Sample records for antinucleons

  1. Nucleon-antinucleon interaction

    International Nuclear Information System (INIS)

    The current status of our understanding of the low energy nucleon-antinucleon (N anti N) interaction is reviewed. We compare several phenomenological models which fit the available N anti N cross section data. The more realistic of these models employ an annihilation potential W(r) which is spin, isospin and energy dependent. The microscopic origins for these dependences are discussed in terms of quark rearrangement and annihilation processes. It is argued that the study of N anti N annihilation offers a powerful means of studying quark dynamics at short distances. We also discuss how one may try to isolate coherent meson exchange contributions to the medium and long range part of the N anti N potential. These pieces of the N anti N interaction are calculable via the G-parity transformation from a model for the NN potential; their effects are predicted to be seen in N anti N spin observables, to be measured at LEAR. The possible existence of quasi-stable bound states or resonances of the anti N plus one or more nucleons is discussed, with emphasis on few-body systems. 42 references

  2. Antinucleon nucleon annihilations into two mesons

    International Nuclear Information System (INIS)

    We study two aspects of the antinucleon-nucleon annihilation into two mesons (antiNN → M1M2), starting from simple Born diagrams. On one hand, we discuss the possibility of modelling the antiNN optical potential with the box diagrams related to the M1M2 channels. We include the lightest pseudoscalar, scalar and vector mesons with effective coupling constants. Much more channels appear to be needed in order to achieve sensible results. On the other hand, we show that a simple phenomenological optical potential, successfull in reproducing antiNN elastic scattering and total annihilation data can be further used to make predictions on the antiNN → M1M2 processes, which prove to be in good agreement with experiment. We find a lower bound of 17% on the relative contribution of these reactions to the antiNN annihilation. Also, the model favours a rather small effective radius for the nucleon

  3. Nucleon-antinucleon interaction from the modified Skyrme model

    International Nuclear Information System (INIS)

    We calculate the static nucleon-antinucleon interaction potential from the modified Skyrme model with an additional BμBμ term using the product ansatz. The static properties of the single baryon are improved in the modified Skyrme model. State mixing is taken into account by perturbation theory, which substantially increases the strength of the central attraction. We obtain a long- and mid-range potential which is in qualitative agreement with some phenomenological potentials

  4. Nucleon-antinucleon interaction from the Skyrme model

    International Nuclear Information System (INIS)

    We calculate the nucleon-antinucleon static potential in the Skyrme model using the product ansatz and including some finite NC (number of colors) corrections. The mid- and long-range part of the spin-spin and tensor force are mostly correctly given in both isospin channels while the central interaction has insufficient midrange attraction. This is a well-known problem of the product ansatz that should be repaired with better Skyrme dynamics. copyright 1996 The American Physical Society

  5. Nucleon-antinucleon Interaction from the Modified Skyrme Model

    CERN Document Server

    Ding, G J; Ding, Gui-Jun; Yan, Mu-Lin


    We calculate the static nucleon-antinucleon interaction potential from the modified Skyrme model with additional $B^{\\mu}B_{\\mu}$ term using the product ansatz. The static properties of single baryon are improved in the modified Skyrme model. State mixing is taken into account by perturbation theory, which substantially increases the strength of the central attraction. We obtain a long and mid range potential which is in qualitative agreement with some phenomenological potentials.

  6. Nucleon-antinucleon resonance spectrum in a potential model (United States)

    Lacombe, M.; Loiseau, B.; Moussallam, B.; Mau, R. Vinh


    We investigate the spectrum of antinucleon-nucleon resonances, using an optical potential we derived recently. An effective method to compute the S-matrix poles is presented. The corresponding phase shifts do not behave as ordinary resonances in the Argand diagram. We show, however, that the poles can be located by extrapolating the phase shifts with the aid of polynomial fits. The annihilation part of our potential is state and energy dependent and of short range. It yields a richer spectrum than that given by a longer ranged annihilation model.

  7. Contribution to the study of the antinucleon-nucleon interactions

    International Nuclear Information System (INIS)

    A potential for the antinucleon-nucleon system is constructed. It has an imaginary part of very short range, respecting theoretical constraints. This implies a significant dependence on spin and isospin, and also on the energy. The spectrum of resonances is computed using an original method. One state (I=0 jPC=0++) could be easily detected. A model is proposed for a class of inelastic reactions: NantiN #-> # 2 mesons. Using a distorted-wave-Born approximation, comparisons with experiment are made. Finally, we consider some aspects of the atomic pantip system (protonium)

  8. The signal of $Z^\\pm(4430)$ in nucleon-antinucleon scattering


    Ke, Hong-Wei; Liu, Xiang(Research Center for Hadron and CSR Physics, Lanzhou University and Institute of Modern Physics of CAS, 730000, Lanzhou , China)


    We study the production of $Z^\\pm(4430)$ at a nucleon-antinucleon scattering experiment. Considering the PANDA experiment to be an ideal platform to explore the production of the charmonium and charmonim-like states, we suggest the forthcoming PANDA experiment to pay attention to the production of $Z^\\pm(4430)$.

  9. Heavy ion collisions, the quark-gluon plasma and antinucleon annihilation

    International Nuclear Information System (INIS)

    Studies in high energy physics have indicated that nucleon and mesons are composed of quarks confined in bags by the strong colours mediated by gluons. It is reasonably expected that at suitably high baryon density and temperature of the nucleus, these bags of nucleon and mesons fuse into a big bag of quarks or gluons i.e. hadronic matter undergoes transition to a quark-gluon phase. Two techniques to achieve this transition in a laboratory are: (1) collision of two heavy nuclei, and (2) annihilation of antinucleons and antinuclei in nuclear matter. Theoretical studies as well as experimental studies associated with the transition to quark-gluon phase are reviewed. (author)

  10. Something, but not much follows from the quark line rule in nucleon-antinucleon annihilations

    International Nuclear Information System (INIS)

    Validity and consequences of the quark line rule (QLR) in nucleon(N)-antinucleon(anti N)annihilations into two or three mesons at LEAR energies are investigated. Recent data on proton-antiproton annihilation into an η or η' together with additional non-strange pseudoscalar or vector meson(s) is used to successfully test the rule. We find that for present data any pseudoscalar meson mixing angle ΦPS restricted to -26deg PS0π0, ηη, π0ρ0, π0ω, ηρ0, ηω, ρ0ρ0, ωω. As a main consequence, dominance of annihilation predicts without any ambiguity equality of the proton-antiproton annihilation cross sections σ(ωω) and σ(ρ0ρ0). Further consequences of dominance of either annihilation or rearrangement diagrams for proton-antiproton annihilation into two or three mesons are also worked out. We compare the predictions of the models we discuss to the sparse present data. It is emphasized that our predictions only exploit the quark flavor flux within the quark line diagrams that are assumed to dominate. They thus are independent of gluon contributions to these diagrams. (orig.)

  11. Contribution at the study of nucleon-antinucleon interaction at low energy and at the proton-antiproton transition in two pions or kaons

    International Nuclear Information System (INIS)

    This thesis contains a semi-phenomenological study of the Nucleon-Antinucleon interaction at low energy, and in particular of the annihilation of Proton-Antiproton system into two charged pions or kaons. This annihilation reaction is calculated within the DWBA (Distorted-Wave Born-Approximation) formalism: the transition into two mesons is treated as perturbation around the solution computed out of the whole interaction, including elastic forces and absorption. We first review the optical-potential models which describe the Nucleon-Antinucleon scattering in term of meson exchange supplemented by a complex core to simulate the effects of absorption. Those optical potentials provide the initial state for the annihilation reactions. The transition itself is described by mean of two models, a local one and a separable one. As for the local model, the results are generally in good agreement with experimental data, especially for the analyzing power, but the backward hemisphere for annihilation into two kaons cannot be reproduced. The separable model restricts the transition to S and P waves only, but leads rather naturally to an enhancement of the P wave with respect to the S wave, improving the global description of the angular distribution. This P to S ratio is intimately connected to the relative weight of quark annihilation and quark rearrangement diagrams. The true dynamics of those annihilation reactions presumably mixes our two models, with a transition operator being almost local in the high partial waves and nearly separable for the S and the P waves

  12. 有限核真空中的反核子能谱%Spectra of Anti-Nucleons in the Vacuum of Finite Nuclei

    Institute of Scientific and Technical Information of China (English)



    The quantum vacuum in a many-body system of finite nuclei has been investigated within the relativistic Hartree approach which describes the bound states of nucleons and anti-nucleons consistently. The contributions of the Dirac sea to the source terms of the meson-field equations are taken into account up to the one-nucleon loop and one-meson loop. The tensor couplings for the ω- and ρ-meson are included in the model. After adjusting the parameters of the model to the properties of spherical nuclei, a large effective nucleon mass m */MN ≈ 0. 78 is obtained. The overall nucleon spectra of shell-model states are in agreement with the data. The computed anti-nucleon spectra in the vacuum differ about 20-30MeV with and without the tensor-coupling effects.%通过建立能够自洽地描述核子和反核子束缚态的相对论Hartree模型来研究有限核中的量子真空,其中狄拉克海对介子场方程的贡献由单圈图考虑,模型中还引入了ω介子和ρ介子的张量耦合项.在拟合球形核的性质后得到模型的参数,给出核子有效质量为m*/MN≈0.78;计算得到的核子壳模型能级与实验值相一致,在考虑张量耦合项的效应后真空反核子位阱深度增大了20-30 MeV.

  13. Antinucleon-nucleus interactions

    Energy Technology Data Exchange (ETDEWEB)

    Dover, C.B.


