihilating dark matter

    Directory of Open Access Journals (Sweden)

    Haipeng An

    2017-10-01

    Full Text Available We consider a dark sector consisting of dark matter that is a Dirac fermion and a scalar mediator. This model has been extensively studied in the past. If the scalar couples to the dark matter in a parity conserving manner then dark matter annihilation to two mediators is dominated by the P-wave channel and hence is suppressed at very low momentum. The indirect detection constraint from the anisotropy of the Cosmic Microwave Background is usually thought to be absent in the model because of this suppression. In this letter we show that dark matter annihilation via bound state formation occurs through the S-wave and hence there is a constraint on the parameter space of the model from the Cosmic Microwave Background.

  19. Dark matter distribution and annihilation at the Galactic center

    International Nuclear Information System (INIS)

    Dokuchaev, V I; Eroshenko, Yu N

    2016-01-01

    We describe a promising method for measuring the total dark matter mass near a supermassive black hole at the Galactic center based on observations of nonrelativistic precession of the orbits of fast S0 stars. An analytical expression for the precession angle has been obtained under the assumption of a power-law profile of the dark matter density. The awaited weighing of the dark matter at the Galactic center provides the strong constraints on the annihilation signal from the neuralino dark matter particle candidate. The mass of the dark matter necessary for the explanation of the observed excess of gamma-radiation owing to the annihilation of the dark matter particles has been calculated with allowance for the Sommerfeld effect. (paper)

  20. Determination of the solubility of neodymium in iron by positron annihilation

    International Nuclear Information System (INIS)

    Yu, W.Y.; Qing, L.N.; Zhuo, T.Z.; Rong, C.X.

    1985-01-01

    The authors have measured the lineshape parameters and lifetimes of positron annihilation in eleven samples of iron containing various concentration of Nd between 0 and 0.87 wt. %, which have been heat-treated at two different temperatures successively. According to the abrupt increase, for the two conditions of heat-treatment the solubility of Nd in iron is interpreted to be 0.082 wt. % and 0.088 wt. % respectively. Using positron annihilation technique for determining the solubility of Nd in iron appears to be more sensitive and accurate than metallography method and X-ray diffraction analysis

  1. Positron-annihilation 2D-ACAR studies of disordered and defected alloys

    International Nuclear Information System (INIS)

    Bansil, A.; Prasad, R.; Smedskjaer, L.C.; Benedek, R.; Mijnarends, P.E.

    1987-09-01

    Theoretical and experimental progess in connection with 2D-ACAR positron annihilation studies of ordered, disordered, and defected alloys is discussed. We present, in particular, some of the recent developments concerning the electronic structure of disordered alloys, and the work in the area of annihilation from positrons trapped at vacancy-type defects in metals and alloys. The electronic structure and properties of a number of compounds are also discussed briefly; we comment specifically on high T/sub c/ ceramic superconductors, Heusler alloys, and transition-metal aluminides. 58 refs., 116 figs

  2. Production of charmed particles in nuN collisions due to neutral weak currents

    International Nuclear Information System (INIS)

    Rekalo, M.P.

    1980-01-01

    A study is made of associated production of charmed particles in neutrino-nucleon interactions due to neutral weak currents. The angular distribution of the jets of charmed hadrons in nN interactions is determined in the lowest approximation in the quark-gluon coupling constant, according to which a charmed quark and antiquark are produced in an annihilation of a vector gluon and a virtual Z boson. It is shown that only a P-even dependence on the azimuthal angle v occurs in the studied approximation, the P-odd dependence which is possible in the general case being equal to zero. The total cross section for charmed-particle production in neutrino-nucleon interactions is calculated, and the origin of the violation of scale invariance is demonstrated

  3. Impact of semi-annihilations on dark matter phenomenology - an example of ZN symmetric scalar dark matter

    International Nuclear Information System (INIS)

    Belanger, G.; Kannike, K.; Pukhov, A.; Raidal, M.

    2012-01-01

    We study the impact of semi-annihilations χχ ↔ χX; where χ is dark matter and X is any standard model particle, on dark matter phenomenology. We formulate scalar dark matter models with minimal field content that predict non-trivial dark matter phenomenology for different discrete Abelian symmetries Z N , N > 2, and contain semi-annihilation processes. We implement such an example model in micrOMEGAs and show that semi-annihilations modify the phenomenology of this type of models. (authors)

  4. Moessbauer and positron annihilation studies of microstructural peculiarities of iron-dextran complexes

    International Nuclear Information System (INIS)

    Oshtrakh, M.I.; Kopelyan, E.A.; Semionkin, V.A.; Livshits, A.B.; Kozlov, A.A.

    1995-01-01

    The microstructural peculiarities of pharmaceutically important iron-dextran complexes were studied by Moessbauer and positron annihilation techniques. The results of Moessbauer spectroscopy showed variations of the iron cores in iron-dextran complexes containing different forms of FeOOH and different electronic and magnetic states of iron. The results of angular correlations of annihilation radiation and positron life-time spectroscopies showed microstructural variations of the dextran shell of the iron-dextran complexes. (author) 19 refs.; 4 tabs

  5. Positron annihilation characteristics in multi-wall carbon nanotubes with different average diameters

    International Nuclear Information System (INIS)

    Tuyen, L A; Khiem, D D; Phuc, P T; Kajcsos, Zs; Lázár, K; Tap, T D

    2013-01-01

    Positron lifetime spectroscopy was used to study multi-wall carbon nanotubes. The measurements were performed in vacuum on the samples having different average diameters. The positron lifetime values depend on the nanotube diameter. The results also show an influence of the nanotube diameter on the positron annihilation intensity on the nanotube surface. The change in the annihilation probability is described and interpreted by the modified diffusion model introducing the positron escape rate from the nanotubes to their external surface.

  6. Early Stages of Precipitation Process in Al-(Mn-)Sc-Zr Alloy Characterized by Positron Annihilation

    KAUST Repository

    Vlach, Martin; Cizek, Jakub; Melikhova, Oksana; Stulikova, Ivana; Smola, Bohumil; Kekule, Tomas; Kudrnova, Hana; Gemma, Ryota; Neubert, Volkmar

    2015-01-01

    Thermal effects on the precipitation stages in as-cast Al-0.70 at. pct Mn-0.15 at. pct Sc-0.05 at. pct Zr alloy were studied. The role of lattice defects was elucidated by positron annihilation spectroscopy (lifetime and coincidence Doppler broadening) enabling investigation of solutes clustering at the atomic scale. This technique has never been used in the Al-Sc- and/or Al-Zr-based alloys so far. Studies by positron annihilation were combined with resistometry, hardness measurements, and microstructure observations. Positrons trapped at defects are preferentially annihilated by Sc electrons. Lifetime of trapped positrons indicates that Sc atoms segregate at dislocations. Maximum fraction of positrons annihilated by Sc electrons occurring at 453 K (180 °C) suggests that clustering of Sc bound with vacancies takes place. It is followed by peak of this fraction at 573 K (300 °C). A rise of the contribution of trapped positrons annihilated by Zr electrons starting at 513 K (240 °C) and attaining maximum also at 573 K (300 °C) confirms that Zr participates in precipitation of the Al3Sc particles already at these temperatures. The pronounced hardening at 573 K (300 °C) has its nature in the precipitation of the Al3Sc particles with a Zr-rich shell. The contribution of trapped positrons annihilated by Mn electrons was found to be negligible. © 2015, The Minerals, Metals & Materials Society and ASM International.

  7. Early Stages of Precipitation Process in Al-(Mn-)Sc-Zr Alloy Characterized by Positron Annihilation

    KAUST Repository

    Vlach, Martin

    2015-01-29

    Thermal effects on the precipitation stages in as-cast Al-0.70 at. pct Mn-0.15 at. pct Sc-0.05 at. pct Zr alloy were studied. The role of lattice defects was elucidated by positron annihilation spectroscopy (lifetime and coincidence Doppler broadening) enabling investigation of solutes clustering at the atomic scale. This technique has never been used in the Al-Sc- and/or Al-Zr-based alloys so far. Studies by positron annihilation were combined with resistometry, hardness measurements, and microstructure observations. Positrons trapped at defects are preferentially annihilated by Sc electrons. Lifetime of trapped positrons indicates that Sc atoms segregate at dislocations. Maximum fraction of positrons annihilated by Sc electrons occurring at 453 K (180 °C) suggests that clustering of Sc bound with vacancies takes place. It is followed by peak of this fraction at 573 K (300 °C). A rise of the contribution of trapped positrons annihilated by Zr electrons starting at 513 K (240 °C) and attaining maximum also at 573 K (300 °C) confirms that Zr participates in precipitation of the Al3Sc particles already at these temperatures. The pronounced hardening at 573 K (300 °C) has its nature in the precipitation of the Al3Sc particles with a Zr-rich shell. The contribution of trapped positrons annihilated by Mn electrons was found to be negligible. © 2015, The Minerals, Metals & Materials Society and ASM International.

  8. Production of new particles in electron-positron annihilation

    International Nuclear Information System (INIS)

    Gilman, F.J.

    1977-02-01

    A number of areas are reviewed where there is important progress in the production of new particles in electron--positron annihilation, but of a more detailed quantitative nature. Charmonium states, charmed mesons, and evidence for a charged heavy lepton are covered. 50 references

  9. Neutralino-stop co-annihilation into electroweak gauge and Higgs bosons at one loop

    Energy Technology Data Exchange (ETDEWEB)

    Harz, J. [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany); Herrmann, B. [Univ. Savoie/CNRS, Annecy-le-Vieux (France). LAPTh; Klasen, M. [Muenster Univ. (Germany). Inst. fuer Theoretische Physik 1; Kovarik, K. [Karlsruhe Institute of Technology, Karlsruhe (Germany). Inst. for Theoretical Physics; Le Boulc' h, Q. [Grenoble Univ. (France). CNRS-IN2P3/INPG

    2012-12-15

    We compute the full O({alpha}{sub s}) supersymmetric QCD corrections for neutralino-stop co-annihilation into electroweak gauge and Higgs bosons in the Minimal Supersymmetric Standard Model (MSSM). We show that these annihilation channels are phenomenologically relevant within the so-called phenomenological MSSM, in particular in the light of the observation of a Higgs-like particle with a mass of about 126 GeV at the LHC. We present in detail our calculation, including the renormalization scheme, the infrared treatment, and the kinematical subtleties to be addressed. Numerical results for the co-annihilation cross sections and the predicted neutralino relic density are presented. We demonstrate that the impact of including the corrections on the cosmologically preferred region of parameter space is larger than the current experimental uncertainty from WMAP data.

  10. Positron annihilation in PI189 and PI304 polyimides

    Energy Technology Data Exchange (ETDEWEB)

    Shantarovich, V.P. [N.N. Semenov Institute of Chemical Physics, Russian Academy of Sciences, ul Kosygina 4 st., 119334 Moscow (Russian Federation)]. E-mail: shant@center.chph.ras.ru; Suzuki, T. [High Energy Accelerator Research Organization KEK, Tsukuba 305-0801 (Japan); He, C. [High Energy Accelerator Research Organization KEK, Tsukuba 305-0801 (Japan); Ito, Y. [Reasearch Center for Nuclear Science and Technology, The University of Tokyo, Tokai, Ibaraki 319-1106 (Japan); Yampolskii, Y.P. [A.V. Topchiev Institute of Petrochemical Synthesis, Russian Academy of Sciences, 29 Leninskii Pr., 117912 Moscow (Russian Federation); Alentiev, A.Yu. [A.V. Topchiev Institute of Petrochemical Synthesis, Russian Academy of Sciences, 29 Leninskii Pr., 117912 Moscow (Russian Federation)

    2005-05-01

    Temperature dependence of the lifetime {tau}3 and intensity I{sub 3} of the long-lived ortho-positronium (o-Ps) component was measured for two polyimides PI189 and PI304 both below and above glass-transition temperatures Tg of these polymers. First heating runs of the experiments revealed anomalous, irregular behavior of the lifetime {tau}3 in both PI in the vicinity (below) of the glass transition temperature. The effect was similar to that discussed recently for a number of PI. However, on the cooling stage of the first cycle and on the heating run of the second cycle, such irregularities disappeared. These results show that anomalous behavior of annihilation characteristics of o-Ps in our PI samples were due not to anomalous behavior of PI structure itself close to Tg point (not to a specific phase transition), but to removal of residual solvent in vicinity of Tg during the first heating cycle. Different approaches to estimations of the specific hole volume and of the holes number density N on the basis of positron annihilation data are discussed. Final estimation for PI189 gives the fractional free volume h=3.35% and N=0.44x1027m-3. The effects of positron trapping by polar-CO groups on annihilation characteristics of PI and on the obtained value of N are also considered.

