Soft gluon contributions to hard processes
International Nuclear Information System (INIS)
Ciafaloni, M.
1981-10-01
The main concern of this paper is in trying to elucidate the origin of large QCD perturbative corrections and explain how to deal with them to all orders. They come essentially from the phase space regions close to the kinematical boundary of a hard process, in which one or many gluons become soft
Energy Technology Data Exchange (ETDEWEB)
Hautmann, F. [Rutherford Appleton Laboratory, Chilton (United Kingdom); Oxford Univ. (United Kingdom). Dept. of Theoretical Physics; Antwerpen Univ. (Belgium). Elementaire Deeltjes Fysica; Jung, H.; Lelek, A.; Zlebcik, R. [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany); Radescu, V. [European Organization for Nuclear Research (CERN), Geneva (Switzerland)
2017-08-15
We study parton-branching solutions of QCD evolution equations and present a method to construct both collinear and transverse momentum dependent (TMD) parton densities from this approach. We work with next-to-leading-order (NLO) accuracy in the strong coupling. Using the unitarity picture in terms of resolvable and non-resolvable branchings, we analyze the role of the soft-gluon resolution scale in the evolution equations. For longitudinal momentum distributions, we find agreement of our numerical calculations with existing evolution programs at the level of better than 1 percent over a range of five orders of magnitude both in evolution scale and in longitudinal momentum fraction. We make predictions for the evolution of transverse momentum distributions. We perform fits to the high-precision deep inelastic scattering (DIS) structure function measurements, and we present a set of NLO TMD distributions based on the parton branching approach.
Dynamical instabilities in quark-gluon plasma with hard jet
International Nuclear Information System (INIS)
Pavlenko, O.P.
1990-01-01
The dynamical instabilities, whose development can be expected under the hard jet propagating through the quark-gluon plasma, are analyzed. The possible signals of the quark-gluon plasma formation in ultrarelativistic nuclear collisions connected with the development of the plasma-jet instabilities are discussed. 10 refs
Soft gluon resummation formulae for hard proton processes in QCD
International Nuclear Information System (INIS)
Craigie, N.S.; Jones, H.F.
1980-01-01
We briefly review the treatment of leading logarithmic behaviour of the parton distributions in QCD within the Bethe-Salpeter framework by analysing directly parton hadron Green functions in the limit of parton four-momentum k 2 → - infinitely in a special light-like gauge involving a spectator vector. This technique allows us to derive the factorization of parton probabilities in leading logarithmic order in QCD in the various inclusive processes involving a single short-distance scale. The proof requires us to show that the use of planar gauges eta = psub(A) + psub(B) + ..., where psub(A), psub(B)... are the observed hadron momenta, reduces to choosing the appropriate light-like gauge for each hadron-parton BS channel, after demonstrating a Bloch-Nordsieck cancellation of the real and virtual soft left-over gluons. In the case where two large momentum scales appear, by restricting the transverse phase space into which the gluons are radiated, we derive the double logarithmic eikonal renormalization of the hard scattering formula of the type proposed recently by Parisi and Petronzio. (orig.)
The hard gluon component of the QCD Pomeron
International Nuclear Information System (INIS)
White, A.R.
1996-01-01
The authors argue that deep-inelastic diffractive scaling provides fundamental insight into the QCD Pomeron. The logarithmic scaling violations seen experimentally are in conflict with the scale-invariance of the BFKL Pomeron and with phenomenological two-gluon models. Instead the Pomeron appears as a single gluon at short-distances, indicating the appearance of a Super-Critical phase of Reggeon Field Theory. That the color compensation takes place at a longer distance is consistent with the Pomeron carrying odd color charge parity
Diffractive hard photoproduction at HERA and evidence for the gluon content of the pomeron
International Nuclear Information System (INIS)
Derrick, M.; Krakauer, D.; Magill, S.
1995-01-01
Inclusive jet cross sections for events with a large rapidity gap with respect to the proton direction from the reaction ep→jet+X with quasi-real photons have been measured with the ZEUS detector. The cross sections refer to jets with transverse energies E T jet >8 GeV. The data show the characteristics of a diffractive process mediated by pomeron exchange. Assuming that the events are due to the exchange of a pomeron with partonic structure, the quark and gluon content of the pomeron is probed at a scale ∼(E T jet ) 2 . A comparison of the measurements with model predictions based on QCD plus Regge phenomenology requires a contribution of partons with a hard momentum density in the pomeron. A combined analysis of the jet cross sections and recent ZEUS measurements of the diffractive structure function in deep inelastic scattering gives the first experimental evidence for the gluon content of the pomeron in diffractive hard scattering processes. The data indicate that between 30% and 80% of the momentum of the pomeron carried by partons is due to hard gluons. (orig.)
The Quark-Gluon Plasma Collective Dynamics and Hard Thermal Loops
Blaizot, J P; Blaizot, Jean-Paul; Iancu, Edmond
2002-01-01
We present a unified description of the high temperature phase of QCD, the so-called quark-gluon plasma, in a regime where the effective gauge coupling $g$ is sufficiently small to allow for weak coupling calculations. The main focuss is the construction of the effective theory for the collective excitations which develop at a typical scale $gT$, which is well separated from the typical energy of single particle excitations which is the temperature $T$. We show that the plasma particles provide a source for long wavelength oscillations of average fields which carry the quantum numbers of the plasma constituents, the quarks and the gluons. To leading order in $g$, the plasma particles obey simple gauge-covariant kinetic equations, whose derivation from the general Dyson-Schwinger equations is outlined. As a by-product, the ``hard thermal loops'' emerge naturally in a physically transparent framework. We show that the collective excitations can be described in terms of classical fields, and develop for these a ...
Inclusive observables and hard gluon emission in neutrino deep inelastic scattering
International Nuclear Information System (INIS)
Bouchiat, C.; Meyer, P.; Mezard, M.
1980-01-01
We derive the predictions of perturbative QCD together with non-perturbative corrections for a set of inclusive observables connected with the angular distribution of light-cone energy in deep inelastic neutrino scattering. Our particular choice of observables has been made in order to meet important physical requirements besides the necessary condition of infrared regularity. Our inclusive observables receive their dominant contribution from the quark fragmentation region. The non-perturbative contribution is calculable in a rather model-independent way and stays at an acceptable level in realistic experimental conditions. The QCD perturbative contribution, which takes the simple form of a convolution product, exhibits a strongly decreasing behaviour as a function of the Bjorken scaling variable x, superimposed on a constant background associated with the non-perturbative terms, allowing a rather clean separation of the two effects. The perturbative term being dominated by the process of hard-gluon emission, an experimental investigation of the observables discussed here may be a good way to detect the effect of gluon emission in deep inelastic neutrino scattering. (orig.)
Collinear limits beyond the leading order from the scattering equations
Energy Technology Data Exchange (ETDEWEB)
Nandan, Dhritiman; Plefka, Jan; Wormsbecher, Wadim [Institut für Physik and IRIS Adlershof, Humboldt-Universität zu Berlin,Zum Großen Windkanal 6, D-12489 Berlin (Germany)
2017-02-08
The structure of tree-level scattering amplitudes for collinear massless bosons is studied beyond their leading splitting function behavior. These near-collinear limits at sub-leading order are best studied using the Cachazo-He-Yuan (CHY) formulation of the S-matrix based on the scattering equations. We compute the collinear limits for gluons, gravitons and scalars. It is shown that the CHY integrand for an n-particle gluon scattering amplitude in the collinear limit at sub-leading order is expressed as a convolution of an (n−1)-particle gluon integrand and a collinear kernel integrand, which is universal. Our representation is shown to obey recently proposed amplitude relations in which the collinear gluons of same helicity are replaced by a single graviton. Finally, we extend our analysis to effective field theories and study the collinear limit of the non-linear sigma model, Einstein-Maxwell-Scalar and Yang-Mills-Scalar theory.
Hard probes (and soft ones) to test the quark-gluon soup
Preuss, Paul
2006-01-01
"We need the hardest probes of all to study the hot, dense state of matter that exists when two heavy nuclei like gold collide with enough energy to temporarily free the quarks and gluons in their constituent protons and neutrons." (3 pages)
Soft-collinear factorization in effective field theory
International Nuclear Information System (INIS)
Bauer, Christian W.; Pirjol, Dan; Stewart, Iain W.
2002-01-01
The factorization of soft and ultrasoft gluons from collinear particles is shown at the level of operators in an effective field theory. Exclusive hadronic factorization and inclusive partonic factorization follow as special cases. The leading-order Lagrangian is derived using power counting and gauge invariance in the effective theory. Several species of gluons are required, and softer gluons appear as background fields to gluons with harder momenta. Two examples are given: the factorization of soft gluons in B→Dπ and the soft-collinear convolution for the B→X s γ spectrum
Bridging soft-hard transport properties of quark-gluon plasmas with CUJET3.0
Energy Technology Data Exchange (ETDEWEB)
Xu, Jiechen [Department of Physics, Columbia University,538 West 120th Street, New York, NY 10027 (United States); Liao, Jinfeng [Physics Department and Center for Exploration of Energy and Matter, Indiana University,2401 North Milo B. Sampson Lane, Bloomington, IN 47408 (United States); RIKEN BNL Research Center, Brookhaven National Laboratory,Building 510A, Upton, NY 11973 (United States); Gyulassy, Miklos [Department of Physics, Columbia University,538 West 120th Street, New York, NY 10027 (United States)
2016-02-25
A new model (CUJET3.0) of jet quenching in nuclear collisions coupled to bulk data constrained (VISH2+1D) viscous hydrodynamic backgrounds is constructed by generalizing the perturbative QCD based (CUJET2.0) model to include two complementary non-perturbative chromodynamical features of the QCD confinement cross-over phase transition near T{sub c}≈160 MeV: (1) the suppression of quark and gluon chromo-electric-charged (cec) degrees of freedom and (2) the emergence of chromo-magnetic-monopole (cmm) degrees of freedom. Such a semi Quark Gluon Monopole Plasma (sQGMP) microscopic scenario is tested by comparing predictions of the leading hadron nuclear modification factors, R{sub AA}{sup h}(p{sub T}>10GeV/c,√s), and their azimuthal elliptic asymmetry v{sub 2}{sup h}(p{sub T}>10GeV/c,√s) with available data on h=π,D,B jet fragments from nuclear collisions at RHIC(√s=0.2 ATeV) and LHC(√s=2.76 ATeV). The cmm degrees of freedom in the sQGMP model near T{sub c} are shown to solve robustly the long standing R{sub AA} vs v{sub 2} puzzle by predicting a maximum of the jet quenching parameter field q̂(E,T)/T{sup 3} near T{sub c}. The robustness of CUJET3.0 model to a number of theoretical uncertainties is critically tested. Moreover the consistency of jet quenching with observed bulk perfect fluidity is demonstrated by extrapolating the sQGMP q̂ down to thermal energy E∼3T scales and showing that the sQGMP shear viscosity to entropy density ratio η/s≈T{sup 3}/q̂ falls close to the unitarity bound, 1/4π, in the range (1−2)T{sub c}. Detailed comparisons of the CUJET2.0 and CUJET3.0 models reveal the fact that remarkably different q̂(T) dependence could be consistent with the same R{sub AA} data and could only be distinguished by anisotropy observables. These findings demonstrate clearly the inadequacy of focusing on the jet path averaged quantity 〈q̂〉 as the only relevant medium property to characterize jet quenching, and point to the crucial roles of
Soft gluons and superleading logarithms in QCD
Forshaw, J R
2009-01-01
After a brief introduction to the physics of soft gluons in QCD we present a surprising prediction. Dijet production in hadron-hadron collisions provides the paradigm, i.e. h_1 +h_2 \\to jj+X. In particular, we look at the case where there is a restriction placed on the emission of any further jets in the region in between the primary (highest p_T) dijets. Logarithms in the ratio of the jet scale to the veto scale can be summed to all orders in the strong coupling. Surprisingly, factorization of collinear emissions fails at scales above the veto scale and triggers the appearance of double logarithms in the hard sub-process. The effect appears first at fourth order relative to the leading order prediction and is subleading in the number of colours.
One-loop triple collinear splitting amplitudes in QCD
Energy Technology Data Exchange (ETDEWEB)
Badger, Simon; Buciuni, Francesco; Peraro, Tiziano [Higgs Centre for Theoretical Physics, School of Physics and Astronomy, University of Edinburgh,Edinburgh EH9 3JZ, Scotland (United Kingdom)
2015-09-28
We study the factorisation properties of one-loop scattering amplitudes in the triple collinear limit and extract the universal splitting amplitudes for processes initiated by a gluon. The splitting amplitudes are derived from the analytic Higgs plus four partons amplitudes. We present compact results for primitive helicity splitting amplitudes making use of super-symmetric decompositions. The universality of the collinear factorisation is checked numerically against the full colour six parton squared matrix elements.
International Nuclear Information System (INIS)
Weiler, T.
1981-01-01
An overview is presented of the attributes of gluons, deducible from experimental data. Particular attention is given to the photon-gluon fusion model of charm leptoproduction. The agreement with QCD and theoretical prejudice is qualitatively good
Two-gluon emission and interference in a thin QCD medium: insights into jet formation
International Nuclear Information System (INIS)
Casalderrey-Solana, Jorge; Pablos, Daniel; Tywoniuk, Konrad
2016-01-01
In heavy-ion collisions, an abundant production of high-energy QCD jets allows to study how these multiparticle sprays are modified as they pass through the quark-gluon plasma. In order to shed new light on this process, we compute the inclusive two-gluon rate off a hard quark propagating through a color deconfined medium at first order in medium opacity. We explicitly impose an energy ordering of the two emitted gluons, such that the “hard” gluon can be thought of as belonging to the jet substructure while the other is a “soft” emission (which can be collinear or medium-induced). Our analysis focusses on two specific limits that clarify the modification of the additional angle- and formation time-ordering of splittings. In one limit, the formation time of the “hard” gluon is short compared to the “soft” gluon formation time, leading to a probabilistic formula for production of and subsequent radiation off a quark-gluon antenna. In the other limit, the ordering of formation is reverted, which automatically leads to the fact that the jet substructure is resolved by the medium. We observe in this case a characteristic delay: the jet radiates as one color current (quark) up to the formation of the “hard” gluon, at which point we observe the onset of radiation of the new color current (gluon). Within our kinematic constraints, our computation supports a picture in which the in-medium jet dynamics are described as a collection of subsequent antennas which are resolved by the medium according to their transverse extent.
CERN. Geneva
2017-01-01
Emissions of soft gluons from energetic particles play an important role in collider processes. While the basic physics of soft emissions is simple, it gives rise to a variety of interesting and intricate phenomena (non-global logs, Glauber phases, super-leading logs, factorization breaking). After an introduction, I will review progress in resummation methods such as Soft-Collinear Effective Theory driven by a better understanding of soft emissions. I will also show some new results for computations of soft-gluon effects in gap-between-jets and isolation-cone cross sections.
Duality and multi-gluon scattering
International Nuclear Information System (INIS)
Mangano, M.; Parke, S.; Xu Zhan
1988-01-01
For the six-gluon scattering process we give explicit and simple expressions for the amplitude and its square. To achieve this we use an analogy with string theories to identify a unique procedure for writing the multi-gluon scattering amplitudes in terms of a sum of gauge invariant dual sub-amplitudes multiplied by an appropriate color (Chan-Paton) factor. The sub-amplitudes defined in this way are invariant under cyclic permutations, satisfy powerful identities which relate different non-cyclic permutations and factorize in the soft gluon limit, the two-gluon collinear limit and on multi-gluon poles. Also, to leading order in the number of colors these sub-amplitudes sum incoherently in the square of the full matrix element. The results contained here are important for Monte Carlo studies of multi-jet processes at hadron colliders as well as for understanding the general structure of QCD. (orig.)
Infrared behaviour of three and four gluon vertices in Yang-Mills theory
International Nuclear Information System (INIS)
Brandt, F.T.; Frenkel, J.
1985-01-01
The structure of the 3-point function with one and two external gluons on-shell is studied in a general covariant gauge. The contributions which result in one loop approximation are expressed in terms of simple functions containing collinear and soft singularities. Furthermore, the contributions associated with the 4-point vertex when all external gluons are on-shell are analysed. As an application of these results, the infrared structure of gluon-gluon scattering amplitude is studied. (Author) [pt
Diffractive open charm production at DESY HERA. Experiment versus two-gluon exchange model
Energy Technology Data Exchange (ETDEWEB)
Baranov, S.P. [P.N. Lebedev Inst. of Physics, Moscow (Russian Federation)
2010-03-15
Diffractive production of D{sup *} mesons at HERA conditions is considered in the framework of collinear two-gluon exchange model. Theoretical results are compared with recent experimental data. (orig.)
Energy Technology Data Exchange (ETDEWEB)
Cohen, Timothy [Institute of Theoretical Science, University of Oregon,Eugene, OR 97403 (United States); Elor, Gilly [Institute of Theoretical Science, University of Oregon,Eugene, OR 97403 (United States); Center for Theoretical Physics, Massachusetts Institute of Technology,Cambridge, MA 02139 (United States); Larkoski, Andrew J. [Physics Department, Reed College,Portland, OR 97202 (United States); Center for Fundamental Laws of Nature, Harvard University,Cambridge, MA 02138 (United States)
2017-03-03
Soft-Collinear Effective Theory (SCET) is a framework for modeling the infrared structure of theories whose long distance behavior is dominated by soft and collinear divergences. This paper demonstrates that SCET can be made compatible with supersymmetry (SUSY). Explicitly, the effective Lagrangian for N=1 SUSY Yang-Mills is constructed and shown to be a complete description for the infrared of this model. For contrast, we also construct the effective Lagrangian for chiral SUSY theories with Yukawa couplings, specifically the single flavor Wess-Zumino model. Only a subset of the infrared divergences are reproduced by the Lagrangian — to account for the complete low energy description requires the inclusion of local operators. SCET is formulated by expanding fields along a light-like direction and then subsequently integrating out degrees-of-freedom that are away from the light-cone. Defining the theory with respect to a specific frame obfuscates Lorentz invariance — given that SUSY is a space-time symmetry, this presents a possible obstruction. The cleanest language with which to expose the congruence between SUSY and SCET requires exploring two novel formalisms: collinear fermions as two-component Weyl spinors, and SCET in light-cone gauge. By expressing SUSY Yang-Mills in “collinear superspace', a slice of superspace derived by integrating out half the fermionic coordinates, the light-cone gauge SUSY SCET theory can be written in terms of superfields. As a byproduct, bootstrapping up to the full theory yields the first algorithmic approach for determining the SUSY Yang-Mills on-shell superspace action. This work paves the way toward discovering the effective theory for the collinear limit of N=4 SUSY Yang-Mills.
On the collinear singularity problem of hot QCD
International Nuclear Information System (INIS)
Candelpergher, B.; Grandou, T.
2002-01-01
The collinear singularity problem of hot QCD is revisited within a perturbative resummation scheme (PR) of the leading thermal fluctuations. On the basis of actual calculations, new aspects are discovered concerning the origin of the singularity plaguing the soft real photon emission rate out of a quark-gluon plasma at thermal equilibrium, when the latter is calculated by means of the Resummation Program (RP)
International Nuclear Information System (INIS)
Ayala, A.L.
1996-01-01
In this talk we present our detailed study (theory and numbers) on the shadowing corrections to the gluon structure functions for nuclei. Starting from rather controversial information on the nucleon structure function which is originated by the recent HERA data, we develop the Glauber approach for the gluon density in a nucleus based on Mueller formula and estimate the value of the shadowing corrections in this case. Then we calculate the first corrections to the Glauber approach and show that these corrections are big. Based on this practical observation we suggest the new evolution equation which takes into account the shadowing corrections and solve it. We hope to convince you that the new evolution equation gives a good theoretical tool to treat the shadowing corrections for the gluons density in a nucleus and, therefore, it is able to provide the theoretically reliable initial conditions for the time evolution of the nucleus-nucleus cascade. The initial conditions should be fixed both theoretically and phenomenologically before to attack such complicated problems as the mixture of hard and soft processes in nucleus-nucleus interactions at high energy or the theoretically reliable approach to hadron or/and parton cascades for high energy nucleus-nucleus interaction. 35 refs., 24 figs., 1 tab
Collinear wake field acceleration
International Nuclear Information System (INIS)
Bane, K.L.F.; Chen, P.; Wilson, P.B.
1985-04-01
In the Voss-Weiland scheme of wake field acceleration a high current, ring-shaped driving bunch is used to accelerate a low current beam following along on axis. In such a structure, the transformer ratio, i.e., the ratio of maximum voltage that can be gained by the on-axis beam and the voltage lost by the driving beam, can be large. In contrast, it has been observed that for an arrangement in which driving and driven bunches follow the same path, and where the current distribution of both bunches is gaussian, the transformer ratio is not normally greater than two. This paper explores some of the possibilities and limitations of a collinear acceleration scheme. In addition to its application to wake field acceleration in structures, this study is also of interest for the understanding of the plasma wake field accelerator. 11 refs., 4 figs
Two-Loop Gluon to Gluon-Gluon Splitting Amplitudes in QCD
International Nuclear Information System (INIS)
Bern, Z.
2004-01-01
Splitting amplitudes are universal functions governing the collinear behavior of scattering amplitudes for massless particles. We compute the two-loop g → gg splitting amplitudes in QCD, N = 1, and N = 4 super-Yang-Mills theories, which describe the limits of two-loop n-point amplitudes where two gluon momenta become parallel. They also represent an ingredient in a direct x-space computation of DGLAP evolution kernels at next-to-next-to-leading order. To obtain the splitting amplitudes, we use the unitarity sewing method. In contrast to the usual light-cone gauge treatment, our calculation does not rely on the principal-value or Mandelstam-Leibbrandt prescriptions, even though the loop integrals contain some of the denominators typically encountered in light-cone gauge. We reduce the integrals to a set of 13 master integrals using integration-by-parts and Lorentz invariance identities. The master integrals are computed with the aid of differential equations in the splitting momentum fraction z. The ε-poles of the splitting amplitudes are consistent with a formula due to Catani for the infrared singularities of two-loop scattering amplitudes. This consistency essentially provides an inductive proof of Catani's formula, as well as an ansatz for previously-unknown 1/ε pole terms having non-trivial color structure. Finite terms in the splitting amplitudes determine the collinear behavior of finite remainders in this formula
TMD splitting functions in kT factorization. The real contribution to the gluon-to-gluon splitting
International Nuclear Information System (INIS)
Hentschinski, M.; Kusina, A.; Kutak, K.; Serino, M.
2018-01-01
We calculate the transverse momentum dependent gluon-to-gluon splitting function within k T -factorization, generalizing the framework employed in the calculation of the quark splitting functions in Hautmann et al. (Nucl Phys B 865:54-66, arXiv:1205.1759, 2012), Gituliar et al. (JHEP 01:181, arXiv:1511.08439, 2016), Hentschinski et al. (Phys Rev D 94(11):114013, arXiv:1607.01507, 2016) and demonstrate at the same time the consistency of the extended formalism with previous results. While existing versions of k T factorized evolution equations contain already a gluon-to-gluon splitting function i.e. the leading order Balitsky-Fadin-Kuraev-Lipatov (BFKL) kernel or the Ciafaloni-Catani-Fiorani-Marchesini (CCFM) kernel, the obtained splitting function has the important property that it reduces both to the leading order BFKL kernel in the high energy limit, to the Dokshitzer-Gribov-Lipatov-Altarelli-Parisi (DGLAP) gluon-to-gluon splitting function in the collinear limit as well as to the CCFM kernel in the soft limit. At the same time we demonstrate that this splitting kernel can be obtained from a direct calculation of the QCD Feynman diagrams, based on a combined implementation of the Curci-Furmanski-Petronzio formalism for the calculation of the collinear splitting functions and the framework of high energy factorization. (orig.)
Double collinear splitting amplitudes at next-to-leading order
Energy Technology Data Exchange (ETDEWEB)
Sborlini, Germán F.R. [Departamento de Física and IFIBA, FCEyN, Universidad de Buenos Aires (1428) Pabellón 1 Ciudad Universitaria, Capital Federal (Argentina); Instituto de Física Corpuscular, Universitat de València -Consejo Superior de Investigaciones Científicas,Parc Científic, E-46980 Paterna (Valencia) (Spain); Florian, Daniel de [Departamento de Física and IFIBA, FCEyN, Universidad de Buenos Aires (1428) Pabellón 1 Ciudad Universitaria, Capital Federal (Argentina); Rodrigo, Germán [Instituto de Física Corpuscular, Universitat de València -Consejo Superior de Investigaciones Científicas,Parc Científic, E-46980 Paterna (Valencia) (Spain)
2014-01-07
We compute the next-to-leading order (NLO) QCD corrections to the 1→2 splitting amplitudes in different dimensional regularization (DREG) schemes. Besides recovering previously known results, we explore new DREG schemes and analyze their consistency by comparing the divergent structure with the expected behavior predicted by Catani’s formula. Through the introduction of scalar-gluons, we show the relation among splittings matrices computed using different schemes. Also, we extended this analysis to cover the double collinear limit of scattering amplitudes in the context of QCD+QED.
Vertex of three and four gluons in the Yang-Mills theory
International Nuclear Information System (INIS)
Brandt, F.T.C.
1986-01-01
In a general covariant gauge, the structure of the three-point function with one and two external gluons on shell is studied. The contributions which result in the one-loop approximation are expressed in terms of simple functions containing collinear and soft singularities. Furthermore, the contributions asociated with the four-point vertex when all external gluons are on-sheel, are analysed. As an application of these results, the infrared structure of the gluon-gluon scattering amplitude, is studied. (author) [pt
The mechanisms of collinear integration.
Cass, John; Alais, David
2006-08-11
Low-contrast visual contour fragments are easier to detect when presented in the context of nearby collinear contour elements (U. Polat & D. Sagi, 1993). The spatial and temporal determinants of this collinear facilitation have been studied extensively (J. R. Cass & B. Spehar, 2005; Y. Tanaka & D. Sagi, 1998; C. B. Williams & R. F. Hess, 1998), although considerable debate surrounds the neural mechanisms underlying it. Our study examines this question using a novel stimulus, whereby the flanking "contour" elements are rotated around their own axis. By measuring contrast detection thresholds to a brief foveal target presented at various phases of flanker rotation, we find peak facilitation after flankers have rotated beyond their collinear phase. This optimal facilitative delay increases monotonically as a function of target-flanker separation, yielding estimates of cortical propagation of 0.1 m/s, a value highly consistent with the dynamics of long-range horizontal interactions observed within primary visual cortex (V1). A curious new finding is also observed: Facilitative peaks also occur when the target flash precedes flanker collinearity by 20-80 ms, a range consistent with contrast-dependent cortical onset latencies. Together, these data suggest that collinear facilitation involves two separate mechanisms, each possessing distinct dynamics: (i) slowly propagating horizontal interactions within V1 and (ii) a faster integrative mechanism, possibly driven by synchronous collinear cortical onset.
International Nuclear Information System (INIS)
Koller, K.; Krasemann, H.
1979-08-01
We investigate the Dalitz plot population and thrust angular distribution for the Orthoquarkonium decay Q anti Q → 3 scalar gluons. The Dalitz plot for scalar gluons is populated in corners where events are 2 jet like and this disagrees with existing Upsilon data. The scalar gluon thrust angular distribution is also in striking disagreement with the UPSILON data and so scalar gluons are completely ruled out. (orig.)
International Nuclear Information System (INIS)
Koller, K.; Walsh, T.
1978-03-01
We discuss what can be learned of the 3 S 1 quarkonium decay QantiQ → 3 gluoans QantiQ → γ + 2 gluons. The former is a way to find gluon jets and test QCD. The latter also allows us to measure gluoan + gluon → hadrons and look for pure gluonic resonances (glueballs). (orig.) [de
Introduction to soft-collinear effective theory
Becher, Thomas; Ferroglia, Andrea
2015-01-01
Among resummation techniques for perturbative QCD in the context of collider and flavor physics, soft-collinear effective theory (SCET) has emerged as both a powerful and versatile tool, having been applied to a large variety of processes, from B-meson decays to jet production at the LHC. This book provides a concise, pedagogical introduction to this technique. It discusses the expansion of Feynman diagrams around the high-energy limit, followed by the explicit construction of the effective Lagrangian - first for a scalar theory, then for QCD. The underlying concepts are illustrated with the quark vector form factor at large momentum transfer, and the formalism is applied to compute soft-gluon resummation and to perform transverse-momentum resummation for the Drell-Yan process utilizing renormalization group evolution in SCET. Finally, the infrared structure of n-point gauge-theory amplitudes is analyzed by relating them to effective-theory operators. This text is suitable for graduate students and non-spe...