    Recent experimental and theoretical results on anti p-nucleus interactions are reviewed. We focus on determinations of the anti p optical potential from elastic scattering, the use of (anti p, anti p') inelastic scattering to reveal aspects of the spin-isospin dependence of N anti N amplitudes, and some puzzling features of (anti p, anti n) charge exchange reactions on nuclei. 47 refs., 7 figs.

  14. Analysis of sensitivity of the reaction cross section and the forward scattering amplitude to the structure of the nuclear optical potential for intermediate-energy nucleons and antinucleons

    International Nuclear Information System (INIS)

    Within the framework of the optical model with phenomenological optical potentials describing elastic scattering we calculate the total cross section, the reaction cross section, and the real part of the forward scattering amplitude for nucleons and antinucleons in the energy range 50--200 MeV for a broad range of nuclei. It is shown that with a significantly different spatial dependence of the real part of the optical potential (the Woods-Saxon form and the ''wine-bottle bottom'' form) the real parts of the proton forward scattering amplitude differ from each other by several times, while the difference in the total cross sections and reaction cross sections is not larger than tens of per cent. The calculations are performed in first-order perturbation theory in deviation of the wave function of the incident particle from the eikonal approximation. Comparison of the results of the approximate and exact calculations shows that the error of the approximate approach in the energy range considered is not larger than 10%. We compare our results with the results of calculations of the reaction cross section for antiprotons in light nuclei in the Glauber theory

  15. Analysis of sensitivity of cross section and zero-angle scattering amplitude to structure of nuclear optical potential for intermediate energy nucleons and antinucleons

    International Nuclear Information System (INIS)

    Total cross section, reaction cross section and the real of the forward scattering amplitude for nucleons and antinucleons in the energy range from 50 to 200 MeV are calculated for a wide set of nuclei by means of the optical model with phenomenological optical potentials which describe the elastic scattering. It is shown that for substantialy different radial dependences of the part of the optical potential (the Woods-Saxon potential and the ''wine-bottle'' potential) the real parts of the proton forward scattering amplitude are different by a factor of several times, while the differences in the total cross sections and in the reaction cross sections do not exceed a few dozen percent. The calculations have been performed in the first order of the perturbation theory in a deviation of the incident particle wave function from the eikonal approximation. A comparison between the results of the aproximate and exact calculations shows that in the considered energy region an error of the approximation does not exceed 10%. The results have been compared with the Glauber theory for the antiproton reaction cross sections on light nuclei

  16. Quasinuclear resonances and annihilation in nucleon-antinucleon scattering

    International Nuclear Information System (INIS)

    The author sketches some of the current problems of the N-anti N system, both in experiment and theory and investigates the general properties like levels, cross sections and amplitudes near the N-anti N threshold given a one boson exchange interaction and using a G-parity transformed non-static potential. A multi-channel N/D formalism is used to calculate the levels and amplitudes and a thorough description of the pole structure near the N-anti N threshold is presented. Based on the results of the model for the N-anti N system, the annihilation of the e+-e- pairs into hadrons is considered and the antipd system is described. (Auth./C.F.)

  17. Nucleon-antinucleon annihilation in chiral soliton model

    International Nuclear Information System (INIS)

    We investigate annihilation process of nucleons in chiral soliton model by path integral method. Soliton-antisoliton pair is shown to decay into pions at range of order of about 1 fm, defined by SS-bar potential. Contribution of annihilation channel into elastic scattering is discussed. (author). 14 refs, 1 fig

  18. Low-Energy Antinucleon-Nucleus Interaction Revisited

    CERN Document Server

    Friedman, E


    Annihilation cross sections of antiprotons and antineutrons on the proton between 50 and 400 MeV/c show Coulomb focusing below 200 MeV/c and almost no charge-dependence above 200 MeV/c. Similar comparisons for heavier targets are not possible for lack of overlap between nuclear targets studied with $\\bar p$ and $\\bar n$ beams. Interpolating between $\\bar p$-nucleus annihilation cross sections with the help of an optical potential to compare with $\\bar n$-nucleus annihilation cross sections reveal unexpected features of Coulomb interactions in the latter. Direct comparisons between $\\bar n$-nucleus and $\\bar p$-nucleus annihilations at very low energies could be possible if $\\bar p$ cross sections are measured on the same targets and at the same energies as the available cross sections for $\\bar n$. Such measurements may be feasible in the foreseeable future.

  19. Nucleon-antinucleon annihilation in chiral soliton model

    International Nuclear Information System (INIS)

    We investigate annihilation process of nucleons in the chiral soliton model by the path integral method. A soliton-antisoliton pair is shown to decay into mesons at range of about 1fm, defined by the S bar S potential. Contribution of the annihilation channel to the elastic scattering is discussed

  20. The nucleon-antinucleon interaction at low energies

    International Nuclear Information System (INIS)

    A theoretical analysis is made of recent low energy data relative to scattering process p sup(-)d → p + pions from 300 to 600 Mev/c laboratory incident momentum, with the purpose of obtaining information about resonances in the pure iso-spin system p sup(-)n (I = 1). The single and double term of the multiple scattering series are evaluated using a formalism based on Glauber theory and Feynman rules. Then, the differential cross section with respect to the invariant mass of the produced pions is obtained. The theoretical results are used to analyse the available data, which are then shown to be consistent with a non resonant behavior of the p sup(-)n system. (Author)

  1. Conference summary: antinucleon- and nucleon-nucleus interactions

    International Nuclear Information System (INIS)

    Topics summarized include: the hadronic substructure, the EMC effect, observations on relativity and the Dirac equation, and relativistic Lagrangian field theories for N-N interactions and nuclear matter

  2. Coupled-channel analysis of low energy nucleon-antinucleon interactions

    International Nuclear Information System (INIS)

    Multichannel M-matrix method is applied to an NN-bar-system with taking into account elastic pp-bar-scattering, charge-exchange pp-bar→nn-bar reaction and pp-bar annihilation. It is shown that contrary to standard assumptions the isotopic invariance due the large influence of the charge exchange channel affects very significantly the parameters of strong interactions. Contrary to previous descriptions, M-matrix elements are treated as real functions. The differential and total cross-sections for pp-bar→pp-bar and pp-bar→nn-bar processes, cross-section δtot(pp-bar) and the real-to-imaginary ratio of the forward amplitude of elastic pp-bar scattering up to beam momenta plab=600 MeV/c are described. The fitting leads to a resonance in the s-wave at about plab=500 MeV/c and to bound states in p-wave near the pp-bar threshold. 33 refs.; 8 figs.; 3 tabs

  3. Antinucleon-nucleus interaction near threshold from the Paris $\\bar NN$ potential

    CERN Document Server

    Friedman, E; Loiseau, B; Wycech, S


    A general algorithm for handling the energy dependence of hadron-nucleon amplitudes in the nuclear medium, consistently with their density dependence, has been recently applied to antikaons, eta mesons and pions interacting with nuclei. Here we apply this approach to antiprotons below threshold, analyzing experimental results for antiprotonic atoms across the periodic table. It is also applied to antiproton and antineutron interaction with nuclei up to 400~MeV/c, comparing with elastic scattering and annihilation cross sections. The underlying $\\bar pN$ scattering amplitudes are derived from the Paris $\\bar NN$ potential, including modifications in the medium. Emphasis is placed on the role of the $P$-wave amplitudes with respect to the repulsive $S$-wave amplitudes.

  4. Hadronic model for the consistent description of the scattering and annihilation of the antinucleon-nucleon system

    International Nuclear Information System (INIS)

    In this work a consistent description of the anti NN scattering and annihilation with a hadronic model is presented. The elastic anti NN interaction is obtained from the Bonn NN potential via a G-parity transformation. For the annihilation part, a consistent, partly microscopic description is constructed treating the most important two meson channels explicitly and accounting for the rest by a phenomenological optical potential of Gaussian form. Transitions from the antibaryon-baryon sector to the meson sector are mediated via the exchange of N, Δ, Λ, Σ and Y* baryons. anti NN scattering observables, branching ratios and cross sections for the annihilation into two mesons and bound states are calculated consistently. Results are compared with former calculations and the experimental data. The agreement with the data is good. The importance of meson-meson interactions in the final state is studied at the example of the particular annihilation channel anti NN → ππ. A full coupled channels calculation with the channels anti NN, ππ, anti KK and ρρ is performed. Interactions and transitions in the meson sector are described by meson-exchange diagrams. Integrated as well as differential cross sections and analyzing powers for the annihilation process anti NN → ππ are described with good quality. Results of the coupled channels model for ππ phase shifts and inelasticities above the anti NN threshold are discussed. Effects of the meson-meson interactions on anti NN scattering observables are small. The importance of two-step processes and meson-meson interactions in the final state for the description of the angle-dependent observables in the annihilation process anti NN → ππ can be demonstrated. (orig.)

  5. Narrow n anti n resonances

    International Nuclear Information System (INIS)

    The present status of the problem of quasinuclear states in systems of nucleons and antinucleons is reviewed. The theoretical predictions are compared with experimental data on narrow meson resonances near N anti N threshold which appeared in 1971-74

  6. Antiproton-proton resonant like channels in J/Psi decays into photon, proton and antiproton

    CERN Document Server

    Loiseau, B


    The BES collaboration has recently observed a strong enhancement close to the proton-antiproton threshold in the J/Psi decays into photon, proton and antiproton. Such a structure can be explained by a traditional nucleon-antinucleon model. The near threshold 1S0 bound state and/or the well-established 3P0 resonant state found in this nucleon-antinucleon interaction can adequately describe the BES data.