  11. Efficient kinetic Monte Carlo method for reaction-diffusion problems with spatially varying annihilation rates

    Science.gov (United States)

    Schwarz, Karsten; Rieger, Heiko

    2013-03-01

    We present an efficient Monte Carlo method to simulate reaction-diffusion processes with spatially varying particle annihilation or transformation rates as it occurs for instance in the context of motor-driven intracellular transport. Like Green's function reaction dynamics and first-passage time methods, our algorithm avoids small diffusive hops by propagating sufficiently distant particles in large hops to the boundaries of protective domains. Since for spatially varying annihilation or transformation rates the single particle diffusion propagator is not known analytically, we present an algorithm that generates efficiently either particle displacements or annihilations with the correct statistics, as we prove rigorously. The numerical efficiency of the algorithm is demonstrated with an illustrative example.

  12. Positron annihilation in Si and Si-related materials in thermal equilibrium at high temperature

    International Nuclear Information System (INIS)

    Uedono, A.; Muramatsu, M.; Ubukata, T.; Tanino, H.; Shiraishi, T.; Tanigawa, S.; Takasu, S.

    2001-01-01

    Annihilation characteristics of positrons in the carbon/Si structure in thermal equilibrium at high temperature were studied using a monoenergetic positron beam. Doppler broadening spectra of the annihilation radiation were measured as a function of incident positron energy in the temperature range between 298 K and 1473 K. Above 1173 K, the value of S corresponding to the annihilation of positrons near the carbon/Si interface started to increase, which was attributed to the carbonization of Si and the introduction of open-space defects due to the diffusion of Si atoms toward the carbon layer. The behavior of Ps in a thermally grown SiO 2 film was also studied at 298-1523 K. (orig.)

  13. Data of evolutionary structure change: 1ONAD-1H9WA [Confc[Archive

    Lifescience Database Archive (English)

    Full Text Available 1ONAD-1H9WA 1ONA 1H9W D A ADTIVAVELDTYPNTDIGDPSYPHIGIDIKSVRSKKTAK...WNMQNGKVGTAHIIYNSVDKRLSAVVSYPNADSATVSYDVDLDNVLPEWVRVGLSASTGLYKETNTILSWSFTSKLK-TNALHFMFNQFSKDQKDLILQGDATTGTDG...yChain> 1ONA D 1ONAD

  14. Baryon production in e+e- annihilation

    International Nuclear Information System (INIS)

    Saxon, D.H.

    1988-11-01

    The phenomenology of baryon production in high energy e + e - annihilation is described. Much can be understood in terms of mass effects. Comparisons with the rates for different flavours and spins, with momentum and transverse momentum spectra and with particle correlations are used to confront models. Diquark models give good descriptions, except for the on/off Υ(1s) rates. Areas for experimental and theoretical development are indicated. (author)

  15. Water Accounting Plus (WA+ – a water accounting procedure for complex river basins based on satellite measurements

    Directory of Open Access Journals (Sweden)

    P. Karimi

    2013-07-01

    Full Text Available Coping with water scarcity and growing competition for water among different sectors requires proper water management strategies and decision processes. A pre-requisite is a clear understanding of the basin hydrological processes, manageable and unmanageable water flows, the interaction with land use and opportunities to mitigate the negative effects and increase the benefits of water depletion on society. Currently, water professionals do not have a common framework that links depletion to user groups of water and their benefits. The absence of a standard hydrological and water management summary is causing confusion and wrong decisions. The non-availability of water flow data is one of the underpinning reasons for not having operational water accounting systems for river basins in place. In this paper, we introduce Water Accounting Plus (WA+, which is a new framework designed to provide explicit spatial information on water depletion and net withdrawal processes in complex river basins. The influence of land use and landscape evapotranspiration on the water cycle is described explicitly by defining land use groups with common characteristics. WA+ presents four sheets including (i a resource base sheet, (ii an evapotranspiration sheet, (iii a productivity sheet, and (iv a withdrawal sheet. Every sheet encompasses a set of indicators that summarise the overall water resources situation. The impact of external (e.g., climate change and internal influences (e.g., infrastructure building can be estimated by studying the changes in these WA+ indicators. Satellite measurements can be used to acquire a vast amount of required data but is not a precondition for implementing WA+ framework. Data from hydrological models and water allocation models can also be used as inputs to WA+.

  16. Positron and positronium annihilation in low-dielectric-constant films studied by a pulsed positron beam

    International Nuclear Information System (INIS)

    Suzuki, R.; Ohdaira, T.; Kobayashi, Y.; Ito, K.; Yu, R.S.; Shioya, Y.; Ichikawa, H.; Hosomi, H.; Ishikiriyama, K.; Shirataki, H.; Matsuno, S.; Xu, J.

    2004-01-01

    Positron and positronium annihilation in porous low-dielectric-constant (low-k) films deposited by plasma-enhanced chemical vapor deposition (PECVD) and spin-on dielectric (SOD) have been investigated by means of positron annihilation lifetime spectroscopy (PALS) and age-momentum correlation (AMOC) spectroscopy with a pulsed slow positron beam. The ortho-positronium (o-Ps) lifetime strongly depends on the deposition condition. In general, PECVD low-k films have shorter o-Ps lifetimes than SOD low-k films, indicating PECVD low-k films have smaller pores. Since o-Ps diffusion and escaping from the surface occurs in most of porous SOD films, three-gamma annihilation measurement is important. To investigate o-Ps behavior in SOD films, we have carried out two-dimensional (2D) PALS measurement, which measures annihilation time and pulse-height of the scintillation detector simultaneously. Monte-Carlo simulation of the o-Ps diffusion and escaping in porous films has been carried out to simulate the 2D-PALS results. (orig.)

  17. Kinetics of fragmentation-annihilation processes

    OpenAIRE

    Filipe, JAN; Rodgers, GJ

    1996-01-01

    We investigate the kinetics of systems in which particles of one species undergo binary fragmentation and pair annihilation. In the latter, nonlinear process, fragments react at collision to produce an inert species, causing loss of mass. We analyze these systems in the reaction-limited regime by solving a continuous model within the mean-field approximation. The rate of fragmentation for a particle of mass x to break into fragments of masses y and x-y has the form x(lambda-1) (lambda > 0), a...

  18. On hadron jet multiplicity in e+e- annihilation

    International Nuclear Information System (INIS)

    Kiselev, A.V.

    1982-01-01

    The Q 2 -dependence of the average hadron multiplicity in e + e - -annihilation jets is found in QCD within the framework of planar diagram approximation (Q-transfer momentum). It is shown that account for kinematical restrictions alters the result obtained previously by other authors

  19. Positron annihilation in low-temperature rare gases. II. Argon and neon

    International Nuclear Information System (INIS)

    Canter, K.F.; Roellig, L.O.

    1975-01-01

    Lifetime measurements of slow-positron and ortho-positronium (o-Ps) annihilation were made in argon and neon gases at room temperature and below. The argon experiments cover the temperature range 115 to 300 0 K and the density range 0.0356 to 0.0726 g/cm 3 (approximately equal to 20 to 40 amagat). The slow-positron spectra in argon exhibit a departure from free-positron annihilation below 200 0 K. The departure becomes more marked as the temperature is lowered. No deviation from free o-Ps pickoff annihilation is observed in argon at low temperatures. The neon measurements cover the temperature range 30 to 300 0 K and the density range 0.032 to 0.89 g/cm 3 (approximately equal to 35 to 980 amagat). No effect of temperature on the slow-positron spectra throughout the temperature and density ranges investigated in neon is observed. The spectra are very exponential with a corresponding decay rate which is temperature as well as time independent and is directly proportional to density over the ranges investigated. The o-Ps data are more eventful in that the o-Ps lifetime at near-liquid densities is approximately 20 nsec, a factor of nearly 4 greater than the value obtained using the pickoff-annihilation coefficient obtained at lower densities. This is evidence for positronium-induced cavities in low-temperature neon. A brief discussion of the argon and neon results is given in the context of the explanations offered for the low-temperature effects observed in helium gas

  20. Positron annihilation studies on structural materials for nuclear reactors

    International Nuclear Information System (INIS)

    Rajaraman, R.; Amarendra, G.; Sundar, C.S.

    2012-01-01

    Structural steels for nuclear reactors have renewed interest owing to the future advanced fission reactor design with increased burn-up goals as well as for fusion reactor applications. While modified austenitic steels continue to be the main cladding materials for fast breeder reactors, Ferritic/martensitic steels and oxide dispersion strengthened ferritic steels are the candidate materials for future reactors applications in India. Sensitivity and selectivity of positron annihilation spectroscopy to open volume type defects and nano clusters have been extensively utilized in studying reactor materials. We have recently reviewed the application of positron techniques to reactor structural steels. In this talk, we will present successful application of positron annihilation spectroscopy to probe various structural materials such as D9, ferritic/martensitic, oxide dispersion strengthened (ODS) steels and related model alloys, highlighting our recent studies. (author)

  1. Antiproton-neutron annihilations at rest: Search for broad states

    International Nuclear Information System (INIS)

    Kalogeropoulos, T.E.

    1985-01-01

    The searches so far for meson states produced in p-bar annihilations at rest into π+X have been sensitive to narrow X states. The combinatorial background and the narrow phase space width in missing mass spectra are the main problems. Most of the theoretical models predict broad states. We have measured in a high statistis experiment p-bar(at rest)d→π/sup +- /+Anything inclusive spectra. Using a novel analysis technique the π + π - difference spectra, it is shown that the p-barn annihilation is dominated by two-body cascades. Two new states of opposite G-parity of (mass, width) = (1480, 100) MeV/c 2 are dominant. The G = +1 state has a large decay branching ratio into rho 0 rho 0 . Other features are presented

  2. e+e- annihilation into hadrons at SPEAR

    International Nuclear Information System (INIS)

    Feldman, G.J.