Four-loop collinear anomalous dimension in N=4 Yang-Mills theory
International Nuclear Information System (INIS)
Cachazo, Freddy; Spradlin, Marcus; Volovich, Anastasia
2007-01-01
We report a calculation in N=4 Yang-Mills of the four-loop term g (4) in the collinear anomalous dimension g(λ) which governs the universal subleading infrared structure of gluon scattering amplitudes. Using the method of obstructions to extract this quantity from the 1/ε singularity in the four-gluon iterative relation at four loops, we find g (4) =-1240.9 with an estimated numerical uncertainty of 0.02%. We also analyze the implication of our result for the strong coupling behavior of g(λ), finding support for the string theory prediction computed recently by Alday and Maldacena using AdS/CFT
Soft-Collinear Effective Theory
CERN. Geneva
2017-01-01
I will review the basic principles about Soft-Collinear Effective Theory. I will focus on how it can be used to understand factorization properties and how one can resum large logarithms arising from infrared physics using the renormalization group evolution.
International Nuclear Information System (INIS)
Sugano, K.
1987-01-01
The properties of gluon jets are reviewed, and the measured characteristics are compared to the theoretical expectations. Although neither data nor models for the gluon jets are in the mature stage, in general the agreement between experiment and theory is remarkable. There are some intriguing differences. Since the properties of gluon jets are deeply rooted in the basic structure of non-Abelian gauge theory, the study of gluon jets casts further light on our understanding of QCD. Finally, the future prospects are discussed
International Nuclear Information System (INIS)
Sugano, K.
1988-01-01
The properties of gluon jets are reviewed from an experimental point of view. The measured characteristics are compared to theoretical expectations. Although neither data nor models for the gluon jets are in the mature stage, there are remarkable agreements and also intriguing disagreements between experiment and theory. Since much interesting data have begun to emerge from various experiments and the properties of gluon jets are deeply rooted in the basic structure of non-Abelian gauge theory, the study of gluon jets casts further light on understanding of QCD. The future prospects are discussed
QCD collinear factorization, its extensions and the partonic distributions
Szymanowski, Lech
2012-01-01
I review the basics of the collinear factorization theorem applied primarily to deep inelastic scattering (DIS) involving forward parton distributions (PDFs) and the extensions of this theorem for exclusive processes probing non-forward parton distributions (GPDs), the generalized distribution amplitudes (GDAs) and the transition distribution amplitudes (TDAs). These QCD factorization theorem is an important tool in the description of hard processes in QCD. Whenever valid, it permits to repre...
Unintegrated gluon distributions in D*± and dijet associated photoproduction at HERA
International Nuclear Information System (INIS)
Lipatov, A.V.; Zotov, N.P.
2006-01-01
We consider the photoproduction of D *± mesons associated with two hadron jets at HERA collider in the framework of the k T -factorization approach. The unintegrated gluon densities in a proton are obtained from the full CCFM, from unified BFKL-DGLAP evolution equations as well as from the Kimber-Martin-Ryskin prescription. Resolved photon contributions are reproduced by the initial-state gluon radiation. We investigate different production rates and make a comparison with the recent experimental data taken by the ZEUS collaboration. Special attention is given to the specific dijet correlations which can provide unique information about non-collinear gluon evolution dynamics. (orig.)
Modelling the gluon propagator
Energy Technology Data Exchange (ETDEWEB)
Leinweber, D.B.; Parrinello, C.; Skullerud, J.I.; Williams, A.G
1999-03-01
Scaling of the Landau gauge gluon propagator calculated at {beta} = 6.0 and at {beta} = 6.2 is demonstrated. A variety of functional forms for the gluon propagator calculated on a large (32{sup 3} x 64) lattice at {beta} = 6.0 are investigated.
Factorization of heavy-to-light form factors in soft-collinear effective theory
Beneke, Martin; Feldmann, Th.
2004-01-01
Heavy-to-light transition form factors at large recoil energy of the light meson have been conjectured to obey a factorization formula, where the set of form factors is reduced to a smaller number of universal form factors up to hard-scattering corrections. In this paper we extend our previous investigation of heavy-to-light currents in soft-collinear effective theory to final states with invariant mass Lambda^2 as is appropriate to exclusive B meson decays. The effective theory contains soft modes and two collinear modes with virtualities of order m_b*Lambda (`hard-collinear') and Lambda^2. Integrating out the hard-collinear modes results in the hard spectator-scattering contributions to exclusive B decays. We discuss the representation of heavy-to-light currents in the effective theory after integrating out the hard-collinear scale, and show that the previously conjectured factorization formula is valid to all orders in perturbation theory. The naive factorization of matrix elements in the effective theory ...
Regularization of the light-cone gauge gluon propagator singularities using sub-gauge conditions
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Chirilli, Giovanni A.; Kovchegov, Yuri V.; Wertepny, Douglas E. [Department of Physics, The Ohio State University,191 W Woodruff Ave, Columbus, OH 43210 (United States)
2015-12-21
Perturbative QCD calculations in the light-cone gauge have long suffered from the ambiguity associated with the regularization of the poles in the gluon propagator. In this work we study sub-gauge conditions within the light-cone gauge corresponding to several known ways of regulating the gluon propagator. Using the functional integral calculation of the gluon propagator, we rederive the known sub-gauge conditions for the θ-function gauges and identify the sub-gauge condition for the principal value (PV) regularization of the gluon propagator’s light-cone poles. The obtained sub-gauge condition for the PV case is further verified by a sample calculation of the classical Yang-Mills field of two collinear ultrarelativistic point color charges. Our method does not allow one to construct a sub-gauge condition corresponding to the well-known Mandelstam-Leibbrandt prescription for regulating the gluon propagator poles.
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Sichtermann, Ernst
2016-12-15
The fundamental structure of nucleons and nuclear matter is described by the properties and dynamics of quarks and gluons in quantum chromodynamics. Electron-nucleon collisions are a powerful method to study this structure. As one increases the energy of the collisions, the interaction process probes regions of progressively higher gluon density. This density must eventually saturate. An high-energy polarized Electron-Ion Collider (EIC) has been proposed to observe and study the saturated gluon density regime. Selected measurements will be discussed, following a brief introduction.
Resummations in QCD hard-scattering at large and small x
Kidonakis, Nikolaos; Stephens, Philip
2008-01-01
We discuss different resummations of large logarithms that arise in hard-scattering cross sections of quarks and gluons in regions of large and small x. The large-x logarithms are typically dominant near threshold for the production of a specified final state. These soft and collinear gluon corrections produce large enhancements of the cross section for many processes, notably top quark and Higgs production, and typically the higher-order corrections reduce the factorization and renormalization scale dependence of the cross section. The small-x logarithms are dominant in the regime where the momentum transfer of the hard sub-process is much smaller than the total collision energy. These logarithms are important to describe multijet final states in deep inelastic scattering and hadron colliders, and in the study of parton distribution functions. The resummations at small and large x are linked by the eikonal approximation and are dominated by soft gluon anomalous dimensions. We will review their role in both c...
Casimir meets Poisson: improved quark/gluon discrimination with counting observables
Frye, Christopher; Larkoski, Andrew J.; Thaler, Jesse; Zhou, Kevin
2017-09-01
Charged track multiplicity is among the most powerful observables for discriminating quark- from gluon-initiated jets. Despite its utility, it is not infrared and collinear (IRC) safe, so perturbative calculations are limited to studying the energy evolution of multiplicity moments. While IRC-safe observables, like jet mass, are perturbatively calculable, their distributions often exhibit Casimir scaling, such that their quark/gluon discrimination power is limited by the ratio of quark to gluon color factors. In this paper, we introduce new IRC-safe counting observables whose discrimination performance exceeds that of jet mass and approaches that of track multiplicity. The key observation is that track multiplicity is approximately Poisson distributed, with more suppressed tails than the Sudakov peak structure from jet mass. By using an iterated version of the soft drop jet grooming algorithm, we can define a "soft drop multiplicity" which is Poisson distributed at leading-logarithmic accuracy. In addition, we calculate the next-to-leading-logarithmic corrections to this Poisson structure. If we allow the soft drop groomer to proceed to the end of the jet branching history, we can define a collinear-unsafe (but still infrared-safe) counting observable. Exploiting the universality of the collinear limit, we define generalized fragmentation functions to study the perturbative energy evolution of collinear-unsafe multiplicity.
Non-collinear magnetism in multiferroic perovskites.
Bousquet, Eric; Cano, Andrés
2016-03-31
We present an overview of the current interest in non-collinear magnetism in multiferroic perovskite crystals. We first describe the different microscopic mechanisms giving rise to the non-collinearity of spins in this class of materials. We discuss, in particular, the interplay between non-collinear magnetism and ferroelectric and antiferrodistortive distortions of the perovskite structure, and how this can promote magnetoelectric responses. We then provide a literature survey on non-collinear multiferroic perovskites. We discuss numerous examples of spin cantings driving weak ferromagnetism in transition metal perovskites, and of spin-induced ferroelectricity as observed in the rare-earth based perovskites. These examples are chosen to best illustrate the fundamental role of non-collinear magnetism in the design of multiferroicity.
The structure of gluon radiation in QCD
International Nuclear Information System (INIS)
Parke, S.; Mangano, M.
1989-08-01
For massless QCD the hard scattering amplitudes are naturally written in terms of the dual color expansion. here I present this expansion for purely gluonic processes and processes involving quark-antiquark pairs and gluons. The properties of the sub-amplitudes as well as explicit algebraic expressions are given for a number of these processes. Also, I demonstrate how to recover massless QED amplitudes from the dual expansion of massless QCD. 16 refs., 3 figs., 1 tab
From Color Fields to Quark Gluon Plasma
Energy Technology Data Exchange (ETDEWEB)
Fries, Rainer J. [School of Physics and Astronomy, University of Minnesota, Minneapolis MN 55455 (United States); Kapusta, Joseph I. [School of Physics and Astronomy, University of Minnesota, Minneapolis MN 55455 (United States); Li, Yang [School of Physics and Astronomy, University of Minnesota, Minneapolis MN 55455 (United States)
2006-08-07
We discuss a model for the energy distribution and the early space-time evolution of a heavy ion collision. We estimate the gluon field generated in the wake of hard processes and through primordial fluctuations of the color charges in the nuclei. Without specifying the dynamical mechanism of thermalization we calculate the energy momentum tensor of the following plasma phase. The results of this model can be used as initial conditions for a further hydrodynamic evolution.
The structure of gluon radiation in QCD
International Nuclear Information System (INIS)
Parke, S.; Mangano, M.
1990-01-01
For massless QCD the hard scattering amplitudes are naturally written in terms of the dual color expansion. Here I present this expansion for purely gluonic processes and processes involving quark-antiquark pairs and gluons. The properties of the sub-amplitudes as well as explicit algebraic expressions are given for a number of these processess. Finally, I demonstrate how to recover massless QED amplitudes from the dual expansion of massless QCD
Chala, Mikael; Perez, Gilad; Santiago, Jose
2015-01-01
We study the phenomenology of vector resonances in the context of natural composite Higgs models. A mild hierarchy between the fermionic partners and the vector resonances can be expected in these models based on the following arguments. Both direct and indirect (electroweak and flavor precision) constraints on fermionic partners are milder than the ones on spin one resonances. Also the naturalness pressure coming from the top partners is stronger than that induced by the gauge partners. This observation implies that the search strategy for vector resonances at the LHC needs to be modified. In particular, we point out the importance of heavy gluon decays (or other vector resonances) to top partner pairs that were overlooked in previous experimental searches at the LHC. These searches focused on simplified benchmark models in which the only new particle beyond the Standard Model was the heavy gluon. It turns out that, when kinematically allowed, such heavy-heavy decays make the heavy gluon elusive, and the bou...
All-order results for infrared and collinear singularities in massless gauge theories
Dixon, Lance J; Magnea, Lorenzo
2010-01-01
We review recent results concerning the all-order structure of infrared and collinear divergences in massless gauge theory amplitudes. While the exponentiation of these divergences for nonabelian gauge theories has been understood for a long time, in the past couple of years we have begun to unravel the all-order structure of the anomalous dimensions that build up the perturbative exponent. In the large-Nc limit, all infrared and collinear divergences are determined by just three functions; one of them, the cusp anomalous dimension, plays a key role also for non-planar contributions. Indeed, all infrared and collinear divergences of massless gauge theory amplitudes with any number of hard partons may be captured by a surprisingly simple expression constructed as a sum over color dipoles. Potential corrections to this expression, correlating four or more hard partons at three loops or beyond, are tightly constrained and are currently under study.
International Nuclear Information System (INIS)
Khadkikar, S.B.; Vinodkumar, P.C.
1987-04-01
Confinement model for gluons using a 'colour super current' is formulated. An attempt has been made to derive a suitable dielectric function corresponding to the current confinement model. A simple inhomogeneous dielectric confinement model for gluons is studied for comparison. The model Hamiltonians are second quantized and the glueball states are constructed. The spurious motion of the centre of confinement is accounted for. The results of the current confinement scheme are found to be in good agreement with the experimental candidates for glueballs. (author). 16 refs, 3 tabs
International Nuclear Information System (INIS)
Granier de Cassagnac, R.
2010-01-01
The quark-gluon plasma (QGP) is a state of matter in which the universe was expected to be a few micro-seconds after the big-bang. Violent collisions of heavy ions are supposed to re-create this state in particle accelerators. Numerous signatures of this fugacious state have already been observed at the RHIC (relativistic heavy ion collider). The first evidence of the violence of collisions is the number of generated particles: about 6000 per collision, mostly hadrons. This figure seems high but in fact is less than theoretically expected and is the first sign of the formation of a QGP that saturates the density of gluons. Another sign, observed at the RHIC is the damping of the particle jets that are produced in the collision. This damping is consistent with the crossing of a medium whose density is so high that it can not be made of hadrons but of partons. In the RHIC experiments the collective behaviour of quarks and gluons shows that they are strongly interacting with one another. This fact supports the idea that the QGP is more a perfect liquid rather than an ideal gas in which quarks and gluons move freely. (A.C.)
Comments on gluon 6-point scattering amplitudes in N = 4 SYM at strong coupling
International Nuclear Information System (INIS)
Astefanesei, Dumitru; Dobashi, Suguru; Ito, Katsushi; Nastase, Horatiu
2007-01-01
We use the AdS-CFT prescription of Alday and Maldacena [1] to analyze gluon 6-point scattering amplitudes at strong coupling in N = 4 SYM. By cutting and gluing we obtain AdS 6-point amplitudes that contain extra boundary conditions and come close to matching the field theory results. We interpret them as parts of the field theory amplitudes, containing only certain diagrams. We also analyze the collinear limits of 6- and 5-point amplitudes and discuss the results
Magnetization dynamics of imprinted non-collinear spin textures
Energy Technology Data Exchange (ETDEWEB)
Streubel, Robert, E-mail: r.streubel@ifw-dresden.de; Kopte, Martin; Makarov, Denys, E-mail: d.makarov@ifw-dresden.de [Institute for Integrative Nanosciences, IFW Dresden, 01069 Dresden (Germany); Fischer, Peter [Center for X-Ray Optics, Lawrence Berkeley National Laboratory, Berkeley, California 94720 (United States); Physics Department, UC Santa Cruz, Santa Cruz, California 95064 (United States); Schmidt, Oliver G. [Institute for Integrative Nanosciences, IFW Dresden, 01069 Dresden (Germany); Material Systems for Nanoelectronics, Chemnitz University of Technology, 09107 Chemnitz (Germany)
2015-09-14
We study the magnetization dynamics of non-collinear spin textures realized via imprint of the magnetic vortex state in soft permalloy into magnetically hard out-of-plane magnetized Co/Pd nanopatterned heterostructures. Tuning the interlayer exchange coupling between soft- and hard-magnetic subsystems provides means to tailor the magnetic state in the Co/Pd stack from being vortex- to donut-like with different core sizes. While the imprinted vortex spin texture leads to the dynamics similar to the one observed for vortices in permalloy disks, the donut-like state causes the appearance of two gyrofrequencies characteristic of the early and later stages of the magnetization dynamics. The dynamics are described using the Thiele equation supported by the full scale micromagnetic simulations by taking into account an enlarged core size of the donut states compared to magnetic vortices.
Quantum chromodynamics as effective theory of quarks and composite gluons
International Nuclear Information System (INIS)
Fuss, T.
2004-01-01
The dynamics of quarks is described by a nonperturbatively regularized NJL model which is canonically quantized and fulfil a probability interpretation. The quantum field theory of this model is formulated in a functional space. The wave functions of the quarks and gluons are calculated as eigenstates of Hard-Core equations and the gluons are considered as relativistic bound states of colored quark-antiquark pairs. The effective dynamics of the quarks and gluons is derived from weak mapping in functional space. This leads to the functional formulation of the phenomenological SU(3) local gauge invariant quark-gluon equations in temporal gauge. This means that the local gauge symmetry is a dynamical effect resulting from the quark model
1990-01-01
This volume contains 14 review articles on the theory and phenomenology of the creation and diagnosis of quark-gluon plasma. They are written by active investigators of in the various research topics, which range from the QCD foundation through transport theory and thermalization models to the examination of possible signatures. The monograph should be useful not only to the experienced researchers in the subject but also to newcomers.
Energy Technology Data Exchange (ETDEWEB)
Chala, Mikael [Granada Univ. (Spain). CAFPE; Granada Univ. (Spain). Dept. de Fisica Teorica y del Cosmos; Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany); Juknevich, Jose [International School for Advanced Studies, Trieste (Italy); Istituto Nazionale di Fisica Nucleare, Trieste (Italy); Perez, Gilad [Weizmann Institute of Science, Rehovot (Israel). Dept. of Particle Physics and Astrophysics; Santiago, Jose [Granada Univ. (Spain). CAFPE; Granada Univ. (Spain). Dept. de Fisica Teorica y del Cosmos; European Organization for Nuclear Research (CERN), Geneva (Switzerland)
2014-11-15
We study the phenomenology of vector resonances in the context of natural composite Higgs models. A mild hierarchy between the fermionic partners and the vector resonances can be expected in these models based on the following arguments. Both direct and indirect (electroweak and flavor precision) constraints on fermionic partners are milder than the ones on spin one resonances. Also the naturalness pressure coming from the top partners is stronger than that induced by the gauge partners. This observation implies that the search strategy for vector resonances at the LHC needs to be modified. In particular, we point out the importance of heavy gluon decays (or other vector resonances) to top partner pairs that were overlooked in previous experimental searches at the LHC. These searches focused on simplified benchmark models in which the only new particle beyond the Standard Model was the heavy gluon. It turns out that, when kinematically allowed, such heavy-heavy decays make the heavy gluon elusive, and the bounds on its mass can be up to 2 TeV milder than in the simpler models considered so far for the LHC14. We discuss the origin of this difference and prospects for dedicated searches.
Nayak, Tapan; Sarkar, Sourav
2014-01-01
At extremely high temperatures and densities, protons and neutrons may dissolve into a "soup" of quarks and gluons, called the Quark-Gluon Plasma (QGP). For a few microseconds, shortly after the Big Bang, the Universe was filled with the QGP matter. The search and study of Quark-Gluon Plasma (QGP) is one of the most fundamental research topics of our times. The QGP matter has been probed by colliding heavy ions at the Relativistic Heavy Ion Collider at Brookhaven National Laboratory, New York and the Large Hadron Collider at CERN, Geneva. By colliding heavy-ions at a speed close to that of light, scientists aim to obtain - albeit over a tiny volume of the size of a nucleus and for an infinitesimally short instant - a QGP state. This QGP state can be observed by dedicated experiments, as it reverts to hadronic matter through expansion and cooling. This volume presents some of the current theoretical and experimental understandings in the field of QGP.
International Nuclear Information System (INIS)
Chala, Mikael; Juknevich, Jose; Perez, Gilad
2014-11-01
We study the phenomenology of vector resonances in the context of natural composite Higgs models. A mild hierarchy between the fermionic partners and the vector resonances can be expected in these models based on the following arguments. Both direct and indirect (electroweak and flavor precision) constraints on fermionic partners are milder than the ones on spin one resonances. Also the naturalness pressure coming from the top partners is stronger than that induced by the gauge partners. This observation implies that the search strategy for vector resonances at the LHC needs to be modified. In particular, we point out the importance of heavy gluon decays (or other vector resonances) to top partner pairs that were overlooked in previous experimental searches at the LHC. These searches focused on simplified benchmark models in which the only new particle beyond the Standard Model was the heavy gluon. It turns out that, when kinematically allowed, such heavy-heavy decays make the heavy gluon elusive, and the bounds on its mass can be up to 2 TeV milder than in the simpler models considered so far for the LHC14. We discuss the origin of this difference and prospects for dedicated searches.
Elastic energy loss and longitudinal straggling of a hard jet
International Nuclear Information System (INIS)
Majumder, A.
2009-01-01
The elastic energy loss encountered by jets produced in deep-inelastic scattering (DIS) off a large nucleus is studied in the collinear limit. In close analogy to the case of (nonradiative) transverse momentum broadening, which is dependent on the medium transport coefficient q, a class of medium enhanced higher twist operators which contribute to the nonradiative loss of the forward light-cone momentum of the jet (q - ) are identified and the leading correction in the limit of asymptotically high q - is isolated. Based on these operator products, a new transport coefficient e is motivated which quantifies the energy loss per unit length encountered by the hard jet. These operator products are then computed, explicitly, in the case of a similar hard jet traversing a deconfined quark-gluon plasma (QGP) in the hard-thermal-loop (HTL) approximation. This is followed by an evaluation of subleading contributions which are suppressed by the inverse light-cone momentum q - , which yields the longitudinal 'straggling', i.e., a slight change in light cone momentum due to the Brownian propagation through a medium with a fluctuating color field.
Relating hard QCD processes through universality of mass singularities
International Nuclear Information System (INIS)
Amati, D.; Petronzio, R.; Veneziano, G.
1978-01-01
Hard QCD processes involving final jets are studied and compared by means of a simple approach to mass singularities. This is based on the Lee-Nauenberg-Kinoshita theorem and on a rather subtle use of gauge invariance in hard collinear gluon bremsstrahlung. One-loop results are easily derived for processes involving any number of initial quarks and/or currents. The method greatly simplifies the computation of higher-order loops at the leading log level and the preliminary results allow one to conclude that the crucial features encountered at the one-loop level will persist. The authors are thus able to relate different hard processes and to show that suitable ratios of cross sections, being free from mass singularities, can be computed perturbatively, as usually assumed in QCD-inspired parton models. It is also possible to relate the universal leading mass singularities to leading scaling violations and to extend therefor the results of the operator product expansion method to processes outside the range of the light-cone analysis. Some delicate points caused by confinement-related singularities (e.g. narrow resonance poles) are also discussed. (Auth.)
Energy Technology Data Exchange (ETDEWEB)
Baranov, S.P. [P.N. Lebedev Physics Institute, Moscow (Russian Federation); Jung, H. [Deutsches Elektronen-Synchrotron, Hamburg (Germany); Lipatov, A.V. [Moscow State University, Skobeltsyn Institute of Nuclear Physics, Moscow (Russian Federation); Joint Institute for Nuclear Research, Dubna (Russian Federation); Malyshev, M.A. [Moscow State University, Skobeltsyn Institute of Nuclear Physics, Moscow (Russian Federation)
2017-11-15
We consider the production of Z bosons associated with beauty quarks at the LHC using a combined k{sub T} + collinear QCD factorization approach, which interpolates between small x and large x physics. Our consideration is based on the off-shell gluon-gluon fusion subprocess g*g* → ZQ anti Q at the leading order O(αα{sub s}{sup 2}) (where the Z boson further decays into a lepton pair), calculated in the k{sub T}-factorization approach, and several subleading O(αα{sub s}{sup 2}) and O(αα{sub s}{sup 3}) subprocesses involving quark-antiquark and quark-gluon interactions, taken into account in conventional (collinear) QCD factorization. The contributions from double parton scattering are discussed as well. The transverse momentum dependent (or unintegrated) gluon densities in a proton are derived from Catani-Ciafaloni-Fiorani-Marchesini (CCFM) evolution equation. We achieve reasonably good agreement with the latest data taken by CMS and ATLAS Collaborations. The comparison of our results with next-to-leading-order pQCD predictions, obtained in the collinear QCD factorization, is presented. We discuss the uncertainties of our calculations and demonstrate the importance of subleading quark-involving contributions in describing the LHC data in the whole kinematic region. (orig.)
Energy Technology Data Exchange (ETDEWEB)
Baranov, S.P. [P.N. Lebedev Physical Institute, Moscow (Russian Federation); Jung, H. [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany); Lipatov, A.V. [Moscow State Univ. (Russian Federation). Skobeltsyn Inst. of Nuclear Physics; Joint Institute for Nuclear Research, Dubna (Russian Federation); Malyshev, M.A. [Moscow State Univ. (Russian Federation). Skobeltsyn Inst. of Nuclear Physics
2017-08-15
We consider the production of Z bosons associated with beauty quarks at the LHC using a combined k{sub T}+collinear QCD factorization approach, that interpolates between small x and large x physics. Our consideration is based on the off-shell gluon-gluon fusion subprocess g{sup *}g{sup *}→ZQ anti Q at the leading order O(αα{sup 2}{sub s}) (where the Z boson further decays into a lepton pair), calculated in the k{sub T}-factorization approach, and several subleading O(αα{sup 2}{sub s}) and O(αα{sup 3}{sub s}) subprocesses involving quark-antiquark and quark-gluon interactions, taken into account in conventional (collinear) QCD factorization. The contributions from double parton scattering are discussed as well. The transverse momentum dependent (or unintegrated) gluon densities in a proton are derived from Catani-Ciafaloni-Fiorani-Marchesini (CCFM) evolution equation. We achieve reasonably good agreement with the latest data taken by CMS and ATLAS Collaborations. The comparison of our results with next-to-leading-order pQCD predictions, obtained in the collinear QCD factorization, is presented. We discuss the uncertainties of our calculations and demonstrate the importance of subleading quark involving contributions in describing the LHC data in the whole kinematic region.
International Nuclear Information System (INIS)
Gelis, Francois
1998-12-01
The general framework of this work is thermal field theory, and more precisely the perturbative calculation of thermal Green's functions. In a first part, I consider the problems closely related to the formalism itself. After two introductory chapters devoted to set up the framework and the notations used afterwards, a chapter is dedicated to a clarification of certain aspects of the justification of the Feynman rules of the real time formalism. Then, I consider in the chapter 4 the problem of cutting rules in the real time formalisms. In particular, after solving a controversy on this subject, I generalize these cutting rules to the 'retarded-advanced' version of this formalism. Finally, the last problem considered in this part is that of the pion decay into two photons in a thermal bath. I show that the discrepancies found in the literature are due to peculiarities of the analytical properties of the thermal Green's functions. The second part deals with the calculations of the photons or dilepton (virtual photon) production rate by a quark gluon plasma. The framework of this study is the effective theory based on the resummation of hard thermal loops. The first aspects of this study is related to the production of virtual photons, where we show that important contributions arise at two loops, completing the result already known at one loop. In the case of real photon production, we show that extremely strong collinear singularities make two loop contributions dominant compared to one loop ones. In both cases, the importance of two loop contributions can be interpreted as weaknesses of the hard thermal loop approximation. (author)
Analysis of the proton longitudinal structure function from the gluon distribution function
International Nuclear Information System (INIS)
Boroun, G.R.; Rezaei, B.
2012-01-01
We make a critical, next-to-leading order, study of the relationship between the longitudinal structure function F L and the gluon distribution proposed in Cooper-Sarkar et al. (Z. Phys. C 39:281, 1988; Acta Phys. Pol. B 34:2911 2003), which is frequently used to extract the gluon distribution from the proton longitudinal structure function at small x. The gluon density is obtained by expanding at particular choices of the point of expansion and compared with the hard Pomeron behavior for the gluon density. Comparisons with H1 data are made and predictions for the proposed best approach are also provided. (orig.)