  7. KNO scaling in isospin-connected reactions

    International Nuclear Information System (INIS)

    The generation of correct KNO scaling is presented. It permits one to describe the multiplicity distributions of both π+ and π- mesons in different nucleon-nucleon and nonannihilation antinucleon-nucleon interactions by the same scaling function Ψ(z) and the same energy dependence of the scale parameters. Multiplicity distributions in different antinucleon-nucleon annihilation reactions are described by another function Ψ(z). In this case the slope of the scale-parameter energy dependence is about 1.5 times greater than for nucleon-nucleon interaction

  8. Low energy p anti p strong interactions: theoretical perspective

    International Nuclear Information System (INIS)

    Several of the frontier problems in low energy nucleon-antinucleon phenomenology are addressed. Spin observables and dynamical selection rules in N anti N annihilation are used as examples of phenomena which offer particularly strong constraints on theoretical models, formulated either in terms of meson and baryon exchange or as effective operators in a non-perturbative quark-gluon picture. 24 refs

  9. Multiplicity of charged particles in anti-pp-interactions at 32 GeV/c

    International Nuclear Information System (INIS)

    The study of antipp-interaction is especially interesting because it yields information about the specific mechanism of the nucleon-antinucleon annihilation. It is also of interest to estimate to what extent this specific channel of interaction of antiprotons produced in atmosphere by cosmic particles can affect the EAS characteristics

  10. Pion interactions at medium energies. Progress report, December 1, 1982-January 31, 1984

    International Nuclear Information System (INIS)

    Research summaries are given on the following topics: spin dependence of nucleon-nucleon amplitudes, kaon and hypernuclear physics, kaon reactions at higher momentum, anti-nucleon reactions, and double charge exchange with heavy ions. A feasibility study for a 1 to 2 GeV separated kaon beam at the AGS is included. Publications are listed

  11. Virtual pair creation in nuclear Dirac phenomenology

    International Nuclear Information System (INIS)

    We discuss the importance of virtual nucleon-antinucleon pair (VP) creation in the scalar-vector model of nucleon-nucleus scattering. In a model based upon the Hartree approximation to nuclear matter, we find such VP terms to be crucial in order to reproduce the 'wine-bottle-bottom' shape of the real component of the optical potential. (orig.)

  12. Pion interactions at medium energies. Progress report, February 1, 1984-January 31, 1985

    International Nuclear Information System (INIS)

    Our research program has developed into two major thrusts. The first uses kaons produced at the Brookhaven National Laboratory (BNL) Alternating Gradient Synchrotron (AGS) to study the properties of hyperons embedded in nuclear matter. Specifically we have had under investigation for some time the spectra of both lambda and sigma hypernuclei and the extraction of the hyperon-nucleon interaction parameters. The second thrust uses antinucleons produced by the AGS to study the antinucleon nucleon interaction and the properties of the annihilation reaction. Both thrusts have an approved program at the AGS which will last several years. Experiments are listed and abstracts of current research are given. Some preliminary results from experiments are presented, and new approved proposals are detailed

  13. Measurement of interaction between antiprotons

    CERN Document Server



    One of the primary goals of nuclear physics is to understand the force between nucleons, which is a necessary step for understanding the structure of nuclei and how nuclei interact with each other. Rutherford discovered the atomic nucleus in 1911, and the large body of knowledge about the nuclear force since acquired was derived from studies made on nucleons or nuclei. Although antinuclei up to antihelium-4 have been discovered and their masses measured, we have no direct knowledge of the nuclear force between antinucleons. Here, we study antiproton pair correlations among data taken by the STAR experiment at the Relativistic Heavy Ion Collider and show that the force between two antiprotons is attractive. In addition, we report two key parameters that characterize the corresponding strong interaction: namely, the scattering length (f0) and effective range (d0). As direct information on the interaction between two antiprotons, one of the simplest systems of antinucleons, our result provides a fundamental ingr...

  14. International Conference on Spin Observables of Nuclear Probes

    CERN Document Server

    Goodman, Charles; Walker, George; Spin Observables of Nuclear Probes


    The proceedings of the "International Conference on Spin Observables of Nuclear Probes" are presented in this volume. This conference was held in Telluride, Colorado, March 14 -17, 1988, and was the fourth in the Telluride series of nuclear physics conferences. A continuing theme in the Telluride conference series has been the complementarity of various intermediate-energy projectiles for elucidating the nucleon-nucleon interaction and nuclear structure. Earlier conferences have contributed significantly to an understanding of spin currents in nuclei, in particular the distribution of Gamow-Teller strength using charge-exchange reactions. The previous conference on "Antinucleon and Nucleon Nucleus Interactions" compared nuclear information from tra­ tional probes to recent results from antinucleon reactions. The 1988 conference on Spin Observables of Nuclear Probes, put special emphasis on spin observables and brought together experts using spin information to probe nuclear structure. Spin observabl...

  15. Bubble chamber studies of hadron and photon interactions. Progress report, April 1, 1983-March 31, 1984

    International Nuclear Information System (INIS)

    Progress is briefly reported on a number of experiments on hadron and photon interactions. Stand-alone bubble chamber experiments were completed, and current efforts focus on hybrid chamber research. Two new projects are being proposed-mu neutrinos in the Kitigaki bubble chamber at Fermilab, and a search for a threshold enhancement in the production of sigma particles in the SLAC 40 hybrid chamber. Photoproduction and antinucleon physics are covered. Experiments at CERN were run to observe diffractive strange particle production

  16. πN TDAs from charmonium production in association with a forward pion at P̅ANDA

    Directory of Open Access Journals (Sweden)

    Ma B.


    Full Text Available Charmonium production in association with a forward or backward pion in nucleon-antinucleon annihilation is one of the most promising reaction to access nucleon-to-pion transition distribution amplitudes (TDAs at P̅ANDA. We briefly review the description of this reaction in terms of πN TDAs within the collinear factorization approach and present the first results of dedicated feasibility studies for the P̅ANDA experimental setup.

  17. Verifying Unmatter by Experiments, More Types of Unmatter, and a Quantum Chromodynamics Formula

    Directory of Open Access Journals (Sweden)

    Smarandache F.


    Full Text Available As shown, experiments registered unmatter: a new kind of matter whose atoms include both nucleons and anti-nucleons, while their life span was very short, no more than 10^−20 sec. Stable states of unmatter can be built on quarks and anti-quarks: applying the unmatter principle here it is obtained a quantum chromodynamics formula that gives many combinations of unmatter built on quarks and anti-quarks.

  18. Physics with antiprotons at LEAR in the ACOL ERA. Proceedings of the 3. LEAR Workshop

    Energy Technology Data Exchange (ETDEWEB)

    Gastaldi, U.; Klapisch, R.; Richard, J.M.; Tran Thanh Van, J. (eds.)


    The programme covered the following topics: accelerator aspects (anti-p production, LEAR, advanced developments, cooling, LEAR design inspired machines). Nucleon antinucleon interactions (panti-p atom, scattering, annihilation, spin effects, antineutron physics, antibaryon physics). Spectroscopy (light mesons, hybrids, glueballs, baryonia, quarkonia). Rare channels (form factors, CP, CPT, C, T violation, quantum mechanics tests) anti-p nucleus interactions (exotic atoms, scattering, annihilation, hypernuclei). New ideas (antigravity, high precision experiments). New detectors (new experiments, general and/or technical aspects).

  19. Physics with antiprotons at LEAR in the ACOL ERA

    International Nuclear Information System (INIS)

    The programme covered the following topics: accelerator aspects (anti-p production, LEAR, advanced developments, cooling, LEAR design inspired machines). Nucleon antinucleon interactions (panti-p atom, scattering, annihilation, spin effects, antineutron physics, antibaryon physics). Spectroscopy (light mesons, hybrids, glueballs, baryonia, quarkonia). Rare channels (form factors, CP, CPT, C, T violation, quantum mechanics tests) anti-p nucleus interactions (exotic atoms, scattering, annihilation, hypernuclei). New ideas (antigravity, high precision experiments). New detectors (new experiments, general and/or technical aspects)

  20. Midrapidity Antiproton-to-Proton Ratio in pp Collisons root s=0.9 and 7 TeV Measured by the ALICE Experiment

    Czech Academy of Sciences Publication Activity Database

    Aamodt, K.; Abel, N.; Abeysekara, U.; Quintana, A.A.; Abramyan, A.; Adamová, Dagmar; Bielčík, Jaroslav; Bielčíková, Jana; Kapitán, Jan; Kushpil, Svetlana; Kushpil, Vasilij; Pachr, M.; Petráček, Vojtěch; Rak, Jan; Šumbera, Michal; Tlustý, David; Wagner, Vladimír; Mareš, Jiří A.; Polák, Karel; Závada, Petr


    Roč. 105, č. 7 (2010), 072002/1-072002/12. ISSN 0031-9007 R&D Projects: GA MŠk LA08015 Institutional research plan: CEZ:AV0Z10480505; CEZ:AV0Z10100502 Keywords : TOTAL CROSS-SECTIONS * ANTINUCLEON-NUCLEON * STRING MODEL Subject RIV: BG - Nuclear, Atomic and Molecular Physics, Colliders Impact factor: 7.621, year: 2010

  1. Firestreak model predictions for strange particle and lightest hyperfragment production in heavy ion collisions

    International Nuclear Information System (INIS)

    The predictions are made for relative yields kaons, hyperons, antinucleons, and lightest sub(ΛΛ)sup(4)He, sub(ΛΛ)sup(6)He and sub(ΛΛ)sup(10)B hyperfragments for various combinations of colliding nuclei up to 10 GeV/nucleon within the firestreak model taking account of the associated nature of the strange particle production. These results may be used to identify the signs of a possible phase transition of hadrons into the quark-gluon plasma

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

    Directory of Open Access Journals (Sweden)

    Masahiro Kawasaki


    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.