    1975-08-01

    The review of e + e - annihilation includes the detectors, total hadronic cross sections, charged multiplicity, and inclusive distributions. The new particles are excluded. Some results on the search for new particles, searches for monochromatic photons from the psi 1 , a search for nonleptonic decays of charmed mesons, and evidence for anomalous lepton production are also given. 20 references

  3. Positron annihilation lifetime study of extended defects in semiconductor glasses and polymers

    Energy Technology Data Exchange (ETDEWEB)

    Boyko, Olha [Department of Pediatric Dentistry, Danylo Halytsky Lviv National Medical University, Pekarska str. 69, 79010 Lviv (Ukraine); Shpotyuk, Yaroslav [Department of Optoelectronics and Information Technologies, Ivan Franko National University of Lviv, Dragomanova str. 50, 79005 Lviv (Ukraine); Lviv Scientific Research Institute of Materials, Scientific Research Company ' ' Carat' ' , Stryjska str. 202, 79031 Lviv (Ukraine); Filipecki, Jacek [Institute of Physics, Jan Dlugosz University in Czestochowa, Armii Krajowej al. 13/15, 42200 Czestochowa (Poland)

    2013-01-15

    The processes of atomic shrinkage in network-forming solids initiated by external influences are tested using technique of positron annihilation lifetime spectroscopy at the example of chalcogenide vitreous semiconductors of arsenic sulphide type and acrylic polymers for dental application. Two state positron trapping is shown to be responsible for atomic shrinkage in chalcogenide glasses, while mixed trapping and ortho-positronium decaying is character for volumetric densification and stress propagation in acrylic dental polymers. At the basis of the obtained results it is concluded that correct analysis of externally-induced shrinkage in polymer networks under consideration can be developed by using original positron lifetime data treatment algorithms to compensate defect-free bulk annihilation channel within two-state positron trapping model and account for an interbalance between simultaneously co-existing positron trapping and orth-positronium related decaying channels within mixed three-state positron annihilation model (copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  4. Positron annihilation lifetime study of extended defects in semiconductor glasses and polymers

    International Nuclear Information System (INIS)

    Boyko, Olha; Shpotyuk, Yaroslav; Filipecki, Jacek

    2013-01-01

    The processes of atomic shrinkage in network-forming solids initiated by external influences are tested using technique of positron annihilation lifetime spectroscopy at the example of chalcogenide vitreous semiconductors of arsenic sulphide type and acrylic polymers for dental application. Two state positron trapping is shown to be responsible for atomic shrinkage in chalcogenide glasses, while mixed trapping and ortho-positronium decaying is character for volumetric densification and stress propagation in acrylic dental polymers. At the basis of the obtained results it is concluded that correct analysis of externally-induced shrinkage in polymer networks under consideration can be developed by using original positron lifetime data treatment algorithms to compensate defect-free bulk annihilation channel within two-state positron trapping model and account for an interbalance between simultaneously co-existing positron trapping and orth-positronium related decaying channels within mixed three-state positron annihilation model (copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  5. Connecting dark matter annihilation to the vertex functions of Standard Model fermions

    Energy Technology Data Exchange (ETDEWEB)

    Kumar, Jason; Light, Christopher, E-mail: jkumar@hawaii.edu, E-mail: lightc@hawaii.edu [Department of Physics and Astronomy, University of Hawaii, Honolulu, HI 96822, Hawaii (United States)

    2017-07-01

    We consider scenarios in which dark matter is a Majorana fermion which couples to Standard Model fermions through the exchange of charged mediating particles. The matrix elements for various dark matter annihilation processes are then related to one-loop corrections to the fermion-photon vertex, where dark matter and the charged mediators run in the loop. In particular, in the limit where Standard Model fermion helicity mixing is suppressed, the cross section for dark matter annihilation to various final states is related to corrections to the Standard Model fermion charge form factor. These corrections can be extracted in a gauge-invariant manner from collider cross sections. Although current measurements from colliders are not precise enough to provide useful constraints on dark matter annihilation, improved measurements at future experiments, such as the International Linear Collider, could improve these constraints by several orders of magnitude, allowing them to surpass the limits obtainable by direct observation.

  6. Land Use Planning and Housing Situation in the WA and Offinso ...

    African Journals Online (AJOL)

    Housing insufficiency is a major problem confronting most Ghanaian households. The paper examines the state of housing in the Wa and the Offinso South municipalities of Ghana. It investigates the liveability of housing in these municipalities. The housing adequacy across the municipalities is compared. One hundred and ...

  7. Positron annihilation in sodium and copper β-vanadium oxide bronzes

    International Nuclear Information System (INIS)

    Dryzek, J.; Rogowska, E.

    1990-01-01

    Studies of copper and sodium β-vanadium oxide bronzes are performed using positron annihilation measured with a long slit angular correlation apparatus. The dependences of peak coincidence rate on temperature (40 to 310deg C) are obtained for different concentrations of donor atoms in the case of copper vanadium oxide bronzes. A three-states model corresponding to the annihilation of positrons in donor atom sublattice is applied for the description of the experimental data. The creation enthalpy of vacancies for that sublattice is equal to (0.60 ± 0.01) eV for Na 0.33 V 2 O 5 and equal to (0.64 ± 0.01) eV for Cu x V 2 O 5 . (author)

  8. Single-quantum annihilation of positrons with shell-bound atomic electrons

    International Nuclear Information System (INIS)

    Palathingal, J.C.; Asoka-Kumar, P.; Lynn, K.G.; Posada, Y.; Wu, X.Y.

    1991-01-01

    The single-quantum annihilation of positrons has been studied experimentally with a positron beam and a thin lead target, at energies 1 MeV and higher. Spectral peaks corresponding to the K, L, and M shells have been resolved and observed distinctly for the first time. The shell ratios L/K and M/K have been determined. An analysis of the L peak has yielded the (LII+LIII)/L ratio. The first measurements of the directional distributions of the annihilation quanta of the three individual electron shells are also reported. The results are in agreement with theory. They also point out the potential for applying the phenomena to the development of a tunable, highly directional gamma-ray source

  9. Violation of G-parity in antinucleon-nucleon annihilation

    International Nuclear Information System (INIS)

    Green, A.M.; Sainio, M.E.; Moussallam, B.; Niskanen, J.A.; Wycech, S.

    1991-01-01

    A strategy is proposed for investigating the violation of G-parity in the annihilation reaction anti np → π + π 0 . As illustrations π 0 -η mixing and the mass difference effects are considered. This leads to an asymmetry of about 1% in the cross section. (orig.)

  10. Positron annihilation and tribological studies of nano-embedded Al ...

    Indian Academy of Sciences (India)

    Administrator

    Positron annihilation studies of aluminium alloys with nanodispersions of insoluble elements, i.e.,. In, Sn, Pb and Au ... potential objects of different studies and applications. ... dence Doppler broadening spectroscopy is the high sensi- tivity to ...

  11. Positron annihilation lifetime characterization of oxygen ion irradiated rutile TiO2

    Science.gov (United States)

    Luitel, Homnath; Sarkar, A.; Chakrabarti, Mahuya; Chattopadhyay, S.; Asokan, K.; Sanyal, D.

    2016-07-01

    Ferromagnetic ordering at room temperature has been induced in rutile phase of TiO2 polycrystalline sample by O ion irradiation. 96 MeV O ion induced defects in rutile TiO2 sample has been characterized by positron annihilation spectroscopic techniques. Positron annihilation results indicate the formation of cation vacancy (VTi, Ti vacancy) in these irradiated TiO2 samples. Ab initio density functional theoretical calculations indicate that in TiO2 magnetic moment can be induced either by creating Ti or O vacancies.

  12. Antiproton-proton annihilations into four prongs at 7.2 GeV/c

    International Nuclear Information System (INIS)

    Leeuw, A. de.

    1979-01-01

    Annihilation reactions are described in which four charged pions and also maybe uncharged particles are produced. Data was acquired in an antiproton-proton experiment at a beam momentum of 7.2 GeV/c and 220K pictures of the CERN 2m HBC were measured. Cross sections have been determined and angular distributions of the pions and of some resonances are given. Two models that describe annihilation reactions are treated, the so called CLA model and a simple quark model. (C.F./Auth.)

  13. Weak-anisotropy moveout approximations for P-waves in homogeneous TOR layers

    Czech Academy of Sciences Publication Activity Database

    Farra, V.; Pšenčík, Ivan

    2017-01-01

    Roč. 82, č. 4 (2017), WA23-WA32 ISSN 0016-8033 R&D Projects: GA ČR(CZ) GA16-05237S Institutional support: RVO:67985530 Keywords : anisotropic media * velocity * seismic waves Subject RIV: DC - Siesmology, Volcanology, Earth Structure OBOR OECD: Volcanology Impact factor: 2.391, year: 2016

  14. Semi-inclusive production of two back-to-back hadron pairs in e+e- annihilation revisited

    Science.gov (United States)

    Matevosyan, Hrayr H.; Bacchetta, Alessandro; Boer, Daniël; Courtoy, Aurore; Kotzinian, Aram; Radici, Marco; Thomas, Anthony W.

    2018-04-01

    The cross section for back-to-back hadron pair production in e+e- annihilation provides access to the dihadron fragmentation functions (DiFF) needed to extract nucleon parton distribution functions from the semi-inclusive deep inelastic scattering (SIDIS) experiments with two detected final state hadrons. Particular attention is given to the so-called interference DiFF (IFF), which makes it possible to extract the transversity parton distribution of the nucleon in the collinear framework. However, previously unnoticed discrepancies were recently highlighted between the definitions of the IFFs appearing in the collinear kinematics when reconstructed from DiFFs entering the unintegrated fully differential cross sections of SIDIS and e+e- annihilation processes. In this work, to clarify this problem we re-derive the fully differential cross section for e+e- annihilation at the leading-twist approximation. We find a mistake in the definition of the kinematics in the original expression that systematically affects a subset of terms and that leads to two significant consequences. First, the discrepancy between the IFF definitions in the cross sections for SIDIS and e+e- annihilation is resolved. Second, the previously derived azimuthal asymmetry for accessing the helicity dependent DiFF G1⊥ in e+e- annihilation vanishes, which explains the nonobservation of this asymmetry in the recent experimental searches by the BELLE collaboration. We discuss the recently proposed alternative option to extract G1⊥.

  15. Christianity in Early Kenyan Novels: Ngugi Wa Thiong'o's Weep Not ...

    African Journals Online (AJOL)

    In light of this, we read the two novels as attempts by the writer to project the trauma caused by and the tensions of Christianity among the colonized subjects as important influences in the formation and development of (post)colonial Kenyan subjects. Key Words: Ngugi Wa Thiong'o, Christianity, postcolonial, subjects.

  16. The exploration and the U'wa

    International Nuclear Information System (INIS)

    Santiago Reyes, Miguel Angel

    2003-01-01

    The document analyzes the different actions taken to harmonize the oil development without impacting the customs of the indigenous communities; like it is the case of the community U'wa in Colombia, where conflicts were generated in the relationship that the oil companies, that which led during some years to the suspension of the activity and the postponement of exploratory projects until the achievement of an understanding that has looked for to harmonize the rights clearly based in the Colombian constitution, according to which the state has right to the property of the underground and its exploitation in benefit of the whole nation, and the indigenous towns that are entitled to the protection of its cultural, social and economic integrity

  17. Application of positron annihilation induced auger electron spectroscopy to the study of surface chemistry

    International Nuclear Information System (INIS)

    Weiss, A.H.; Yang, G.; Nangia, A.; Kim, J.H.; Fazleev, N.G.

    1996-01-01

    Positron annihilation induced Auger Electron Spectroscopy (PAES), makes use a beam of low energy positrons to excite Auger transitions by annihilating core electrons. This novel mechanism provides PAES with a number of unique features which distinguishes it from other methods of surface analysis. In PAES the very large collisionally induced secondary electron background which is present under the low energy Auger peaks using conventional techniques can be eliminated by using a positron beam whose energy is below the range of Auger electron energies. In addition, PAES is more surface selective than conventional Auger Spectroscopy because the PAES signal originates almost exclusively from the topmost atomic layer due to the fact that the positrons annihilating with the core electrons are trapped in an image correlation well just outside the surface. In this paper, recent applications of Positron Annihilation Induced Auger Electron Spectroscopy (PAES) to the study of surface structure and surface chemistry will be discussed including studies of the growth, alloying and inter-diffusion of ultrathin layers of metals, metals on semiconductors, and semiconductors on semiconductors. In addition, the possibilities for future application of PAES to the study of catalysis and surface chemistry will be outlined. (author)

  18. Structural and functional analysis of the finished genome of the recently isolated toxic Anabaena sp. WA102.

    Science.gov (United States)

    Brown, Nathan M; Mueller, Ryan S; Shepardson, Jonathan W; Landry, Zachary C; Morré, Jeffrey T; Maier, Claudia S; Hardy, F Joan; Dreher, Theo W

    2016-06-13

    Very few closed genomes of the cyanobacteria that commonly produce toxic blooms in lakes and reservoirs are available, limiting our understanding of the properties of these organisms. A new anatoxin-a-producing member of the Nostocaceae, Anabaena sp. WA102, was isolated from a freshwater lake in Washington State, USA, in 2013 and maintained in non-axenic culture. The Anabaena sp. WA102 5.7 Mbp genome assembly has been closed with long-read, single-molecule sequencing and separately a draft genome assembly has been produced with short-read sequencing technology. The closed and draft genome assemblies are compared, showing a correlation between long repeats in the genome and the many gaps in the short-read assembly. Anabaena sp. WA102 encodes anatoxin-a biosynthetic genes, as does its close relative Anabaena sp. AL93 (also introduced in this study). These strains are distinguished by differences in the genes for light-harvesting phycobilins, with Anabaena sp. AL93 possessing a phycoerythrocyanin operon. Biologically relevant structural variants in the Anabaena sp. WA102 genome were detected only by long-read sequencing: a tandem triplication of the anaBCD promoter region in the anatoxin-a synthase gene cluster (not triplicated in Anabaena sp. AL93) and a 5-kbp deletion variant present in two-thirds of the population. The genome has a large number of mobile elements (160). Strikingly, there was no synteny with the genome of its nearest fully assembled relative, Anabaena sp. 90. Structural and functional genome analyses indicate that Anabaena sp. WA102 has a flexible genome. Genome closure, which can be readily achieved with long-read sequencing, reveals large scale (e.g., gene order) and local structural features that should be considered in understanding genome evolution and function.