Energy Technology Data Exchange (ETDEWEB)
Weinzierl, Stefan, E-mail: weinzierl@uni-mainz.de
2017-03-13
This report is centred around tree-level scattering amplitudes in pure Yang–Mills theories, the most prominent example is given by the tree-level gluon amplitudes of QCD. I will discuss several ways of computing these amplitudes, illustrating in this way recent developments in perturbative quantum field theory. Topics covered in this review include colour decomposition, spinor and twistor methods, off- and on-shell recursion, MHV amplitudes and MHV expansion, the Grassmannian and the amplituhedron, the scattering equations and the CHY representation. At the end of this report there will be an outlook on the relation between pure Yang–Mills amplitudes and scattering amplitudes in perturbative quantum gravity.
A new prescription for soft gluon resummation
International Nuclear Information System (INIS)
Abbate, Riccardo; Forte, Stefano; Ridolfi, Giovanni
2007-01-01
We present a new prescription for the resummation of the divergent series of perturbative corrections, due to soft gluon emission, to hard processes near threshold in perturbative QCD (threshold resummation). This prescription is based on Borel resummation, and contrary to the commonly used minimal prescription, it does not introduce a dependence of resummed physical observables on the kinematically unaccessible x→0 region of parton distributions. We compare results for resummed deep-inelastic scattering obtained using the Borel prescription and the minimal prescription and exploit the comparison to discuss the ambiguities related to the resummation procedure
The quark-gluon model for particle production processes
International Nuclear Information System (INIS)
Volkovitskij, P.E.
1983-01-01
The quark-gluon model for hadronization of strings produced in soft and hard processes is suggested. The model is based on the distribution functions of valence quarks in hadrons which have correct Regge behaviour. The simplest case is discussed in which only the longitudinal degrees of freedom are taken into account
Quark and Gluon Relaxation in Quark-Gluon Plasmas
Heiselberg, H.; Pethick, C. J.
1993-01-01
The quasiparticle decay rates for quarks and gluons in quark-gluon plasmas are calculated by solving the kinetic equation. Introducing an infrared cutoff to allow for nonperturbative effects, we evaluate the quasiparticle lifetime at momenta greater than the inverse Debye screening length to leading order in the coupling constant.
Non-perturbative inputs for gluon distributions in the hadrons
Energy Technology Data Exchange (ETDEWEB)
Ermolaev, B.I. [Ioffe Physico-Technical Institute, Saint Petersburg (Russian Federation); Troyan, S.I. [St. Petersburg Institute of Nuclear Physics, Gatchina (Russian Federation)
2017-03-15
Description of hadronic reactions at high energies is conventionally done in the framework of QCD factorization. All factorization convolutions comprise non-perturbative inputs mimicking non-perturbative contributions and perturbative evolution of those inputs. We construct inputs for the gluon-hadron scattering amplitudes in the forward kinematics and, using the optical theorem, convert them into inputs for gluon distributions in the hadrons, embracing the cases of polarized and unpolarized hadrons. In the first place, we formulate mathematical criteria which any model for the inputs should obey and then suggest a model satisfying those criteria. This model is based on a simple reasoning: after emitting an active parton off the hadron, the remaining set of spectators becomes unstable and therefore it can be described through factors of the resonance type, so we call it the resonance model. We use it to obtain non-perturbative inputs for gluon distributions in unpolarized and polarized hadrons for all available types of QCD factorization: basic, K{sub T}-and collinear factorizations. (orig.)
Non-perturbative inputs for gluon distributions in the hadrons
International Nuclear Information System (INIS)
Ermolaev, B.I.; Troyan, S.I.
2017-01-01
Description of hadronic reactions at high energies is conventionally done in the framework of QCD factorization. All factorization convolutions comprise non-perturbative inputs mimicking non-perturbative contributions and perturbative evolution of those inputs. We construct inputs for the gluon-hadron scattering amplitudes in the forward kinematics and, using the optical theorem, convert them into inputs for gluon distributions in the hadrons, embracing the cases of polarized and unpolarized hadrons. In the first place, we formulate mathematical criteria which any model for the inputs should obey and then suggest a model satisfying those criteria. This model is based on a simple reasoning: after emitting an active parton off the hadron, the remaining set of spectators becomes unstable and therefore it can be described through factors of the resonance type, so we call it the resonance model. We use it to obtain non-perturbative inputs for gluon distributions in unpolarized and polarized hadrons for all available types of QCD factorization: basic, K_T-and collinear factorizations. (orig.)
Jet-medium interactions at NLO in a weakly-coupled quark-gluon plasma
International Nuclear Information System (INIS)
Ghiglieri, Jacopo; Moore, Guy D.; Teaney, Derek
2016-01-01
We present an extension to next-to-leading order in the strong coupling constant g of the AMY effective kinetic approach to the energy loss of high momentum particles in the quark-gluon plasma. At leading order, the transport of jet-like particles is determined by elastic scattering with the thermal constituents, and by inelastic collinear splittings induced by the medium. We reorganize this description into collinear splittings, high-momentum-transfer scatterings, drag and diffusion, and particle conversions (momentum-preserving identity-changing processes). We show that this reorganized description remains valid to NLO in g, and compute the appropriate modifications of the drag, diffusion, particle conversion, and inelastic splitting coefficients. In addition, a new kinematic regime opens at NLO for wider-angle collinear bremsstrahlung. These semi-collinear emissions smoothly interpolate between the leading order high-momentum-transfer scatterings and collinear splittings. To organize the calculation, we introduce a set of Wilson line operators on the light-cone which determine the diffusion and identity changing coefficients, and we show how to evaluate these operators at NLO.
The role of three-gluon correlation functions in the single spin asymmetry
Directory of Open Access Journals (Sweden)
Beppu Hiroo
2015-01-01
Full Text Available We study the twist-3 three-gluon contribution to the single spin asymmetry in the light-hadron production in pp collision in the framework of the collinear factorization. We derive the corresponding cross section formula in the leading order with respect to the QCD coupling constant. We also present a numerical calculation of the asymmetry at the RHIC energy, using a model for the three-gluon correlation functions suggested by the asymmetry for the D-meson production at RHIC. We found that the asymmetries for the light-hadron and the jet productions are very useful to constrain the magnitude and form of the correlation functions. Since the three-gluon correlation functions shift the asymmetry for all kinds of hadrons in the same direction, it is unlikely that they become a main source of the asymmetry.
Energy Technology Data Exchange (ETDEWEB)
Zaraket, H
2000-06-01
This work is devoted to photon and dilepton production in a quark gluon plasma. The theoretical framework in which the study is carried out is Thermal Field Theory, more precisely the hard thermal loop effective theory. Several features of the observables preclude a straightforward application of the effective theory and new tools had to be developed such as the counter term method to avoid double counting. The first part of my study concerns static virtual photon production where I show that important physical contributions are missing in the effective theory at one loop level and hence a two loop calculation is indispensable. Furthermore I give an analytic leading logarithmic estimate of this two loop result showing clearly the insufficiency of the effective theory. The second part of the work focuses on real and quasi real photon production. Again, important contributions arise at two loop level due to collinear divergences. For high mass dilepton the two loop calculation is sufficient. On the other hand, near the light cone photon production rate is non perturbative. Getting closer to the light cone coherent scattering effects (Landau-Pomeranchuk-Migdal effect) arise, which imply the resummation of an infinite series of diagrams. Still nearer the light cone we found a dependence on the non perturbative magnetic mass due to infrared singularities. (author)
Soft gluon resummation in the infrared region and the Froissart bound
Pancheri, Giulia; Godbole, Rohini M; Srivastava, Yogendra N
2010-01-01
We describe the taming effect induced by soft gluon $k_t$-resummation on the rapid rise of QCD mini-jet contributions to the total cross-sections.This results from an eikonal model in which the rise of the total cross-section is due to mini-jet contribution. We perform the calculation with current Parton Density Functions (PDFs). The impact parameter distribution we use is obtained as the Fourier transform of the resummed $k_t$-distribution of soft gluons emitted from the initial state during the collision.The emission, which is energy dependent, destroys the initial collinearity of partons.In this model, the strong power-like rise due to the increasing number of low-x gluon collisions is tamed by the acollinearity induced by soft gluon kt-resummation down to zero gluon momenta. It explicitly links a singular soft gluon coupling in the infrared region to the behaviour dictated by the Froissart bound for the total cross-section. The model describes well both proton and photon processes at present accelerator e...
Production and recombination of gluons
International Nuclear Information System (INIS)
Temiraliev, A.T.
2006-01-01
Full text: Nonlinear Markov process of parton production has been considered. The Kolmogorov equation is applied for the evolution equation based on the approximation of independent gluons production in every decay act. We introduced a 'crossing' parameter and used the combination relations to obtain nonlinear recombination equation for the evolution of gluon structure function. (author)
Collinear light scattering using electromagnetically induced transparency
International Nuclear Information System (INIS)
Harris, S.E.; Sokolov, A.V.; Walker, D.R.; Yavuz, D.D.; Yin, G.Y.
2001-01-01
The paper describes two types of nonlinear optical processes which are based on electromagnetically induced transparency. These are: (1) Collinear generation of FM-like Raman sidebands and (2) a type of pondermotive light scattering which is inherent to the interaction of slow light with cold atoms. Connections to other areas of EIT-based nonlinear optics are also described
International Nuclear Information System (INIS)
Fredriksson, S.
1984-01-01
The Stockholm diquark is a very small (0.1-0.2 fm), bound pair of two unequal quarks in spin 0 and colour 3*. If it exists, it is expected to simulate many of the trends presently attributed to perturbative gluon processes. The Stockholm group (S. Ekelin, M. Jaendel, T.I. Larson and myself) is therefore looking for reactions where the non-perturbative QCD phenomenon of diquark formation would give signatures completely different from those of perturbative gluonic contributions. I report here on some new suggestions for diquark effects in deep inelastic scattering, with emphasis on neutron-proton differences, proton production in the current fragmentation region and nuclear target (''EMC'') effects
The soft-gluon current at one-loop order
Catani, S
2000-01-01
We study the soft limit of one-loop QCD amplitudes and we derive the process-independent factorization formula that controls the singular behaviour in this limit. This is obtained from the customary eikonal factorization formula valid at tree (classical) level by introducing a generalized soft-gluon current that embodies the quantum corrections. We compute the explicit expression of the soft-gluon current at one-loop order. It contains purely non-abelian correlations between the colour charges of each pair of hard-momentum partons in the matrix element. This leads to colour correlations between (two and) three hard partons in the matrix element squared. Exploiting colour conservation, we recover QED-like factorization for the square of the matrix elements with two and three hard partons.
Quark jets, gluon jets and the three-gluon vertex
International Nuclear Information System (INIS)
Fodor, Z.
1989-11-01
Using hadronic jets in electron-positron annihilation, we suggest a simple and model-independent method to see the differences between quark and gluon jets. We define and analyse special energy dependent moments of jets and choose those which are the most characteristic to the jet type. The method handles the energy of a jet in an adequate way. We discuss new methods using jet flavor tagging, ordinary flavor tagging of a definite quark jet or discrimination between quark and gluon jets, to test the triple-gluon vertex in electron-positron annihilation. An enriched sample of gluon jets, jets with the smallest energy in four-jet events, as well as a continuous tagging variable are also studied. 21 refs., 6 figs. (Author)
Neural network classification of quark and gluon jets
International Nuclear Information System (INIS)
Graham, M.A.; Jones, L.M.; Herbin, S.
1995-01-01
We demonstrate that there are characteristics common to quark jets and to gluon jets regardless of the interaction that produced them. The classification technique we use depends on the mass of the jet as well as the center-of-mass energy of the hard subprocess that produces the jet. In addition, we present the quark-gluon separability results of an artificial neural network trained on three-jet e + e - events at the Z 0 mass, using a back-propagation algorithm. The inputs to the network are the longitudinal momenta of the leading hadrons in the jet. We tested the network with quark and gluon jets from both e + e - →3 jets and bar pp→2 jets. Finally, we compare the performance of the artificial neural network with the results of making well chosen physical cuts
Transverse momentum of gluons in ep-scattering at HERA
International Nuclear Information System (INIS)
Cholewa, A.
2005-11-01
A Monte Carlo analysis of the phase space of hard interacting gluons in ep-scattering is presented. The event generator CASCADE is used in combination with the program HZTOOL to identify the accessible regions of phase space of present HERA measurements. A map of the k t -x g -plane is presented to show that in the region -3≤log g ≤-1 transverse gluon momenta of up to k t >or sim 20 GeV are accessible to HERA measurements. Furthermore the observables x γ and the transverse jet energy E T are found to be highly sensitive to the transverse momentum and the longitudinal momentum fraction of gluons. (orig.) (orig.)
The Higgs transverse momentum distribution in gluon fusion as multiscale problem
International Nuclear Information System (INIS)
Bagnaschi, E.; Vicini, A.
2015-05-01
We consider Higgs production in gluon fusion and in particular the prediction of the Higgs transverse momentum distribution. We discuss the ambiguities affecting the matching procedure between fixed order matrix elements and the resummation to all orders of the terms enhanced by log(p H T /m H ) factors. Following a recent proposal (Grazzini et al., hep-ph/1306.4581), we argue that the gluon fusion process, computed considering two active quark flavors, is a multiscale problem from the point of view of the resummation of the collinear singular terms. We perform an analysis at parton level of the collinear behavior of the real emission amplitudes and we derive an upper limit to the range of transverse momenta where the collinear approximation is valid. This scale is then used as the value of the resummation scale in the analytic resummation framework or as the value of the h parameter in the POWHEG-BOX code. Finally, we provide a phenomenological analysis in the Standard Model, in the Two Higgs Doublet Model and in the Minimal Supersymmetric Standard Model. In the two latter cases, we provide an ansatz for the central value of the matching parameters not only for a Standard Model-like Higgs boson, but also for heavy scalars and in scenarios where the bottom quark may play the dominant role.
Soft collinear effective theory for gravity
Okui, Takemichi; Yunesi, Arash
2018-03-01
We present how to construct a soft collinear effective theory (SCET) for gravity at the leading and next-to-leading powers from the ground up. The soft graviton theorem and decoupling of collinear gravitons at the leading power are manifest from the outset in the effective symmetries of the theory. At the next-to-leading power, certain simple structures of amplitudes, which are completely obscure in Feynman diagrams of the full theory, are also revealed, which greatly simplifies calculations. The effective Lagrangian is highly constrained by effectively multiple copies of diffeomorphism invariance that are inevitably present in gravity SCET due to mode separation, an essential ingredient of any SCET. Further explorations of effective theories of gravity with mode separation may shed light on Lagrangian-level understandings of some of the surprising properties of gravitational scattering amplitudes. A gravity SCET with an appropriate inclusion of Glauber modes may serve as a powerful tool for studying gravitational scattering in the Regge limit.
Bootstrapping quarks and gluons
Energy Technology Data Exchange (ETDEWEB)
Chew, G.F.
1979-04-01
Dual topological unitarization (DTU) - the approach to S-matrix causality and unitarity through combinatorial topology - is reviewed. Amplitudes associated with triangulated spheres are shown to constitute the core of particle physics. Each sphere is covered by triangulated disc faces corresponding to hadrons. The leading current candidate for the hadron-face triangulation pattern employs 3-triangle basic subdiscs whose orientations correspond to baryon number and topological color. Additional peripheral triangles lie along the hadron-face perimeter. Certain combinations of peripheral triangles with a basic-disc triangle can be identified as quarks, the flavor of a quark corresponding to the orientation of its edges that lie on the hadron-face perimeter. Both baryon number and flavor are additively conserved. Quark helicity, which can be associated with triangle-interior orientation, is not uniformly conserved and interacts with particle momentum, whereas flavor does not. Three different colors attach to the 3 quarks associated with a single basic subdisc, but there is no additive physical conservation law associated with color. There is interplay between color and quark helicity. In hadron faces with more than one basic subdisc, there may occur pairs of adjacent flavorless but colored triangles with net helicity +-1 that are identifiable as gluons. Broken symmetry is an automatic feature of the bootstrap. T, C and P symmetries, as well as up-down flavor symmetry, persist on all orientable surfaces.
Bootstrapping quarks and gluons
International Nuclear Information System (INIS)
Chew, G.F.
1979-04-01
Dual topological unitarization (DTU) - the approach to S-matrix causality and unitarity through combinatorial topology - is reviewed. Amplitudes associated with triangulated spheres are shown to constitute the core of particle physics. Each sphere is covered by triangulated disc faces corresponding to hadrons. The leading current candidate for the hadron-face triangulation pattern employs 3-triangle basic subdiscs whose orientations correspond to baryon number and topological color. Additional peripheral triangles lie along the hadron-face perimeter. Certain combinations of peripheral triangles with a basic-disc triangle can be identified as quarks, the flavor of a quark corresponding to the orientation of its edges that lie on the hadron-face perimeter. Both baryon number and flavor are additively conserved. Quark helicity, which can be associated with triangle-interior orientation, is not uniformly conserved and interacts with particle momentum, whereas flavor does not. Three different colors attach to the 3 quarks associated with a single basic subdisc, but there is no additive physical conservation law associated with color. There is interplay between color and quark helicity. In hadron faces with more than one basic subdisc, there may occur pairs of adjacent flavorless but colored triangles with net helicity +-1 that are identifiable as gluons. Broken symmetry is an automatic feature of the bootstrap. T, C and P symmetries, as well as up-down flavor symmetry, persist on all orientable surfaces
The gluon contribution to polarised nucleon structure functions
International Nuclear Information System (INIS)
Ross, G.G.; Roberts, R.G.
1990-08-01
As with all parton distributions in quantum chromodynamics (QCD) the separation of polarised nucleon structure functions into gluon and quark contributions must be specified. We consider a definition of the gluon contribution to polarised nucleon structure functions based on exclusive processes which is explicitly gauge invariant, has no regularisation ambiguities, is insensitive to infrared singularities and can be related to other polarised scattering processes. We discuss the relationship of this gluon definition to others that have recently been used and to the estimates that have been made of the gluon contribution using current algebra and other methods. A quantitative analysis of the structure function g 1 (x,Q 2 ) for polarised deep inelastic scattering is carried out, with the aim of examining the importance of the gluon contribution. Using the positivity of parton distributions the magnitude of Δg(x,Q 2 ) is constrained by a realistic estimate of the unpolarised glue. With the appropriate choice of the hard scattering cross-section, Δσ γg , we find that even with a maximally polarised glue (for x > 0.1), some polarised strange quark contribution is still needed by the data of the EMC. (author)
The PLUTO experiment at DORIS (DESY) and the discovery of the gluon (A recollection)
Energy Technology Data Exchange (ETDEWEB)
Stella, Bruno R. [Rome-3 Univ. (Italy). Dipt. di Fisica; Istituto Nazionale di Fisica Nucleare, Rome (Italy); Meyer, Hans-Juergen
2010-08-15
With the aim of determining the contribution of the PLUTO experiment at the DORIS e{sup +}e{sup -} storage ring to the discovery of the gluon, as members of this former collaboration we have reconsidered all the scientific material produced by PLUTO in 1978 and the first half of 1979. It is clear that the experiment demonstrated the main decay of the Y(9.46 GeV) resonance to be mediated by 3 gluons, by providing evidence for the agreement of this hypothesis with average values and differential distributions of all possible experimental variables and by excluding all other possible alternative models. Moreover PLUTO measured in June 1979 the matrix element of the 3-gluon decay to be quantitatively as expected by QCD (even after hadronization) and, having checked the possibility to correctly trace the gluons' directions, demonstrated the spin 1 nature of the gluon by excluding spin 0 and spin 1/2. The hadronization of the gluon like a quark jet, hypothesized in the 3-gluon jet Monte Carlo simulation, was compatible with the topological data at this energy and was shown to be an approximation at 10% level for the multiplicity ({approx} < p {sub vertical} {sub stroke} {sub vertical} {sub stroke} {sub >}{sup -1}); the right expected gluon fragmentation was needed for the inclusive distributions; this was the first experimental study of (identified) gluon jets. In the following measurements at the PETRA storage ring, these results were confirmed by PLUTO and by three contemporaneous experiments by evidencing at higher energies the gluon radiation (''bremsstrahlung''), the softer one, by jet broadening, and the hard one, by the emission of (now clearly visible) gluon jets by quarks. The gluon's spin 1 particle nature was also confirmed. The PLUTO results on Y decays had been confirmed both by contemporaneous experiments at DORIS (partially) and later (also partially) were confirmed by more sophisticated detectors. (orig.)
The PLUTO experiment at DORIS (DESY) and the discovery of the gluon (A recollection)
International Nuclear Information System (INIS)
Stella, Bruno R.; Meyer, Hans-Juergen
2010-08-01
With the aim of determining the contribution of the PLUTO experiment at the DORIS e + e - storage ring to the discovery of the gluon, as members of this former collaboration we have reconsidered all the scientific material produced by PLUTO in 1978 and the first half of 1979. It is clear that the experiment demonstrated the main decay of the Y(9.46 GeV) resonance to be mediated by 3 gluons, by providing evidence for the agreement of this hypothesis with average values and differential distributions of all possible experimental variables and by excluding all other possible alternative models. Moreover PLUTO measured in June 1979 the matrix element of the 3-gluon decay to be quantitatively as expected by QCD (even after hadronization) and, having checked the possibility to correctly trace the gluons' directions, demonstrated the spin 1 nature of the gluon by excluding spin 0 and spin 1/2. The hadronization of the gluon like a quark jet, hypothesized in the 3-gluon jet Monte Carlo simulation, was compatible with the topological data at this energy and was shown to be an approximation at 10% level for the multiplicity (∼ vertical stroke vertical stroke > -1 ); the right expected gluon fragmentation was needed for the inclusive distributions; this was the first experimental study of (identified) gluon jets. In the following measurements at the PETRA storage ring, these results were confirmed by PLUTO and by three contemporaneous experiments by evidencing at higher energies the gluon radiation (''bremsstrahlung''), the softer one, by jet broadening, and the hard one, by the emission of (now clearly visible) gluon jets by quarks. The gluon's spin 1 particle nature was also confirmed. The PLUTO results on Y decays had been confirmed both by contemporaneous experiments at DORIS (partially) and later (also partially) were confirmed by more sophisticated detectors. (orig.)
Initial States: IR and Collinear Divergences
International Nuclear Information System (INIS)
Lavelle, Martin; McMullan, David
2007-01-01
The standard approach to the infra-red problem is to use the Bloch-Nordsieck trick to handle soft divergences and the Lee-Nauenberg (LN) theorem for collinear singularities. We show that this is inconsistent in the presence of massless initial particles. Furthermore, we show that using the LN theorem with such initial states introduces a non-convergent infinite series of diagrams at any fixed order in perturbation theory
Triple collinear emissions in parton showers
Energy Technology Data Exchange (ETDEWEB)
Höche, Stefan; Prestel, Stefan
2017-10-01
A framework to include triple collinear splitting functions into parton showers is presented, and the implementation of flavor-changing NLO splitting kernels is discussed as a first application. The correspondence between the Monte-Carlo integration and the analytic computation of NLO DGLAP evolution kernels is made explicit for both timelike and spacelike parton evolution. Numerical simulation results are obtained with two independent implementations of the new algorithm, using the two independent event generation frameworks Pythia and Sherpa.
Non-collinear upconversion of infrared light
DEFF Research Database (Denmark)
Pedersen, Christian; Hu, Qi; Høgstedt, Lasse
2014-01-01
Two dimensional mid-infrared upconversion imaging provides unique spectral and spatial information showing good potential for mid- infrared spectroscopy and hyperspectral imaging. However, to extract spectral or spatial information from the upconverted images an elaborate model is needed, which...... includes non-collinear interaction. We derive here a general theory providing the far field of the upconverted light when two arbitrary fields interact inside a non linear crystal. Theoretical predictions are experimentally verified for incoherent radiation and subsequently applied to previously published...
Energy Technology Data Exchange (ETDEWEB)
Gelis, Francois [Savoie Univ., 73 - Chambery (France)
1998-12-01
The general framework of this work is thermal field theory, and more precisely the perturbative calculation of thermal Green`s functions. In a first part, I consider the problems closely related to the formalism itself. After two introductory chapters devoted to set up the framework and the notations used afterwards, a chapter is dedicated to a clarification of certain aspects of the justification of the Feynman rules of the real time formalism. Then, I consider in the chapter 4 the problem of cutting rules in the real time formalisms. In particular, after solving a controversy on this subject, I generalize these cutting rules to the `retarded-advanced` version of this formalism. Finally, the last problem considered in this part is that of the pion decay into two photons in a thermal bath. I show that the discrepancies found in the literature are due to peculiarities of the analytical properties of the thermal Green`s functions. The second part deals with the calculations of the photons or dilepton (virtual photon) production rate by a quark gluon plasma. The framework of this study is the effective theory based on the resummation of hard thermal loops. The first aspects of this study is related to the production of virtual photons, where we show that important contributions arise at two loops, completing the result already known at one loop. In the case of real photon production, we show that extremely strong collinear singularities make two loop contributions dominant compared to one loop ones. In both cases, the importance of two loop contributions can be interpreted as weaknesses of the hard thermal loop approximation. (author) 366 refs., 109 figs.
Collinear cluster tri-partition: Kinematics constraints and stability of collinearity
Holmvall, P.; Köster, U.; Heinz, A.; Nilsson, T.
2017-01-01
Background: A new mode of nuclear fission has been proposed by the FOBOS Collaboration, called collinear cluster tri-partition (CCT), and suggests that three heavy fission fragments can be emitted perfectly collinearly in low-energy fission. This claim is based on indirect observations via missing-energy events using the 2 v 2 E method. This proposed CCT seems to be an extraordinary new aspect of nuclear fission. It is surprising that CCT escaped observation for so long given the relatively high reported yield of roughly 0.5 % relative to binary fission. These claims call for an independent verification with a different experimental technique. Purpose: Verification experiments based on direct observation of CCT fragments with fission-fragment spectrometers require guidance with respect to the allowed kinetic-energy range, which we present in this paper. Furthermore, we discuss corresponding model calculations which, if CCT is found in such verification experiments, could indicate how the breakups proceed. Since CCT refers to collinear emission, we also study the intrinsic stability of collinearity. Methods: Three different decay models are used that together span the timescales of three-body fission. These models are used to calculate the possible kinetic-energy ranges of CCT fragments by varying fragment mass splits, excitation energies, neutron multiplicities, and scission-point configurations. Calculations are presented for the systems 235U(nth,f ) and 252Cf(s f ) , and the fission fragments previously reported for CCT; namely, isotopes of the elements Ni, Si, Ca, and Sn. In addition, we use semiclassical trajectory calculations with a Monte Carlo method to study the intrinsic stability of collinearity. Results: CCT has a high net Q value but, in a sequential decay, the intermediate steps are energetically and geometrically unfavorable or even forbidden. Moreover, perfect collinearity is extremely unstable, and broken by the slightest perturbation. Conclusions
Soft and Collinear Radiation and Factorization in Perturbation Theory and Beyond
Gardi, Einan
2002-01-01
Power corrections to differential cross sections near a kinematic threshold are analysed by Dressed Gluon Exponentiation. Exploiting the factorization property of soft and collinear radiation, the dominant radiative corrections in the threshold region are resummed, yielding a renormalization-scale-invariant expression for the Sudakov exponent. The interplay between Sudakov logs and renormalons is clarified, and the necessity to resum the latter whenever power corrections are non-negligible is emphasized. The presence of power-suppressed ambiguities in the exponentiation kernel suggests that power corrections exponentiate as well. This leads to a non-perturbative factorization formula with non-trivial predictions on the structure of power corrections, which can be contrasted with the OPE. Two examples are discussed. The first is event-shape distributions in the two-jet region, where a wealth of precise data provides a strong motivation for the improved perturbative technique and an ideal situation to study had...