  3. Study of anti-neutron annihilations at low energy

    International Nuclear Information System (INIS)

    The results of a total cross section measurement for the reactions anti np and anti pn are plotted. These results indicate that the annihilation amplitudes are predominantly I = 1 at low energy. The S-wave unitarity limit is shown, and the data support the conclusion drawn from anti pp data that even at the lowest momenta P-wave and higher waves are very important. The technique of using antineutrons to study very low energy antineutrons to study very low energy antinucleon interactions is demonstrated to be feasible

  4. Protonium X-ray spectroscopy

    CERN Document Server

    Gotta, D


    The Lyman and Balmer transitions from antiprotonic hydrogen and deuterium were studied extensively at the low-energy-antiproton ring LEAR at CERN in order to determine the strong interaction effects. A first series of experiments $9 was performed with semiconductor and gaseous X-ray detectors. In the last years of LEAR operation using a Bragg crystal spectrometer, strong interaction parameters in the 2p states of antiprotonic hydrogen and deuterium were measured $9 directly. The results of the measurements support the meson-exchange models describing the medium and long range part of the nucleon-antinucleon interaction. (39 refs).

  5. Mass shift of σ-meson in nuclear matter

    International Nuclear Information System (INIS)

    The propagation of σ-meson in nuclear matter is studied in the Walecka model, by assuming that sigma couples to a pair of nucleon-antinucleon states to particle-hole states. The in-medium effect of σ-ω mixing is also studied. For completeness, the coupling of sigma to two virtual pions was also considered. It is found that the σ-meson mass decreases with respect to its value in vacuum and that the contribution of the σ-ω mixing effect on the mass shift is relatively small. (author)

  6. Low energy antiproton physics

    International Nuclear Information System (INIS)

    This paper summarizes the present experimental and theoretical status of antinucleon-nucleon (bar NN) interactions at low energy (below 2 GeV/c). The authors discuss elastic scattering, hyperon pair production, and annihilation into mesonic channels, including the search for exotic meson states in the annihilation debris. New results from the Low Energy Antiproton Ring (LEAR) at CERN, from KEK in Japan, and from Brookhaven National Laboratory (BNL) are now available. Some of the experiments and their comparison to theoretical predictions have been reviewed earlier. The authors extend these reviews to more recent data and theoretical calculations

  7. Revisiting big-bang nucleosynthesis constraints on dark-matter annihilation (United States)

    Kawasaki, Masahiro; Kohri, Kazunori; Moroi, Takeo; Takaesu, Yoshitaro


    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.

  8. Mass shift of -meson in nuclear matter

    Indian Academy of Sciences (India)

    J R Morones-Ibarra; Mónica Menchaca Maciel; Ayax Santos-Guevara; Felipe Robledo Padilla


    The propagation of -meson in nuclear matter is studied in the Walecka model, by assuming that the sigma couples to a pair of nucleon–antinucleon states and to particle–hole states. The in-medium effect of - mixing is also studied. For completeness, the coupling of sigma to two virtual pions was also considered. It is found that the -meson mass decreases with respect to its value in vacuum and that the contribution of the - mixing effect on the mass shift is relatively small.

  9. Antiproton-nucleus inelastic scattering and the spin-isospin dependence of the N anti N interaction

    International Nuclear Information System (INIS)

    A general overview of the utility of antinucleon (anti N)-nucleus inelastic scattering studies is presented, emphasizing both the sensitivity of the cross sections to various components of the N anti N transition amplitudes and the prospects for the exploration of some novel aspects of nuclear structure. We start with an examination of the relation between NN and N anti N potentials, focusing on the coherences predicted for the central, spin-orbit and tensor components, and how these may be revealed by measurements of two-body spin observables. We next discuss the role of the nucleus as a spin and isospin filter, and show how, by a judicious choice of final state quantum numbers (natural or unnatural parity states, isospin transfer ΔT=0 or 1) and momentum transfer q, one can isolate different components of the N anti N transition amplitude. Various models for the N anti N interaction which give reasonable fits to the available two-body data are shown to lead to strikingly different predictions for certain spin-flip nuclear transitions. We suggest several possible directions for future anti N-nucleus inelastic scattering experiments at LEAR, for instance the study of spin observables which would be accessible with polarized anti N beams, charge exchange reactions, and higher resolution studies of the (anti p, anti p') reaction. We compare the antinucleon and the nucleon as a probe of nuclear modes of excitation. 34 refs

  10. Effective meson masses in a non-linear relativistic mean field model

    Energy Technology Data Exchange (ETDEWEB)

    Agostini, Braulio T.; Duarte, Sergio B. [Centro Brasileiro de Pesquisas Fisicas (CBPF), Rio de Janeiro, RJ (Brazil); Chiapparini, Marcelo [Universidade do Estado do Rio de Janeiro (UERJ), RJ (Brazil). Inst. de Fisica; Rodrigues, Hilario [Centro Federal de Educacao Tecnologica do Rio de Janeiro (CEFET/RJ), RJ (Brazil); Costa, Ricardo S. [Universidade Federal de Rondonia (UNIR), Ji-Parana, RO (Brazil). Dept. de Fisica


    Full text: Relativistic mean field theories, with ({sigma}, {omega})-fields mediating the baryonic interaction, reproduce many important properties of the symmetric nuclear matter. This kind of models, where the nonlinear Walecka's model is a prototype, also has been widely applied to the description of the hadron phase for the thermodynamic treatment of the hadron to quark-gluon phase transition. However the conventional theory does not consider the interaction between the mesonic fields. This kind of interaction could be relevant when applying the theory to the situation involving nucleon and antinuclear matter. In this work we discuss the inclusion of meson-meson interaction in the theory in order to investigate the properties of nucleon-antinucleon matter at high temperature and low net baryonic density regime. This situation is of interest in describing the highest energy density states of the heavy ion collision at ultra-relativistic energies. Our present study includes the interaction between {sigma}-{omega} mesons for different net baryonic densities by changing the ratio of nucleons to antinucleons densities. The particular scenario with null net baryonic density (the so-called 'no-sea' approximation) was already studied in Refs., but without taking into account the interaction between mesons. In the present work, with the interaction between meson included, we also determine the effective masses of the ({sigma}, {omega})-fields. (author)

  11. Effective meson masses in a non-linear relativistic mean field model

    International Nuclear Information System (INIS)

    Full text: Relativistic mean field theories, with (σ, ω)-fields mediating the baryonic interaction, reproduce many important properties of the symmetric nuclear matter. This kind of models, where the nonlinear Walecka's model is a prototype, also has been widely applied to the description of the hadron phase for the thermodynamic treatment of the hadron to quark-gluon phase transition. However the conventional theory does not consider the interaction between the mesonic fields. This kind of interaction could be relevant when applying the theory to the situation involving nucleon and antinuclear matter. In this work we discuss the inclusion of meson-meson interaction in the theory in order to investigate the properties of nucleon-antinucleon matter at high temperature and low net baryonic density regime. This situation is of interest in describing the highest energy density states of the heavy ion collision at ultra-relativistic energies. Our present study includes the interaction between σ-ω mesons for different net baryonic densities by changing the ratio of nucleons to antinucleons densities. The particular scenario with null net baryonic density (the so-called 'no-sea' approximation) was already studied in Refs., but without taking into account the interaction between mesons. In the present work, with the interaction between meson included, we also determine the effective masses of the (σ, ω)-fields. (author)

  12. Search for narrow lines in photon spectra from proton-antiproton annihilations at rest

    International Nuclear Information System (INIS)

    Inclusive photon spectra from annihilation of antiprotons stopped in a liquid hydrogen target were measured at LEAR (CERN) with a magnetic pair spectrometer. The FWHM energy resolution of the spectrometer in the region from 100-700 MeV was in the range from 2 to 4.5%. A total number of about 4.8.106 events with energies up to 1 GeV have been reconstructed. The photon spectra were scanned for possible lines with widths comparable to spectrometer resolution indicating the existence of bound nucleon-antinucleon states. No such structures were found with branching ratios greater than 4 to 8.10-4 at 95% confidence level. Results of former experiments could not be confirmed. (orig.)