  19. Applications of positron annihilation spectroscopy in materials research

    Science.gov (United States)

    Singh, Jag J.

    1988-01-01

    Positron Annihilation Spectroscopy (PAS) has emerged as a powerful technique for research in condensed matter. It has been used extensively in the study of metals, ionic crystals, glasses and polymers. The present review concentrates on applications of positron lifetime measurements for elucidation of the physicochemical structure of polymers.

  20. Moisture dependence of positron annihilation rates in molecular substances

    International Nuclear Information System (INIS)

    Singh, J.J.; Holt, W.H.

    1982-01-01

    Positron annihilation rates have been studied in polymers and graphite-polymer composites as a function of their moisture content. The annihilation rates have been found to increase linearly with increasing moisture content in epoxies and polyamides, whereas no definite trends have been observed in polyimides. These experimental results have been used as the basis for the calculation of moisture content of several polymeric test specimens. For example, the directly measured moisture content of a Kevlar specimen was 45.5 + or - 5.0% of saturation value, whereas the moisture content on the basis of the decrease in positron lifetime was calculated to be 46.5 + or - 3.5%. Similarly, the directly measured moisture content of a graphite-epoxy composite (55 v/o fiber) was 19.2 + or - 0.6% of saturation value as opposed to a calculated value of 16.0 + or - 5.0%

  1. A new class of weight and WA systems of the Kravchenko-Kaiser functions

    Science.gov (United States)

    Kravchenko, V. F.; Pustovoit, V. I.; Churikov, D. V.

    2014-05-01

    A new class of weight and WA-systems of the Kravchenko-Kaiser functions which showed its efficiency in various physical applications is proposed and substantiated. This publication consists of three parts. In the first the Kravchenko-Kaiser weight functions are constructed on basis of the theory of atomic functions (AFs) and the Kaiser windows for the first time. In the second part new constructions of analytic WA-systems of the Kravchenko-Kaiser functions are costructed. In the third part their applications to problems of weight averaging of the difference frequency signals are considered. The numerical experiment and the physical analysis of the results for concrete physical models confirmed their efficiency. This class of functions can find wide physical applications in problems of digital signal processing, restoration of images, radar, radiometry, radio astronomy, remote sensing, etc.

  2. Impacts of dark matter particle annihilation on recombination and the anisotropies of the cosmic microwave background

    International Nuclear Information System (INIS)

    Zhang Le; Chen Xuelei; Lei Yian; Si Zongguo

    2006-01-01

    The recombination history of the Universe provides a useful tool for constraining the annihilation of dark matter particles. Even a small fraction of dark matter particles annihilated during the cosmic dark age can provide sufficient energy to affect the ionization state of the baryonic gas. Although this effect is too small for neutralinos, lighter dark matter particle candidates, e.g. with mass of 1-100 MeV, which was proposed recently to explain the observed excess of positrons in the galactic center, may generate observable differences in the cosmic microwave background (CMB) temperature and polarization anisotropies. The annihilations at the era of recombination affects mainly the CMB anisotropy at small angular scales (large l), and is distinctively different from the effect of early reionization. We perform a multiparameter analysis of the CMB data, including both the Wilkinson Microwave Anisotropy Probe (WMAP) first year and three year data, and the ACBAR, Boomerang, CBI, and VSA data. Assuming that the observed excess of e + e - pairs in the galactic center region is produced by dark matter annihilation, and that a sizable fraction of the energy produced in the annihilation is deposited in the baryonic gas during recombination, we obtain a 95% dark matter mass limit of M<8 MeV with the current data set

  3. On the Sunyaev-Zel'dovich effect from dark matter annihilation or decay in galaxy clusters

    International Nuclear Information System (INIS)

    Lavalle, Julien; Boehm, Céline; Barthès, Julien

    2010-01-01

    We revisit the prospects for detecting the Sunyaev Zel'dovich (SZ) effect induced by dark matter (DM) annihilation or decay. We show that with standard (or even extreme) assumptions for DM properties, the optical depth associated with relativistic electrons injected from DM annihilation or decay is much smaller than that associated with thermal electrons, when averaged over the angular resolution of current and future experiments. For example, we find: τ DM ∼ 10 −9 −10 −5 (depending on the assumptions) for m χ = 1 GeV and a density profile ρ∝r −1 for a template cluster located at 50 Mpc and observed within an angular resolution of 10'', compared to τ th ∼ 10 −3 −10 −2 . This, together with a full spectral analysis, enables us to demonstrate that, for a template cluster with generic properties, the SZ effect due to DM annihilation or decay is far below the sensitivity of the Planck satellite. This is at variance with previous claims regarding heavier annihilating DM particles. Should DM be made of lighter particles, the current constraints from 511 keV observations on the annihilation cross section or decay rate still prevent a detectable SZ effect. Finally, we show that spatial diffusion sets a core of a few kpc in the electron distribution, even for very cuspy DM profiles, such that improving the angular resolution of the instrument, eg with ALMA, does not necessarily improve the detection potential. We provide useful analytical formulæ parameterized in terms of the DM mass, decay rate or annihilation cross section and DM halo features, that allow quick estimates of the SZ effect induced by any given candidate and any DM halo profile

  4. Streetism And Child Labour In The Wa Municipality Of Ghana A ...

    African Journals Online (AJOL)

    The challenge of child labor in Ghana, especially in Wa, has been given attention in recent times by various organizations within the country. An understudied dimension of these efforts at eradicating child labor is its gendered nature. This study was therefore conducted to unearth the gender dimension of the drivers of child ...

  5. Fish abundance, composition, distribution - Recolonization of the Cedar River, WA by Pacific salmon

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The objective of this study is to quantify population, community, and ecosystem level changes as a result of salmon recolonization of the Cedar River, WA above...

  6. Growth, movement and survival - Recolonization of the Cedar River, WA by Pacific salmon

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The objective of this study is to quantify population, community, and ecosystem level changes as a result of salmon recolonization of the Cedar River, WA above...

  7. Materials characterization of free volume and void properties by two-dimensional positron annihilation lifetime spectroscopy

    Science.gov (United States)

    Chen, Hongmin; Van Horn, J. David; Jean, Y. C.; Hung, Wei-Song; Lee, Kueir-Rarn

    2013-04-01

    Positron annihilation lifetime spectroscopy (PALS) has been widely used to determine the free volume and void properties in polymeric materials. Recently, a two dimensional positron annihilation lifetime spectroscopy (2DPALS) system has been developed for membrane applications. The system measures the coincident signals between the lifetime and the energy which could separate the 2γ and 3γ annihilations and improve the accuracy in the determination of the free volume and void properties. When 2D-PALS is used in coupling with a variable mono-energy slow positron beam, it could be applied to a variety of material characterization. Results of free volumes and voids properties in a multi-layer polymer membrane characterized using 2D-PALS are presented.

  8. Defects in fine-grained and porous materials characterized by positron annihilation

    International Nuclear Information System (INIS)

    Staab, T.E.M.; Krause-Rehberg, R.; Kieback, B.

    2003-01-01

    We investigate the annihilation parameters (lifetimes and intensities) for positrons becoming trapped at grain boundaries and at inner surfaces (pores), examining fine-grained nickel powder compacts (effective powder particle size 1 - 10 μm with grains in or even below the micron size). Furthermore, we can monitor grain growth and sintering (volume shrinkage) during successive heat treatment of powder compacts. To reach this aim, we correlate the annihilation parameters with results of a Monte-Carlo simulation and analytical solutions of the positron diffusion. We find that it is possible to determine an effective average powder particle size as well as grain sizes by positron lifetime spectroscopy. (author)

  9. Dark matter annihilations search in dwarf spheroidal galaxies with fermi

    International Nuclear Information System (INIS)

    Farnier, C.; Nuss, E.; Cohen-Tanugi, J.

    2011-01-01

    Launched in June 2008, the Fermi Gamma-ray Telescope includes a pair conversion detector designed for the 20 MeV to ∼300GeV gamma-ray sky study, the Large Area Telescope (LAT). Operating in all-sky survey mode, its excellent sensitivity and angular resolution will allow either to discover or constrain a signal coming through the annihilation of dark matter particles. Predicted by cold dark matter scenarios as the largest clumps, dwarf spheroidal galaxies are amongst the most attractive targets for indirect search of dark matter by gamma-ray experiments. We present here an overview of the Fermi LAT Dark Matter and New Physics Working Group efforts in the searches of gamma-ray fluxes coming from WIMP pair annihilations in dwarf spheroidal galaxies.

  10. Annihilation and gravitational clumping of monopoles in the early universe

    International Nuclear Information System (INIS)

    Izawa, Mizuo; Sato, Katsuhiko.

    1983-01-01

    In order to avoid the overproduction of magnetic monopoles in the early Universe, we investigate how monopoles evolve in the Big Bang Universe for arbitrary mass of monopoles and the arbitrary initial abundance. First, we calculate pair annihilation of monopoles by taking into account the entropy production due to the annihilations. Second, we investigate the formation of monopole stars and black holes due to gravitational clumping of monopoles. In particular, we take into account the entropy and baryon number generation by black hole evaporation. It is shown, however, that the burning of monopole stars or the evaporation of black holes cannot dilute the monopole abundance sufficiently without conflicts with present baryon/entropy ratio and primordial nucleosynthesis regardless of monopole mass. (author)

  11. Intermittency study in e+e- annihilations at 29 GeV

    International Nuclear Information System (INIS)

    Sugano, K.

    1990-01-01

    The intermittency and fractal behavior in e + e - annihilations has been studied using the HRS detector at PEP (√s = 29 GeV). The factorial moments F i (i = 2 ∼ 5) in small rapidity intervals show stronger intermittency slopes than those for the πp, bar pp, and AA reactions. This direct measurement confirms our previous data derived from the k-values in the negative binomial fits to the multiplicity distributions in various central rapidity windows. The fractal moments G q have been measured for the first time in e + e - annihilations. The Legendre transform f(α) derived from the fractal moments show a self-similar behavior which is consistent with the jet cascading mechanism. 95 refs., 46 figs., 2 tabs

  12. Applications of positron annihilation spectroscopy in materials research

    International Nuclear Information System (INIS)

    Singh, J.J.

    1988-01-01

    Positron Annihilation Spectroscopy (PAS) has emerged as a powerful technique for research in condensed matter. It has been used extensively in the study of metals, ionic crystals, glasses and polymers. The present review concentrates on applications of positron lifetime measurements for elucidation of the physicochemical structure of polymers. 10 references

  13. Annihilation of antiprotons stopped in liquid hydrogen and deuterium

    International Nuclear Information System (INIS)

    Dalkarov, O.D.; Kerbikov, B.O.; Markushin, V.E.

    1976-01-01

    Detailed analysis is given of stopping antiproton annihilation in liquid hydrogen and deuterium. Connection between capture schedule and properties of bound states in nucleon-antinucleon system is established. The theoretical predictions are compared with experimental data which appeared in 1971-75

  14. 77 FR 33307 - Drawbridge Operation Regulation; Lake Washington Ship Canal, Seattle, WA

    Science.gov (United States)

    2012-06-06

    ...The Coast Guard has issued a temporary deviation from the operating schedule that governs the Montlake Bridge across the Lake Washington Ship Canal, mile 5.2, at Seattle, WA. This deviation is necessary to accommodate maintenance to the metro trolley system which crosses the bridge.