One gluon, two gluon: multigluon production via high energy evolution
International Nuclear Information System (INIS)
Kovner, Alex; Lublinsky, Michael
2006-01-01
We develop an approach for calculating the inclusive multigluon production within the JIMWLK high energy evolution. We give a formal expression of multigluon cross section in terms of a generating functional for arbitrary number of gluons n. In the dipole limit the expression simplifies dramatically. We recover the previously known results for single and double gluon inclusive cross section and generalize those for arbitrary multigluon amplitude in terms of Feynman diagramms of Pomeron - like objects coupled to external rapidity dependent field s(η). We confirm the conclusion that the AGK cutting rules in general are violated in multigluon production. However we present an argument to the effect that for doubly inclusive cross section the AGK diagramms give the leading contribution at high energy, while genuine violation only occurs for triple and higher inclusive gluon production. We discuss some general properties of our expressions and suggest a line of argument to simplify the approach further
Gluon Polarisation Measurements at COMPASS
Silva, Luís
2012-01-01
One of the missing keys in the present understanding of the spin structure of the nucleon is the contribution from the gluons: the so-called gluon polarisation. This quantity can be determined in DIS through the photon-gluon fusion process, in which two analysis methods may be used: (i) identifying open charm events or (ii) selecting events with high $p_{T}$ hadrons. The data used in the present work were collected in the COMPASS experiment, where a 160 GeV/c naturally polarised muon beam, impinging on a polarised nucleon fixed target is used. Preliminary results for the gluon polarisation from high $p_{T}$ and open charm analyses are presented. The gluon polarisation result for high $p_{T}$ hadrons is divided, for the first time, into three statistically independent measurements at LO. The result from open charm analysis is obtained at LO and NLO. In both analyses a new weighted method based on a neural network approach is used.
Non-collinear configuration for dichromatic squeezing
Energy Technology Data Exchange (ETDEWEB)
Andreoni, A.; Bondani, M. [Como Univ. (Italy). Dipt. di Scienze Chimiche Fisiche e Matematiche; Mauro D' Ariano, G.; Paris, M.G.A. [Como Univ. (Italy). Dipt. di Scienze Chimiche Fisiche e Matematiche; Quantum Optics Group, Unita INFM and Dipt. di Fisica ' Alessandro Volta' , Univ. di Pavia (Italy)
2001-02-01
We propose a non-collinear experimental scheme for the joint generation of two amplitude-squeezed beams at the frequencies {omega}{sub 1} and {omega}{sub 2}, fundamental and second harmonics of a Nd:YAG laser pulse. The scheme consists of two successive steps, both involving second-order non-linear interactions in {beta}-BaB{sub 2}O{sub 4} non-linear crystals. One of the output beams show subPoissonian photon statistics, and this allows to use photodetection instead of homodyne detection for diagnostics. (orig.)
Non-collinear configuration for dichromatic squeezing
International Nuclear Information System (INIS)
Andreoni, A.; Bondani, M.
2001-01-01
We propose a non-collinear experimental scheme for the joint generation of two amplitude-squeezed beams at the frequencies ω 1 and ω 2 , fundamental and second harmonics of a Nd:YAG laser pulse. The scheme consists of two successive steps, both involving second-order non-linear interactions in β-BaB 2 O 4 non-linear crystals. One of the output beams show subPoissonian photon statistics, and this allows to use photodetection instead of homodyne detection for diagnostics. (orig.)
Pire, B.; Szymanowski, L.
2017-12-01
We calculate at the leading order in αs the QCD amplitude for exclusive neutrino production of a D* or Ds* charmed vector meson on a nucleon. We work in the framework of the collinear QCD approach where generalized parton distributions (GPDs) factorize from perturbatively calculable coefficient functions. We include O (mc) terms in the coefficient functions and the O (mD) term in the definition of heavy meson distribution amplitudes. The show that the analysis of the angular distribution of the decay D(s) *→D(s )π allows us to access the transversity gluon GPDs.
Gluon field distribution in baryons
International Nuclear Information System (INIS)
Bissey, F.; Cao, F-G.; Kitson, A.; Lasscock, B.G.; Leinweber, D.B.; Signal, A.I.; Williams, A.G.; Zanotti, J.M.
2005-01-01
Methods for revealing the distribution of gluon fields within the three-quark static-baryon potential are presented. In particular, we outline methods for studying the sensitivity of the source on the emerging vacuum response for the three-quark system. At the same time, we explore the possibility of revealing gluon-field distributions in three-quark systems in QCD without the use of gauge-dependent smoothing techniques. Renderings of flux tubes from a preliminary high-statistics study on a 12 3 x 24 lattice are presented
The unconfined quarks and gluons
International Nuclear Information System (INIS)
Abdus Salam
1977-01-01
The consequences of the lepton-hadron gauge unification hypothesis with unconfined quarks and gluons being the hall-mark are discussed. Quark and gluon decays into leptons are shown to provide a new source of multileptonic production in NN, νN and μN collisions. A theorem is stated and proved which highlights the differences between the dynamics of gauge versus non-gauge 1 - particles. Empirical manifestations of gauge coloured mesons are discussed. The question of exact confinement or not is concluded to be in the end an empirical one and must be settled in the laboratory
Lansberg, Jean-Philippe
2016-12-27
We propose a simple and model-independent procedure to account for the impact of the nuclear modification of the gluon density as encoded in nuclear collinear PDF sets on two-to-two partonic hard processes in proton-nucleus collisions. This applies to a good approximation to quarkonium, D and B meson production, generically referred to H. Our procedure consists in parametrising the square of the parton scattering amplitude, A_{gg -> H X} and constraining it from the proton-proton data. Doing so, we have been able to compute the corresponding nuclear modification factors for J/psi, Upsilon and D^0 as a function of y and P_T at sqrt(s_NN)=5 and 8 TeV in the kinematics of the various LHC experiments in a model independent way. It is of course justified since the most important ingredient in such evaluations is the probability of each kinematical configuration. Our computations for D mesons can also be extended to B meson production. To further illustrate the potentiality of the tool, we provide --for the first t...
Collinearity, convergence and cancelling infrared divergences
International Nuclear Information System (INIS)
Lavelle, Martin; McMullan, David
2006-01-01
The Lee-Nauenberg theorem is a fundamental quantum mechanical result which provides the standard theoretical response to the problem of collinear and infrared divergences. Its argument, that the divergences due to massless charged particles can be removed by summing over degenerate states, has been successfully applied to systems with final state degeneracies such as LEP processes. If there are massless particles in both the initial and final states, as will be the case at the LHC, the theorem requires the incorporation of disconnected diagrams which produce connected interference effects at the level of the cross-section. However, this aspect of the theory has never been fully tested in the calculation of a cross-section. We show through explicit examples that in such cases the theorem introduces a divergent series of diagrams and hence fails to cancel the infrared divergences. It is also demonstrated that the widespread practice of treating soft infrared divergences by the Bloch-Nordsieck method and handling collinear divergences by the Lee-Nauenberg method is not consistent in such cases
Fragmentation of quarks and gluons
International Nuclear Information System (INIS)
Soeding, P.
1983-10-01
The author presents a review about quark and gluon jets. He describes the particle contents of the different types of jets. Finally he considers the hadronization mechanism with special regards to three-jet events in e + e - annihilation and hadronization in nuclear matter. (HSI)
1995-01-01
This is a sequel to the review volume Quark-Gluon Plasma. There are 13 articles contributed by leading investigators in the field, covering a wide range of topics about the theoretical approach to the subject. These contributions are timely reviews of nearly all the actively pursued problems, written in a pedagogical style suitable for beginners as well as experienced researchers.
Vogt, Ramona
1998-01-01
Aspects of quark-gluon plasma signatures that can be measured by CMS are discussed. First the initial conditions of the system from minijet production are introduced, including shadowing effects. Color screening of the Upsilon family is then presented, followed by energy loss effects on charm and bottom hadrons, high Pt jets and global observables.
Collinear integration affects visual search at V1.
Chow, Hiu Mei; Jingling, Li; Tseng, Chia-huei
2013-08-29
Perceptual grouping plays an indispensable role in figure-ground segregation and attention distribution. For example, a column pops out if it contains element bars orthogonal to uniformly oriented element bars. Jingling and Tseng (2013) have reported that contextual grouping in a column matters to visual search behavior: When a column is grouped into a collinear (snakelike) structure, a target positioned on it became harder to detect than on other noncollinear (ladderlike) columns. How and where perceptual grouping interferes with selective attention is still largely unknown. This article contributes to this little-studied area by asking whether collinear contour integration interacts with visual search before or after binocular fusion. We first identified that the previously mentioned search impairment occurs with a distractor of five or nine elements but not one element in a 9 × 9 search display. To pinpoint the site of this effect, we presented the search display with a short collinear bar (one element) to one eye and the extending collinear bars to the other eye, such that when properly fused, the combined binocular collinear length (nine elements) exceeded the critical length. No collinear search impairment was observed, implying that collinear information before binocular fusion shaped participants' search behavior, although contour extension from the other eye after binocular fusion enhanced the effect of collinearity on attention. Our results suggest that attention interacts with perceptual grouping as early as V1.
Gluon mass generation without seagull divergences
International Nuclear Information System (INIS)
Aguilar, Arlene C.; Papavassiliou, Joannis
2010-01-01
Dynamical gluon mass generation has been traditionally plagued with seagull divergences, and all regularization procedures proposed over the years yield finite but scheme-dependent gluon masses. In this work we show how such divergences can be eliminated completely by virtue of a characteristic identity, valid in dimensional regularization. The ability to trigger the aforementioned identity hinges crucially on the particular Ansatz employed for the three-gluon vertex entering into the Schwinger-Dyson equation governing the gluon propagator. The use of the appropriate three-gluon vertex brings about an additional advantage: one obtains two separate (but coupled) integral equations, one for the effective charge and one for the gluon mass. This system of integral equations has a unique solution, which unambiguously determines these two quantities. Most notably, the effective charge freezes in the infrared, and the gluon mass displays power-law running in the ultraviolet, in agreement with earlier considerations.
Physics of the quark - gluon plasma
International Nuclear Information System (INIS)
2001-09-01
This document gathers 31 contributions to the workshop on the physics of quark-gluon plasma that took place in Palaiseau in september 2001: 1) gamma production in heavy collisions, 2) BRAHMS, 3) experimental conference summary, 4) modelling relativistic nuclear collisions, 5) microscopic reaction dynamics at SPS and RHIC, 6) direct gamma and hard scattering at SPS, 7) soft physics at RHIC, 8) results from the STAR experiment, 9) quarkonia: experimental possibilities, 10) elliptic flow measurements with PHENIX, 11) charmonium production in p-A collisions, 12) anisotropic flow at the SPS and RHIC, 13) deciphering the space-time evolution of heavy ion collisions with correlation measurements, 14) 2-particle correlation at RHIC, 15) particle spectra at AGS, SPS and RHIC, 16) strangeness production in STAR, 17) strangeness production in Pb-Pb collisions at SPS, 18) heavy ion physics at CERN after 2000 and before LHC, 19) NEXUS guideline and theoretical consistency, 20) introduction to high p T physics at RHIC, 21) a novel quasiparticle description of the quark-gluon plasma, 22) dissociation of excited quarkonia states, 23) high-mass dimuon and B → J/Ψ production in ultrarelativistic heavy ion collisions, 24) strange hyperon production in p + p and p + Pb interactions from NA49, 25) heavy quarkonium hadron cross-section, 26) a new method of flow analysis, 27) low mass dilepton production and chiral symmetry restoration, 28) classical initial conditions for nucleus-nucleus collisions, 29) numerical calculation of quenching weights, 30) strangeness enhancement energy dependence, and 31) heavy quarkonium dissociation
Physics of the quark - gluon plasma
Energy Technology Data Exchange (ETDEWEB)
NONE
2001-09-01
This document gathers 31 contributions to the workshop on the physics of quark-gluon plasma that took place in Palaiseau in september 2001: 1) gamma production in heavy collisions, 2) BRAHMS, 3) experimental conference summary, 4) modelling relativistic nuclear collisions, 5) microscopic reaction dynamics at SPS and RHIC, 6) direct gamma and hard scattering at SPS, 7) soft physics at RHIC, 8) results from the STAR experiment, 9) quarkonia: experimental possibilities, 10) elliptic flow measurements with PHENIX, 11) charmonium production in p-A collisions, 12) anisotropic flow at the SPS and RHIC, 13) deciphering the space-time evolution of heavy ion collisions with correlation measurements, 14) 2-particle correlation at RHIC, 15) particle spectra at AGS, SPS and RHIC, 16) strangeness production in STAR, 17) strangeness production in Pb-Pb collisions at SPS, 18) heavy ion physics at CERN after 2000 and before LHC, 19) NEXUS guideline and theoretical consistency, 20) introduction to high p{sub T} physics at RHIC, 21) a novel quasiparticle description of the quark-gluon plasma, 22) dissociation of excited quarkonia states, 23) high-mass dimuon and B {yields} J/{psi} production in ultrarelativistic heavy ion collisions, 24) strange hyperon production in p + p and p + Pb interactions from NA49, 25) heavy quarkonium hadron cross-section, 26) a new method of flow analysis, 27) low mass dilepton production and chiral symmetry restoration, 28) classical initial conditions for nucleus-nucleus collisions, 29) numerical calculation of quenching weights, 30) strangeness enhancement energy dependence, and 31) heavy quarkonium dissociation.
Thermal single-gluon exchange potential for heavy quarkonium in the static limit
International Nuclear Information System (INIS)
Zhu, Jia-Qing; Ma, Zhi-Lei; Shi, Chao-Yi; Li, Yun-De
2015-01-01
The calculations of thermal single-gluon exchange potential for heavy quarkonium in Feynman and Coulomb gauges are presented, and the comparisons between them and the hard thermal loop approximation ones which were first calculated by Laine et al. are illustrated. The numerical results show that the hard thermal loop thermal single-gluon exchange potential (especially its imaginary part) which used in many researches make some errors in the practical calculations at the temperature range accessible in the present experiment, and the problem of gauge dependent cannot be avoided when the complete self energy is used in the derivation of potential
Deciphering the quark-gluon structure of the photon in electronγ collisions
International Nuclear Information System (INIS)
Eboli, O.J.P.; Gonzalez-Garcia, M.C.; Halzen, F.; Novaes, S.F.
1992-11-01
The capability of an electron γ collider to unravel the hadronic content of the photon is investigated. The experimental problem for probing the gluonic structure of the photon is that small-x triggers overwhelmingly select soft photons rather than soft gluons in hard photons. It is showed that the problem can be finessed in experiments where laser back-scattering is used to prepare a source of very hard photons. It is illustrated their power for studying the parton distribution of the photon and, specifically, for separating the quark and gluon components in events where dijets, jet-γ pairs, and heavy quark pairs are produced. (author)
Thermalization of mini-jets in a quark–gluon plasma
Energy Technology Data Exchange (ETDEWEB)
Iancu, Edmond, E-mail: edmond.iancu@cea.fr; Wu, Bin, E-mail: bin.wu.phys@gmail.com [Institut de Physique Théorique, CEA Saclay, CNRS UMR 3681, F-91191 Gif-sur-Yvette (France); Department of Physics, The Ohio State University, Columbus, OH 43210 (United States)
2016-12-15
We present the complete physical picture for the evolution of a high-energy jet propagating through a weakly-coupled quark-gluon plasma (QGP) by analytical and numerical investigation of thermalization of the soft components of the jet. Our results support the following physical picture: the leading particle emits a significant number of mini-jets which promptly evolve via multiple branching and thus degrade into a myriad of soft gluons, with energies of the order of the medium temperature T. Via elastic collisions with the medium constituents, these soft gluons relax to local thermal equilibrium with the plasma over a time scale which is considerably shorter than the typical lifetime of the mini-jet. The thermalized gluons form a tail which lags behind the hard components of the jet. Together with the background QGP, they behave hydrodynamically.
Gluon exchange in elastic hadron scattering
International Nuclear Information System (INIS)
Jenkovszky, L.L.; Paccanoni, F.; Chikovani, Z.E.
1991-01-01
It is generally accepted that the Pomeron, which determines the long-range component of the strong interaction, corresponds to exchange of gluons with the corresponding quantum numbers (the minimum number of such gluons is two). The C-odd partner of the Pomeron, the odderon, corresponds to exchange of an odd number of gluons (three or more). By means of a model of the nonperturbative gluon propagator, restrictions are obtained on the parameters of two-gluon (Pomeron) and three-gluon (odderon) exchange in hadron scattering. In the framework of this model an interpretation is proposed for the various asymptotic regimes in the behavior of the total cross section and of the differential cross section of elastic scattering at high energies
Collinear laser spectroscopy of atomic cadmium
Frömmgen, Nadja; Bissell, Mark L.; Bieroń, Jacek; Blaum, Klaus; Cheal, Bradley; Flanagan, Kieran; Fritzsche, Stephan; Geppert, Christopher; Hammen, Michael; Kowalska, Magdalena; Kreim, Kim; Krieger, Andreas; Neugart, Rainer; Neyens, Gerda; Rajabali, Mustafa M.; Nörtershäuser, Wilfried; Papuga, Jasna; Yordanov, Deyan T.
2015-01-01
Hyperfine structure $A$ and $B$ factors of the atomic $5s\\,5p\\,\\; ^3\\rm{P}_2 \\rightarrow 5s\\,6s\\,\\; ^3\\rm{S}_1$ transition are determined from collinear laser spectroscopy data of $^{107-123}$Cd and $^{111m-123m}$Cd. Nuclear magnetic moments and electric quadrupole moments are extracted using reference dipole moments and calculated electric field gradients, respectively. The hyperfine structure anomaly for isotopes with $s_{1/2}$ and $d_{5/2}$ nuclear ground states and isomeric $h_{11/2}$ states is evaluated and a linear relationship is observed for all nuclear states except $s_{1/2}$. This corresponds to the Moskowitz-Lombardi rule that was established in the mercury region of the nuclear chart but in the case of cadmium the slope is distinctively smaller than for mercury. In total four atomic and ionic levels were analyzed and all of them exhibit a similar behaviour. The electric field gradient for the atomic $5s\\,5p\\,\\; ^3\\mathrm{P}_2$ level is derived from multi-configuration Dirac-Hartree-Fock calculatio...
Collinear resonance ionization spectroscopy of radium ions
We propose to study the neutron-deficient radium isotopes with high-resolution collinear resonance ionization spectroscopy. Probing the hyperfine structure of the $7{s}\\,^2\\!{S}\\!_{1/2}\\,\\rightarrow\\,7{p}\\,^{2}\\!{P}\\!_{1/2}$ and $7{s}\\,^{2}\\!{S}\\!_{1/2}\\,\\rightarrow\\,7{p}\\,^{2}\\!{P}\\!_{3/2}$ transitions in Ra II will provide atomic-structure measurements that have not been achieved for $^{{A}<208}$Ra. Measurement of the $7{s}\\,^{2}\\!{S}\\!_{1/2}\\,\\rightarrow\\,7{p}\\,^{2}\\!{P}\\!_{3/2}$ transition in $^{{A}<214}$Ra will allow the spectroscopic quadrupole moments to be directly measured for the first time. In addition, the technique will allow tentative spin assignments to be confirmed and the magnetic dipole moments measured for $^{\\textit{A}<208}$Ra. Measurement of the hyperfine structure (in particular the isotope shifts) of the neutron-deficient radium will provide information to further constrain the nuclear models away from the N=126 shell closure.
High energy evolution of soft gluon cascades
International Nuclear Information System (INIS)
Shuvaev, A.; Wallon, S.
2006-01-01
In this paper we derive an evolution equation for the gluon density in soft gluon cascades emitted from any colored source, in the leading logarithmic approximation of perturbative QCD. We show that this equation has the same form as the BFKL equation in the forward case. An explicit expression for the total cascade wavefunction involving an arbitrary number of soft gluons is obtained. Renormalization of the colored source wavefunction turns out to be responsible for the reggeization of the source. (orig.)
High energy evolution of soft gluon cascades
Energy Technology Data Exchange (ETDEWEB)
Shuvaev, A. [St. Petersburg Nuclear Physics Institute, Gatchina, St. Petersburg district (Russian Federation); Wallon, S. [Universite Paris XI, Laboratoire de Physique Theorique, Orsay Cedex (France)
2006-04-15
In this paper we derive an evolution equation for the gluon density in soft gluon cascades emitted from any colored source, in the leading logarithmic approximation of perturbative QCD. We show that this equation has the same form as the BFKL equation in the forward case. An explicit expression for the total cascade wavefunction involving an arbitrary number of soft gluons is obtained. Renormalization of the colored source wavefunction turns out to be responsible for the reggeization of the source. (orig.)
Evidence for Hard Gluon Bremsstrahlung in a Neutrino Experiment
Energy Technology Data Exchange (ETDEWEB)
Sokoloff, Michael David [Univ. of California, Berkeley, CA (United States)
1983-06-01
The uncorrelated jet model (UJM) and the hydrodynamical model for particle production in very high energy scattering of two protons have been investigated. The differential cross-section for elastic scattering has been calculated in the UJM with Regge phase and the shrinkage of the diffraction peak has been discussed . Inclusive two-particle correlations due to energy-momentum conservation have been computed in the UJM and compared to experiment. Statistical quantities for particle production have been defined using t he analogy between the phase-space integral in particle production and the definition of the grand canonical partition function in statistical mechanics. The statistical quantities have been used in the hydrodynamical model of Landau to calculate the inclusive single particle rapidity distribution for pions and thermodynamical properties of the two colliding hadrons .
Quark ACM with topologically generated gluon mass
Choudhury, Ishita Dutta; Lahiri, Amitabha
2016-03-01
We investigate the effect of a small, gauge-invariant mass of the gluon on the anomalous chromomagnetic moment (ACM) of quarks by perturbative calculations at one-loop level. The mass of the gluon is taken to have been generated via a topological mass generation mechanism, in which the gluon acquires a mass through its interaction with an antisymmetric tensor field Bμν. For a small gluon mass ( ACM at momentum transfer q2 = -M Z2. We compare those with the ACM calculated for the gluon mass arising from a Proca mass term. We find that the ACM of up, down, strange and charm quarks vary significantly with the gluon mass, while the ACM of top and bottom quarks show negligible gluon mass dependence. The mechanism of gluon mass generation is most important for the strange quarks ACM, but not so much for the other quarks. We also show the results at q2 = -m t2. We find that the dependence on gluon mass at q2 = -m t2 is much less than at q2 = -M Z2 for all quarks.
Gluon radiation in diffractive electroproduction
International Nuclear Information System (INIS)
Buchmueller, W.; McDermott, M.F.; Hebecker, A.
1996-07-01
Order α s -correlations to the diffractive structure functions F L D and F 2 D at large Q 2 and small x are evaluated in the semiclassical approach, where the initial proton is treated as a classical colour field. The diffractive final state contains a fast gluon in addition to a quark-antiquark pair. Two of these partons may have large transverse momentum. Our calculations lead to an intuitive picture of deep-inelastic diffractive processes which is very similar to Bjorken's aligned-jet model. Both diffractive structure functions contain leading twist contributions from high-p perpendicular to jets. (orig.)
Burrows, J.; Johnson, V.; Henckel, D.
2016-01-01
Work Hard / Play Hard was a participatory performance/workshop or CPD experience hosted by interdisciplinary arts atelier WeAreCodeX, in association with AntiUniversity.org. As a socially/economically engaged arts practice, Work Hard / Play Hard challenged employees/players to get playful, or go to work. 'The game changes you, you never change the game'. Employee PLAYER A 'The faster the better.' Employer PLAYER B
Quarks and gluons in the nucleon: Proceedings. Volume 6
Energy Technology Data Exchange (ETDEWEB)
NONE
1997-12-31
The purpose of the symposium was to discuss the quark and gluon structure of the nucleon as probed experimentally by hard processes with lepton and hadron beams and studied theoretically by perturbative QCD, lattice QCD and effective models on the one hand and to stimulate research activities in the fields related to RHIC and RHIC-SPIN projects on the other hand. There were 18 talks and 2 discussion sessions. About 50, including 5 from abroad participated in the symposium. An excellent summary in the form of 5 most important transparencies and a one-page explanation is included for each of the invited talks.
Quarks and gluons in the nucleon: Proceedings. Volume 6
International Nuclear Information System (INIS)
1997-01-01
The purpose of the symposium was to discuss the quark and gluon structure of the nucleon as probed experimentally by hard processes with lepton and hadron beams and studied theoretically by perturbative QCD, lattice QCD and effective models on the one hand and to stimulate research activities in the fields related to RHIC and RHIC-SPIN projects on the other hand. There were 18 talks and 2 discussion sessions. About 50, including 5 from abroad participated in the symposium. An excellent summary in the form of 5 most important transparencies and a one-page explanation is included for each of the invited talks
A new approach to perturbative and non-perturbative dynamics: Regge intercept and the gluon spin
International Nuclear Information System (INIS)
Bishari, M.
1979-01-01
Relations connecting long distance with short distance dynamics are proposed. These relations are independent of the (apiori unknown) matching length scale, and provide interrelations among parameters characterizing soft and hard scattering processes. In particular, the observed planar Regge intercept imply an underlying field theory mediated by vector gluons. (author)
Gluon chains and multiquark hadrons
International Nuclear Information System (INIS)
Jadach, S.; Jezabek, M.
1979-01-01
A monopole approximation to the confining potential is proposed. In this approximation spatially separated groups of quarks carry a definite total colour charge. The potentials which lead to the formation of gluon chains are discussed. The generalization of a (3,3bar) chain notion, studied by Tiktopoulos, to the case of arbitrary colour charges is given. It is argued that these generalized chains may be unstable with respect to splitting into a system of weakly interacting chains of the (3,3bar) type. A unified picture of the high energy hadronic collisions, based on the gluon chain notion and the monopole approximation is proposed. In the meson-meson sector this picture is equivalent to the topological approach. For the other processes it is similar to the approach of Rossi and Veneziano. However, it is argued that the introduction of the junction line into the quark frame is superfluous. The results are expressed in the language of the coloured dual diagrams which provide a generalization of those of Harari and Rosner. (author)
Ward identities for amplitudes with reggeized gluons
International Nuclear Information System (INIS)
Bartles, J.; Vacca, G.P.
2012-05-01
Starting from the effective action of high energy QCD we derive Ward identities for Green's functions of reggeized gluons. They follow from the gauge invariance of the effective action, and allow to derive new representations of amplitudes containing physical particles as well as reggeized gluons. We explicitly demonstrate their validity for the BFKL kernel, and we present a new derivation of the kernel.
Soft gluon resummation for gluon-induced Higgs Strahlung
Energy Technology Data Exchange (ETDEWEB)
Harlander, Robert; Zirke, Tom [Fachbereich C, Bergische Universitaet Wuppertal (Germany); Kulesza, Anna; Theeuwes, Vincent [Institute for Theoretical Physics, WWU Muenster (Germany)
2015-07-01
We study the effect of soft gluon emission on the total cross section predictions for the gg → HZ associated Higgs production process at the LHC. To this end, we perform resummation of threshold corrections at the NLL accuracy in the absolute threshold production limit and in the threshold limit for production of a ZH system with a given invariant mass. Analytical results and numerical predictions for various possible LHC collision energies are presented. The perturbative stability of the results is verified by including universal NNLL effects. We find that resummation significantly reduces the scale uncertainty of the gg → HZ contribution, which is the dominant source of perturbative uncertainty to ZH production. We use our results to evaluate updated numbers for the total inclusive cross section of associated pp → ZH production at the LHC. The reduced scale uncertainty of the gg → HZ component translates into a decrease of the overall scale error by about a factor of two.
HUNTING THE QUARK GLUON PLASMA.
Energy Technology Data Exchange (ETDEWEB)
LUDLAM, T.; ARONSON, S.
2005-04-11
The U.S. Department of Energy's Relativistic Heavy Ion Collider (RHIC) construction project was completed at BNL in 1999, with the first data-taking runs in the summer of 2000. Since then the early measurements at RHIC have yielded a wealth of data, from four independent detectors, each with its international collaboration of scientists: BRAHMS, PHENIX, PHOBOS, and STAR [1]. For the first time, collisions of heavy nuclei have been carried out at colliding-beam energies that have previously been accessible only for high-energy physics experiments with collisions of ''elementary'' particles such as protons and electrons. It is at these high energies that the predictions of quantum chromodynamics (QCD), the fundamental theory that describes the role of quarks and gluons in nuclear matter, come into play, and new phenomena are sought that may illuminate our view of the basic structure of matter on the sub-atomic scale, with important implications for the origins of matter on the cosmic scale. The RHIC experiments have recorded data from collisions of gold nuclei at the highest energies ever achieved in man-made particle accelerators. These collisions, of which hundreds of millions have now been examined, result in final states of unprecedented complexity, with thousands of produced particles radiating from the nuclear collision. All four of the RHIC experiments have moved quickly to analyze these data, and have begun to understand the phenomena that unfold from the moment of collision as these particles are produced. In order to provide benchmarks of simpler interactions against which to compare the gold-gold collisions, the experiments have gathered comparable samples of data from collisions of a very light nucleus (deuterium) with gold nuclei, as well as proton-proton collisions, all with identical beam energies and experimental apparatus. The early measurements have revealed compelling evidence for the existence of a new form of nuclear
HUNTING THE QUARK GLUON PLASMA
International Nuclear Information System (INIS)
LUDLAM, T.; ARONSON, S.