  13. 23rd Annual seminar on theoretical physics, Grahamstown, 5-8 July 1988

    International Nuclear Information System (INIS)

    This seminar contains 18 papers. Twelve papers are indexed separately. Topics covered include: the Dirac equation in arbitrary space-time dimensions; next-to-leading corrections to jet multiplicity distributions in QCD; propagators and one loop diagrams in cavity field theory; cavity quantum chromodynamics in the presence of a classical background field; quark gluon plasma and hadronic matter in the early universe; deconfinement and chiral transitions in lattice QCD; J/Ψ suppression as a signal for quark deconfinement; geometrical interpretation of boson models of nuclear structure; the interacting boson model, BCS-RPA theory and the theory of pairing interactions applied to the Ge-nuclei; fluctuations and chaotic behaviour; test of the Bonn nucleon-nucleon potential in nucleon-antinucleon scattering; and new relativistic centre-of-mass corrections for the nucleon

  14. The 3rd Nordic meeting on high energy reactions in nuclei

    International Nuclear Information System (INIS)

    Abstracts of the 31 lectures given at the meeting are presented. Major emphasis was placed on the nucleon-nucleon and nucleon-antinucleon interaction in bound and unbound systems. Four of the ten sessions were devoted to this subject. Two sessions contained lecture and seminars on 'Isobars in nuclei', two were devoted to hadron-nucleus reactions, one to high-energy heavy-ion reactions and one to new developments of experimental tools. This latter session had two talks, one about channeling with GeV particles and the other about the planned low-energy antiproton facility LEAR at CERN. Talks of more general character were 'The experimental programme at the CERN SC', 'Accelerator produced nuclear fuel' and 'The upsilons, a new family of quark-antiquark bound state'. (JIW)

  15. LEAR's physics legacy

    CERN Multimedia

    Philippe Bloch


    By providing an intense and clean source of antiprotons for the first time, LEAR has opened many fields of research. Although it is not easy to summarise its versatile physics programme in a few lines, this article is an attempt to do justice to the 27 experiments performed during 14 years of running and to their successful results.   LEAR complex, September 1983. In the early days of LEAR operation, the antiproton intensity was quite limited and the machine was mostly used for studying antiprotonic atoms and interactions of low-energy antiprotons with nuclei. Physicists were also performing measurements of cross-sections (total, elastic, charge exchange) as a function of the antiproton momentum. These first experiments provided valuable insights into the properties of nucleon-antinucleon interactions, including their spin structure, and ruled out the existence of hypothesized multiquark states of matter referred to as “baryonium”. The ASTERIX experiment...

  16. Search for the glueball content of hadrons in gamma p interactions at GlueX

    CERN Document Server

    Gutsche, Thomas; Lyubovitskij, Valery E; Obukhovsky, Igor T


    We suggest a theoretical framework for the description of double photon and nucleon-antinucleon photoproduction off the proton gamma + p -> 2 gamma + p and gamma + p -> antiN + N + p with takes into account the contribution of the scalar mesons f0(1370), f0(1500) and f0(1710). These scalars are considered as mixed states of a glueball, nonstrange and strange quarkonia. Our framework is based on the use of effective hadronic Lagrangians which phenomenologically take into account two-gluon exchange effects governing the gamma + p -> 2 gamma + p and gamma + p -> antiN + N + p processes. Present results can be used to guide the possible search for these reactions by the GlueX Collaboration at JLab.

  17. Symmetry tests with intense hadron beams

    International Nuclear Information System (INIS)

    The Government of Canada has pulled the plug on funding of the KAON facility in Canada. But the science opportunities for symmetry tests with the kinds of beams that KAON would have provided remain. For example, the full intensity of kaons, which KAON would have provided, is needed to find the magnitude and phase of Vtd and therefore to describe direct CP violation. The combination of K+ → π+νν- and KLo → πoνν- serve this purpose. A variety of other symmetry tests are possible with the kind of intense beams of kaons, antinucleons, other hadrons and neutrinos which KAON would have provided. A perspective will be given for such experiments and their future prospects, now that KAON will not be built. (author). 10 refs., 1 tab., 2 figs

  18. Status of the MCNPX transport code

    International Nuclear Information System (INIS)

    The Monte Carlo particle transport code MCNPX and its associated data have been the focus of a major development effort at Los Alamos for several years. The system has reached a mature state, and has become a significant tool for many intermediate and high-energy particle transport applications. A recent version has been released to the Radiation Safety Information Computational Center (RSICC). A recent report provides an overview of the code and an extensive set of references for the component physics modules used in the code. In this paper we review the status of the developmental version of MCNPX, and describe some important new enhancements, including the use of evaluated nuclear data files for proton transport; the use of photonuclear reaction data; improved elastic and inelastic react ion cross sections for nucleons, antinucleons, pions, and kaons; and two new modes of operation of the code. We also illustrate the use of the new proton and photonuclear data in two representative applications

  19. Pseudospin Symmetry as a Bridge between Hadrons and Nuclei

    Directory of Open Access Journals (Sweden)

    Joseph N. Ginocchio


    Full Text Available Atomic nuclei exhibit approximate pseudospin symmetry. We review the arguments that this symmetry is a relativistic symmetry. The condition for this symmetry is that the sum of the vector and scalar potentials in the Dirac Hamiltonian is a constant. We give the generators of pseudospin symmetry. We review some of the predictions that follow from the insight that pseudospin symmetry has relativistic origins . We show that approximate pseudospin symmetry in nuclei predicts approximate spin symmetry in anti-nucleon scattering from nuclei. Since QCD sum rules predict that the sum of the scalar and vector potentials is small, we discuss the quark origins of pseudospin symmetry in nuclei and spin symmetry in hadrons.

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

    Energy Technology Data Exchange (ETDEWEB)

    Pacifico, N., E-mail: [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


    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.

  1. The analytic pion form factor

    CERN Document Server

    Lomon, Earle L


    The pion electromagnetic form factor and two-pion production in electron-positron collisions are simultaneously fitted by a vector dominance model evolving to perturbative QCD at large momentum transfer. This model was previously successful in simultaneously fitting the nucleon electromagnetic form factors (space-like region) and the electromagnetic production of nucleon-antinucleon pairs (time-like region). For this pion case dispersion relations are used to produce the analytic connection of the space-like and time-like regions. The fit to all the data is good. The description of high-$q^2$ data, in the time-like region, requires one more meson with $\\rho$ quantum numbers than listed in the 2014 Particle Data Group review.

  2. Propagation and secondary production of low energy antiprotons in the atmosphere (United States)

    Bowen, T.; Moats, A.


    Current theories, in which the observed antiproton component is attributed strictly to secondary production in high energy inelastic collisions of protons with the interstellar medium or the atmosphere, apparently fail to explain the relatively high p vertical intensities measured at mountain and balloon altitudes. Therefore, a more careful calculation of the theoretical secondary intensity spectra is required before more exotic sources for these excess p's can be explored. A one dimensional diffusion equation is used to calculate the expected vertical intensity of p's due only to secondary production in the atmosphere; any assumed primary p spectrum is also included. Two adjustable parameters, the inelasticity and charge exchange in nucleon-nucleus collisions, were included in the algorithm. In order to obtain an independent estimate of their values the proton vertical intensities in the atmosphere were calculated, adjusting the parameters until the curves fit the experimental proton data, and then assumed that these values were identical in antinucleon-nucleus collisions.

  3. Neutron-antineutron oscillations on the lattice

    CERN Document Server

    Buchoff, Michael I; Wasem, Joseph


    One possible low energy process due to beyond the Standard Model (BSM) physics is the neutron-antineutron transition, where baryon number changes by two units. In addition to providing a source of baryon number violation in the early universe, interactions of this kind are natural in grand unified theories (GUTs) with Majorana neutrinos that violate lepton number. Bounds on these oscillations can greatly restrict a variety of GUTs, while a non-zero signal would be a "smoking gun" for new physics; however, to make a reliable prediction, the six-quark nucleon-antinucleon matrix elements must first be calculated non-perturbatively via lattice QCD. We review the current understanding of this quantity, describe the lattice formalism, and present preliminary results from $32^3\\times256$ clover-Wilson lattices with a pion mass of 390 MeV.

  4. Antiproton-Nucleus Interaction and Coulomb Effect at High Energies

    Institute of Scientific and Technical Information of China (English)

    ZHOU Li-Juan; WU Qing; GU Yun-Ting; MA Wei-Xing; TAN Zhen-Qiang; HU Zhao-Hui


    The Coulomb effect in high energy antiproton-nucleus elastic and inelastic scattering from 12C and 16O is studied in the framework of Glauber multiple scattering theory for five kinetic energies ranged from 0.23 to 1.83 GeV.A microscopic shell-model nuclear wave functions, Woods-Saxon single-particle wave functions, and experimental pN amplitudes are used in the calculations. The results show that the Coulomb effect is of paramount importance for filling up the dips of differential cross sections. We claim that the present result for inelastic scattering of antiproton-12C is sufficiently reliable to be a guide for measurements in the very near future. We also believe that antiproton nucleus elastic and inelastic scattering may produce new information on both the nuclear structure and the antinucleon-nucleon interaction, in particular the p-neutron interaction.

  5. Inclusive production of protons in heavy-ion collisions at high energy

    International Nuclear Information System (INIS)

    Inclusive distribution of protons in nucleus-nucleus collisions at high energy has been studied in both forward and backward regions according to the hard scattering model. It is observed that proton production may occur in two ways: (1) the emitted proton is one of the interacting protons in the nucleus and (2) the proton is emitted from a secondary virtual pion along with an antinucleon. Process (1) is dominant in the interaction BA→px in the region 0 or = 1 with X/sub F/ < or = 1 where the cross section shows a sharp fall with X/sub F/. This feature is found to be in good agreement with experiments. Besides, it is predicted that though there will be approximate scaling (very small change with energy) in the forward region, in the backward region scale breaking will be dominant

  6. High energy nucleonic component of cosmic rays at mountain altitudes

    CERN Document Server

    Stora, Raymond Félix

    The diffusion equations describing the unidimensional propagation of .the high energy nucleonic component of cosmic rays throughout the atmosphere are sol"V'ed under two assumptions: (l) The nucleon-nucleon collisions are described according to Fermi's therlnOdynamical model involving completely inelastic pion and.nucleon-antinucleon pair production. (2) A somewhat opposite assumption is made assuming partially elastic collisions without nucleon-anti.nucleon pair production. Due to the present inaccuracy of experiments, we are able to derive only tentati v.e conclusions. The values computed under both hypotheses for the absorption mean free path and the charged to neutral particles ratio are found in acceptable ranges when compared to experimental data. The diffeential energy spectrum at a given depth is always found steeper than the primary, and steeper than indicated by experimental values if the primary is taken proportional to the 2.5 inverse power of energy.