  15. Malaria treatment-seeking behaviour and related factors of Wa ethnic minority in Myanmar: a cross-sectional study

    Science.gov (United States)

    2012-01-01

    Background In Southeast Asia, data on malaria treatment-seeking behaviours and related affecting factors are rare. The population of the Wa ethnic in Myanmar has difficulty in accessing formal health care. To understand malaria treatment-seeking behaviour and household-affecting factors of the Wa people, a cross-sectional study carried out in Shan Special Region II, Myanmar. Methods The two methods, questionnaire-based household surveys to household heads and in-depth interviews to key informants, were carried out independently. The proportion of treatment-seeking patterns was calculated. Logistic regression was used to determine affecting factors of treatment-seeking. Qualitative data were analysed by using Text Analysis Markup System. Results Overall, 87.5% of the febrile population sought treatment, but only 32.0% did so within 24 hours. The proportion accessing the retail sector (79.6%) was statistically significant higher (Paffecting factors include health service systems, social and cultural factors in Wa State of Myanmar. PMID:23237576

  16. Positron annihilation spectroscopic studies of solvothermally synthesized ZnO nanobipyramids and nanoparticles

    Science.gov (United States)

    Ghoshal, Tandra; Biswas, Subhajit; Kar, Soumitra; Chaudhuri, Subhadra; Nambissan, P. M. G.

    2008-02-01

    Zinc oxide (ZnO) samples in the form of hexagonal-based bipyramids and particles of nanometer dimensions were synthesized through solvothermal route and characterized by x-ray diffraction and transmission electron microscopy. Positron annihilation experiments were performed to study the structural defects such as vacancies and surfaces in these nanosystems. From coincidence Doppler broadening measurements, the positron trapping sites were identified as Zn vacancies or Zn-O-Zn trivacancy clusters. The positron lifetimes, their relative intensities, and the Doppler broadened lineshape parameter S all showed characteristic changes across the nanobipyramid size corresponding to the thermal diffusion length of positrons. In large nanobipyramids, vacancies within the crystallites also trapped positrons and the effects of agglomeration of such vacancies due to increased temperatures of synthesis were reflected in the variation of the annihilation parameters with their base diameters. The sizes of the nanoparticles used were all in the limit of thermal diffusion length of positrons and the annihilation characteristics were in accordance with the decreasing contribution from surfaces with increasing particle size.

  17. Reappraisal of dark matter co-annihilating with a top or bottom partner

    Science.gov (United States)

    Keung, Wai-Yee; Low, Ian; Zhang, Yue

    2017-07-01

    We revisit the calculation of the relic density of dark matter particles co-annihilating with a top or bottom partner by properly including the QCD bound-states (onia) effects of the colored partners as well as the relevant electroweak processes, which become important in the low-mass region. We carefully set up the complete framework that incorporates the relevant contributions and investigate their effects on the cosmologically preferred mass spectrum, which turn out to be comparable in size to those coming from the Sommerfeld enhancement. We apply the calculation to three scenarios: bino-stop and bino-sbottom co-annihilations in supersymmetry and a vector dark matter co-annihilating with a fermionic top partner. In addition, we confront our analysis of the relic abundance with recent direct detection experiments and collider searches at the LHC, which have important implications in the bino-stop and bino-sbottom scenarios. In particular, in the bino-stop case, recent LHC limits have excluded regions of parameter space with a direct detection rate that is above the neutrino floor.

  18. Positron annihilation studies in lysozyme and catalase

    International Nuclear Information System (INIS)

    Rohilla, Y.; Singh, K.P.; Roy Choudhury, S.; Jain, P.C.

    1992-01-01

    Positron annihilation studies have been carried out in two enzymes, lysozyme and catalase. Temperature dependence of the positron lifetimes in these two enzymes has been investigated. The results explained in terms of the free volume model and fluctuations between different conformational micro states of enzyme structures provide a new insight into the mechanism of bio-activity of these enzymes. (author). 15 refs., 4 figs

  19. Source theory analysis of electron--positron annihilation experiments

    International Nuclear Information System (INIS)

    Schwinger, J.

    1975-01-01

    The phenomenological viewpoint already applied to deep inelastic scattering is extended to the discussion of electron-positron annihilation experiments. Some heuristic arguments lead to simple forms for the pion differential cross section that are in reasonable accord with the published experimental data in the energy interval 3 to 4.8 GeV

  20. Moisture dependence of positron annihilation rates in molecular substances

    International Nuclear Information System (INIS)

    Singh, J.J.; Holt, W.H.; Mock, W. Jr.

    1982-01-01

    Positron annihilation rates have been studied in polymers and graphite-polymer composites as a function of their moisture content. The annihilation rates have been found to increase linearly with increasing moisture content in epoxies and polyamides, whereas no definite trends have been observed in the polymides. These experimental results have been used as the basis for the calculation of moisture content of several polymeric test specimens. For example, the directly measured moisture content of a Kevlar/epoxy specimen (55 v/o fiber) was 45.5 +- 5.0% of saturation value, whereas the moisture content on the basis of the decrease in positron lifetime was calculated to be 46.5 +- 3.5%. Similarly, the directly measured moisture content of a graphite/epoxy composite (55 v/o fiber) was 19.2 +- 0.6% of saturation value as opposed to a calculated value of 16.0 +- 5.0%. (orig.)

  1. 78 FR 5151 - Proposed Amendment of Class E Airspace; Omak, WA

    Science.gov (United States)

    2013-01-24

    ... extending upward from 700 feet above the surface and 1,200 feet above the surface at Omak Airport, Omak, WA.... The size and shape of the airspace will remain the same by using the Airport Reference Point in... amended as follows: Paragraph 6005 Class E airspace areas extending upward from 700 feet or more above the...

  2. Positron annihilation lifetime measurements of austenitic stainless and ferritic/martensitic steels irradiated in the SINQ target irradiation program

    Energy Technology Data Exchange (ETDEWEB)

    Sato, K., E-mail: ksato@rri.kyoto-u.ac.jp [Research Reactor Institute, Kyoto University, Kumatori-cho, Sennan-gun, Osaka 590-0494 (Japan); Xu, Q.; Yoshiie, T. [Research Reactor Institute, Kyoto University, Kumatori-cho, Sennan-gun, Osaka 590-0494 (Japan); Dai, Y. [Spallation Neutron Source Division, Paul Scherrer Institute, CH-5232 Villigen PSI (Switzerland); Kikuchi, K. [Frontier Research Center for Applied Atomic Sciences, Ibaraki University, Tokai-mura, Naka-gun, Ibaraki 319-1106 (Japan)

    2012-12-15

    Titanium-doped austenitic stainless steel (JPCA) and reduced activated ferritic/martensitic steel (F82H) irradiated with high-energy protons and spallation neutrons were investigated by positron annihilation lifetime measurements. Subnanometer-sized (<{approx}0.8 nm) helium bubbles, which cannot be observed by transmission electron microscopy, were detected by positron annihilation lifetime measurements for the first time. For the F82H steel, the positron annihilation lifetime of the bubbles decreased with increasing irradiation dose and annealing temperature because the bubbles absorb additional He atoms. In the case of JPCA steel, the positron annihilation lifetime increased with increasing annealing temperature above 773 K, in which case the dissociation of complexes of vacancy clusters with He atoms and the growth of He bubbles was detected. He bubble size and density were also discussed.

  3. Positron annihilation lifetime measurements of austenitic stainless and ferritic/martensitic steels irradiated in the SINQ target irradiation program

    International Nuclear Information System (INIS)

    Sato, K.; Xu, Q.; Yoshiie, T.; Dai, Y.; Kikuchi, K.

    2012-01-01

    Titanium-doped austenitic stainless steel (JPCA) and reduced activated ferritic/martensitic steel (F82H) irradiated with high-energy protons and spallation neutrons were investigated by positron annihilation lifetime measurements. Subnanometer-sized (<∼0.8 nm) helium bubbles, which cannot be observed by transmission electron microscopy, were detected by positron annihilation lifetime measurements for the first time. For the F82H steel, the positron annihilation lifetime of the bubbles decreased with increasing irradiation dose and annealing temperature because the bubbles absorb additional He atoms. In the case of JPCA steel, the positron annihilation lifetime increased with increasing annealing temperature above 773 K, in which case the dissociation of complexes of vacancy clusters with He atoms and the growth of He bubbles was detected. He bubble size and density were also discussed.

  4. Event shapes in e+e- annihilation and deep inelastic scattering

    International Nuclear Information System (INIS)

    Dasgupta, Mrinal; Salam, Gavin P

    2004-01-01

    This review examines the status of event-shape studies in e + e - annihilation and DIS. It includes discussions of perturbative calculations, of various approaches to modelling hadronization and of comparisons to data. (topical review)

  5. Experimental tests of QCD: Deep inelastic scattering, e+e- annihilation and hard hadron-hadron scattering

    International Nuclear Information System (INIS)

    Hansl-Kozanecka, T.

    1992-01-01

    In this set of lectures the author examines phenomenological aspects of quantum chromodynamics (QCD) which are relevant for lepton-hadron, electron-positron, and hadron-hadron collisions. He points how the strength of the strong coupling constant, αs, makes QCD calculations converge much more slowly in powers of αs, and missing higher order terms must be carefully estimated. The most stringent test of QCD can be performed in deep inelastic lepton scattering and in e + e - annihilation. In deep inelastic scattering the virtual γ or W/Z are used as a probe of the nucleon structure. They couple to quarks, not gluons. Only the incoming and outgoing lepton have to be measured. The hadronic fluid state does not have to be analyzed. In e + e - annihilation the virtual γ or Z 0 decays to lepton and quark pairs. The branching ratio into quarks is a counter for the number of colours available, the detailed structure of the final state reflects the radiation of gluons as the initial quark-antiquark separate from each other. Quarks and gluons are observed here, though in the presence of hadron formation. Hard hadron-hadron, or parton-parton collisions provide cross sections dominated by the gluon component, which is only weakly measured in deep inelastic collisions. Recent experimental results in these three areas are reviewed, and compared to QCD calculations. Scaling violations and analysis of structure functions in deep inelastic scattering are reviewed. QCD in e + e - branching to hadrons is reviewed near the Z 0 resonance, and a number of cross sections and jet related properties which can be calculated as a function of the single parameter αs are reviewed. Hadron-hadron collisions are reviewed for three processes; jet production, direct photon production, and high p perpendicular W/Z boson production

  6. Search for structure in the low-energy anti p-p annihilation cross section

    International Nuclear Information System (INIS)

    Jastrzembski, E.; Haik, N.; McFarlane, W.K.; Mandelkern, M.A.; Schultz, D.C.; Amsler, C.; Hermann, C.C.; Wolfe, D.M.

    1980-01-01

    The relative cross section for annihilation of antiprotons on hydrogen into one or more charged pions was measured. Incident beam momentum was 600 MeV/c. Numbers of observed events (relative) were compared with those expected from the sensitivity of the apparatus. A phase-space model was used for p-barp annihilation. Relative cross sections are plotted vs invariant mass. Upper limits on cross sections for the formation of narrow resonances in the S region are given; previously reported structures are not confirmed. 2 figures, 1 table

  7. Inactivation of Adenovirus Type 5, Rotavirus WA and Male Specific Coliphage (MS2 in Biosolids by Lime Stabilization

    Directory of Open Access Journals (Sweden)

    Aaron B. Margolin

    2007-03-01

    Full Text Available The use of lime to reduce or eliminate pathogen content is a cost-effective treatment currently employed in many Class B biosolids production plants in the United States. A bench scale model of lime stabilization was designed to evaluate the survival of adenovirus type 5, rotavirus Wa, and the male specific bacteriophage, MS2, in various matrices. Each virus was initially evaluated independently in a reverse osmosis treated water matrix limed with an aqueous solution of calcium hydroxide for 24-hr at 22 ± 5°C. In all R/O water trials, adenovirus type 5, rotavirus Wa and MS2 were below detectable levels (<100.5 TCID50/mL and <1 PFU/mL respectively following 0.1-hr of liming. Adenovirus type 5, rotavirus Wa, and MS2, were inoculated into composted, raw and previously limed matrices, representative of sludge and biosolids, to achieve a final concentration of approximately 104 PFU or TCID50/mL. Each matrix was limed for 24-hr at 22 ± 5°C and 4 ± 2°C. In all trials virus was below detectable levels following a 24-hr incubation. The time required for viral inactivation varied depending on the temperature and sample matrix. This research demonstrates reduction of adenovirus type 5, rotavirus Wa, and male-specific bacteriophage, in water, sludge and biosolids matrices following addition of an 8% calcium hydroxide slurry to achieve a pH of 12 for 2-hr reduced to 11.5 for 22-hr by addition of 0.1 N HCl. In these trials, MS2 was a conservative indicator of the efficacy of lime stabilization of adenovirus Type 5 and rotavirus Wa and therefore is proposed as a useful indicator organism.