2005-01-01
The U.S. Department of Energy's Relativistic Heavy Ion Collider (RHIC) construction project was completed at BNL in 1999, with the first data-taking runs in the summer of 2000. Since then the early measurements at RHIC have yielded a wealth of data, from four independent detectors, each with its international collaboration of scientists: BRAHMS, PHENIX, PHOBOS, and STAR [1]. For the first time, collisions of heavy nuclei have been carried out at colliding-beam energies that have previously been accessible only for high-energy physics experiments with collisions of ''elementary'' particles such as protons and electrons. It is at these high energies that the predictions of quantum chromodynamics (QCD), the fundamental theory that describes the role of quarks and gluons in nuclear matter, come into play, and new phenomena are sought that may illuminate our view of the basic structure of matter on the sub-atomic scale, with important implications for the origins of matter on the cosmic scale. The RHIC experiments have recorded data from collisions of gold nuclei at the highest energies ever achieved in man-made particle accelerators. These collisions, of which hundreds of millions have now been examined, result in final states of unprecedented complexity, with thousands of produced particles radiating from the nuclear collision. All four of the RHIC experiments have moved quickly to analyze these data, and have begun to understand the phenomena that unfold from the moment of collision as these particles are produced. In order to provide benchmarks of simpler interactions against which to compare the gold-gold collisions, the experiments have gathered comparable samples of data from collisions of a very light nucleus (deuterium) with gold nuclei, as well as proton-proton collisions, all with identical beam energies and experimental apparatus. The early measurements have revealed compelling evidence for the existence of a new form of nuclear matter at extremely high
Quarkonium states in an anisotropic quark-gluon plasma
Energy Technology Data Exchange (ETDEWEB)
Guo Yun
2009-09-10
In this work we study the properties of quarkonium states in a quark-gluon plasma which, due to expansion and non-zero viscosity, exhibits a local anisotropy in momentum space. We determine the hard-loop resummed gluon propagator in an anisotropic QCD plasma in general linear gauges and define a potential between heavy quarks from the Fourier transform of its static limit. This potential which arises due to one-gluon exchange describes the force between a quark and anti-quark at short distances. It is closer to the vacuum potential as compared to the isotropic Debye screened potential which indicates the reduced screening in an anisotropic QCD plasma. In addition, angular dependence appears in the potential; we find that there is stronger attraction on distance scales on the order of the inverse Debye mass for quark pairs aligned along the direction of anisotropy than for transverse alignment. The potential at long distances, however, is non-perturbative and modeled as a QCD string which is screened at the same scale as the Coulomb field. At asymptotic separation the potential energy is non-zero and inversely proportional to the temperature. With a phenomenological potential model which incorporates the different behaviors at short and long distances, we solve the three-dimensional Schroedinger equation. Our numerical results show that quarkonium binding is stronger at non-vanishing viscosity and expansion rate, and that the anisotropy leads to polarization of the P-wave states. Furthermore, we determine viscosity corrections to the imaginary part of the heavy-quark potential in the weak-coupling hard-loop approximation. The imaginary part is found to be smaller (in magnitude) than at vanishing viscosity. This implies a smaller decay width of quarkonium bound states in an anisotropic plasma. (orig.)
Quarkonium states in an anisotropic quark-gluon plasma
International Nuclear Information System (INIS)
Guo Yun
2009-01-01
In this work we study the properties of quarkonium states in a quark-gluon plasma which, due to expansion and non-zero viscosity, exhibits a local anisotropy in momentum space. We determine the hard-loop resummed gluon propagator in an anisotropic QCD plasma in general linear gauges and define a potential between heavy quarks from the Fourier transform of its static limit. This potential which arises due to one-gluon exchange describes the force between a quark and anti-quark at short distances. It is closer to the vacuum potential as compared to the isotropic Debye screened potential which indicates the reduced screening in an anisotropic QCD plasma. In addition, angular dependence appears in the potential; we find that there is stronger attraction on distance scales on the order of the inverse Debye mass for quark pairs aligned along the direction of anisotropy than for transverse alignment. The potential at long distances, however, is non-perturbative and modeled as a QCD string which is screened at the same scale as the Coulomb field. At asymptotic separation the potential energy is non-zero and inversely proportional to the temperature. With a phenomenological potential model which incorporates the different behaviors at short and long distances, we solve the three-dimensional Schroedinger equation. Our numerical results show that quarkonium binding is stronger at non-vanishing viscosity and expansion rate, and that the anisotropy leads to polarization of the P-wave states. Furthermore, we determine viscosity corrections to the imaginary part of the heavy-quark potential in the weak-coupling hard-loop approximation. The imaginary part is found to be smaller (in magnitude) than at vanishing viscosity. This implies a smaller decay width of quarkonium bound states in an anisotropic plasma. (orig.)
International Nuclear Information System (INIS)
Cipriano, P.; Dooling, S.; Grebenyuk, A.; Gunnellini, P.; Katsas, P.; Hautmann, F.; Oxford Univ.; Jung, H.; Antwerpen Univ.
2013-08-01
In the forthcoming high-luminosity phase at the LHC many of the most interesting QCD measurements so far become prohibitively difficult due to the high pile-up. We suggest a program of QCD measurements based on the observed Higgs boson which can be started now and can be carried through also in the large pile-up environment at high luminosity. It focuses on gluonic processes at high mass scales, and their distinctive QCD features compared to classic probes such as Drell-Yan. It explores the strong-interaction sector of the Standard Model both at high transverse momenta and at low transverse momenta, by investigating issues on gluon fusion processes which have never been addressed experimentally before. We discuss a few specific examples and present results of Monte Carlo simulations.
Energy Technology Data Exchange (ETDEWEB)
Cipriano, P.; Dooling, S.; Grebenyuk, A.; Gunnellini, P.; Katsas, P. [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany); Hautmann, F. [Sussex Univ., Brighton (United Kingdom). Dept. of Physics and Astronomy; Oxford Univ. (United Kingdom). Dept. of Physics; Jung, H. [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany); Antwerpen Univ. (Belgium). Elementaire Deeltjes Fysica
2013-08-15
In the forthcoming high-luminosity phase at the LHC many of the most interesting QCD measurements so far become prohibitively difficult due to the high pile-up. We suggest a program of QCD measurements based on the observed Higgs boson which can be started now and can be carried through also in the large pile-up environment at high luminosity. It focuses on gluonic processes at high mass scales, and their distinctive QCD features compared to classic probes such as Drell-Yan. It explores the strong-interaction sector of the Standard Model both at high transverse momenta and at low transverse momenta, by investigating issues on gluon fusion processes which have never been addressed experimentally before. We discuss a few specific examples and present results of Monte Carlo simulations.
Magnetic phase diagrams from non-collinear canonical band theory
DEFF Research Database (Denmark)
Shallcross, Sam; Nordstrom, L.; Sharma, S.
2007-01-01
A canonical band theory of non-collinear magnetism is developed and applied to the close packed fcc and bcc crystal structures. This is a parameter-free theory where the crystal and magnetic symmetry and exchange splitting uniquely determine the electronic bands. In this way, we are able...... hybridization, and on this basis we are able to analyze the microscopic reasons behind the occurrence of non-collinear magnetism in the elemental itinerant magnets....... to construct phase diagrams of magnetic order for the fcc and bcc lattices. Several examples of non-collinear magnetism are seen to be canonical in origin, in particular, that of gamma-Fe. In this approach, the determination of magnetic stability results solely from changes in kinetic energy due to spin...
Soft-collinear factorization and zero-bin subtractions
International Nuclear Information System (INIS)
Chiu Juiyu; Fuhrer, Andreas; Kelley, Randall; Manohar, Aneesh V.; Hoang, Andre H.
2009-01-01
We study the Sudakov form factor for a spontaneously broken gauge theory using a (new) Δ-regulator. To be well defined, the effective theory requires zero-bin subtractions for the collinear sectors. The zero-bin subtractions depend on the gauge boson mass M and are not scaleless. They have both finite and 1/ε contributions and are needed to give the correct anomalous dimension and low-scale matching contributions. We also demonstrate the necessity of zero-bin subtractions for soft-collinear factorization. We find that after zero-bin subtractions the form factor is the sum of the collinear contributions minus a soft mass-mode contribution, in agreement with a previous result of Idilbi and Mehen in QCD. This appears to conflict with the method-of-regions approach, where one gets the sum of contributions from different regions.
Constituent gluon interpretation of glueballs and gluelumps
International Nuclear Information System (INIS)
Boulanger, N.; Buisseret, F.; Mathieu, V.; Semay, C.
2008-01-01
Arguments are given that support the interpretation of the lattice QCD glueball and gluelump spectra in terms of bound states of massless constituent gluons with helicity 1. In this scheme, we show that the mass hierarchy of the currently known gluelumps and glueballs is mainly due to the number of constituent gluons and can be understood within a simple flux tube model. It is also argued that the lattice QCD 0 +- glueball should be seen as a four-gluon bound state. We finally predict the mass of the 0 - state, not yet computed in lattice QCD. (orig.)
The gluon Sivers asymmetry measurements at COMPASS
Szabelski, Adam
2018-01-01
The Sivers function describes the correlation between the transverse spin of a nucleon and the transverse motion of its partons. As such, a nonzero Sivers effect for gluons could be a signature of their nonzero orbital angular momentum inside the nucleon. COMPASS has collected data of semi-inclusive deep inelastic scattering by impinging 160 GeV/$c$ muons on transversely polarised proton and deuteron targets. The gluon Sivers asymmetry is extracted from a high-$p_T$ hadron pair sample with the use of monte carlo simulations and the a neural network approach. The results of a similar analysis for a Collins-like asymmetry for gluons will also be given.
The gluon Sivers asymmetry measurements at COMPASS
Szabelski, Adam
2017-01-01
The Sivers function describes the correlation between the transverse spin of a nucleon and the transverse motion of its partons. As such, a nonzero Sivers effect for gluons could be a signature of their nonzero orbital angular momentum inside the nucleon. COMPASS has collected data of semi-inclusive deep inelastic scattering by impinging 160 GeV/$c$ muons on transversely polarised proton and deuteron targets. The gluon Sivers asymmetry is extracted from a high-$p_T$ hadron pair sample with the use of monte carlo simulations and the a neural network approach. The results of a similar analysis for a Collins-like asymmetry for gluons will also be given.
Cancellation of soft and collinear divergences in noncommutative QED
International Nuclear Information System (INIS)
Mirza, B.; Zarei, M.
2006-01-01
In this paper, we investigate the behavior of noncommutative IR divergences and will also discuss their cancellation in the physical cross sections. The commutative IR (soft) divergences existing in the nonplanar diagrams will be examined in order to prove an all-order cancellation of these divergences using the Weinberg's method. In noncommutative QED, collinear divergences due to triple photon splitting vertex, were encountered, which are shown to be canceled out by the noncommutative version of KLN theorem. This guarantees that there is no mixing between the Collinear, soft divergences and noncommutative IR divergences
Dynamical behavior connection of the gluon distribution and the proton structure function at small x
International Nuclear Information System (INIS)
Boroun, G.R.
2014-01-01
We make a critical study of the relationship between the singlet structure function F 2 S and the gluon distribution G(x,Q 2 ) proposed in the past two decades, which is frequently used to extract the gluon distribution from the proton structure function. We show that a simple relation is not generally valid in the simplest state. We complete this relation by using a Laplace transform method and hard-pomeron behavior at LO and NLO at small x. Our study shows that this relation is dependent on the splitting functions and initial conditions at Q 2 =Q 2 0 and running coupling constant at NLO. The resulting analytic expression allows us to predict the proton structure function with respect to the gluon distributions and to compare the results with H1 data and a QCD analysis fit. Comparisons with other results are made and predictions for the proposed best approach are also provided. (orig.)
Experimental test of the flavor independence of the quark-gluon coupling constant
International Nuclear Information System (INIS)
Althoff, M.; Braunschweig, W.; Kirschfink, F.J.; Luebelsmeyer, K.; Martyn, H.U.; Rimkus, J.; Rosskamp, P.; Sander, H.G.; Schmitz, D.; Siebke, H.; Wallraff, W.; Duchovni, E.; Karshon, U.; Mikenberg, G.; Mir, R.; Revel, D.; Ronat, E.; Shapira, A.; Yekutieli, G.; Baranko, G.; Barklow, T.; Caldwell, A.; Cherney, M.; Izen, J.M.; Mermikides, M.; Rudolph, G.; Strom, D.; Takashima, M.; Venkataramania, H.; Wicklund, E.; Sau Lan Wu; Zobernig, G.; Eisenberg, Y.; Eskreys, A.; Gather, K.; Hultschig, H.; Joos, P.; Koetz, U.; Kowalski, H.; Ladage, A.; Loehr, B.; Lueke, D.; Maettig, P.; Maettig, P.; Notz, D.; Nowak, R.J.; Pyrlik, J.; Rushton, M.; Schuette, W.; Trines, D.; Wolf, G.; Xiao, C.
1984-01-01
Reconstruction of charged Dsup(*)'s produced inclusively in e + e - annhilations at c.m. energies near 34.4 GeV is accomplished in the decay modes Dsup(*+) -> D 0 π + -> K - π + π 0 π + and Dsup(*+) -> D 0 π + -> K - π + π - π + π + and their charge conjugates. Using these and previously reported Dsup(*+) -> D 0 π + -> K - π + π + and Dsup(*+) -> D 0 π + -> K - π + π + + missing π 0 channels we present evidence for hard gluon bremsstrahlung from charm quarks and show that the ratio of the quark-gluon coupling constant of charm quarks to the coupling constant obtained in the average hadronic event, αsub(s)sup(c)/αsub(s) = 1.00 +- 0.20 +- 0.20. Our result provides evidence that the quark-gluon coupling constant is independent of flavor. (orig.)
A T-matrix calculation for in-medium heavy-quark gluon scattering
International Nuclear Information System (INIS)
Huggins, K.; Rapp, R.
2012-01-01
The interactions of charm and bottom quarks in a quark-gluon plasma (QGP) are evaluated using a thermodynamic 2-body T-matrix. We specifically focus on heavy-quark (HQ) interactions with thermal gluons with an input potential motivated by lattice-QCD computations of the HQ free energy. The latter is implemented into a field-theoretic ansatz for color-Coulomb and (remnants of) confining interactions. This, in particular, enables to discuss corrections to the potential approach, specifically hard-thermal-loop corrections to the vertices, relativistic corrections deduced from pertinent Feynman diagrams, and a suitable projection on transverse thermal gluons. The resulting potentials are applied to compute scattering amplitudes in different color channels and utilized for a calculation of the corresponding HQ drag coefficient in the QGP. A factor of ∼2-3 enhancement over perturbative results is obtained, mainly driven by the resummation in the attractive color-channels.
Energy Technology Data Exchange (ETDEWEB)
Benić, Sanjin [Physics Department, Faculty of Science, University of Zagreb,Zagreb 10000 (Croatia); Department of Physics, The University of Tokyo,7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033 (Japan); Fukushima, Kenji [Department of Physics, The University of Tokyo,7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033 (Japan); Garcia-Montero, Oscar [Institut für Theoretische Physik, Universität Heidelberg,Philosophenweg 16, 69120 Heidelberg (Germany); Venugopalan, Raju [Physics Department, Brookhaven National Laboratory,Bldg. 510A, Upton, NY 11973 (United States)
2017-01-26
We compute the cross section for photons emitted from sea quarks in proton-nucleus collisions at collider energies. The computation is performed within the dilute-dense kinematics of the Color Glass Condensate (CGC) effective field theory. Albeit the result obtained is formally at next-to-leading order in the CGC power counting, it provides the dominant contribution for central rapidities. We observe that the inclusive photon cross section is proportional to all-twist Wilson line correlators in the nucleus. These correlators also appear in quark-pair production; unlike the latter, photon production is insensitive to hadronization uncertainties and therefore more sensitive to multi-parton correlations in the gluon saturation regime of QCD. We demonstrate that k{sub ⊥} and collinear factorized expressions for inclusive photon production are obtained as leading twist approximations to our result. In particular, the collinearly factorized expression is directly sensitive to the nuclear gluon distribution at small x. Other results of interest include the realization of the Low-Burnett-Kroll soft photon theorem in the CGC framework and a comparative study of how the photon amplitude is obtained in Lorenz and light-cone gauges.
Gluon saturation in a saturated environment
International Nuclear Information System (INIS)
Kopeliovich, B. Z.; Potashnikova, I. K.; Schmidt, Ivan
2011-01-01
A bootstrap equation for self-quenched gluon shadowing leads to a reduced magnitude of broadening for partons propagating through a nucleus. Saturation of small-x gluons in a nucleus, which has the form of transverse momentum broadening of projectile gluons in pA collisions in the nuclear rest frame, leads to a modification of the parton distribution functions in the beam compared with pp collisions. In nucleus-nucleus collisions all participating nucleons acquire enhanced gluon density at small x, which boosts further the saturation scale. Solution of the reciprocity equations for central collisions of two heavy nuclei demonstrate a significant, up to several times, enhancement of Q sA 2 , in AA compared with pA collisions.
Charmed quark production as a gluon probe
International Nuclear Information System (INIS)
Phillips, R.J.N.
1980-09-01
The lowest-order QCD mechanisms for producing cc or other heavy quarks depend on the gluon distributions in hadrons; hence the latter can be extracted directly from experiment. Recent results are described. (author)
International Nuclear Information System (INIS)
Koller, K.; Zerwas, P.M.; Walsh, T.F.
1978-12-01
We show how the Q 2 evolution of gluon jets can be used to provide indirect but strong evidence for the 3 gluon vertex of QCD. We propose looking for this evolution in the QantiQ → 3G → hadrons decay of successive 1 3 S 1 quarkonium states. The results apply to other processes if G jets can be isolated. (orig.) [de
The structure of the gluon propagator
Energy Technology Data Exchange (ETDEWEB)
Leinweber, D.B.; Parrinello, C.; Skullerud, J.I.; Williams, A.G
1999-03-01
The gluon propagator has been calculated for quenched QCD in the Landau gauge at {beta} = 6.0 for volumes 16{sup 3} x 48 and 32{sup 3} x 64, and at {beta} 6.2 for volume 24{sup 3} x 48. The large volume and different lattice spacings allow us to identify and minimise finite volume and finite lattice spacing artefacts. We also study the tensor structure of the gluon propagator, confirming that it obeys the lattice Landau gauge condition.
Describing gluons at zero and finite temperature
International Nuclear Information System (INIS)
Maas, A.
2010-01-01
Any description of gluons requires a well-defined gauge. This is complicated non-perturbatively by Gribov copies. A possible method-independent gauge definition to resolve this problem is presented and afterwards used to study the properties of gluons at any temperature. It is found that only chromo-electric properties reflect the phase transition. From these the gauge-invariant phase transition temperature is determined for SU(2) and SU(3) Yang-Mills theory independently. (author)
Identified particles in quark and gluon jets
Abreu, P; Adye, T; Ajinenko, I; Alekseev, G D; Alemany, R; Allport, P P; Almehed, S; Amaldi, Ugo; Amato, S; Andreazza, A; Andrieux, M L; Antilogus, P; Apel, W D; Åsman, B; Augustin, J E; Augustinus, A; Baillon, Paul; Bambade, P; Barão, F; Barbi, M S; Barbiellini, Guido; Bardin, Dimitri Yuri; Barker, G; Baroncelli, A; Bärring, O; Barrio, J A; Bartl, Walter; Bates, M J; Battaglia, Marco; Baubillier, M; Baudot, J; Becks, K H; Begalli, M; Beillière, P; Belokopytov, Yu A; Benvenuti, Alberto C; Berggren, M; Bertini, D; Bertrand, D; Besançon, M; Bianchi, F; Bigi, M; Bilenky, S M; Billoir, P; Bizouard, M A; Bloch, D; Blume, M; Bolognese, T; Bonesini, M; Bonivento, W; Booth, P S L; Bosio, C; Botner, O; Boudinov, E; Bouquet, B; Bourdarios, C; Bowcock, T J V; Bozzo, M; Branchini, P; Brand, K D; Brenke, T; Brenner, R A; Bricman, C; Brown, R C A; Brückman, P; Brunet, J M; Bugge, L; Buran, T; Burgsmüller, T; Buschmann, P; Cabrera, S; Caccia, M; Calvi, M; Camacho-Rozas, A J; Camporesi, T; Canale, V; Canepa, M; Cankocak, K; Cao, F; Carena, F; Carroll, L; Caso, Carlo; Castillo-Gimenez, M V; Cattai, A; Cavallo, F R; Chabaud, V; Charpentier, P; Chaussard, L; Checchia, P; Chelkov, G A; Chen, M; Chierici, R; Chliapnikov, P V; Chochula, P; Chorowicz, V; Chudoba, J; Cindro, V; Collins, P; Contri, R; Cortina, E; Cosme, G; Cossutti, F; Cowell, J H; Crawley, H B; Crennell, D J; Crosetti, G; Cuevas-Maestro, J; Czellar, S; Dahl-Jensen, Erik; Dahm, J; D'Almagne, B; Dam, M; Damgaard, G; Dauncey, P D; Davenport, Martyn; Da Silva, W; Defoix, C; Deghorain, A; Della Ricca, G; Delpierre, P A; Demaria, N; De Angelis, A; de Boer, Wim; De Brabandere, S; De Clercq, C; La Vaissière, C de; De Lotto, B; De Min, A; De Paula, L S; De Saint-Jean, C; Dijkstra, H; Di Ciaccio, Lucia; Di Diodato, A; Djama, F; Djannati, A; Dolbeau, J; Doroba, K; Dracos, M; Drees, J; Drees, K A; Dris, M; Durand, J D; Edsall, D M; Ehret, R; Eigen, G; Ekelöf, T J C; Ekspong, Gösta; Elsing, M; Engel, J P; Erzen, B; Espirito-Santo, M C; Falk, E; Fassouliotis, D; Feindt, Michael; Ferrer, A; Fichet, S; Filippas-Tassos, A; Firestone, A; Fischer, P A; Föth, H; Fokitis, E; Fontanelli, F; Formenti, F; Franek, B J; Frenkiel, P; Fries, D E C; Frodesen, A G; Frühwirth, R; Fulda-Quenzer, F; Fuster, J A; Galloni, A; Gamba, D; Gandelman, M; García, C; García, J; Gaspar, C; Gasparini, U; Gavillet, P; Gazis, E N; Gelé, D; Gerber, J P; Gerdyukov, L N; Gokieli, R; Golob, B; Gopal, Gian P; Gorn, L; Górski, M; Guz, Yu; Gracco, Valerio; Graziani, E; Green, C; Grefrath, A; Gris, P; Grosdidier, G; Grzelak, K; Gumenyuk, S A; Gunnarsson, P; Günther, M; Guy, J; Hahn, F; Hahn, S; Hajduk, Z; Hallgren, A; Hamacher, K; Harris, F J; Hedberg, V; Henriques, R P; Hernández, J J; Herquet, P; Herr, H; Hessing, T L; Heuser, J M; Higón, E; Hilke, Hans Jürgen; Hill, T S; Holmgren, S O; Holt, P J; Holthuizen, D J; Hoorelbeke, S; Houlden, M A; Hrubec, Josef; Huet, K; Hultqvist, K; Jackson, J N; Jacobsson, R; Jalocha, P; Janik, R; Jarlskog, C; Jarlskog, G; Jarry, P; Jean-Marie, B; Johansson, E K; Jönsson, L B; Jönsson, P E; Joram, Christian; Juillot, P; Kaiser, M; Kapusta, F; Karafasoulis, K; Karlsson, M; Karvelas, E; Katargin, A; Katsanevas, S; Katsoufis, E C; Keränen, R; Khokhlov, Yu A; Khomenko, B A; Khovanskii, N N; King, B J; Kjaer, N J; Klapp, O; Klein, H; Klovning, A; Kluit, P M; Köne, B; Kokkinias, P; Koratzinos, M; Korcyl, K; Kostyukhin, V; Kourkoumelis, C; Kuznetsov, O; Krammer, Manfred; Kreuter, C; Kronkvist, I J; Krumshtein, Z; Krupinski, W; Kubinec, P; Kucewicz, W; Kurvinen, K L; Lacasta, C; Laktineh, I; Lamsa, J; Lanceri, L; Lane, D W; Langefeld, P; Lapin, V; Laugier, J P; Lauhakangas, R; Leder, Gerhard; Ledroit, F; Lefébure, V; Legan, C K; Leitner, R; Lemonne, J; Lenzen, Georg; Lepeltier, V; Lesiak, T; Libby, J; Liko, D; Lindner, R; Lipniacka, A; Lippi, I; Lörstad, B; Loken, J G; López, J M; Loukas, D; Lutz, P; Lyons, L; MacNaughton, J N; Maehlum, G; Mahon, J R; Malmgren, T G M; Malychev, V; Mandl, F; Marco, J; Marco, R P; Maréchal, B; Margoni, M; Marin, J C; Mariotti, C; Markou, A; Martínez-Rivero, C; Martínez-Vidal, F; Martí i García, S; Masik, J; Matorras, F; Matteuzzi, C; Matthiae, Giorgio; Mazzucato, M; McCubbin, M L; McKay, R; McNulty, R; Medbo, J; Merk, M; Meroni, C; Meyer, S; Meyer, W T; Michelotto, M; Migliore, E; Mirabito, L; Mitaroff, Winfried A; Mjörnmark, U; Moa, T; Møller, R; Mönig, K; Monge, M R; Morettini, P; Müller, H; Münich, K; Mulders, M; Mundim, L M; Murray, W J; Muryn, B; Myatt, Gerald; Naraghi, F; Navarria, Francesco Luigi; Navas, S; Nawrocki, K; Negri, P; Neumann, W; Neumeister, N; Nicolaidou, R; Nielsen, B S; Nieuwenhuizen, M; Nikolaenko, V; Niss, P; Nomerotski, A; Normand, Ainsley; Novák, M; Oberschulte-Beckmann, W; Obraztsov, V F; Olshevskii, A G; Onofre, A; Orava, Risto; Österberg, K; Ouraou, A; Paganini, P; Paganoni, M; Pagès, P; Pain, R; Palka, H; Papadopoulou, T D; Papageorgiou, K; Pape, L; Parkes, C; Parodi, F; Passeri, A; Pegoraro, M; Peralta, L; Pernicka, Manfred; Perrotta, A; Petridou, C; Petrolini, A; Petrovykh, M; Phillips, H T; Piana, G; Pierre, F; Pimenta, M; Podobnik, T; Podobrin, O; Pol, M E; Polok, G; Poropat, P; Pozdnyakov, V; Privitera, P; Pukhaeva, N; Pullia, Antonio; Radojicic, D; Ragazzi, S; Rahmani, H; Rames, J; Ratoff, P N; Read, A L; Reale, M; Rebecchi, P; Redaelli, N G; Regler, Meinhard; Reid, D; Reinhardt, R; Renton, P B; Resvanis, L K; Richard, F; Richardson, J; Rídky, J; Rinaudo, G; Ripp, I; Romero, A; Roncagliolo, I; Ronchese, P; Roos, L; Rosenberg, E I; Roudeau, Patrick; Rovelli, T; Rückstuhl, W; Ruhlmann-Kleider, V; Ruiz, A; Rybicki, K; Rybin, A; Saarikko, H; Sacquin, Yu; Sadovskii, A; Sahr, O; Sajot, G; Salt, J; Sánchez, J; Sannino, M; Schimmelpfennig, M; Schneider, H; Schwickerath, U; Schyns, M A E; Sciolla, G; Scuri, F; Seager, P; Sedykh, Yu; Segar, A M; Seitz, A; Sekulin, R L; Serbelloni, L; Shellard, R C; Siegrist, P; Silvestre, R; Simonetti, S; Simonetto, F; Sissakian, A N; Sitár, B; Skaali, T B; Smadja, G; Smirnov, N; Smirnova, O G; Smith, G R; Sosnowski, R; Souza-Santos, D; Spassoff, Tz; Spiriti, E; Sponholz, P; Squarcia, S; Stampfer, D; Stanescu, C; Stanic, S; Stapnes, Steinar; Stavitski, I; Stevenson, K; Stocchi, A; Strauss, J; Strub, R; Stugu, B; Szczekowski, M; Szeptycka, M; Tabarelli de Fatis, T; Tavernet, J P; Chikilev, O G; Thomas, J; Tilquin, A; Timmermans, J; Tkatchev, L G; Todorov, T; Todorova, S; Toet, D Z; Tomaradze, A G; Tomé, B; Tonazzo, A; Tortora, L; Tranströmer, G; Treille, D; Tristram, G; Trombini, A; Troncon, C; Tsirou, A L; Turluer, M L; Tyapkin, I A; Tyndel, M; Tzamarias, S; Überschär, B; Ullaland, O; Uvarov, V; Valenti, G; Vallazza, E; Van der Velde, C; van Apeldoorn, G W; van Dam, P; Van Doninck, W K; Van Eldik, J; Van Lysebetten, A; Vassilopoulos, N; Vegni, G; Ventura, L; Venus, W A; Verbeure, F; Verlato, M; Vertogradov, L S; Vilanova, D; Vincent, P; Vitale, L; Vlasov, E; Vodopyanov, A S; Vrba, V; Wahlen, H; Walck, C; Weierstall, M; Weilhammer, Peter; Weiser, C; Wetherell, Alan M; Wicke, D; Wickens, J H; Wielers, M; Wilkinson, G R; Williams, W S C; Winter, M; Witek, M; Wlodek, T; Woschnagg, K; Yip, K; Yushchenko, O P; Zach, F; Zaitsev, A; Zalewska-Bak, A; Zalewski, Piotr; Zavrtanik, D; Zevgolatakos, E; Zimin, N I; Zito, M; Zontar, D; Zucchelli, G C; Zumerle, G
1997-01-01
A sample of about 1.4 million hadronic \\z decays, selected among the data recorded by the DELPHI detector at LEP during 1994, was used to measure for the first time the momentum spectra of \\kp, \\ko, \\p, \\l and their antiparticles in gluon and quark jets. As observed for inclusive charged particles, the production spectra of identified particles were found to be softer in gluon jets than in quark jets, with a higher total multiplicity.