  7. Ludwig Tauscher (1939-2008)

    CERN Document Server


    Dear Colleagues, It is with deep sorrow and regret that we inform you that our colleague and friend Ludwig Tauscher passed away on Sunday 23 November after a heart attack. Ludwig studied physics at the University of Heidelberg, where he obtained his PhD in 1966. After several postdoctoral appointments at the MPI Heidelberg, and the Universities of Konstanz and Karlsruhe, he joined the University of Basel, where he became Professor of Physics in 1985. Ludwig devoted his entire professional life to teaching and experimental physics. He arrived at CERN in the early seventies, where he performed several experiments at the SC and at the PS, studying exotic atoms with various probes such as μ-, π-, K-, and Σ-. In the early eighties he searched for the production of nucleon-antinucleon bound states at the PS, a subject that was the main motivation for the construction of the LEAR storage ring. At LEAR he studied neutral meson productio...

  8. Theory of the low-energy pion--nucleon interaction

    Energy Technology Data Exchange (ETDEWEB)

    Banerjee, M.K.; Cammarata, J.B.


    A once-subtracted form of the Low equation for the pion-nucleon scattering amplitude is derived, with PCAC used to define the amplitude when one pion is off the mass shell. The static approximation is not made and both the seagull terms and the antinucleon contribution (z-graphs) are retained. The theory is applied to calculate the S-wave amplitudes in the elastic scattering region. Good agreement is found with the phase shift fits to the data when we use mod(g/sub ..pi../(4M/sup 2/)) = 11.69 and 25.5 MeV for the ..pi..N sigma-commutator. The implications of this work for the analysis of low-energy elastic scattering of pions from nuclei are discussed. In particular, it is pointed out how this work establishes the presence of a Laplacian term in the pion-nucleus optical potential with a magnitude that is fixed from the value of the sigma-commutator.

  9. Measurement of the Spin–Dependence of the $\\overline{p}-p$ Interaction at the AD–Ring

    CERN Document Server

    Barschel, C; Dietrich, J; Dolfus, N; Engels, R; Gebel, R; Hadamek, H; Haidenbauer, J; Hanhart, C; Kacharava, A; Krol, G; Küven, M; Langenberg, G; Lehrach, A; Lorentz, B; Maier, R; Martin, S; Meissner, U G; Nekipelov, M; Nikolaev, N N; Oellers, D; d'Orsaneo, G; Prasuhn, D; Rathmann, F; Retzlaff, M; Sarkadi, J; Schleichert, R; Seyfarth, H; Sibirtsev, A; Spölgen, D; Stein, H J; Stockhorst, H; Ströher, H; Weidemann, Chr; Welsch, D; Wieder, P; Barion, L; Bertelli, S; Carassiti, V; Ciullo, G; Contalbrigo, M; Cotta-Ramusino, A; Dalpiaz, P F; Drago, A; Guidoboni, G; Lenisa, P; Pappalardo, L; Stancari, G; Stancari, M; Statera, M; Azarian, T; Kulikov, A; Kurbatov, V; Macharashvili, G; Merzliakov, S; Meshkov, I N; Smirnov, A; Tsirkov, D; Uzikov, Yu; Barsov, S; Belostotskii, S; Grigoryev, K; Kravtsov, P; Mikirtychiants, M; Mikirtychiants, S; Vasilyev, A; Esser, F M; Greven, R; Hansen, G; Jadgfeld, F; Klehr, F; Soltner, H; Straatmann, H; Chiladze, D; Garishvili, A; Lomidze, N; Mchedlishvili, D; Nioradze, M; Tabidze, M; Akopov, N; Avetisyan, A; Elbakyan, G; Marukyan, H; Taroian, S; Benati, P; Erven, W; Kayser, F J; Kleines, H; Wüstner, P; Bruncko, D; Ferencei, J; Musinsky, J; Urbán, J; Augustyniak, W; Marianski, B; Trzcinski, A; Zupranski, P; Dymov, S; Nass, A; Steffens, E; Rathsman, K; Tegnér, P E; Engblom, P Thoerngren; De Leo, R; Tagliente, G; Kämpfer, B; Trusov, S; Buttimore, N; Meyer, H O; CERN. Geneva. SPS and PS Experiments Committee; SPSC


    We propose to use an internal polarized hydrogen storage cell gas target in the AD ring to determine for the first time the two total spin–dependent pbar-p cross sections σ1 and σ2 at antiproton beam energies in the range from 50 to 450 MeV. The data obtained are of interest by themselves for the general theory of pbar-p interactions since they will provide a first experimental constraint of the spin–spin dependence of the nucleon–antinucleon potential in the energy range of interest. In addition, measurements of the polarization buildup of stored antiprotons are required to define the optimum parameters of a future, dedicated Antiproton Polarizer Ring (APR), intended to feed a double–polarized asymmetric pbar-p collider with polarized antiprotons. Such a machine has recently been proposed by the PAX collaboration for the new Facility for Antiproton and Ion Research (FAIR) at GSI in Darmstadt, Germany. The availability of an intense stored beam of polarized antiprotons will provide access to a wealt...

  10. Hidden pseudospin and spin symmetries and their origins in atomic nuclei

    CERN Document Server

    Liang, Haozhao; Zhou, Shan-Gui


    Symmetry plays a fundamental role in physics. The quasi-degeneracy between single-particle orbitals $(n, l, j = l + 1/2)$ and $(n-1, l + 2, j = l + 3/2)$ indicates a hidden symmetry in atomic nuclei, the so-called pseudospin symmetry (PSS). Since the introduction of the concept of PSS in atomic nuclei, there have been comprehensive efforts to understand its origin. Both splittings of spin doublets and pseudospin doublets play critical roles in the evolution of magic numbers in exotic nuclei discovered by modern spectroscopic studies with radioactive ion beam facilities. Since the PSS was recognized as a relativistic symmetry in 1990s, many special features, including the spin symmetry (SS) for anti-nucleon, and many new concepts have been introduced. In the present Review, we focus on the recent progress on the PSS and SS in various systems and potentials, including extensions of the PSS study from stable to exotic nuclei, from non-confining to confining potentials, from local to non-local potentials, from ce...

  11. Antimatter H4Λ hypernucleus production and the H3Λ /3He puzzle in relativistic heavy-ion collisions (United States)

    Sun, Kai-Jia; Chen, Lie-Wen


    We show that the measured yield ratio H3Λ /3He(H¯3¯Λ /¯3He ) in Au +Au collisions at √{sN N}=200 GeV and in Pb +Pb collisions at √{sN N}=2.76 TeV can be understood within a covariant coalescence model if (anti-)Λ particles freeze out earlier than (anti-)nucleons but their relative freeze-out time is closer at √{sN N}=2.76 TeV than at √{sN N}=200 GeV. The earlier (anti-)Λ freeze-out can significantly enhance the yield of (anti)hypernucleus H4Λ (H¯4¯Λ ), leading to that H¯4¯Λ has a comparable abundance with ¯4He and thus provides an easily measured antimatter candidate heavier than ¯4He. The future measurement on H4Λ (H¯4¯Λ ) would be very useful to understand the (anti-)Λ freeze-out dynamics and the production mechanism of (anti)hypernuclei in relativistic heavy-ion collisions.

  12. Precision measurement of the mass difference between light nuclei and anti-nuclei

    CERN Document Server

    Adam, Jaroslav; Aggarwal, Madan Mohan; Aglieri Rinella, Gianluca; Agnello, Michelangelo; Agrawal, Neelima; Ahammed, Zubayer; Ahmed, Ijaz; Ahn, Sang Un; Aimo, Ilaria; Aiola, Salvatore; Ajaz, Muhammad; Akindinov, Alexander; Alam, Sk Noor; Aleksandrov, Dmitry; Alessandro, Bruno; Alexandre, Didier; Alfaro Molina, Jose Ruben; Alici, Andrea; Alkin, Anton; Alme, Johan; Alt, Torsten; Altinpinar, Sedat; Altsybeev, Igor; Alves Garcia Prado, Caio; Andrei, Cristian; Andronic, Anton; Anguelov, Venelin; Anielski, Jonas; Anticic, Tome; Antinori, Federico; Antonioli, Pietro; Aphecetche, Laurent Bernard; Appelshaeuser, Harald; Arcelli, Silvia; Armesto Perez, Nestor; Arnaldi, Roberta; Aronsson, Tomas; Arsene, Ionut Cristian; Arslandok, Mesut; Augustinus, Andre; Averbeck, Ralf Peter; Azmi, Mohd Danish; Bach, Matthias Jakob; Badala, Angela; Baek, Yong Wook; Bagnasco, Stefano; Bailhache, Raphaelle Marie; Bala, Renu; Baldisseri, Alberto; Ball, Markus; Baltasar Dos Santos Pedrosa, Fernando; Baral, Rama Chandra; 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Zyzak, Maksym


    The measurement of the mass differences for systems bound by the strong force has reached a very high precision with protons and anti-protons. The extension of such measurement from (anti-)baryons to (anti-)nuclei allows one to probe any difference in the interactions between nucleons and anti-nucleons encoded in the (anti-)nuclei masses. This force is a remnant of the underlying strong interaction among quarks and gluons and can be described by effective theories, but cannot yet be directly derived from quantum chromodynamics. Here we report a measurement of the difference between the ratios of the mass and charge of deuterons (d) and anti-deuterons ($\\bar{d}$), and $^{3}{\\rm He}$ and $^3\\overline{\\rm He}$ nuclei carried out with the ALICE (A Large Ion Collider Experiment) detector in Pb-Pb collisions at a centre-of-mass energy per nucleon pair of 2.76 TeV. Our direct measurement of the mass-over-charge differences confirm CPT invariance to an unprecedented precision in the sector of light nuclei. This funda...