  8. Hydrodynamic and kinetic models for spin-1/2 electron-positron quantum plasmas: Annihilation interaction, helicity conservation, and wave dispersion in magnetized plasmas

    International Nuclear Information System (INIS)

    Andreev, Pavel A.

    2015-01-01

    We discuss the complete theory of spin-1/2 electron-positron quantum plasmas, when electrons and positrons move with velocities mach smaller than the speed of light. We derive a set of two fluid quantum hydrodynamic equations consisting of the continuity, Euler, spin (magnetic moment) evolution equations for each species. We explicitly include the Coulomb, spin-spin, Darwin and annihilation interactions. The annihilation interaction is the main topic of the paper. We consider the contribution of the annihilation interaction in the quantum hydrodynamic equations and in the spectrum of waves in magnetized electron-positron plasmas. We consider the propagation of waves parallel and perpendicular to an external magnetic field. We also consider the oblique propagation of longitudinal waves. We derive the set of quantum kinetic equations for electron-positron plasmas with the Darwin and annihilation interactions. We apply the kinetic theory to the linear wave behavior in absence of external fields. We calculate the contribution of the Darwin and annihilation interactions in the Landau damping of the Langmuir waves. We should mention that the annihilation interaction does not change number of particles in the system. It does not related to annihilation itself, but it exists as a result of interaction of an electron-positron pair via conversion of the pair into virtual photon. A pair of the non-linear Schrodinger equations for the electron-positron plasmas including the Darwin and annihilation interactions is derived. Existence of the conserving helicity in electron-positron quantum plasmas of spinning particles with the Darwin and annihilation interactions is demonstrated. We show that the annihilation interaction plays an important role in the quantum electron-positron plasmas giving the contribution of the same magnitude as the spin-spin interaction

  9. 78 FR 45056 - Drawbridge Operation Regulation; Lake Washington Ship Canal, Seattle, WA

    Science.gov (United States)

    2013-07-26

    ... Seattle, WA. The deviation is necessary to accommodate vehicular traffic attending football games at Husky... traffic to facilitate timely movement of pre-game and post game football traffic. The Montlake Bridge... in emergency response operations during this closure period. In accordance with 33 CFR 117.35(e), the...

  10. A search for gamma-ray imprints of annihilating dark matter in the galaxy, and the astrophysical implications of ultra-light fundamental vector bosons

    Energy Technology Data Exchange (ETDEWEB)

    Zechlin, Hannes-Sebastian

    2013-12-15

    Standard Model extensions imply new elementary particles that can lead to specific astrophysical signatures. In particular, weakly interacting massive particles (WIMPs) can constitute the unknown non-luminous cold dark matter, which contributes approximately 84% to the matter content of the Universe. Annihilation or decay of WIMPs may lead to high-energy gamma-rays. In this thesis, new methods of searching for gamma-ray signals from annihilating dark matter are developed and applied. Moreover, astrophysical imprints of new ultra-light hidden U(1) gauge bosons in radio data are investigated. Hierarchical structure formation predicts a variety of smaller bound dark matter sub-halos in Milky-Way-like galactic hosts. It is shown that the Fermi-LAT is sufficiently sensitive for detecting up to a few nearby dark matter subhalos in terms of faint gamma-ray sources with a moderate angular extent. Searches in the first and second Fermi-LAT source catalogs reveal about ten candidate sources each. To discriminate the source candidates from conventional astrophysical objects, an analysis for spectral, spatial, positional, and temporal gamma-ray properties using 3.5 years of Fermi-LAT data is carried out. In addition, a multi-wavelength analysis of archival data or follow-up observations in the radio, infrared, optical, UV, X-ray, high-energy, and very-high energy gamma-ray bands is carried out. The broad-band spectra of all promising candidates are compatible with AGN, in particular high-energy peaked BL-Lac type objects (HBLs). Dark matter annihilation can contribute to the small-scale angular anisotropy spectrum of the diffuse gamma-ray background (DGB). The detection capabilities of currently operating imaging atmospheric Cherenkov telescopes and the planned Cherenkov Telescope Array (CTA) are studied. With CTA, a relative gamma-ray contribution from annihilating dark matter of 10% to the extragalactic DGB can be resolved via angular anisotropies. In terms of the dark

  11. A search for gamma-ray imprints of annihilating dark matter in the galaxy, and the astrophysical implications of ultra-light fundamental vector bosons

    International Nuclear Information System (INIS)

    Zechlin, Hannes-Sebastian

    2013-12-01

    Standard Model extensions imply new elementary particles that can lead to specific astrophysical signatures. In particular, weakly interacting massive particles (WIMPs) can constitute the unknown non-luminous cold dark matter, which contributes approximately 84% to the matter content of the Universe. Annihilation or decay of WIMPs may lead to high-energy gamma-rays. In this thesis, new methods of searching for gamma-ray signals from annihilating dark matter are developed and applied. Moreover, astrophysical imprints of new ultra-light hidden U(1) gauge bosons in radio data are investigated. Hierarchical structure formation predicts a variety of smaller bound dark matter sub-halos in Milky-Way-like galactic hosts. It is shown that the Fermi-LAT is sufficiently sensitive for detecting up to a few nearby dark matter subhalos in terms of faint gamma-ray sources with a moderate angular extent. Searches in the first and second Fermi-LAT source catalogs reveal about ten candidate sources each. To discriminate the source candidates from conventional astrophysical objects, an analysis for spectral, spatial, positional, and temporal gamma-ray properties using 3.5 years of Fermi-LAT data is carried out. In addition, a multi-wavelength analysis of archival data or follow-up observations in the radio, infrared, optical, UV, X-ray, high-energy, and very-high energy gamma-ray bands is carried out. The broad-band spectra of all promising candidates are compatible with AGN, in particular high-energy peaked BL-Lac type objects (HBLs). Dark matter annihilation can contribute to the small-scale angular anisotropy spectrum of the diffuse gamma-ray background (DGB). The detection capabilities of currently operating imaging atmospheric Cherenkov telescopes and the planned Cherenkov Telescope Array (CTA) are studied. With CTA, a relative gamma-ray contribution from annihilating dark matter of 10% to the extragalactic DGB can be resolved via angular anisotropies. In terms of the dark

  12. 78 FR 68088 - Dungeness National Wildlife Refuge, Clallam County, WA; Comprehensive Conservation Plan and...

    Science.gov (United States)

    2013-11-13

    ... management activities, and we will reduce the Refuge's carbon footprint. Invasive species will be monitored...: Download the CCP and FONSI at http://www.fws.gov/pacific/planning/main/docs/wa/docsdungeness.htm . Email...

  13. anti ee annihilation into hadrons from dual unitarisation

    International Nuclear Information System (INIS)

    Hong-mo, C.

    1976-09-01

    By grafting to the dual unitarisation scheme for hadron reactions a quark-current coupling suggested by the parton model, a model is obtained for anti ee annihilations in which the conversion of quarks into final hadrons is specific. As a first application, the correction to the value of R given by the parton model is estimated. (author)

  14. Precise tests of QCD in e+e- annihilation

    International Nuclear Information System (INIS)

    Burrows, P.N.

    1997-03-01

    A pedagogical review is given of precise tests of QCD in electron-positron annihilation. Emphasis is placed on measurements that have served to establish QCD as the correct theory of strong interactions, as well as measurements of the coupling parameter α s . An outlook is given for future important tests at a high-energy e + e - collider

  15. Production of φ-Mesons in anti NN-Annihilation

    International Nuclear Information System (INIS)

    Sapozhnikov, M.G.

    1994-01-01

    Recent results from the experiments on the φ-meson production in the annihilation of stopped antiprotons have demonstrated a significant (by a factor of 30-50) violation of the OZI rule. Experimental information on the φ-meson production is discussed and possible theoretical explanations of the strong OZI rule violation are reviewed. 37 refs., 4 figs., 2 tabs

  16. The Kinetics of Joined Action of Triplet-Triplet Annihilation and First-Order Decay of Molecules in T1 State in the Case of Nondominant First-Order Process: The Kinetic Model in the Case of Spatially Periodic Excitation

    Directory of Open Access Journals (Sweden)

    Paweł Borowicz

    2013-01-01

    Full Text Available In this paper the model developed for estimation of the diffusion coefficient of the molecules in the triplet state is presented. The model is based on the intuitive modification of the Smoluchowski equation for the time-dependent rate parameter. Since the sample is irradiated with the spatially periodic pattern nonexponential effects can be expected in the areas of the constructive interference of the exciting laser beams. This nonexponential effects introduce changes in the observed kinetics of the diffusion-controlled triplet-triplet annihilation. Due to irradiation with so-called long excitation pulse these non-exponential effects are very weak, so they can be described with introducing very simple correction to the kinetic model described in the first paper of this series. The values of diffusion coefficient of anthracene are used to calculate the annihilation radius from the data for spatially homogeneous excitation.

  17. Studies Of Oxidation And Thermal Reduction Of The Cu(100) Surface Using Positron Annihilation Induced Auger Electron Spectroscopy

    Science.gov (United States)

    Fazleev, N. G.; Nadesalingam, M. P.; Maddox, W.; Weiss, A. H.

    2011-06-01

    Positron annihilation induced Auger electron spectroscopy (PAES) measurements from the surface of an oxidized Cu(100) single crystal show a large increase in the intensity of the annihilation induced Cu M2,3VV Auger peak as the sample is subjected to a series of isochronal anneals in vacuum up to annealing temperature 300 °C. The PAES intensity then decreases monotonically as the annealing temperature is increased to ˜550 °C. Experimental positron annihilation probabilities with Cu 3p and O 1s core electrons are estimated from the measured intensities of the positron annihilation induced Cu M2,3VV and O KLL Auger transitions. PAES results are analyzed by performing calculations of positron surface states and annihilation probabilities of the surface-trapped positrons with relevant core electrons taking into account the charge redistribution at the surface and various surface structures associated with low and high oxygen coverages. The variations in atomic structure and chemical composition of the topmost layers of the oxidized Cu(100) surface are found to affect localization and spatial extent of the positron surface state wave function. The computed positron binding energy and annihilation characteristics reveal their sensitivity to charge transfer effects, atomic structure and chemical composition of the topmost layers of the oxidized Cu(100) surface. Theoretical positron annihilation probabilities with Cu 3p and O 1s core electrons computed for the oxidized Cu(100) surface are compared with experimental ones. The obtained results provide a demonstration of thermal reduction of the copper oxide surface after annealing at 300 °C followed by re-oxidation of the Cu(100) surface at higher annealing temperatures presumably due to diffusion of subsurface oxygen to the surface.

  18. Studies Of Oxidation And Thermal Reduction Of The Cu(100) Surface Using Positron Annihilation Induced Auger Electron Spectroscopy

    International Nuclear Information System (INIS)

    Fazleev, N. G.; Nadesalingam, M. P.; Maddox, W.; Weiss, A. H.