Hard electronics; Hard electronics
Energy Technology Data Exchange (ETDEWEB)
NONE
1997-03-01
Hard material technologies were surveyed to establish the hard electronic technology which offers superior characteristics under hard operational or environmental conditions as compared with conventional Si devices. The following technologies were separately surveyed: (1) The device and integration technologies of wide gap hard semiconductors such as SiC, diamond and nitride, (2) The technology of hard semiconductor devices for vacuum micro- electronics technology, and (3) The technology of hard new material devices for oxides. The formation technology of oxide thin films made remarkable progress after discovery of oxide superconductor materials, resulting in development of an atomic layer growth method and mist deposition method. This leading research is expected to solve such issues difficult to be easily realized by current Si technology as high-power, high-frequency and low-loss devices in power electronics, high temperature-proof and radiation-proof devices in ultimate electronics, and high-speed and dense- integrated devices in information electronics. 432 refs., 136 figs., 15 tabs.
First measurement of the Sivers asymmetry for gluons using SIDIS data
Directory of Open Access Journals (Sweden)
C. Adolph
2017-09-01
Full Text Available The Sivers function describes the correlation between the transverse spin of a nucleon and the transverse motion of its partons. For quarks, it was studied in previous measurements of the azimuthal asymmetry of hadrons produced in semi-inclusive deep inelastic scattering of leptons off transversely polarised nucleon targets, and it was found to be non-zero. In this letter the evaluation of the Sivers asymmetry for gluons is presented. The contribution of the photon–gluon fusion subprocess is enhanced by requiring two high transverse-momentum hadrons. The analysis method is based on a Monte Carlo simulation that includes three hard processes: photon–gluon fusion, QCD Compton scattering and the leading-order virtual-photon absorption process. The Sivers asymmetries of the three processes are simultaneously extracted using the LEPTO event generator and a neural network approach. The method is applied to samples of events containing at least two hadrons with large transverse momentum from the COMPASS data taken with a 160 GeV/c muon beam scattered off transversely polarised deuterons and protons. With a significance of about two standard deviations, a negative value is obtained for the gluon Sivers asymmetry. The result of a similar analysis for a Collins-like asymmetry for gluons is consistent with zero.
Schmidt decomposition for non-collinear biphoton angular wave functions
International Nuclear Information System (INIS)
Fedorov, M V
2015-01-01
Schmidt modes of non-collinear biphoton angular wave functions are found analytically. The experimentally realizable procedure for their separation is described. Parameters of the Schmidt decomposition are used to evaluate the degree of the biphoton's angular entanglement. (paper)
Implicit collinearity effect in linear regression: Application to basal ...
African Journals Online (AJOL)
Collinearity of predictor variables is a severe problem in the least square regression analysis. It contributes to the instability of regression coefficients and leads to a wrong prediction accuracy. Despite these problems, studies are conducted with a large number of observed and derived variables linked with a response ...
The gluon structure of hadrons and nuclei from lattice QCD
Energy Technology Data Exchange (ETDEWEB)
Shanahan, Phiala A. [College of William and Mary, Williamsburg, VA (United States); Thomas Jefferson National Accelerator Facility (TJNAF), Newport News, VA (United States); Massachusetts Inst. of Technology (MIT), Cambridge, MA (United States)
2018-04-01
I discuss recent lattice QCD studies of the gluon structure of hadrons and light nuclei. After very briefly highlighting new determinations of the gluon contributions to the nucleon's momentum and spin, presented by several collaborations over the last year, I describe first calculations of gluon generalised form factors. The generalised transversity gluon distributions are of particular interest since they are purely gluonic; they do not mix with quark distributions at leading twist. In light nuclei they moreover provide a clean signature of non-nucleonic gluon degrees of freedom, and I present the first evidence for such effects, based on lattice QCD calculations. The planned Electron-Ion Collider, designed to access gluon structure quantities, will have the capability to test this prediction, and measure a range of gluon observables including generalised gluon distributions and transverse momentum dependent gluon distributions, within the next decade.
The gluon structure of hadrons and nuclei from lattice QCD
Shanahan, Phiala
2018-03-01
I discuss recent lattice QCD studies of the gluon structure of hadrons and light nuclei. After very briefly highlighting new determinations of the gluon contributions to the nucleon's momentum and spin, presented by several collaborations over the last year, I describe first calculations of gluon generalised form factors. The generalised transversity gluon distributions are of particular interest since they are purely gluonic; they do not mix with quark distributions at leading twist. In light nuclei they moreover provide a clean signature of non-nucleonic gluon degrees of freedom, and I present the first evidence for such effects, based on lattice QCD calculations. The planned Electron-Ion Collider, designed to access gluon structure quantities, will have the capability to test this prediction, and measure a range of gluon observables including generalised gluon distributions and transverse momentum dependent gluon distributions, within the next decade.
Gluon quasidistribution function at one loop
Energy Technology Data Exchange (ETDEWEB)
Wang, Wei; Zhao, Shuai [Shanghai Jiao Tong University, INPAC, Shanghai Key Laboratory for Particle Physics and Cosmology, School of Physics and Astronomy, Shanghai (China); Zhu, Ruilin [Shanghai Jiao Tong University, INPAC, Shanghai Key Laboratory for Particle Physics and Cosmology, School of Physics and Astronomy, Shanghai (China); Nanjing Normal University, Department of Physics and Institute of Theoretical Physics, Nanjing, Jiangsu (China)
2018-02-15
We study the unpolarized gluon quasidistribution function in the nucleon at one loop level in the large momentum effective theory. For the quark quasidistribution, power law ultraviolet divergences arise in the cut-off scheme and an important observation is that they all are subjected to Wilson lines. However for the gluon quasidistribution function, we first point out that the linear ultraviolet divergences also exist in the real diagram which is not connected to any Wilson line. We then study the one loop corrections to parton distribution functions in both cut-off scheme and dimensional regularization to deal with the ultraviolet divergences. In addition to the ordinary quark and gluon distributions, we also include the quark to gluon and gluon to quark splitting diagrams. The complete one-loop matching factors between the quasi and light cone parton distribution functions are presented in the cut-off scheme. We derive the P{sup z} evolution equation for quasi parton distribution functions, and find that the P{sup z} evolution kernels are identical to the DGLAP evolution kernels. (orig.)
A Study of Effects of MultiCollinearity in the Multivariable Analysis.
Yoo, Wonsuk; Mayberry, Robert; Bae, Sejong; Singh, Karan; Peter He, Qinghua; Lillard, James W
2014-10-01
A multivariable analysis is the most popular approach when investigating associations between risk factors and disease. However, efficiency of multivariable analysis highly depends on correlation structure among predictive variables. When the covariates in the model are not independent one another, collinearity/multicollinearity problems arise in the analysis, which leads to biased estimation. This work aims to perform a simulation study with various scenarios of different collinearity structures to investigate the effects of collinearity under various correlation structures amongst predictive and explanatory variables and to compare these results with existing guidelines to decide harmful collinearity. Three correlation scenarios among predictor variables are considered: (1) bivariate collinear structure as the most simple collinearity case, (2) multivariate collinear structure where an explanatory variable is correlated with two other covariates, (3) a more realistic scenario when an independent variable can be expressed by various functions including the other variables.
Surface emission of quark gluon plasma at RHIC and LHC
International Nuclear Information System (INIS)
Xiang Wenchang; Wan Renzhou; Zhou Daicui
2008-01-01
Within the framework of a factorization model, we study the behaviour of nuclear modification factor in Au-Au collisions at RHIC and Pb-Pb collisions at LHC. We find that the nuclear modification factor is inversely proportional to the radius of the quark-gluon plasma and is dominated by the surface emission of hard jets. We predict the nuclear modification factor P AALHS ∼0.15 in central Pb-Pb collisions at LHC. The study shows that the factorization model can be used to describe the centrality dependence of nuclear modification factor of the high transverse momentum particles produced in heavy ion collisions at both RHIC and LHC. (authors)
Spectator interactions in soft-collinear effective theory
International Nuclear Information System (INIS)
Hill, Richard J.; Neubert, Matthias
2003-01-01
Soft-collinear effective theory is generalized to include soft massless quarks in addition to collinear fields. This extension is necessary for the treatment of interactions with the soft spectator quark in a heavy meson. The power counting of the relevant fields and the construction of the effective Lagrangian are discussed at leading order in Λ/m b . Several novel effects occur in the matching of full-theory amplitudes onto effective-theory operators containing soft light quarks, such as the appearance of an intermediate mass scale and large non-localities of operators on scales of order 1/Λ. Important examples of effective-theory operators with soft light quarks are studied and their renormalization properties explored. The formalism presented here forms the basis for a systematic analysis of factorization and power corrections for any exclusive B-meson decay into light particles
Spectator Interactions in Soft-Collinear Effective Theory
International Nuclear Information System (INIS)
Hill, Richard J
2002-01-01
Soft-collinear effective theory is generalized to include soft massless quarks in addition to collinear fields. This extension is necessary for the treatment of interactions with the soft spectator quark in a heavy meson. The power counting of the relevant fields and the construction of the effective Lagrangian are discussed at leading order in Λ/m b . Several novel effects occur in the matching of full-theory amplitudes onto effective-theory operators containing soft light quarks, such as the appearance of an intermediate mass scale and large non-localities of operators on scales of order 1/Λ. Important examples of effective-theory operators with soft light quarks are studied and their renormalization properties explored. The formalism presented here forms the basis for a systematic analysis of factorization and power corrections for any exclusive B-meson decay into light particles
Gluon Bremsstrahlung in Weakly-Coupled Plasmas
International Nuclear Information System (INIS)
Arnold, Peter
2009-01-01
I report on some theoretical progress concerning the calculation of gluon bremsstrahlung for very high energy particles crossing a weakly-coupled quark-gluon plasma. (i) I advertise that two of the several formalisms used to study this problem, the BDMPS-Zakharov formalism and the AMY formalism (the latter used only for infinite, uniform media), can be made equivalent when appropriately formulated. (ii) A standard technique to simplify calculations is to expand in inverse powers of logarithms ln(E/T). I give an example where such expansions are found to work well for ω/T≥10 where ω is the bremsstrahlung gluon energy. (iii) Finally, I report on perturbative calculations of q.
Gluon bremsstrahlung and elastic scattering of hadrons
International Nuclear Information System (INIS)
Povh, B.
2001-01-01
The differential and the total cross sections in high energy hadron-proton interactions give a beautiful insight in the low Q 2 structure of the nucleon. The cross section is composed of two parts: a large energy independent part corresponding to the interaction of the valence quark with the target without gluon radiation and an energy dependent part caused by gluon bremsstrahlung. The gluons are located at small transverse distances of about 0.3 fm from the valence quarks. The model with two scales, the size of the hadron (R 2 ∼ 1 fm 2 ) and the size of the gluonic cloud (r 0 2 ∼ 0.1 fm 2 ), correctly predicts the total and the differential cross sections and the behaviour of diffractive dissociation in hadronic and deep inelastic events. (orig.)
Constituent gluons and the static quark potential
Energy Technology Data Exchange (ETDEWEB)
Greensite, Jeff [San Francisco State Univ., CA (United States); Szczepaniak, Adam P. [Indiana Univ., Bloomington, IN (United States); Thomas Jefferson National Accelerator Facility (TJNAF), Newport News, VA (United States)
2016-04-01
We suggest that Hamiltonian matrix elements between physical states in QCD might be approximated, in Coulomb gauge, by "lattice-improved" tree diagrams; i.e. tree diagram contributions with dressed ghost, transverse gluon, and Coulomb propagators obtained from lattice simulations. Such matrix elements can be applied to a variational treatment of hadronic states which include constituent gluons. As an illustration and first application of this hybrid approach, we derive a variational estimate of the heavy quark potential for distances up to 2.5 fm. The Coulomb string tension in SU(3) gauge theory is about a factor of four times greater than the asymptotic string tension. In our variational approach, using for simplicity a single variational parameter, we can reduce this overshoot by nearly the factor required. The building blocks of our approach are Coulomb gauge propagators, and in this connection we present new lattice results for the ghost and transverse gluon propagators in position space.
Quark vs Gluon Jet Tagging at ATLAS
Rubbo, Francesco; The ATLAS collaboration
2017-01-01
Distinguishing quark-initiated from gluon-initiated jets is useful for many measurements and searches at the LHC. We present a quark-initiated versus gluon-initiated jet tagger from the ATLAS experiment using the number of reconstructed charged particles inside the jet. The measurement of the charged-particle multiplicity inside jets from Run 1 is used to derive uncertainties on the tagger performance for Run 2. With an efficiency of 60% to select quark-initiated jets, the efficiency to select gluon-initiated jets is between 10 and 20% across a wide range in jet pT up to 1.5 TeV with about an absolute 5% systematic uncertainty on the efficiencies. In addition, we also present preliminary studies on a tagger for the ATLAS experiment using the full radiation pattern inside a jet processed as images in deep neural network classifiers.
Phenomenological aspects of an anisotropic quark-gluon plasma
International Nuclear Information System (INIS)
Martinez Guerrero, Mauricio
2010-01-01
In this work we investigate phenomenological aspects of an anisotropic quark-gluon plasma. In the first part of this thesis, we formulate phenomenologicalmodels that take into account the momentumspace anisotropy of the system developed during the expansion of the fireball at early-times. By including the proper-time dependence of the parton hard momentum scale, p hard (τ), and the plasma anisotropy parameter, ξ(τ), the proposed models allow us to interpolate from 0+1 pre-equilibrated expansion at early-times to 0+1 ideal hydrodynamics at late times. We study dilepton production as a valuable observable to experimentally determine the isotropization time of the system as well as the degree of anisotropy developed at early-times. We generalize our interpolating models to include the rapidity dependence of p hard and consider its impact on forward dileptons. Next, we discuss how to constrain the onset of hydrodynamics by demanding two requirements of the solutions to the equations of motion of viscous hydrodynamics. We show this explicitly for 0+1 dimensional 2nd-order conformal viscous hydrodynamics and find that the initial conditions are non-trivially constrained. Finally, we demonstrate how to match the initial conditions for 0+1 dimensional viscous hydrodynamics from pre-equilibrated expansion. We analyze the dependence of the entropy production on the pre-equilibrium phase and discuss limitations of the standard definitions of the non-equilibrium entropy in kinetic theory. (orig.)
Phenomenological aspects of an anisotropic quark-gluon plasma
Energy Technology Data Exchange (ETDEWEB)
Martinez Guerrero, Mauricio
2010-04-30
In this work we investigate phenomenological aspects of an anisotropic quark-gluon plasma. In the first part of this thesis, we formulate phenomenologicalmodels that take into account the momentumspace anisotropy of the system developed during the expansion of the fireball at early-times. By including the proper-time dependence of the parton hard momentum scale, p{sub hard}({tau}), and the plasma anisotropy parameter, {xi}({tau}), the proposed models allow us to interpolate from 0+1 pre-equilibrated expansion at early-times to 0+1 ideal hydrodynamics at late times. We study dilepton production as a valuable observable to experimentally determine the isotropization time of the system as well as the degree of anisotropy developed at early-times. We generalize our interpolating models to include the rapidity dependence of p{sub hard} and consider its impact on forward dileptons. Next, we discuss how to constrain the onset of hydrodynamics by demanding two requirements of the solutions to the equations of motion of viscous hydrodynamics. We show this explicitly for 0+1 dimensional 2nd-order conformal viscous hydrodynamics and find that the initial conditions are non-trivially constrained. Finally, we demonstrate how to match the initial conditions for 0+1 dimensional viscous hydrodynamics from pre-equilibrated expansion. We analyze the dependence of the entropy production on the pre-equilibrium phase and discuss limitations of the standard definitions of the non-equilibrium entropy in kinetic theory. (orig.)
Energy Technology Data Exchange (ETDEWEB)
Goncalves, V.P. [Lund University, Department of Astronomy and Theoretical Physics, Lund (Sweden); Universidade Federal de Pelotas, Instituto de Fisica e Matematica, Pelotas, RS (Brazil); Martins, L.A.S.; Sauter, W.K. [Universidade Federal de Pelotas, Instituto de Fisica e Matematica, Pelotas, RS (Brazil)
2016-02-15
The current uncertainty on the gluon density extracted from the global parton analysis is large in the kinematical range of small values of the Bjorken-x variable and low values of the hard scale Q{sup 2}. An alternative to reduces this uncertainty is the analysis of the exclusive vector meson photoproduction in photon-hadron and hadron-hadron collisions. This process offers a unique opportunity to constrain the gluon density of the proton, since its cross section is proportional to the gluon density squared. In this paper we consider current parametrisations for the gluon distribution and estimate the exclusive vector meson photoproduction cross section at HERA and LHC using the leading logarithmic formalism. We perform a fit of the normalisation of the γh cross section and the value of the hard scale for the process and demonstrate that the current LHCb experimental data are better described by models that assume a slow increasing of the gluon distribution at small x and low Q{sup 2}. (orig.)
Gluon fragmentation in T(1S) decays
International Nuclear Information System (INIS)
Bienlein, J.K.
1983-05-01
In T(1S) decays most observables (sphericity, charged multiplicity, photonic energy fraction, inclusive spectra) can be understood assuming that gluons fragment like quarks. New results from LENA use the (axis-independent) Fox-Wolfram moments for the photonic energy deposition. Continuum reactions show 'standard' Field-Feynman fragmentation. T(1S) decays show a significant difference in the photonic energy topology. It is more isotropic than with the Field-Feynman fragmentation scheme. Gluon fragmentation into isoscalar mesons (a la Peterson and Walsh) is excluded. But if one forces the leading particle to be isoscalar, one gets good agreement with the data. (orig.)
Effects of gluon radiation in hadronic collisions
International Nuclear Information System (INIS)
Gustafson, Goesta.
1989-10-01
In this talk I discuss effects of gluon emission in soft collisions, the so-called 'soft radiation' in the Fritjof model. It is seen e.g. that the pT in the fragmentation regions, the seagull effect, increases with energy in fair agreement with experiments. I also discuss the content of strange and heavier quarks in high-pT gluon jets. Within the dipole scheme for QCD cascades on finds a larger production of heavier quarks than in previous approaches. Qualitative agreement with data is obtained for the K/π ratio and D meson production
Quark-gluon plasma, and strangeness
International Nuclear Information System (INIS)
Rafelski, Johann; Letessier, Jean
2002-01-01
In order to recognize the new form of matter created at RHIC and SPS as the deconfined quark-gluon plasma state (QGP), we need to understand the expected properties of this phase near to the conditions of its formation and disintegration. Thus, we first develop a model of QGP considering the constrains arising from QCD properties and lattice results, and explore its properties. In the second part, we describe the kinetic theory of strangeness production in the QGP phase. We show that gluon fusion dominate and evaluate the degree of equilibration expected at RHIC
Gluon amplitudes as 2 d conformal correlators
Pasterski, Sabrina; Shao, Shu-Heng; Strominger, Andrew
2017-10-01
Recently, spin-one wave functions in four dimensions that are conformal primaries of the Lorentz group S L (2 ,C ) were constructed. We compute low-point, tree-level gluon scattering amplitudes in the space of these conformal primary wave functions. The answers have the same conformal covariance as correlators of spin-one primaries in a 2 d CFT. The Britto-Cachazo-Feng-Witten (BCFW) recursion relation between three- and four-point gluon amplitudes is recast into this conformal basis.
High energy multi-gluon exchange amplitudes
International Nuclear Information System (INIS)
Jaroszewicz, T.
1980-11-01
We examine perturbative high energy n-gluon exchange amplitudes calculated in the Coulomb gauge. If n exceeds the minimum required by the t-channel quantum numbers, such amplitudes are non-leading in lns. We derive a closed system of coupled integral equations for the corresponding two-particle n-gluon vertices, obtained by summing the leading powers of ln(N μ psup(μ)), where psup(μ) is the incident momentum and Nsup(μ) the gauge-defining vector. Our equations are infra-red finite, provided the external particles are colour singlets. (author)
Attempt at phenomenological allowance for confinement in quark-gluon jets
International Nuclear Information System (INIS)
Dremin, I.M.; Leonidov, A.V.
1982-01-01
A study is made of a system of modified equations for the evolution of hard jets, in which terms are introduced to take into account phenomenologically the confinement of quarks and gluons. The mean multiplicity of hard partons in a jet and the energy carried by them are calculated. It is shown that in the initial stage of development of a jet these characteristics agree with those calculated on the basis of the ordinary evolution equations with a definite cutoff in the parton energy
Squeezed colour states in gluon jet
Kilin, S. YA.; Kuvshinov, V. I.; Firago, S. A.
1993-01-01
The possibility of the formation of squeezed states of gluon fields in quantum chromodynamics due to nonlinear nonperturbative self interaction during jet evolution in the process of e(+)e(-) annihilation into hadrons, which are analogous to the quantum photon squeezed states in quantum electrodynamics, is demonstrated. Additionally, the squeezing parameters are calculated.
Gluon gas viscosity in nonperturbative region
International Nuclear Information System (INIS)
Il'in, S.V.; Mogilevskij, O.A.; Smolyanskij, S.A.; Zinov'ev, G.M.
1992-01-01
Using the Green-Kubo-type formulae and the cutoff model motivated by Monte Carlo lattice gluodynamics simulations we find the temperature behaviour of shear viscosity of gluon gas in the region of deconfinement phase transition. 22 refs.; 1 fig. (author)
Phenomenology of gluon TMDs at NNLL
Garcia, M.
2015-01-01
All the leading-Twist (un)polarized gluon transverse momentum dependent parton distribution functions have the same evolution, once they are properly defined in order to cancel spurious rapidity divergences. Currently known perturbative ingredients can be used to resum large logarithms up to
Electromagnetic signals of quark gluon plasma
Indian Academy of Sciences (India)
Successive equilibration of quark degrees of freedom and its effects on electromagnetic signals of quark gluon plasma are discussed. The effects of the variation of vector meson masses and decay widths on photon production from hot strongly interacting matter formed after Pb + Pb and S + Au collisions at CERN SPS ...
Inflating metastable quark-gluon plasma universe
International Nuclear Information System (INIS)
Jenkovszky, L.L.; Kaempfer, B.; Sysoev, V.M.
1990-01-01
We show within the Friedmann model with the equation of state p(T)=aT 4 -AT that our universe has expanded exponentially when it was in a metastable quark-gluon plasma state. The scale factor during that epoch increased by many orders of magnitude. 13 refs.; 5 figs
Bosonization with inclusion of the gluon condensate
International Nuclear Information System (INIS)
Ebert, D.; Volkov, M.K.
1994-01-01
The effects of the gluon condensate on the quark condensate and on masses and coupling constants of composite mesons are discussed within a QCD-motivated Nambu-Jona-Lasinio model for zero temperature as well as for the case of finite temperature and baryon number density. (orig.)
Quark-gluon plasma (Selected Topics)
International Nuclear Information System (INIS)
Zakharov, V. I.
2012-01-01
Introductory lectures to the theory of (strongly interacting) quark-gluon plasma given at the Winter School of Physics of ITEP (Moscow, February 2010). We emphasize theoretical issues highlighted by the discovery of the low viscosity of the plasma. The topics include relativistic hydrodynamics, manifestations of chiral anomaly in hydrodynamics, superfluidity, relativistic superfluid hydrodynamics, effective stringy scalars, holographic models of Yang-Mills theories.
Polarized photons from quark-gluon plasma
International Nuclear Information System (INIS)
Goloviznin, V.V.; Snigirev, A.M.; Zinov'ev, G.M.
1988-01-01
The degree of polarization of magnetic bremsstrahlung radiation resulting from the interaction of escaping quarks with a collective confining color field is calculated. For a wide rapidity interval the angle at which the photon is registered and constitutes about 25%. This could signal about quark-gluon plasma formation
Exploring Quarks, Gluons and the Higgs Boson
Johansson, K. Erik
2013-01-01
With real particle collision data available on the web, the amazing dynamics of the fundamental particles of the standard model can be explored in classrooms. Complementing the events from the ATLAS experiment with animations of the fundamental processes on the quark and gluon level makes it possible to better understand the invisible world of…
Searching for the quarks and gluons plasma
International Nuclear Information System (INIS)
Gerschel, C.; Kluberg, L.
1989-01-01
Some investigations involving quark matter, at CERN, are discussed. The CERN available oxygen and sulfur beams, with energy about 200 GeV/nuclei, allow the obtention of high energy densities, never reached before. The possibilities of investigating (at CERN) the quarks and gluons plasma are considered. The first and unexpected results obtained from the NA38 experiment are overviewed [fr
Bose–Einstein condensation and thermalization of the quark–gluon plasma
International Nuclear Information System (INIS)
Blaizot, Jean-Paul; Gelis, François; Liao, Jinfeng; McLerran, Larry; Venugopalan, Raju
2012-01-01
In ultra-relativistic heavy ion collisions, the matter formed shortly after the collision is a dense, out of equilibrium, system of gluons characterized by a semi-hard momentum scale Q s . Simple power counting arguments indicate that this system is over-occupied: the gluon occupation number is parametrically large when compared to a system in thermal equilibrium with the same energy density. On short time scales, soft elastic scattering tends to drive the system toward the formation of a Bose–Einstein condensate that contains a large fraction of the gluons while contributing little to the energy density. The lifetime and existence of this condensate depends on whether inelastic processes, that occur on the same time scale as elastic processes, preferably increase or decrease the number of gluons. During this overpopulated stage, and all the way to thermalization, the system behaves as a strongly interacting fluid, even though the elementary coupling constant is small. Finally, we argue that while complete isotropization may never be reached, the system may yet evolve for a long time with a fixed anisotropy between average longitudinal and transverse momenta.
Gluon 2- and 3-Point Correlation Functions on the Lattice
Parrinello, Claudio
1993-01-01
I present some preliminary results, obtained in collaboration with C. Bernard and A. Soni, for the lattice evaluation of 2- and 3-point gluon correlation functions in momentum space, with emphasis on the amputated 3-gluon vertex function. The final goal of this approach is the study of the running QCD coupling constant as defined from the amputated 3-gluon vertex.