  13. At the borderline between exclusive and inclusive physics: Study of Drell-Yan fragments in the PANDA experiment (A preliminary simulation)

    CERN Document Server

    Bianconi, Andrea


    Here a preliminary study is presented concerning the detection of the normally unseen Drell-Yan fragments, possible in the PANDA experiment. To work as a multi-purpose apparatus, this experiment will record all the particles produced in the collisions between the antiproton beam and the target, with a rather wide acceptance. So detecting Drell-Yan dileptons with or without analyzing the other fragments is just a matter of applying cutoffs in the data analysis stage. The distribution of the products of 50,000 typical Drell-Yan events is here simulateded using a well-known generator code (Pythia-8). The resulting distributions are inserted within the PANDA acceptance region, to analyze the chances of missing some searched fragment combinations, or of confusing different sets of particles. The most interesting result is that, due to the reduced phase space, the produced states are much simpler than one could imagine: (i) almost 50 \\% of the events just consist of a dilepton plus a nucleon-antinucleon pair; (ii) ...

  14. High precision spectroscopy of pionic and antiprotonic atoms; Spectroscopie de precision des atomes pioniques et antiprotoniques

    Energy Technology Data Exchange (ETDEWEB)

    El-Khoury, P


    The study of exotic atoms, in which an orbiting electron of a normal atom is replaced by a negatively charged particle ({pi}{sup -}, {mu}{sup -}, p, {kappa}{sup -}, {sigma}{sup -},...) may provide information on the orbiting particle and the atomic nucleus, as well as on their interaction. In this work, we were interested in pionic atoms ({pi}{sup -14} N) on the one hand in order to determine the pion mass with high accuracy (4 ppm), and on the other hand in antiprotonic atoms (pp-bar) in order to study the strong nucleon-antinucleon interaction at threshold. In this respect, a high-resolution crystal spectrometer was coupled to a cyclotron trap which provides a high stop density for particles in gas targets at low pressure. Using curved crystals, an extended X-ray source could be imaged onto the detector. Charge-Coupled Devices were used as position sensitive detectors in order to measure the Bragg angle of the transition to a high precision. The use of gas targets resolved the ambiguity owing to the number of K electrons for the value of the pion mass, and, for the first time, strong interaction shift and broadening of the 2p level in antiprotonic hydrogen were measured directly. (author)

  15. A Meson Emission Model of Psi to N Nbar m Charmonium Strong Decays

    CERN Document Server

    Barnes, T; Roberts, W


    In this paper we consider a sequential "meson emission" mechanism for charmonium decays of the type Psi -> N Nbar m, where Psi is a generic charmonium state, N is a nucleon and m is a light meson. This decay mechanism, which may not be dominant in general, assumes that an NNbar pair is created during charmonium annihilation, and the light meson m is emitted from the outgoing nucleon or antinucleon line. A straightforward generalization of this model can incorporate intermediate N* resonances. We derive Dalitz plot event densities for the cases Psi = eta_c, J/psi, chi_c0, chi_c1} and psi' and m = pi0, f0 and omega (and implicitly, any 0^{-+}, 0^{++} or 1^{--} final light meson). It may be possible to separate the contribution of this decay mechanism to the full decay amplitude through characteristic event densities. For the decay subset Psi -> p pbar pi0 the two model parameters are known, so we are able to predict absolute numerical partial widths for Gamma(Psi -> p pbar pi0). In the specific case J/psi -> p ...

  16. Relating pseudospin and spin symmetries through charge conjugation and chiral transformations: The case of the relativistic harmonic oscillator

    International Nuclear Information System (INIS)

    We solve the generalized relativistic harmonic oscillator in 1+1 dimensions, i.e., including a linear pseudoscalar potential and quadratic scalar and vector potentials which have equal or opposite signs. We consider positive and negative quadratic potentials and discuss in detail their bound-state solutions for fermions and antifermions. The main features of these bound states are the same as the ones of the generalized three-dimensional relativistic harmonic oscillator bound states. The solutions found for zero pseudoscalar potential are related to the spin and pseudospin symmetry of the Dirac equation in 3+1 dimensions. We show how the charge conjugation and γ5 chiral transformations relate the several spectra obtained and find that for massless particles the spin and pseudospin symmetry-related problems have the same spectrum but different spinor solutions. Finally, we establish a relation of the solutions found with single-particle states of nuclei described by relativistic mean-field theories with scalar, vector, and isoscalar tensor interactions and discuss the conditions in which one may have both nucleon and antinucleon bound states

  17. On the strong energy dependence of the e{sup +}e{sup -} {r_reversible} pp-bar amplitude near threshold

    Energy Technology Data Exchange (ETDEWEB)

    Haidenbauer, J. [Institut fuer Kernphysik (Theorie), Forschungszentrum Juelich, D-52425 Juelich (Germany); Hammer, H.-W. [Helmholtz-Institut fuer Strahlen- und Kernphysik (Theorie), Universitaet Bonn, Nussallee 14-16, D-53115 Bonn (Germany)]. E-mail:; Meissner, Ulf-G. [Institut fuer Kernphysik (Theorie), Forschungszentrum Juelich, D-52425 Juelich (Germany); Helmholtz-Institut fuer Strahlen- und Kernphysik (Theorie), Universitaet Bonn, Nussallee 14-16, D-53115 Bonn (Germany); Sibirtsev, A. [Helmholtz-Institut fuer Strahlen- und Kernphysik (Theorie), Universitaet Bonn, Nussallee 14-16, D-53115 Bonn (Germany)


    We study the energy dependence of the e{sup +}e{sup -}{yields}pp-bar cross section close to the two-nucleon threshold, recently reported by the BaBar Collaboration. Our analysis also includes the p-bar p{yields}e{sup +}e{sup -} data collected by PS170 Collaboration and the e{sup +}e{sup -}{yields}NN-bar data from the FENICE Collaboration. We show that the near-threshold enhancement in the e{sup +}e{sup -}{yields}pp-bar cross section can be explained by the final-state interaction between proton and antiproton in the {sup 3}S{sub 1} partial wave, utilizing the Julich nucleon-antinucleon model. As a consequence, the strong dependence of the proton electromagnetic form factors on the momentum transfer close to the two-nucleon threshold is then likewise driven by this final-state interaction effect. This result is in line with our previous studies of the near-threshold enhancement of the pp-bar invariant mass spectrum seen in the J/{psi}{yields}{gamma}pp-bar decay by the BES Collaboration and in the B{sup +}{yields}pp-bar K{sup +} decay by the BaBar Collaboration.

  18. Relativistic interactions for the meson-two-nucleon system in the clothed-particle unitary representation

    CERN Document Server

    Korda, V Y; Shebeko, A V


    The method of unitary clothing transformations put forward in relativistic quantum field theory (QFT) by Greenberg and Schweber and developed by Shirokov is applied to construct a new family of interactions in the meson-two-nucleon system. Along with a brief exposition of its basic elements we show a specific transition from the initial ``bare'' one-meson and one-nucleon operators and states to their physical ``clothed'' counterparts. We emphasize that the clothing transformations in question do not alter the original total Hamiltonian, but provides a conceptually more transparent representation of the same Hamiltonian in terms of a new set of operators for particles with physical properties and their relativistic interactions. The Hermitian and energy-independent interaction operators for the processes piN -> piN, NN -> NN and NN -> pi NN are derived starting from the Yukawa-type couplings between fermions (nucleons and antinucleons) and bosons (pi-, eta-, rho-, omega-mesons, etc.). These types of interactio...

  19. Production of antimatter $^{5,6}$Li nuclei in central Au+Au collisions at $\\sqrt{s_{NN}} = 200$ GeV

    CERN Document Server

    Sun, Kai-Jia


    Combining the covariant coalescence model and a blast-wave-like analytical parametrization for (anti-)nucleon phase-space freezeout configuration, we explore light (anti-)nucleus production in central Au+Au collisions at $\\sqrt{s_{NN}} = 200$ GeV. Using the nucleon freezeout configuration (denoted by FO1) determined from the measured spectra of protons (p), deutrons (d) and $^{3}$He, we find the predicted yield of $^{4}$He is significantly smaller than the experimental data. We show this disagreement can be removed by using a nucleon freezeout configuration (denoted by FO2) in which the nucleons are assumed to freeze out earlier than those in FO1 to effectively consider the effect of large binding energy value of $^{4}$He. Assuming the binding energy effect also exists for the production of $^5\\text{Li}$, $^5\\overline{\\text{Li}}$, $^6\\text{Li}$ and $^6\\overline{\\text{Li}}$ due to their similar binding energy values as $^{4}$He, we find the yields of these heavier (anti-)nuclei can be enhanced by a factor of a...

  20. Antineutron physics

    CERN Document Server

    Bressani, Tullio


    Antineutrons ($\\overline{n}$'s) have been used only in the last few years as projectiles for nuclear and particle physics experiments, mainly in the low momentum region. The reason is that, in spite of some undoubted advantages (absence of Coulomb corrections, pure I=1 state for the ($\\overline{n}p$) system), the difficulties in obtaining beams of $\\overline{n}$'s of suitable intensity and energy definition were overwhelming. The setting-up of suitable beams at BNL and mainly at CERN LEAR (with momentum lower than 400 MeV/c) allowed a first round of interesting experiments. In this review a summary of the most important experimental issues obtained in this field will be presented. They range from studies on the antineutron annihilation dynamics, intended to shed light on the mechanisms responsible for the particles production as well as for the possible formation of quasinuclear nucleon-antinucleon bound states, to meson spectroscopy researches, aiming to identify the existence of new, possibly exotic, resona...