    2011-01-01

    Positron annihilation induced Auger electron spectroscopy (PAES) measurements from the surface of an oxidized Cu(100) single crystal show a large increase in the intensity of the annihilation induced Cu M2,3VV Auger peak as the sample is subjected to a series of isochronal anneals in vacuum up to annealing temperature 300 deg. C. The PAES intensity then decreases monotonically as the annealing temperature is increased to ∼550 deg. C. Experimental positron annihilation probabilities with Cu 3p and O 1s core electrons are estimated from the measured intensities of the positron annihilation induced Cu M 2,3 VV and O KLL Auger transitions. PAES results are analyzed by performing calculations of positron surface states and annihilation probabilities of the surface-trapped positrons with relevant core electrons taking into account the charge redistribution at the surface and various surface structures associated with low and high oxygen coverages. The variations in atomic structure and chemical composition of the topmost layers of the oxidized Cu(100) surface are found to affect localization and spatial extent of the positron surface state wave function. The computed positron binding energy and annihilation characteristics reveal their sensitivity to charge transfer effects, atomic structure and chemical composition of the topmost layers of the oxidized Cu(100) surface. Theoretical positron annihilation probabilities with Cu 3p and O 1s core electrons computed for the oxidized Cu(100) surface are compared with experimental ones. The obtained results provide a demonstration of thermal reduction of the copper oxide surface after annealing at 300 deg. C followed by re-oxidation of the Cu(100) surface at higher annealing temperatures presumably due to diffusion of subsurface oxygen to the surface.

  19. Relevance of slow positron beam research to astrophysical studies of positron interactions and annihilation in the interstellar medium

    International Nuclear Information System (INIS)

    Guessoum, N.; Jean, P.; Gillard, W.

    2006-01-01

    The processes undergone by positrons in the interstellar medium (ISM) from the moments of their birth to their annihilation are examined. Both the physics of the positron interactions with gases and solids (dust grains), and the physical conditions and characteristics of the environments where the processes of energy loss, positronium formation, and annihilation taking place, are reviewed. An explanation is given as to how all the relevant physical information are taken into account in order to calculate annihilation rates and spectra of the 511 keV emission for the various phases of the ISM; special attention is paid to positron interactions with dust and with polycyclic aromatic hydrocarbons. An attempt is made to show to what extent the interactions between positrons and interstellar dust grains are similar to laboratory experiments in which beams of slow positrons impinge upon solids and surfaces. Sample results are shown for the effect of dust grains on positron annihilation spectra in some phases of the ISM which, together with high resolution spectra measured by satellites, can be used to infer useful knowledge about the environment where the annihilation is predominantly taking place and ultimately about the birth place and history of positrons in the Galaxy. The important complementarity between work done by the astrophysical and the solid-state positron communities is strongly emphasized and specific experimental work is suggested which could assist the modeling of the interaction and annihilation of positrons in the ISM

  20. Relevance of slow positron beam research to astrophysical studies of positron interactions and annihilation in the interstellar medium

    Energy Technology Data Exchange (ETDEWEB)

    Guessoum, N. [American University of Sharjah, Physics Department, P.O. Box 26666, Sharjah (United Arab Emirates)]. E-mail: nguessoum@aus.ac.ae; Jean, P. [Centre d' Etude Spatiale des Rayonnements, Toulouse (France); Gillard, W. [Centre d' Etude Spatiale des Rayonnements, Toulouse (France)

    2006-02-28

    The processes undergone by positrons in the interstellar medium (ISM) from the moments of their birth to their annihilation are examined. Both the physics of the positron interactions with gases and solids (dust grains), and the physical conditions and characteristics of the environments where the processes of energy loss, positronium formation, and annihilation taking place, are reviewed. An explanation is given as to how all the relevant physical information are taken into account in order to calculate annihilation rates and spectra of the 511 keV emission for the various phases of the ISM; special attention is paid to positron interactions with dust and with polycyclic aromatic hydrocarbons. An attempt is made to show to what extent the interactions between positrons and interstellar dust grains are similar to laboratory experiments in which beams of slow positrons impinge upon solids and surfaces. Sample results are shown for the effect of dust grains on positron annihilation spectra in some phases of the ISM which, together with high resolution spectra measured by satellites, can be used to infer useful knowledge about the environment where the annihilation is predominantly taking place and ultimately about the birth place and history of positrons in the Galaxy. The important complementarity between work done by the astrophysical and the solid-state positron communities is strongly emphasized and specific experimental work is suggested which could assist the modeling of the interaction and annihilation of positrons in the ISM.

  1. Calculation of gamma spectra for positron annihilation on molecules

    Energy Technology Data Exchange (ETDEWEB)

    Green, Dermot G; Gribakin, G F [Centre for Theoretical Atomic, Molecular and Optical Physics, Queen' s University Belfast, BT7 1NN (United Kingdom); Wang, F [Centre for Molecular Simulation, Sinburne University of Technology, Melbourne, Victoria 3122 (Australia); Surko, C M, E-mail: dgreen09@qub.ac.u [Physics Department, University of California, San Diego, La Jolla, California 92093-0319 (United States)

    2009-11-01

    Gamma spectra for positron annihilation on molecules are calculated based on molecular electron momentum densities and using an atomic adjustment factor that accounts for the positron. Results for H{sub 2} agree well with experiment. Analysis of methane and larger alkanes and their substitutes is underway.

  2. 78 FR 50094 - Notice of Inventory Completion: Maxey Museum, Walla Walla, WA

    Science.gov (United States)

    2013-08-16

    ... Repatriation Act (NAGPRA), 25 U.S.C. 3003, of the completion of an inventory of human remains under the control....R50000] Notice of Inventory Completion: Maxey Museum, Walla Walla, WA AGENCY: National Park Service, Interior. ACTION: Notice. SUMMARY: The Maxey Museum has completed an inventory of human remains in...

  3. Gamma-ray Background Spectrum and Annihilation Rate in the Baryon-symmetric Big-bang Cosmology

    Science.gov (United States)

    Puget, J. L.

    1973-01-01

    An attempt was made to acquire experimental information on the problem of baryon symmetry on a large cosmological scale by observing the annihilation products. Data cover absorption cross sections and background radiation due to other sources for the two main products of annihilation, gamma rays and neutrinos. Test results show that the best direct experimental test for the presence of large scale antimatter lies in the gamma ray background spectrum between 1 and 70 MeV.

  4. Positron annihilation studies of some charge transfer molecular complexes

    CERN Document Server

    El-Sayed, A; Boraei, A A A

    2000-01-01

    Positron annihilation lifetimes were measured for some solid charge transfer (CT) molecular complexes of quinoline compounds (2,6-dimethylquinoline, 6-methoxyquinoline, quinoline, 6-methylquinoline, 3-bromoquinoline and 2-chloro-4-methylquinoline) as electron donor and picric acid as an electron acceptor. The infrared spectra (IR) of the solid complexes clearly indicated the formation of the hydrogen-bonding CT-complexes. The annihilation spectra were analyzed into two lifetime components using PATFIT program. The values of the average and bulk lifetimes divide the complexes into two groups according to the non-bonding ionization potential of the donor (electron donating power) and the molecular weight of the complexes. Also, it is found that the ionization potential of the donors and molecular weight of the complexes have a conspicuous effect on the average and bulk lifetime values. The bulk lifetime values of the complexes are consistent with the formation of stable hydrogen-bonding CT-complexes as inferred...

  5. Extinction and survival in two-species annihilation

    Science.gov (United States)

    Amar, J. G.; Ben-Naim, E.; Davis, S. M.; Krapivsky, P. L.

    2018-02-01

    We study diffusion-controlled two-species annihilation with a finite number of particles. In this stochastic process, particles move diffusively, and when two particles of opposite type come into contact, the two annihilate. We focus on the behavior in three spatial dimensions and for initial conditions where particles are confined to a compact domain. Generally, one species outnumbers the other, and we find that the difference between the number of majority and minority species, which is a conserved quantity, controls the behavior. When the number difference exceeds a critical value, the minority becomes extinct and a finite number of majority particles survive, while below this critical difference, a finite number of particles of both species survive. The critical difference Δc grows algebraically with the total initial number of particles N , and when N ≫1 , the critical difference scales as Δc˜N1 /3 . Furthermore, when the initial concentrations of the two species are equal, the average number of surviving majority and minority particles, M+ and M-, exhibit two distinct scaling behaviors, M+˜N1 /2 and M-˜N1 /6 . In contrast, when the initial populations are equal, these two quantities are comparable M+˜M-˜N1 /3 .

  6. Positron annihilation in calcium-doped barium titanate

    International Nuclear Information System (INIS)

    Li, L.T.; Zhang, X.W.; Smyth, D.M.

    1987-01-01

    The Positron Annihilation Technique (PAT) has been used to study lattice defects in CaO-doped BaTiO/sub 3/ having the general composition BaTi/sub 1-x/Ca/sub x/O/sub 3-x/, with x = 0, 0.005, 0.010, 0.015, and 0.020. The long lifetime, tau/sub 2/, and the mean lifetime, tau/sub m/, of the positrons were both found to increase with increasing Ca content, x, up to x = 0.015-0.020. This is in good agreement wit the solubility limit for Ca on Ti-sites in BaTiO/sub 3/ found by others from measurements of the equilibrium electrical conductivity, and by other investigators from x-ray diffraction studies. In these studies, it was shown that for compositions with (Ba+Ca)/Ti > 1, Ca can be forced to occupy Ti-sites up to 1.5-2%, where it acts as a doubly-charged acceptor center that is compensated by oxygen vacancies. It is suggested that the oxygen vacancies represent places where the annihilation of positrons is delayed because of the low local electron density. These results indicate that the PAT can be a useful tool for the characterization of the defect structure of complex oxides

  7. Boron isotope separation by ion exchange chromatography using weakly basic anion exchange resin

    International Nuclear Information System (INIS)

    Sakuma, Yoichi; Aida, Masao; Okamoto, Makoto; Kakihana, Hidetake

    1980-01-01

    Isotopic plateau displacement chromatography, a useful method for isotope separation is presented. The boric acid band formed in a column of weakly basic anion exchange resin Diaion WA21 can be eluted with pure water. In order to obtain good accumulation of the isotope effect, a series of experiments with different migration length were carried out. The boron-10 enriched part of the boric acid absorbed band was always preceded by the isotopic plateau part, in which the atomic fraction of boron-10 was maintained at its original value. The atomic fraction of boron-10 at the end of the chromatogram increased with migration length, and in the case of 256-m migration, boron-10 was enriched from its original atomic fraction of 19.84 to 91.00%, the separation factor S being constant irrespective of migration length: S = 1.0100 +- 0.0005. (author)

  8. Experimental and theoretical study of yield and spectrum of photons obtained from positron annihilation in flight; Etude experimentale et theorique du nombre total de photons et de la forme de la raie obtenue par annihilation en vol de positons

    Energy Technology Data Exchange (ETDEWEB)

    Audit, G; Botton, N de; Le Poittevin, G; Schuhl, C; Tamas, G [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

    1968-07-01

    A computer program has been used to calculate the spectrum of photons obtained from positron annihilation in flight; the calculation takes account of multiple scattering and energy loss of positrons in the annihilation target. Results are presented in the energy range 150-450 MeV which is the one of Saclay Linear Accelerator. As a check, results of the calculation are compared with measurements carried out at the Saclay Linac of 45 MeV. (author) [French] Nous avons ecrit un programme permettant de calculer le spectre des photons obtenus par annihilation en vol de positons; le calcul tient compte de la diffusion multiple et de la perte d'energie des positons dans la cible d'annihilation. Nous donnons une serie de resultats dans la zone d'energie de 150 a 450 MeV qui correspond aux possibilites de l'Accelerateur Lineaire de Saclay. Les resultats du calcul sont confrontes a des mesures effectuees a l'Accelerateur Lineaire de 45 MeV de Saclay. (auteur)

  9. Constraints on the dark matter annihilation from Fermi-LAT observation of M31

    Energy Technology Data Exchange (ETDEWEB)

    Li, Zhengwei; Yuan, Qiang [Key Laboratory of Dark Matter and Space Astronomy, Purple Mountain Observatory, Chinese Academy of Sciences, 2 West Beijing Road, Nanjing, 210008 (China); Huang, Xiaoyuan [Physik-Department T30d, Technische Universität München, James-Franck-Straße, Garching, D-85748 Germany (Germany); Xu, Yupeng, E-mail: lizw@ihep.ac.cn, E-mail: huangxiaoyuan@gmail.com, E-mail: yuanq@pmo.ac.cn, E-mail: xuyp@ihep.ac.cn [Key Laboratory of Particle Astrophysics, Institute of High Energy Physics, Chinese Academy of Sciences, 19B Yuquan Road, Beijing, 100049 (China)

    2016-12-01

    Gamma-ray is a good probe of dark matter (DM) particles in the Universe. We search for the DM annihilation signals in the direction of the Andromeda galaxy (M31) using 7.5 year Fermi-LAT pass 8 data. Similar to Pshirkov et al. (2016), we find that there is residual excess emission from the direction of M31 if only the galactic disk as traced by the far infrared emission is considered. Adding a point-like source will improve the fitting effectively, although additional slight improvements can be found if an extended component such as a uniform disk or two bubbles is added instead. Taking the far infrared disk plus a point source as the background model, we search for the DM annihilation signals in the data. We find that there is strong degeneracy between the emission from the galaxy and that from 10s GeV mass DM annihilation in the main halo with quark final state. However, the required DM annihilation cross section is about 10{sup −25}–10{sup −24} cm{sup 3}s{sup −1}, orders of magnitude larger than the constraints from observations of dwarf spheroidal galaxies, indicating a non-DM origin of the emission. If DM subhalos are taken into account, the degeneracy is broken. When considering the enhancement from DM subhalos, the constraints on DM model parameters are comparable to (or slightly weaker than) those from the population of dwarf spheroidal galaxies. We also discuss the inverse Compton scattering component from DM annihilation induced electrons/positrons. For the first time we include an energy dependent template of the inverse Compton emission (i.e., a template cube) in the data analysis to take into account the effect of diffusion of charged particles. We find a significant improvement of the constraints in the high mass range of DM particles after considering the inverse Compton emission.