2- and 3-point gluon correlation functions on the lattice
Energy Technology Data Exchange (ETDEWEB)
Parrinello, C. (Dept. of Physics, Univ. of Edinburgh (United Kingdom))
1994-04-01
I present some preliminary results, obtained in collaboration with C. Bernard and A. Soni, for the lattice evaluation of 2- and 3-point gluon correlation functions in momentum space, with emphasis on the amputated 3-gluon vertex function. The final goal of this approach is the study of the running QCD coupling constant as defined from the amputated 3-gluon vertex. (orig.)
Hard diffraction and rapidity gaps
International Nuclear Information System (INIS)
Brandt, A.
1995-09-01
The field of hard diffraction, which studies events with a rapidity gap and a hard scattering, has expanded dramatically recently. A review of new results from CDF, D OE, H1 and ZEUS will be given. These results include diffractive jet production, deep-inelastic scattering in large rapidity gap events, rapidity gaps between high transverse energy jets, and a search for diffractive W-boson production. The combination of these results gives new insight into the exchanged object, believed to be the pomeron. The results axe consistent with factorization and with a hard pomeron that contains both quarks and gluons. There is also evidence for the exchange of a strongly interacting color singlet in high momentum transfer (36 2 ) events
Universality of soft and collinear factors in hard-scattering factorization
International Nuclear Information System (INIS)
Collins, John C.; Metz, Andreas
2004-01-01
Universality in QCD factorization of parton densities, fragmentation functions, and soft factors is endangered by the process dependence of the directions of Wilson lines in their definitions. We find a choice of directions that is consistent with factorization and that gives universality between e + e - annihilation, semi-inclusive deep-inelastic scattering, and the Drell-Yan process. Universality is only modified by a time-reversal transformation of the soft function and parton densities between Drell-Yan and the other processes, whose only effect is the known reversal of sign for T-odd parton densities such as the Sivers function. The modifications of the definitions needed to remove rapidity divergences with lightlike Wilson lines do not affect the results
Collinear Resonance Ionization Spectroscopy of Neutron-Deficient Francium Isotopes
Flanagan, K T; Ruiz, R F Garcia; Budincevic, I; Procter, T J; Fedosseev, V N; Lynch, K M; Cocolios, T E; Marsh, B A; Neyens, G; Strashnov, I; Stroke, H H; Rossel, R E; Heylen, H; Billowes, J; Rothe, S; Bissell, M L; Wendt, K D A; de Groote, R P; De Schepper, S
2013-01-01
The magnetic moments and isotope shifts of the neutron-deficient francium isotopes Fr202-205 were measured at ISOLDE-CERN with use of collinear resonance ionization spectroscopy. A production-to-detection efficiency of 1\\% was measured for Fr-202. The background from nonresonant and collisional ionization was maintained below one ion in 10(5) beam particles. Through a comparison of the measured charge radii with predictions from the spherical droplet model, it is concluded that the ground-state wave function remains spherical down to Fr-205, with a departure observed in Fr-203 (N = 116).
Power suppressed operators and gauge invariance in soft-collinear effective theory
International Nuclear Information System (INIS)
Bauer, Christian W.; Pirjol, Dan; Stewart, Iain W.
2003-01-01
The form of collinear gauge invariance for power suppressed operators in the soft-collinear effective theory (SCET) is discussed. Using a field redefinition we show that it is possible to make any power suppressed ultrasoft-collinear operators invariant under the original leading order gauge transformations. Our manipulations avoid gauge fixing. The Lagrangians to O(λ 2 ) are given in terms of these new fields. We then give a simple procedure for constructing power suppressed soft-collinear operators in SCET II by using an intermediate theory SCET I
Soft-gluon resummation for high-pT inclusive-hadron production at COMPASS
International Nuclear Information System (INIS)
Pfeuffer, Melanie
2013-01-01
One of the experiments that may be used to probe the nucleon's gluon distribution is the fixed-target lepton scattering experiment COMPASS at CERN, where charged hadrons with high transverse momentum are observed. An aspect that makes the COMPASS experiment quite challenging for the theoretical calculation in perturbative QCD is its fixed-target regime. The hadron's transverse momentum is relatively large compared to the available center-of-mass energy. Thus the partonic process is close to the threshold, where all available partonic center-of-mass energy is just used to produce the high-transverse momentum parton that subsequently hadronizes into the observed hadron, and its recoiling counterpart. Additional real gluon radiation is strongly suppressed and therefore mostly constrained to the emission of soft and/or collinear gluons. This results in a strong imbalance between real and virtual gluon diagrams and the cancellation of infrared singularities leaves behind large logarithmic corrections to the leading order cross section. These logarithms are not only present in the next-to-leading (NLO) corrections, but appear also in all higher order corrections in its perturbation expansion. They dominate the cross section in the kinematic region close to the threshold and thus have to be taken into account order-by-order. A technique that addresses these logarithms is known as threshold resummation. The main goal of this work is to investigate the relevance of higher-order QCD corrections of the unpolarized photoproduction reaction in fixed-target scattering at COMPASS, where the hadron is produced at large transverse momentum. In particular the large logarithmic threshold corrections to the partonic cross sections are addressed, which are resummed to all orders at next-to-leading logarithmic (NLL) accuracy. As new technical ingredient to resummation, the rapidity dependence of the cross section in the resummed calculation is fully included in order to account for all
Photon production in an expanding and chemically equilibrating gluon-enriched plasma
International Nuclear Information System (INIS)
Kaempfer, B.; Technische Univ. Dresden; Pavlenko, O.P.; AN Ukrainskoj SSR, Kiev
1993-12-01
Photon production in a longitudinally and transversely expanding gluon plasma with initially little quark admixture is considered. Chemical equilibration of quarks and gluons is followed by rate equations. The yields of hard photons with E ≥ 2 GeV are insensitive to chemical equilibration and depend mainly on the initial thermalized state. Medium-energy photons with E ∼ 1 GeV are more frequently produced in case of faster equilibration, despite of faster cooling. For an assumed fast equilibration we follow the evolution of matter through mixed and hadron phases. The transverse momentum kick, due to transverse expansion, of photons from hadron matter is shown to be reduced for an equation of state with reduced latent heat. The photon yield in the region E > 1 GeV from deconfined matter dominates for conditions, estimated to be achieved at RHIC, in case of a weakly first-order confinement transition. (orig.)
Medium-induced gluon radiation and colour decoherence beyond the soft approximation
Apolinário, Liliana; Milhano, José Guilherme; Salgado, Carlos A
2015-01-01
We derive the in-medium gluon radiation spectrum off a quark within the path integral formalism at finite energies, including all next-to-eikonal corrections in the propagators of quarks and gluons. Results are computed for finite formation times, including interference with vacuum amplitudes. Rewriting the medium averages in a convenient manner we present the spectrum in terms of dipole cross sections and a colour decoherence parameter with the same physical origin as that found in previous studies of the antenna radiation. This factorisation allows us to present a simple physical picture of the medium-induced radiation for any value of the formation time, of interest for a probabilistic implementation of the modified parton shower. Interestingly -- and unexpectedly -- we also find a modification of the contribution from the hard vertex which cannot be factorized, at finite formation time, as the vacuum Altarelli-Parisi splitting function. Known results are recovered for the particular cases of soft radiatio...
Higgs production in gluon fusion beyond NNLO
Energy Technology Data Exchange (ETDEWEB)
Ball, Richard D. [Edinburgh Univ. (United Kingdom). Tait Inst.; Bonvini, Marco [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany); Forte, Stefano [Milano Univ. (Italy). Dipt. di Fisica; INFN, Sezione di Milano (Italy); Marzani, Simone [Durham Univ. (United Kingdom). Inst. for Particle Physics Phenomenology; Ridolfi, Giovanni [Genova Univ. (Italy). Dipt. di Fisica; INFN, Sezione di Genova (Italy)
2013-03-15
We construct an approximate expression for the cross section for Higgs production in gluon fusion at next-to-next-to-next-to-leading order (N{sup 3}LO) in {alpha}{sub s} with finite top mass. We argue that an accurate approximation can be constructed by exploiting the analiticity of the Mellin space cross section, and the information on its singularity structure coming from large N (soft gluon, Sudakov) and small N (high energy, BFKL) all order resummation. We support our argument with an explicit comparison of the approximate and the exact expressions up to the highest (NNLO) order at which the latter are available. We find that the approximate N{sup 3}LO result amounts to a correction of 17% to the NNLO QCD cross section for production of a 125 GeV Higgs at the LHC (8 TeV), larger than previously estimated, and it significantly reduces the scale dependence of the NNLO result.
Quarks and gluons in hadrons and nuclei
International Nuclear Information System (INIS)
Close, F.E.
1989-12-01
These lectures discuss the particle-nuclear interface -- a general introduction to the ideas and application of colored quarks in nuclear physics, color, the Pauli principle, and spin flavor correlations -- this lecture shows how the magnetic moments of hadrons relate to the underlying color degree of freedom, and the proton's spin -- a quark model perspective. This lecture reviews recent excitement which has led some to claim that in deep inelastic polarized lepton scattering very little of the spin of a polarized proton is due to its quarks. This lecture discusses the distribution functions of quarks and gluons in nucleons and nuclei, and how knowledge of these is necessary before some quark-gluon plasma searches can be analyzed. 56 refs., 2 figs
Higgs production in gluon fusion beyond NNLO
International Nuclear Information System (INIS)
Ball, Richard D.; Bonvini, Marco; Forte, Stefano; Marzani, Simone; Ridolfi, Giovanni
2013-01-01
We construct an approximate expression for the cross section for Higgs production in gluon fusion at next-to-next-to-next-to-leading order (N 3 LO) in α s with finite top mass. We argue that an accurate approximation can be constructed by exploiting the analyticity of the Mellin space cross section, and the information on its singularity structure coming from large N (soft gluon, Sudakov) and small N (high energy, BFKL) all order resummation. We support our argument with an explicit comparison of the approximate and the exact expressions up to the highest (NNLO) order at which the latter are available. We find that the approximate N 3 LO result amounts to a correction of 17% to the NNLO QCD cross section for production of a 125 GeV Higgs at the LHC (8 TeV), larger than previously estimated, and it significantly reduces the scale dependence of the NNLO result
Higgs production in gluon fusion beyond NNLO
Energy Technology Data Exchange (ETDEWEB)
Ball, Richard D. [Tait Institute, University of Edinburgh, Edinburgh EH9 3JZ, Scotland (United Kingdom); Bonvini, Marco [Deutsches Elektronen-Synchroton, DESY, Notkestraße 85, D-22603 Hamburg (Germany); Forte, Stefano, E-mail: forte@mi.infn.it [Dipartimento di Fisica, Università di Milano and INFN, Sezione di Milano, Via Celoria 16, I-20133 Milano (Italy); Marzani, Simone [Institute for Particle Physics Phenomenology, Durham University, Durham DH1 3LE, England (United Kingdom); Ridolfi, Giovanni [Dipartimento di Fisica, Università di Genova and INFN, Sezione di Genova, Via Dodecaneso 33, I-16146 Genova (Italy)
2013-09-21
We construct an approximate expression for the cross section for Higgs production in gluon fusion at next-to-next-to-next-to-leading order (N{sup 3}LO) in α{sub s} with finite top mass. We argue that an accurate approximation can be constructed by exploiting the analyticity of the Mellin space cross section, and the information on its singularity structure coming from large N (soft gluon, Sudakov) and small N (high energy, BFKL) all order resummation. We support our argument with an explicit comparison of the approximate and the exact expressions up to the highest (NNLO) order at which the latter are available. We find that the approximate N{sup 3}LO result amounts to a correction of 17% to the NNLO QCD cross section for production of a 125 GeV Higgs at the LHC (8 TeV), larger than previously estimated, and it significantly reduces the scale dependence of the NNLO result.
Higgs production in gluon fusion beyond NNLO
International Nuclear Information System (INIS)
Ball, Richard D.; Forte, Stefano; Marzani, Simone
2013-03-01
We construct an approximate expression for the cross section for Higgs production in gluon fusion at next-to-next-to-next-to-leading order (N 3 LO) in α s with finite top mass. We argue that an accurate approximation can be constructed by exploiting the analiticity of the Mellin space cross section, and the information on its singularity structure coming from large N (soft gluon, Sudakov) and small N (high energy, BFKL) all order resummation. We support our argument with an explicit comparison of the approximate and the exact expressions up to the highest (NNLO) order at which the latter are available. We find that the approximate N 3 LO result amounts to a correction of 17% to the NNLO QCD cross section for production of a 125 GeV Higgs at the LHC (8 TeV), larger than previously estimated, and it significantly reduces the scale dependence of the NNLO result.
Effective gluon interactions from superstring disk amplitudes
Energy Technology Data Exchange (ETDEWEB)
Oprisa, D.
2006-05-15
In this thesis an efficient method for the calculation of the N-point tree-level string amplitudes is presented. Furthermore it is shown that the six-gluon open-superstring disk amplitude can be expressed by a basis of six triple hypergeometric functions, which encode the full {alpha}' dependence. In this connection material for obtaining the {alpha}' expansion of these functions is derived. Hereby many Euler-Zagier sums are calculated including multiple harmonic series. (HSI)
Gluon saturation beyond (naive) leading logs
Energy Technology Data Exchange (ETDEWEB)
Beuf, Guillaume
2014-12-15
An improved version of the Balitsky–Kovchegov equation is presented, with a consistent treatment of kinematics. That improvement allows to resum the most severe of the large higher order corrections which plague the conventional versions of high-energy evolution equations, with approximate kinematics. This result represents a further step towards having high-energy QCD scattering processes under control beyond strict Leading Logarithmic accuracy and with gluon saturation effects.
The gluon propagator in momentum space
Energy Technology Data Exchange (ETDEWEB)
Bernard, C. [Washington Univ., St. Louis, MO (United States). Dept. of Physics; Parrinello, C. [New York Univ., NY (United States). Dept. of Physics]|[Brookhaven National Lab., Upton, NY (United States); Soni, A. [Brookhaven National Lab., Upton, NY (United States)
1992-12-31
We consider quenched QCD on a 16{sup 3}{times}40 lattice at {beta}=6.0. We give preliminary numerical results for the lattice gluon propagator evaluated both in coordinate and momentum space. Our findings are compared with earlier results in the literature at zero momentum. In addition, by considering nonzero momenta we attempt to extract the form of the propagator and compare it to continuum predictions formulated by Gribov and others.
The gluon propagator in momentum space
Energy Technology Data Exchange (ETDEWEB)
Bernard, C. (Washington Univ., St. Louis, MO (United States). Dept. of Physics); Parrinello, C. (New York Univ., NY (United States). Dept. of Physics Brookhaven National Lab., Upton, NY (United States)); Soni, A. (Brookhaven National Lab., Upton, NY (United States))
1992-01-01
We consider quenched QCD on a 16[sup 3][times]40 lattice at [beta]=6.0. We give preliminary numerical results for the lattice gluon propagator evaluated both in coordinate and momentum space. Our findings are compared with earlier results in the literature at zero momentum. In addition, by considering nonzero momenta we attempt to extract the form of the propagator and compare it to continuum predictions formulated by Gribov and others.
The gluon propagator in momentum space
Energy Technology Data Exchange (ETDEWEB)
Bernard, C. (Dept. of Physics, Washington Univ., St. Louis, MO (United States)); Parrinello, C. (Physics Dept., New York Univ., NY (United States) Physics Dept., Brookhaven National Lab., Upton, NY (United States)); Soni, A. (Physics Dept., Brookhaven National Lab., Upton, NY (United States))
1993-03-01
We consider quenched QCD on a 16[sup 3] x 40 lattice at [beta] = 6.0. We give preliminary numerical results for the lattice gluon propagator evaluated both in coordinate and momentum space. Our findings are compared with earlier results in the literature at zero momentum. In addition, by considering nonzero momenta we attempt to extract the form of the propagator and compare it to continuum predictions formulated by Gribov and others. (orig.)
Physics of the quark-gluon plasma
International Nuclear Information System (INIS)
Polonyi, J.; Institut National de Physique Nucleaire et de Physique des Particules; Lorand Eoetvoes Univ., Budapest
1995-01-01
Some features of the high temperature gluonic matter, such as the breakdown of the fundamental group symmetry by the kinetic energy, the screening of test quarks by some unusual gluon states and the explanation of the absence of isolated quarks in the vacuum without the help of infinities are presented in this talk. Special attention is paid to separate the dynamical input inferred from the numerical results of lattice gauge theory from the kinematics. (author)
Soft gluon emission in coloured quark scattering
International Nuclear Information System (INIS)
Frenkel, J.; Meuldemans, R.; Mohammad, I.; Taylor, J.C.
1977-01-01
In order to investigate the infrared behaviour of non-Abelian gauge theories the leading logarithms in the bremsstrahlung of two soft gluons by a coloured quark scattered in an external colourless potential have been calculated. In the calculations only diagrams containing exactly one Yang-Mills vertex have been used alongside with the dimensional infrared regularization. An expression is obtained exhibiting a crucial difference between QCD and QED
Effective gluon interactions from superstring disk amplitudes
International Nuclear Information System (INIS)
Oprisa, D.
2006-05-01
In this thesis an efficient method for the calculation of the N-point tree-level string amplitudes is presented. Furthermore it is shown that the six-gluon open-superstring disk amplitude can be expressed by a basis of six triple hypergeometric functions, which encode the full α' dependence. In this connection material for obtaining the α' expansion of these functions is derived. Hereby many Euler-Zagier sums are calculated including multiple harmonic series. (HSI)
Hadronization of the quark-gluon plasma
International Nuclear Information System (INIS)
Mueller, B.; Sano, M.; Sato, H.; Schaefer, A.
1986-11-01
We construct a model for hadronization of the quark-gluon plasma, based on the relativistic coalescence model. We relate the coalescence amplitude to the one-particle Wigner function for quarks in the plasma. The relation between the Wigner function and the nucleon structure function is pointed out. We derive explicit expressions for the production of mesons and baryons in the framework of the relativistic harmonic oscillator model of hadronic structure. (author)
Signatures of quark-gluon plasma production
International Nuclear Information System (INIS)
Gyulassy, M.
1985-01-01
A critical analysis of a variety of proposed signatures for quark-gluon formation in ultrarelativistic nuclear collisions is given. The authors emphasize that longitudinal growth rather than the nuclear radius controls the time scales for expansion. The author pointed out the qualitative difference of the evolution of the plasma produced in the stopping regime E approx. 10 GeV/nucleon and the scaling regime E > 1 TeV/nucleon. This difference reflects itself in the the rmal profile function
The gluon propagator in momentum space
International Nuclear Information System (INIS)
Bernard, C.; Soni, A.
1992-01-01
We consider quenched QCD on a 16 3 x40 lattice at β=6.0. We give preliminary numerical results for the lattice gluon propagator evaluated both in coordinate and momentum space. Our findings are compared with earlier results in the literature at zero momentum. In addition, by considering nonzero momenta we attempt to extract the form of the propagator and compare it to continuum predictions formulated by Gribov and others
Quark-gluon mixing in scalar mesons
International Nuclear Information System (INIS)
Eremyan, Sh.S.; Nazaryan, A.E.
1986-01-01
Scalar mesons are considered within the quark-gluon mixing model. It is shown that there exists decouplet of scalar particles consisting of S* (975), ε (1400), S*' (1700), δ (980) and κ (1350) resonances. It has turned out that the long ago known S* (975)-resonance is a nearly pure glouball. A good description of all available experimental data on scalar meson decays is obtained
The hadron to quark/gluon transition
International Nuclear Information System (INIS)
Brown, G.E.; Bethe, H.A.; Pizzochero, P.M.
1991-01-01
In this paper we are concerned with the hadron to quark/gluon transition. We describe the equilibrium states of hadronic matter by a Hagedorn spectrum; introducing scaling masses, as dictated by the restoration of chiral invariance with increasing temperature, we show that in the chiral SU(2) f limit there is a maximum hadron temperature (T H ) max ≅ 128 MeV. Since the quark/gluon perturbative phase involves restoration of conformal invariance, we take the bag constant to be the conformal anomaly, i.e. the gluon condensate. The stability condition P QG > 0 for the pressure requires that there is a minimum temperature; we find (T QG ) min ≅ 172 MeV for SU(2) f . According to the simple Hagedorn model, there appears to be a region of temperature between (T H ) max and (T QG ) min in which no admissible equilibrium states exist. Since the two phases cannot exist at a common temperature, in this model there is no QCD phase transition. (orig.)
Quark and gluon condensate in vacuum
International Nuclear Information System (INIS)
Vajnshtejn, A.I.; Zakharov, V.I.; Shifman, M.A.
1979-01-01
The mechanism of quark confinement has been reviewed. The fact that coloured particles in a free state cannot be observed is connected with specific properties of vacuum in quantum chromodynamics. The basic hypothesis consists in the existence of vacuum fields, quark and gluon condensates, which affect the coloured objects. The vacuum transparent relative to noncharged ''white'' states serves as a source of the force acting upon the coloured particles. It has been a sucess to examine strictly the action of the vacuum fields on quarks when the distance between them is relatively small and the force of the vacuum fields on quarks is relatively small too. It is shown that the interaction with the vacuum fields manifests itself earlier than the forces connected with the gluon exchange do. It is assumed that the vacuum condensate of quarks and gluons and its relation to properties of resonances and to the bag model exist in reality. The dispersion sum rules are used for calculating masses and lepton widths of resonances
The Gluon Sivers Distribution: Status and Future Prospects
International Nuclear Information System (INIS)
Zhou, Jian; Boer, Daniël; Pisano, Cristian; Lorcé, Cédric
2015-01-01
We review what is currently known about the gluon Sivers distribution and what are the opportunities to learn more about it. Because single transverse spin asymmetries in p"↑p→πX provide only indirect information about the gluon Sivers function through the relation with the quark-gluon and tri-gluon Qiu-Sterman functions, current data from hadronic collisions at RHIC have not yet been translated into a solid constraint on the gluon Sivers function. SIDIS data, including the COMPASS deuteron data, allow for a gluon Sivers contribution of natural size expected from large N_c arguments, which is O(1/N_c) times the nonsinglet quark Sivers contribution. Several very promising processes to measure the gluon Sivers effect directly have been suggested, which besides RHIC investigations, would strongly favor experiments at AFTER@LHC and a possible future Electron-Ion Collider. Due to the inherent process dependence of TMDs, the gluon Sivers TMD probed in the various processes are different linear combinations of two universal gluon Sivers functions that have different behavior under charge conjugation and that therefore satisfy different theoretical constraints. For this reason both hadronic and DIS type of collisions are essential in the study of the role of gluons in transversely polarized protons.
Varfolomeev, A A
2000-01-01
New non-collinear schemes are suggested for transverse velocity modulation of electron beams and for the generation of coherent spontaneous radiation by these transversely modulated beams. It is shown that due to the non-collinearity some orders of magnitude enhancement can be achieved for the coherent spontaneous radiation (CSR) power at both the fundamental and harmonic frequencies.
Electroweak gauge-boson production at small q T : Infrared safety from the collinear anomaly
Becher, Thomas; Neubert, Matthias; Wilhelm, Daniel
2012-02-01
Using methods from effective field theory, we develop a novel, systematic framework for the calculation of the cross sections for electroweak gauge-boson production at small and very small transverse momentum q T , in which large logarithms of the scale ratio M V /q T are resummed to all orders. These cross sections receive logarithmically enhanced corrections from two sources: the running of the hard matching coefficient and the collinear factorization anomaly. The anomaly leads to the dynamical generation of a non-perturbative scale {q_* } ˜ {M_V}{e^{ - {text{const}}/{α_s}left( {{M_V}} right)}} , which protects the processes from receiving large long-distance hadronic contributions. Expanding the cross sections in either α s or q T generates strongly divergent series, which must be resummed. As a by-product, we obtain an explicit non-perturbative expression for the intercept of the cross sections at q T = 0, including the normalization and first-order α s ( q ∗ ) correction. We perform a detailed numerical comparison of our predictions with the available data on the transverse-momentum distribution in Z-boson production at the Tevatron and LHC.
Directory of Open Access Journals (Sweden)
Arezoo Bagheri
2012-01-01
Full Text Available There is strong evidence indicating that the existing measures which are designed to detect a single high leverage collinearity-reducing observation are not effective in the presence of multiple high leverage collinearity-reducing observations. In this paper, we propose a cutoff point for a newly developed high leverage collinearity-influential measure and two existing measures ( and to identify high leverage collinearity-reducing observations, the high leverage points which hide multicollinearity in a data set. It is important to detect these observations as they are responsible for the misleading inferences about the fitting of the regression model. The merit of our proposed measure and cutoff point in detecting high leverage collinearity-reducing observations is investigated by using engineering data and Monte Carlo simulations.
Three gluon jets as a test of QCD
International Nuclear Information System (INIS)
Koller, K.; Walsh, T.F.
1977-10-01
As a test of quantum chromodynamics (QCD), we suggest looking for gluon jets in the decay of a heavy quark-antiquark bound state produced in e + e - -annihilation, Q anti Q → 3 gluons → 3 gluon jets. In particular, we point out that these events form a jet Dalitz plot, and we calculate the gluon or jet distributions (including the effect of polarized e + e - -beams). This process affords a test of the gluon spin. It is the analogue of two-jet angular distributions in e + e - %→ q anti q → 2 quark jets. We also estimate multiplicities and momentum distributions of hadrons in Q anti Q → 3 gluons → hadrons, using the recently discovered UPSILON (9.4) as an example. (orig.) [de
Dynamical gluon mass in the instanton vacuum model
Musakhanov, M.; Egamberdiev, O.
2018-04-01
We consider the modifications of gluon properties in the instanton liquid model (ILM) for the QCD vacuum. Rescattering of gluons on instantons generates the dynamical momentum-dependent gluon mass Mg (q). First, we consider the case of a scalar gluon, no zero-mode problem occurs and its dynamical mass Ms (q) can be found. Using the typical phenomenological values of the average instanton size ρ = 1 / 3 fm and average inter-instanton distance R = 1 fm we get Ms (0) = 256 MeV. We then extend this approach to the real vector gluon with zero-modes carefully considered. We obtain the following expression Mg2 (q) = 2 Ms2 (q). This modification of the gluon in the instanton media will shed light on nonperturbative aspect on heavy quarkonium physics.
Laminar forced convection in a cylindrical collinear ohmic sterilizer
Directory of Open Access Journals (Sweden)
Pesso Tommaso
2017-01-01
Full Text Available The present work deals with a thermo-fluid analysis of a collinear cylindrical ohmic heater in laminar flow. The geometry of interest is a circular electrically insulated glass pipe with two electrodes at the pipe ends. For this application, since the electrical conductivity of a liquid food depends strongly on the temperature, the thermal analysis of an ohmic heater requires the simultaneous solution of the electric and thermal fields. In the present work the analysis involves decoupling the previous fields by means of an iterative procedure. The thermal field has been calculated using an analytical solution, which leads to fast calculations for the temperature distribution in the heater. Some considerations of practical interest for the design are also given.
Collinear resonance ionization spectroscopy of exotic francium and radium isotopes
AUTHOR|(CDS)2094150
Two experimental campaigns were performed at the Collinear Resonance Ionization Spectroscopy (CRIS) experiment, located at the ISOLDE radioactive-beam facility. The spectroscopic quadrupole moment of $^{203}$Fr was measured. Its magnitude with respect to the other even-$N$ francium isotopes below $N = 126$ suggests an onset of static deformation. However, calculations of the static and total deformation parameters reveal that it cannot be considered as purely statically deformed. The neutron-rich radium isotopes were investigated. The spectroscopic quadrupole moment of $^{231}$Ra was measured and the continuation of increasing quadrupole deformation with neutron number in neutron-rich radium isotopes was further established. Measurements of the changes in mean-square charge radii of $^{231,233}$Ra allowed the odd-even staggering parameter to be calculated for $^{230-232}$Ra. A normal odd-even staggering which increases in magnitude with neutron number was observed in these isotopes.