  1. Exact solution of a model for πd induced reactions and its application to pion-nucleon reactions

    International Nuclear Information System (INIS)

    Reduction techniques are applied to πd elastic scattering and π absorption in a theory without anti-nucleons. In the one-pion approximation we derive two sets of exact coupled-channel equations for respectively the amplitudes Tsub(πd,NN), Tsub(NΔ,NN) and Tsub(π,πdsup3) Tsub(πd,NΔ). Alternatively are expressed all amplitudes in terms of the absorption amplitude Tsub(πd,NΔ) and available solutions for a three-body problem restricted to the πd and NΔ channels. It is explicity demonstrated that the model (which comes close to the one of Thomas, Mutzutani and Koltun) strictly respects the Pauli principle and avoids double-counting. Using the same technique amplitudes for the (π,2N) reaction and for π(in) elastic scattering on general nuclei in terms of amplitudes amongst the NN, NNπ channels are determined. Both the elastic amplitude and the πA optical potential are shown to decompose into a multiple scattering part based on an input πN amplitude without the Psub(11) partial wave and calculable absorption corrections. (author)

  2. The nucleon-nucleon interaction in the framework of the boson exchange model

    International Nuclear Information System (INIS)

    The aim of this thesis was the description of the nucleon-nucleon interaction in a microscopically founded model. For this the description of the 2-nucleon problem by an interacting 2-nucleon-pion system was presented. The starting point of our description was a relativistic eigenvalue equation for the system of mesons and two baryons. The interaction of the baryons with the mesons was described by interaction Hamiltonians. By the elimination of antinucleon states by means of a unitary tansformation (Foldy-Wouthuysen transformation) the interaction Hamiltonians for nucleons could be generated for the field-theoretical Lagrangian densities. The Hamiltonians for resonant baryon states were obtained by means of a simplified procedure from the corresponding Lagrangian densities. Because the determination of Lagrangian densities is not unique, for the pion-nucleon coupling two alternative Lagrangian densities were allowed. For the interaction of positive-energy nucleonic states these two coupling yield nearly equal results; the production or annihilation of negative-energy nucleon states (antiparticles) the predictions however are very different. (orig./HSI)

  3. Relativistic multichannel scattering theory with particle creation

    International Nuclear Information System (INIS)

    The creation of a mathematical rigorous multichannel relativistic quantum scattering theory that includes particle creation and annihilation has been an important goal in theoretical physics for many decades. This problem with a different perspective from the main traditional approaches is reexamined. In particular, it is not a quantum field theory nor is it based on the Bakamjian-Thomas construction. As fundamental interaction a traditional Yukawa-type interaction in which a meson is emitted or absorbed by a nucleon was considered. A vertex function in this interaction is included. The nucleon number is conserved and no antinucleons. The fundamental Hilbert space has the usual Fock-space structure that accommodate a variable number of mesons. The Yukawa nature of the fundamental interaction implies that the nucleons of the Hamiltonian and the fundamental Hilbert space must be bare particles. On the other hand, the asymptotically observed nucleons are dressed, implying that the Fock space of asymptotic states is distinct from fundamental Hilbert space; then it was necessary to consider a two-Hilbert space theory. How to construct the Hilbert space framework for a simplified system consisting of a single bare nucleon and an indeterminated number of a single type of meson is shown. The spin and charge of the nucleon was ignored, the meson is its own antiparticle and has zero charge and spin. 9 refs. (nevyjel)

  4. Hadronic wavefunctions in light-cone quantization

    Energy Technology Data Exchange (ETDEWEB)

    Hyer, T.


    The analysis of light-cone wavefunctions seems the most promising theoretical approach to a detailed understanding of the structure of relativistic bound states, particularly hadrons. However, there are numerous complications in this approach. Most importantly, the light-cone approach sacrifices manifest rotational invariance in exchange for the elimination of negative-energy states. The requirement of rotational invariance of the full theory places important constraints on proposed light-cone wavefunctions, whether they are modelled or extracted from some numerical procedure. A formulation of the consequences of the hidden rotational symmetry has been sought for some time; it is presented in Chapter 2. In lattice gauge theory or heavy-quark effective theory, much of the focus is on the extraction of numerical values of operators which are related to the hadronic wavefunction. These operators are to some extent interdependent, with relations induced by fundamental constraints on the underlying wavefunction. The consequences of the requirement of unitarity are explored in Chapter 3, and are found to have startling phenomenological relevance. To test model light-cone wavefunctions, experimental predictions must be made. The reliability of perturbative QCD as a tool for making such predictions has been questioned. In Chapter 4, the author presents a computation of the rates for nucleon-antinucleon annihilation, improving the reliability of the perturbative computation by taking into account the Sudakov suppression of exclusive processes at large transverse impact parameter. In Chapter 5, he develops the analysis of semiexclusive production. This work focuses on processes in which a single isolated meson is produced perturbatively and recoils against a wide hadronizing system. At energies above about 10 GeV, semiexclusive processes are shown to be the most sensitive experimental probes of hadronic structure.

  5. Bit-string scattering theory

    International Nuclear Information System (INIS)

    We construct discrete space-time coordinates separated by the Lorentz-invariant intervals h/mc in space and h/mc2 in time using discrimination (XOR) between pairs of independently generated bit-strings; we prove that if this space is homogeneous and isotropic, it can have only 1, 2 or 3 spacial dimensions once we have related time to a global ordering operator. On this space we construct exact combinatorial expressions for free particle wave functions taking proper account of the interference between indistinguishable alternative paths created by the construction. Because the end-points of the paths are fixed, they specify completed processes; our wave functions are ''born collapsed''. A convenient way to represent this model is in terms of complex amplitudes whose squares give the probability for a particular set of observable processes to be completed. For distances much greater than h/mc and times much greater than h/mc2 our wave functions can be approximated by solutions of the free particle Dirac and Klein-Gordon equations. Using a eight-counter paradigm we relate this construction to scattering experiments involving four distinguishable particles, and indicate how this can be used to calculate electromagnetic and weak scattering processes. We derive a non-perturbative formula relating relativistic bound and resonant state energies to mass ratios and coupling constants, equivalent to our earlier derivation of the Bohr relativistic formula for hydrogen. Using the Fermi-Yang model of the pion as a relativistic bound state containing a nucleon-antinucleon pair, we find that (GπN2)2 = (2mN/mπ)2 - 1. 21 refs., 1 fig

  6. Inclusive Lambda_c Production in e+e- Annihilations at sqrt{s}=10.54 GeV and in Upsilon(4S) Decays

    Energy Technology Data Exchange (ETDEWEB)

    Aubert, B.


    We present measurements of the total production rates and momentum distributions of the charmed baryon {Lambda}{sub c}{sup +} in e{sup +}e{sup -} {yields} hadrons at a center-of-mass energy of 10.54 GeV and in {Upsilon}(4S) decays. In hadronic events at 10.54 GeV, charmed hadrons are almost exclusively leading particles in e{sup +}e{sup -} {yields} c{bar c} events, allowing direct studies of c-quark fragmentation. We measure a momentum distribution for {Lambda}{sub c}{sup +} baryons that differs significantly from those measured previously for charmed mesons. Comparing with a number of models, we find none that can describe the distribution completely. We measure an average scaled momentum of (x{sub p}) = 0.574 {+-} 0.009 and a total rate of N{sub {Lambda}{sub c}}{sup q{bar q}} = 0.057 {+-} 0.002(exp.) {+-} 0.015(BF) {Lambda}{sub c}{sup +} per hadronic event, where the experimental error is much smaller than that due to the branching fraction into the reconstructed decay mode, pK{sup -} {pi}{sup +}. In {Upsilon}(4S) decays we measure a total rate of N{sub {Lambda}{sub c}}{sup {Upsilon}} = 0.091 {+-} 0.006(exp.) {+-} 0.024(BF) per {Upsilon}(4S) decay, and find a much softer momentum distribution than expected from B decays into a {Lambda}{sub c}{sup +} plus an antinucleon and one to three pions.

  7. Production of antimatter 5,6Li nuclei in central Au+Au collisions at sNN=200 GeV

    Directory of Open Access Journals (Sweden)

    Kai-Jia Sun


    Full Text Available Combining the covariant coalescence model and a blast-wave-like analytical parametrization for (anti-nucleon phase–space freezeout configuration, we explore light (anti-nucleus production in central Au+Au collisions at sNN=200 GeV. Using the nucleon freezeout configuration (denoted by FO1 determined from the measured spectra of protons (p, deutrons (d and 3He, we find the predicted yield of 4He is significantly smaller than the experimental data. We show this disagreement can be removed by using a nucleon freezeout configuration (denoted by FO2 in which the nucleons are assumed to freeze out earlier than those in FO1 to effectively consider the effect of large binding energy value of 4He. Assuming the binding energy effect also exists for the production of 5Li, Li‾5, 6Li and Li‾6 due to their similar binding energy values as 4He, we find the yields of these heavier (anti-nuclei can be enhanced by a factor of about one order, implying that although the stable (anti-6Li nucleus is unlikely to be observed, the unstable (anti-5Li nucleus could be produced in observable abundance in Au+Au collisions at sNN=200 GeV where it may be identified through the p–4He (p‾–He‾4 invariant mass spectrum. The future experimental measurement on (anti-5Li would be very useful to understand the production mechanism of heavier antimatter.