  10. Time of flight spectra of electrons emitted from graphite after positron annihilation

    International Nuclear Information System (INIS)

    Gladen, R W; Chirayath, V A; Chrysler, M D; Mcdonald, A D; Fairchild, A J; Shastry, K; Koymen, A R; Weiss, A H

    2017-01-01

    Low energy (∼2 eV) positrons were deposited onto the surface of highly oriented pyrolytic graphite (HOPG) using a positron beam equipped with a time of flight (TOF) spectrometer. The energy of the electrons emitted as a result of various secondary processes due to positron annihilation was measured using the University of Texas at Arlington’s (UTA) TOF spectrometer. The positron annihilation-induced electron spectra show the presence of a carbon KLL Auger peak at ∼263 eV. The use of a very low energy beam allowed us to observe a new feature not previously seen: a broad peak which reached to a maximum intensity at ∼4 eV and extended up to a maximum energy of ∼15 eV. The low energy nature of the peak was confirmed by the finding that the peak was eliminated when a tube in front of the sample was biased at -15 V. The determination that the electrons in the peak are leaving the surface with energies up to 7 times the incoming positron energy indicates that the electrons under the broad peak were emitted as a result of a positron annihilation related process. (paper)

  11. Neutrinos from WIMP annihilations in the Sun including neutrino oscillations

    International Nuclear Information System (INIS)

    Blennow, Mattias; Edsjö, Joakim; Ohlsson, Tommy

    2011-01-01

    The prospects to detect neutrinos from the Sun arising from dark matter annihilations in the core of the Sun are reviewed. Emphasis is placed on new work investigating the effects of neutrino oscillations on the expected neutrino fluxes.

  12. Neutrinos from WIMP annihilations in the Sun including neutrino oscillations

    International Nuclear Information System (INIS)

    Blennow, Mattias; Edsjoe, Joakim; Ohlsson, Tommy

    2006-01-01

    The prospects for detecting neutrinos from the Sun arising from dark matter annihilations in the core of the Sun are reviewed. Emphasis is placed on new work investigating the effects of neutrino oscillations on the expected neutrino fluxes

  13. Positron annihilation in SiO 2-Si studied by a pulsed slow positron beam

    Science.gov (United States)

    Suzuki, R.; Ohdaira, T.; Uedono, A.; Kobayashi, Y.

    2002-06-01

    Positron and positronium (Ps) behavior in SiO 2-Si have been studied by means of positron annihilation lifetime spectroscopy (PALS) and age-momentum correlation (AMOC) spectroscopy with a pulsed slow positron beam. The PALS study of SiO 2-Si samples, which were prepared by a dry-oxygen thermal process, revealed that the positrons implanted in the Si substrate and diffused back to the interface do not contribute to the ortho-Ps long-lived component, and the lifetime spectrum of the interface has at least two components. From the AMOC study, the momentum distribution of the ortho-Ps pick-off annihilation in SiO 2, which shows broader momentum distribution than that of crystalline Si, was found to be almost the same as that of free positron annihilation in SiO 2. A varied interface model was proposed to interpret the results of the metal-oxide-semiconductor (MOS) experiments. The narrow momentum distribution found in the n-type MOS with a negative gate bias voltage could be attributed to Ps formation and rapid spin exchange in the SiO 2-Si interface. We have developed a two-dimensional positron lifetime technique, which measures annihilation time and pulse height of the scintillation gamma-ray detector for each event. Using this technique, the positronium behavior in a porous SiO 2 film, grown by a sputtering method, has been studied.

  14. Positron annihilation studies of China's and Japan's magnesite refractory in different degree

    International Nuclear Information System (INIS)

    Zou Lin-Juan; Zhang Cai-Guo; Zhu Xiu-Ying; Sun Quin-Ying

    1989-01-01

    Studying the magnesite refractories by positron annihilation technique, the obtained results show that China's and Japan's magnesite refractories in different degree form positron lifetime results have no obvious differences in microscopical properties. According to the positron annihilation lifetime results it was found that 1650 0 C is the best sintering temperature for this material. At this temperature positive ions in MgO are replaced by impurities, the solid solubility is higher. The positron average lifetime is more even and smooth with crystallization grain size changing. When grains increase, the positron average lifetime trends towards decreasing, which is in agreement with the crystal boundary theory of ceramic material. (author)

  15. Positron annihilation studies of mesoporous silica films using a slow positron beam

    International Nuclear Information System (INIS)

    He Chunqing; Muramatsu, Makoto; Ohdaira, Toshiyuki; Kinomura, Atsushi; Suzuki, Ryoichi; Ito, Kenji; Kabayashi, Yoshinori

    2006-01-01

    Positron annihilation lifetime spectra were measured for mesoporous silica films, which were synthesized using triblock copolymer (EO 106 PO 70 EO 106 ) as a structure-directing agent. Different positron lifetime spectra for the deposited and calcined films indicated the formation of meso-structure after calcination, which was confirmed by Fourier transform infrared (FTIR) spectra and field emission-scanning electron microscopy (FE-SEM) observation. Open porosity or pore interconnectivity of a silica film might be evaluated by a two-dimensional positron annihilation lifetime spectrum of an uncapped film. Pore sizes and their distributions in the silica films were found to be affected by thermal treatments

  16. Positron annihilation lifetime spectroscopy source correction determination: A simulation study

    Energy Technology Data Exchange (ETDEWEB)

    Kanda, Gurmeet S.; Keeble, David J., E-mail: d.j.keeble@dundee.ac.uk

    2016-02-01

    Positron annihilation lifetime spectroscopy (PALS) can provide sensitive detection and identification of vacancy-related point defects in materials. These measurements are normally performed using a positron source supported, and enclosed by, a thin foil. Annihilation events from this source arrangement must be quantified and are normally subtracted from the spectrum before analysis of the material lifetime components proceeds. Here simulated PALS spectra reproducing source correction evaluation experiments have been systematically fitted and analysed using the packages PALSfit and MELT. Simulations were performed assuming a single lifetime material, and for a material with two lifetime components. Source correction terms representing a directly deposited source and various foil supported sources were added. It is shown that in principle these source terms can be extracted from suitably designed experiments, but that fitting a number of independent, nominally identical, spectra is recommended.

  17. Application of a digital data acquisition system for time of flight Positron annihilation-induced Auger Electron Spectroscopy

    Science.gov (United States)

    Gladen, R. W.; Chirayath, V. A.; McDonald, A. D.; Fairchild, A. J.; Chrysler, M. D.; Imam, S. K.; Koymen, A. R.; Weiss, A. H.

    We describe herein a digital data acquisition system for a time-of-flight Positron annihilation-induced Auger Electron Spectrometer. This data acquisition system consists of a high-speed digitizer collecting signals induced by Auger electrons and annihilation gammas in a multi-channel plate electron detector and a BaF2 gamma detector, respectively. The time intervals between these two signals is used to determine the times of flight of the Auger electrons, which are analyzed by algorithms based on traditional nuclear electronics methods. Ultimately, this digital data acquisition system will be expanded to incorporate the first coincidence measurements of Auger electron and annihilation gamma energies.

  18. 78 FR 40960 - Drawbridge Operation Regulation; Lake Washington Ship Canal at Seattle, WA

    Science.gov (United States)

    2013-07-09

    ..., WA. The deviation is necessary to accommodate the ``See Jane Run Women's Half Marathon.'' This... Manager, Docket Operations, telephone 202-366-9826. SUPPLEMENTARY INFORMATION: The SDOT requested a... necessary to accommodate the ``See Jane Run Women's Half Marathon''. This deviation allows the bridges to...

  19. Isotropic extragalactic flux from dark matter annihilations: lessons from interacting dark matter scenarios

    Energy Technology Data Exchange (ETDEWEB)

    Moliné, Ángeles [CFTP, Instituto Superior Tecnico, Universidade Tecnica de Lisboa, Av. Rovisco Pais 1, 1049-001 Lisboa (Portugal); Schewtschenko, Jascha A.; Boehm, Céline [Institute for Particle Physics Phenomenology (IPPP), Durham University, Durham DH1 3LE (United Kingdom); Palomares-Ruiz, Sergio [Instituto de Física Corpuscular (IFIC), CSIC-Universitat de València, Apartado de Correos 22085, E-46071 Valencia (Spain); Baugh, Carlton M., E-mail: maria.moline@ist.utl.pt, E-mail: jascha@schewtschenko.net, E-mail: Sergio.Palomares.Ruiz@ific.uv.es, E-mail: c.m.boehm@durham.ac.uk, E-mail: c.m.baugh@durham.ac.uk [Institute for Computational Cosmology (ICC), Durham University, Durham DH1 3LE (United Kingdom)

    2016-08-01

    The extragalactic γ-ray and neutrino emission may have a contribution from dark matter (DM) annihilations. In the case of discrepancies between observations and standard predictions, one could infer the DM pair annihilation cross section into cosmic rays by studying the shape of the energy spectrum. So far all analyses of the extragalactic DM signal have assumed the standard cosmological model (ΛCDM) as the underlying theory. However, there are alternative DM scenarios where the number of low-mass objects is significantly suppressed. Therefore the characteristics of the γ-ray and neutrino emission in these models may differ from ΛCDM as a result. Here we show that the extragalactic isotropic signal in these alternative models has a similar energy dependence to that in ΛCDM, but the overall normalisation is reduced. The similarities between the energy spectra combined with the flux suppression could lead one to misinterpret possible evidence for models beyond ΛCDM as being due to CDM particles annihilating with a much weaker cross section than expected.

  20. Isotropic extragalactic flux from dark matter annihilations: lessons from interacting dark matter scenarios

    International Nuclear Information System (INIS)

    Moliné, Ángeles; Schewtschenko, Jascha A.; Boehm, Céline; Palomares-Ruiz, Sergio; Baugh, Carlton M.

    2016-01-01

    The extragalactic γ-ray and neutrino emission may have a contribution from dark matter (DM) annihilations. In the case of discrepancies between observations and standard predictions, one could infer the DM pair annihilation cross section into cosmic rays by studying the shape of the energy spectrum. So far all analyses of the extragalactic DM signal have assumed the standard cosmological model (ΛCDM) as the underlying theory. However, there are alternative DM scenarios where the number of low-mass objects is significantly suppressed. Therefore the characteristics of the γ-ray and neutrino emission in these models may differ from ΛCDM as a result. Here we show that the extragalactic isotropic signal in these alternative models has a similar energy dependence to that in ΛCDM, but the overall normalisation is reduced. The similarities between the energy spectra combined with the flux suppression could lead one to misinterpret possible evidence for models beyond ΛCDM as being due to CDM particles annihilating with a much weaker cross section than expected.