A preliminary design of the collinear dielectric wakefield accelerator
Energy Technology Data Exchange (ETDEWEB)
Zholents, A.; Gai, W.; Doran, S.; Lindberg, R.; Power, J.G.; Strelnikov, N.; Sun, Y.; Trakhtenberg, E.; Vasserman, I. [ANL, Argonne, IL 60439 (United States); Jing, C.; Kanareykin, A.; Li, Y. [Euclid Techlabs LLC, Solon, OH 44139 (United States); Gao, Q. [Tsinghua University, Beijing (China); Shchegolkov, D.Y.; Simakov, E.I. [LANL, Los Alamos, NM 87545 (United States)
2016-09-01
A preliminary design of the multi-meter long collinear dielectric wakefield accelerator that achieves a highly efficient transfer of the drive bunch energy to the wakefields and to the witness bunch is considered. It is made from ~0.5 m long accelerator modules containing a vacuum chamber with dielectric-lined walls, a quadrupole wiggler, an rf coupler, and BPM assembly. The single bunch breakup instability is a major limiting factor for accelerator efficiency, and the BNS damping is applied to obtain the stable multi-meter long propagation of a drive bunch. Numerical simulations using a 6D particle tracking computer code are performed and tolerances to various errors are defined.
Ultrafast collinear scattering and carrier multiplication in graphene.
Brida, D; Tomadin, A; Manzoni, C; Kim, Y J; Lombardo, A; Milana, S; Nair, R R; Novoselov, K S; Ferrari, A C; Cerullo, G; Polini, M
2013-01-01
Graphene is emerging as a viable alternative to conventional optoelectronic, plasmonic and nanophotonic materials. The interaction of light with charge carriers creates an out-of-equilibrium distribution, which relaxes on an ultrafast timescale to a hot Fermi-Dirac distribution, that subsequently cools emitting phonons. Although the slower relaxation mechanisms have been extensively investigated, the initial stages still pose a challenge. Experimentally, they defy the resolution of most pump-probe setups, due to the extremely fast sub-100 fs carrier dynamics. Theoretically, massless Dirac fermions represent a novel many-body problem, fundamentally different from Schrödinger fermions. Here we combine pump-probe spectroscopy with a microscopic theory to investigate electron-electron interactions during the early stages of relaxation. We identify the mechanisms controlling the ultrafast dynamics, in particular the role of collinear scattering. This gives rise to Auger processes, including charge multiplication, which is key in photovoltage generation and photodetectors.
Measurement of nuclear moments and radii by collinear laser spectroscopy
Geithner, W R; Lievens, P; Kotrotsios, G; Silverans, R; Kappertz, S
2002-01-01
%IS304 %title\\\\ \\\\Collinear laser spectroscopy on a fast beam has proven to be a widely applicable and very efficient tool for measurements of changes in mean square nuclear charge radii, nuclear spins, magnetic dipole and electric quadrupole moments. Recent developments of extremely sensitive non-optical detection schemes enabled for some elements the extension of the measurements towards the very short-lived isotopes in the far wings of the ISOLDE production curves. The gain in sensitivity opens up new perspectives, particularly for measurements on lighter nuclei whose ground-state properties can be interpreted by large scale microscopic calculations instead of the more phenomenologic models used for heavier nuclei.\\\\ \\\\ For the sequence of argon isotopes $^{32-40}$Ar and $^{46}$Ar isotope shifts and nuclear moments were measured by optical pumping followed by state selective collisional ionization and detection of the $\\beta$-decay. Similarly, the low-background $\\alpha$-detection was used to extend earlie...
COMPLIS: COllinear spectroscopy Measurements using a Pulsed Laser Ion Source
2002-01-01
A Pulsed Laser spectroscopy experiment has been installed for the study of hyperfine structure and isotope shift of refractory and daughter elements from ISOLDE beams. It includes decelerated ion-implantation, element-selective laser ionization, magnetic and time-of-flight mass separation. The laser spectroscopy has been performed on the desorbed atoms in a set-up at ISOLDE-3 but later on high resolution laser collinear spectroscopy with the secondary pulsed ion beam is planned for the Booster ISOLDE set-up. During the first operation time of ISOLDE-3 we restricted our experiments to Doppler-limited resonant ionization laser and $\\gamma$-$\\gamma$ nuclear spectroscopy on neutron deficient platinum isotopes of even mass number down to A~=~186 and A~=~179 respectively. These isotopes have been produced by implantation of radioactive Hg and their subsequent $\\beta$-decay.
Novel Aspects of Hard Diffraction in QCD
International Nuclear Information System (INIS)
Brodsky, Stanley J.
2005-01-01
Initial- and final-state interactions from gluon-exchange, normally neglected in the parton model have a profound effect in QCD hard-scattering reactions, leading to leading-twist single-spin asymmetries, diffractive deep inelastic scattering, diffractive hard hadronic reactions, and nuclear shadowing and antishadowing--leading-twist physics not incorporated in the light-front wavefunctions of the target computed in isolation. I also discuss the use of diffraction to materialize the Fock states of a hadronic projectile and test QCD color transparency
Semirelativistic potential model for three-gluon glueballs
International Nuclear Information System (INIS)
Mathieu, Vincent; Semay, Claude; Silvestre-Brac, Bernard
2008-01-01
The three-gluon glueball states are studied with the generalization of a semirelativistic potential model giving good results for two-gluon glueballs. The Hamiltonian depends only on 3 parameters fixed on two-gluon glueball spectra: the strong coupling constant, the string tension, and a gluon size which removes singularities in the potential. The Casimir scaling determines the structure of the confinement. Our results are in good agreement with other approaches and lattice calculation for the odderon trajectory but differ strongly from lattice in the J +- sector. We propose a possible explanation for this problem.
Soft Gluon Radiation off Heavy Quarks beyond Eikonal Approximation
International Nuclear Information System (INIS)
Mazumder, Surasree; Bhattacharyya, Trambak; Abir, Raktim
2016-01-01
We calculate the soft gluon radiation spectrum off heavy quarks (HQs) interacting with light quarks (LQs) beyond small angle scattering (eikonality) approximation and thus generalize the dead-cone formula of heavy quarks extensively used in the literatures of Quark-Gluon Plasma (QGP) phenomenology to the large scattering angle regime which may be important in the energy loss of energetic heavy quarks in the deconfined Quark-Gluon Plasma medium. In the proper limits, we reproduce all the relevant existing formulae for the gluon radiation distribution off energetic quarks, heavy or light, used in the QGP phenomenology.
The Theory of Quark and Gluon Interactions
Ynduráin, Francisco J
2006-01-01
F. J. Ynduráin's book on Quantum Chromodynamics has become a classic among advanced textbooks. First published in 1983, and translated into Russian in 1986, it now sees its fourth edition. It addresses readers with basic knowledge of field theory and particle phenomenology. The author presents the basic facts of quark and gluon physics in pedagogical form. Theory is always confronted with experimental findings. The reader will learn enough to be able to follow modern research articles. This fourth edition presents a new section on heavy quark effective theories, more material on lattice QCD and on chiral perturbation theory.
Gluon fragmentation into 3 PJ quarkonium
International Nuclear Information System (INIS)
Ma, J.P.
1995-01-01
The functions of the gluon fragmentation into 3 P j quarkonium are calculated to order α 2 s . With the recent progress in analysing quarkonium systems in QCD it is possible show how the so called divergence in the limit of the zero-binding energy, which is related to P-wave quarkonia, is treated correctly in the case of fragmentation functions. The obtained fragmentation functions satisfy explicitly at the order of α 2 s the Altarelli-Parisi equation and when z → 0 they behave as z -1 as expected. 19 refs., 7 figs
Quarks, gluons, colour: facts or fiction?
International Nuclear Information System (INIS)
Buchholz, D.
1996-01-01
A general method is presented that allows one to determine from the local gauge invariant observables of a quantum field theory the underlying particle and symmetry structures appearing at the lower (ultraviolet) end of the spatio-temporal scale. Particles that are confined to small scales, i.e. do not appear in the physical spectrum, can be uncovered in this way without taking recourse to gauge fields or indefinite metric spaces. In this way notions such as quark, gluon, colour symmetry and confinement acquire a new and intrinsic meaning which is stable under gauge or duality transformations. The method is illustrated by the example of the Schwinger model. (orig.)
Hydrodynamics of quark-gluon plasmas
International Nuclear Information System (INIS)
Blaizot, J.P.
1986-06-01
This paper reviews some aspects of the hydrodynamics of quark-gluon plasmas. Various stages of ultra-relativistic heavy ion collisions are described. Several estimates of the maximum energy density expected to be achieved in these collisions are compared. Discontinuities which may be induced in the hydrodynamic flow by a phase transition are described and a convenient numerical method designed to deal with such discontinuous flows is briefly presented. Finally, the correlations between particle transverse momenta and multiplicities are analyzed and one discusses to which extent these correlations could signal the occurrence of a phase transition in heavy ion collisions
Effective gluon operators and neutron dipole moment
International Nuclear Information System (INIS)
Bigi, I.; Ural'tsev, N.G.
1991-01-01
The role of the purely gluon CP odd six-dimension effective arising in various CP-breaking models is discussed. This operators of most interest in the nonminimal Higgs sector models, the right W models and supersymmetric theories, where it may induce the neutron dipole moment at the level of the experimental restriction. The method for evaluating the magnitude d n is proposed and the reasons are given in favor that the original Weiberg's estimate based on the naive Dimensional Analysis is overdone significantly. The Peccei -Quinn mechanism, impact on the magnitude of d n , which generally may be very essential, is discussed
Electric and magnetic properties of hot gluons
International Nuclear Information System (INIS)
Hansson, T.H.; Zahed, I.
1987-01-01
The dielectric constant ε and magnetic permeability μ for gluon plasma are calculated from the one-loop gauge-invariant effective action. The real parts are gauge-fixing independent and agree with earlier work. The imaginary part of μ/sup -1/ is zero in any covariant background-field gauge, while the imaginary part of ε is gauge-fixing dependent and negative definite. This result indicates that there is no consistent perturbative description of gluonic plasmons on scale ≥(g 2 T)/sup -1/
The quark gluon plasma; Le plasma de quarks et de gluons
Energy Technology Data Exchange (ETDEWEB)
Granier de Cassagnac, R. [Ecole Polytechnique, Lab. Leprince-Ringuet, 91 - Palaiseau (France)
2010-05-15
The quark-gluon plasma (QGP) is a state of matter in which the universe was expected to be a few micro-seconds after the big-bang. Violent collisions of heavy ions are supposed to re-create this state in particle accelerators. Numerous signatures of this fugacious state have already been observed at the RHIC (relativistic heavy ion collider). The first evidence of the violence of collisions is the number of generated particles: about 6000 per collision, mostly hadrons. This figure seems high but in fact is less than theoretically expected and is the first sign of the formation of a QGP that saturates the density of gluons. Another sign, observed at the RHIC is the damping of the particle jets that are produced in the collision. This damping is consistent with the crossing of a medium whose density is so high that it can not be made of hadrons but of partons. In the RHIC experiments the collective behaviour of quarks and gluons shows that they are strongly interacting with one another. This fact supports the idea that the QGP is more a perfect liquid rather than an ideal gas in which quarks and gluons move freely. (A.C.)
Soft gluon evolution and non-global logarithms
Martínez, René Ángeles; De Angelis, Matthew; Forshaw, Jeffrey R.; Plätzer, Simon; Seymour, Michael H.
2018-05-01
We consider soft-gluon evolution at the amplitude level. Our evolution algorithm applies to generic hard-scattering processes involving any number of coloured partons and we present a reformulation of the algorithm in such a way as to make the cancellation of infrared divergences explicit. We also emphasise the special role played by a Lorentz-invariant evolution variable, which coincides with the transverse momentum of the latest emission in a suitably defined dipole zero-momentum frame. Handling large colour matrices presents the most significant challenge to numerical implementations and we present a means to expand systematically about the leading colour approximation. Specifically, we present a systematic procedure to calculate the resulting colour traces, which is based on the colour flow basis. Identifying the leading contribution leads us to re-derive the Banfi-Marchesini-Smye equation. However, our formalism is more general and can systematically perform resummation of contributions enhanced by the t'Hooft coupling α s N ˜ 1, along with successive perturbations that are parametrically suppressed by powers of 1 /N . We also discuss how our approach relates to earlier work.
Search for gluons in e/sup +/e/sup -/ annihilation
Ellis, Jonathan Richard; Ross, Graham G
1976-01-01
The authors study the deviations to be expected at high energies from the recently observed two jet structure of hadronic final states in e /sup +/e/sup -/ annihilation. Motivated by the approximate validity of the naive parton model and by asymptotic freedom they suggest that hard gluon bremsstrahlung may be the dominant source of hadrons with large momenta transverse to the main jet axes. This process should give rise to three-jet final states. These may be observable at the highest SPEAR or DORIS energies, and should be important at the higher PETRA or PEP energies. (15 refs).
Energy Technology Data Exchange (ETDEWEB)
Deak, Michal; Kutak, Krzysztof [Instytut Fizyki Jadrowej, Krakow (Poland); Tywoniuk, Konrad [CERN, Theoretical Physics Department, Geneva (Switzerland)
2017-11-15
We propose a new framework, merging High Energy Factorization with final-state jet quenching effects due to interactions in a quark-gluon plasma, to compute di-jet rates at mid-rapidity and forward rapidity. It allows one to consistently study the interplay of initial-state effects with medium interactions, opening the possibility for understanding the dynamics of hard probes in heavy-ion collisions and the QGP evolution in rapidity. (orig.)
Adolph, C.; Akhunzyanov, R.; Alexeev, M.G.; Alexeev, G.D.; Amoroso, A.; Andrieux, V.; Anfimov, N.V.; Anosov, V.; Augustyniak, W.; Austregesilo, A.; Azevedo, C.D.R.; Badelek, B.; Balestra, F.; Barth, J.; Beck, R.; Bedfer, Y.; Bernhard, J.; Bicker, K.; Bielert, E.R.; Birsa, R.; Bisplinghoff, J.; Bodlak, M.; Boer, M.; Bordalo, P.; Bradamante, F.; Braun, C.; Bressan, A.; Buchele, M.; Chang, W.C.; Chiosso, M.; Choi, I.; Chung, S.U.; Cicuttin, A.; Crespo, M.L.; Curiel, Q.; Dalla Torre, S.; Dasgupta, S.S.; Dasgupta, S.; Denisov, O.Yu.; Dhara, L.; Donskov, S.V.; Doshita, N.; Duic, V.; Dunnweber, W.; Dziewiecki, M.; Efremov, A.; Eversheim, P.D.; Eyrich, W.; Faessler, M.; Ferrero, A.; Finger, M.; M. Finger jr; Fischer, H.; Franco, C.; von Hohenesche, N. du Fresne; Friedrich, J.M.; Frolov, V.; Fuchey, E.; Gautheron, F.; Gavrichtchouk, O.P.; Gerassimov, S.; Giordano, F.; Gnesi, I.; Gorzellik, M.; Grabmuller, S.; Grasso, A.; Grosse Perdekamp, M.; Grube, B.; Grussenmeyer, T.; Guskov, A.; Haas, F.; Hahne, D.; von Harrach, D.; Hashimoto, R.; Heinsius, F.H.; Heitz, R.; Herrmann, F.; Hinterberger, F.; Horikawa, N.; d'Hose, N.; Hsieh, C.Y.; Huber, S.; Ishimoto, S.; Ivanov, A.; Ivanshin, Yu.; Iwata, T.; Jahn, R.; Jary, V.; Joosten, R.; Jorg, P.; Kabuss, E.; Ketzer, B.; Khaustov, G.V.; Khokhlov, Yu. A.; Kisselev, Yu.; Klein, F.; Klimaszewski, K.; Koivuniemi, J.H.; Kolosov, V.N.; Kondo, K.; Konigsmann, K.; Konorov, I.; Konstantinov, V.F.; Kotzinian, A.M.; Kouznetsov, O.M.; Kramer, M.; Kremser, P.; Krinner, F.; Kroumchtein, Z.V.; Kulinich, Y.; Kunne, F.; Kurek, K.; Kurjata, R.P.; Lednev, A.A.; Lehmann, A.; Levillain, M.; Levorato, S.; Lichtenstadt, J.; Longo, R.; Maggiora, A.; Magnon, A.; Makins, N.; Makke, N.; Mallot, G.K.; Marchand, C.; Marianski, B.; Martin, A.; Marzec, J.; J.Matou s; Matsuda, H.; Matsuda, T.; Meshcheryakov, G.V.; Meyer, W.; Michigami, T.; Mikhailov, Yu. V.; Mikhasenko, M.; Miyachi, Y.; Montuenga, P.; Nagaytsev, A.; Nerling, F.; Neyret, D.; Nikolaenko, V.I.; Novy, J.; Nowak, W.D.; Nukazuka, G.; Nunes, A.S.; Olshevsky, A.G.; Orlov, I.; Ostrick, M.; Panzieri, D.; Parsamyan, B.; Paul, S.; Peng, J.C.; Pereira, F.; M. Pe s; Peshekhonov, D.V.; Platchkov, S.; Pochodzalla, J.; Polyakov, V.A.; Pretz, J.; Quaresma, M.; Quintans, C.; Ramos, S.; Regali, C.; Reicherz, G.; Riedl, C.; Roskot, M.; Rossiyskaya, N.S.; Ryabchikov, D.I.; Rybnikov, A.; Rychter, A.; Salac, R.; Samoylenko, V.D.; Sandacz, A.; Santos, C.; Sarkar, S.; Savin, I.A.; Sawada, T.; Sbrizzai, G.; Schiavon, P.; Schmidt, K.; Schmieden, H.; Schonning, K.; Schopferer, S.; Seder, E.; Selyunin, A.; Shevchenko, O.Yu.; Silva, L.; Sinha, L.; Sirtl, S.; Slunecka, M.; Smolik, J.; Sozzi, F.; Srnka, A.; Stolarski, M.; Sulc, M.; Suzuki, H.; Szabelski, A.; Szameitat, T.; Sznajder, P.; Takekawa, S.; Tasevsky, M.; Tessaro, S.; Tessarotto, F.; Thibaud, F.; Tosello, F.; Tskhay, V.; Uhl, S.; Veloso, J.; Virius, M.; Vondra, J.; Weisrock, T.; Wilfert, M.; Wolbeek, J. ter; Zaremba, K.; Zavada, P.; Zavertyaev, M.; Zemlyanichkina, E.; Ziembicki, M.; Zink, A.
2017-01-01
Using a novel analysis technique, the gluon polarisation in the nucleon is re-evaluated using the longitudinal double-spin asymmetry measured in the cross section of semi-inclusive single-hadron muoproduction with photon virtuality $Q^2>1~({\\rm GeV}/c)^2$. The data were obtained by the COMPASS experiment at CERN using a 160 GeV/$c$ polarised muon beam impinging on a polarised $^6$LiD target. By analysing the full range in hadron transverse momentum $p_T$, the different $p_T$-dependences of the underlying processes are separated using a neural-network approach. In the absence of pQCD calculations at next-to-leading order in the selected kinematic domain, the gluon polarisation $\\Delta g/g$ is evaluated at leading order in pQCD at a hard scale of $\\mu^2 = \\langle Q^2\\rangle = 3(GeV=c)^2$. It is determined in three intervals of the nucleon momentum fraction carried by gluons, $x_g$, covering the range $0.04 \\!<\\! x_{ \\rm g}\\! <\\! 0.28$ . and does not exhibit a significant dependence on $x_{\\rm g}$. Average...
Hard pair production in large-angle Bhabha scattering
International Nuclear Information System (INIS)
Arbuzov, A.B.; Trentadue, L.
1996-01-01
The cross section of hard pair production in large-angle Bhabha scattering calculated in the leading and next-to-leading logarithmic approximations. Eight regions of the collinear kinematics, when the final particles imitate a process of the 2 →2 type, and three semicollinear regions, when the final particles imitate a process of the 2→3 type, are considered. Analytical formulae for differential cross sections are presented. (orig.)
International Nuclear Information System (INIS)
Adolph, C.; Braun, C.; Eyrich, W.; Lehmann, A.; Zink, A.; Aghasyan, M.; Birsa, R.; Dalla Torre, S.; Levorato, S.; Santos, C.; Sozzi, F.; Tessaro, S.; Tessarotto, F.; Akhunzyanov, R.; Alexeev, G.D.; Anfimov, N.V.; Anosov, V.; Efremov, A.; Gavrichtchouk, O.P.; Guskov, A.; Ivanshin, Yu.; Kisselev, Yu.; Kouznetsov, O.M.; Kroumchtein, Z.V.; Meshcheryakov, G.V.; Nagaytsev, A.; Olshevsky, A.G.; Orlov, I.; Peshekhonov, D.V.; Rossiyskaya, N.S.; Rybnikov, A.; Savin, I.A.; Selyunin, A.; Shevchenko, O.Yu.; Slunecka, M.; Smolik, J.; Tasevsky, M.; Zavada, P.; Zemlyanichkina, E.; Alexeev, M.G.; Amoroso, A.; Balestra, F.; Chiosso, M.; Gnesi, I.; Grasso, A.; Ivanov, A.; Kotzinian, A.M.; Longo, R.; Parsamyan, B.; Takekawa, S.; Andrieux, V.; Boer, M.; Curiel, Q.; Ferrero, A.; Fuchey, E.; Hose, N. d'; Kunne, F.; Levillain, M.; Magnon, A.; Marchand, C.; Neyret, D.; Platchkov, S.; Seder, E.; Thibaud, F.; Augustyniak, W.; Klimaszewski, K.; Kurek, K.; Marianski, B.; Sandacz, A.; Szabelski, A.; Sznajder, P.; Austregesilo, A.; Chung, S.U.; Friedrich, J.M.; Grabmueller, S.; Grube, B.; Haas, F.; Huber, S.; Kraemer, M.; Krinner, F.; Paul, S.; Uhl, S.; Azevedo, C.D.R.; Pereira, F.; Veloso, J.; Badelek, B.; Barth, J.; Hahne, D.; Klein, F.; Pretz, J.; Schmieden, H.; Beck, R.; Bisplinghoff, J.; Eversheim, P.D.; Hinterberger, F.; Jahn, R.; Joosten, R.; Ketzer, B.; Mikhasenko, M.; Bedfer, Y.; Bernhard, J.; Bicker, K.; Bielert, E.R.; Mallot, G.K.; Schoenning, K.; Bodlak, M.; Finger, M.; Finger, M. Jr.; Matousek, J.; Pesek, M.; Roskot, M.; Bordalo, P.; Franco, C.; Nunes, A.S.; Quaresma, M.; Quintans, C.; Ramos, S.; Silva, L.; Stolarski, M.; Bradamante, F.; Bressan, A.; Dasgupta, S.; Makke, N.; Martin, A.; Sbrizzai, G.; Schiavon, P.; Buechele, M.; Fischer, H.; Gorzellik, M.; Grussenmeyer, T.; Heinsius, F.H.; Herrmann, F.; Joerg, P.; Koenigsmann, K.; Kremser, P.; Nowak, W.D.; Regali, C.; Schmidt, K.; Schopferer, S.; Sirtl, S.; Szameitat, T.; Wolbeek, J. ter; Chang, W.C.; Hsieh, C.Y.; Sawada, T.; Choi, I.; Giordano, F.; Grosse Perdekamp, M.; Heitz, R.; Kulinich, Y.; Makins, N.; Montuenga, P.; Peng, J.C.; Riedl, C.; Cicuttin, A.; Crespo, M.L.; Dasgupta, S.S.; Dhara, L.; Sarkar, S.; Sinha, L.; Denisov, O.Yu.; Maggiora, A.; Panzieri, D.; Tosello, F.; Donskov, S.V.; Khaustov, G.V.; Khokhlov, Yu.A.; Kolosov, V.N.; Konstantinov, V.F.; Lednev, A.A.; Mikhailov, Yu.V.; Nikolaenko, V.I.; Polyakov, V.A.; Ryabchikov, D.I.; Samoylenko, V.D.; Doshita, N.; Hashimoto, R.; Ishimoto, S.; Iwata, T.; Kondo, K.; Matsuda, H.; Michigami, T.; Miyachi, Y.; Nukazuka, G.; Suzuki, H.; Duic, V.; Dziewiecki, M.; Kurjata, R.P.; Marzec, J.; Rychter, A.; Zaremba, K.; Ziembicki, M.; Fresne von Hohenesche, N. du; Harrach, D. von; Kabuss, E.; Nerling, F.; Ostrick, M.; Pochodzalla, J.; Weisrock, T.; Wilfert, M.
2017-01-01
Using a novel analysis technique, the gluon polarisation in the nucleon is re-evaluated using the longitudinal double-spin asymmetry measured in the cross section of semi-inclusive single-hadron muoproduction with photon virtuality Q"2 > 1 (GeV/c)"2. The data were obtained by the COMPASS experiment at CERN using a 160 GeV/c polarised muon beam impinging on a polarised "6LiD target. By analysing the full range in hadron transverse momentum p_T, the different p_T-dependences of the underlying processes are separated using a neural-network approach. In the absence of pQCD calculations at next-to-leading order in the selected kinematic domain, the gluon polarisation Δg/g is evaluated at leading order in pQCD at a hard scale of μ"2 = left angle Q"2 right angle = 3 (GeV/c)"2. It is determined in three intervals of the nucleon momentum fraction carried by gluons, x_g, covering the range 0.04 < x_g < 0.28 and does not exhibit a significant dependence on x_g. The average over the three intervals, left angle Δg/g right angle = 0.113 ± 0.038_(_s_t_a_t_._) ± 0.036_(_s_y_s_t_._) at left angle x_g right angle ∼ 0.10, suggests that the gluon polarisation is positive in the measured x_g range. (orig.)
Energy Technology Data Exchange (ETDEWEB)
Adolph, C.; Braun, C.; Eyrich, W.; Lehmann, A.; Zink, A. [Universitaet Erlangen-Nuernberg, Physikalisches Institut, Erlangen (Germany); Aghasyan, M.; Birsa, R.; Dalla Torre, S.; Levorato, S.; Santos, C.; Sozzi, F.; Tessaro, S.; Tessarotto, F. [INFN, Trieste (Italy); Akhunzyanov, R.; Alexeev, G.D.; Anfimov, N.V.; Anosov, V.; Efremov, A.; Gavrichtchouk, O.P.; Guskov, A.; Ivanshin, Yu.; Kisselev, Yu.; Kouznetsov, O.M.; Kroumchtein, Z.V.; Meshcheryakov, G.V.; Nagaytsev, A.; Olshevsky, A.G.; Orlov, I.; Peshekhonov, D.V.; Rossiyskaya, N.S.; Rybnikov, A.; Savin, I.A.; Selyunin, A.; Shevchenko, O.Yu.; Slunecka, M.; Smolik, J.; Tasevsky, M.; Zavada, P.; Zemlyanichkina, E. [Joint Institute for Nuclear Research, Dubna, Moscow region (Russian Federation); Alexeev, M.G. [University of Turin, Department of Physics, Turin (Italy); Amoroso, A.; Balestra, F.; Chiosso, M.; Gnesi, I.; Grasso, A.; Ivanov, A.; Kotzinian, A.M.; Longo, R.; Parsamyan, B.; Takekawa, S. [University of Turin, Department of Physics, Turin (Italy); INFN, Turin (Italy); Andrieux, V.; Boer, M.; Curiel, Q.; Ferrero, A.; Fuchey, E.; Hose, N. d'
2017-04-15
Using a novel analysis technique, the gluon polarisation in the nucleon is re-evaluated using the longitudinal double-spin asymmetry measured in the cross section of semi-inclusive single-hadron muoproduction with photon virtuality Q{sup 2} > 1 (GeV/c){sup 2}. The data were obtained by the COMPASS experiment at CERN using a 160 GeV/c polarised muon beam impinging on a polarised {sup 6}LiD target. By analysing the full range in hadron transverse momentum p{sub T}, the different p{sub T}-dependences of the underlying processes are separated using a neural-network approach. In the absence of pQCD calculations at next-to-leading order in the selected kinematic domain, the gluon polarisation Δg/g is evaluated at leading order in pQCD at a hard scale of μ{sup 2} = left angle Q{sup 2} right angle = 3 (GeV/c){sup 2}. It is determined in three intervals of the nucleon momentum fraction carried by gluons, x{sub g}, covering the range 0.04 < x{sub g} < 0.28 and does not exhibit a significant dependence on x{sub g}. The average over the three intervals, left angle Δg/g right angle = 0.113 ± 0.038{sub (stat.)} ± 0.036{sub (syst.)} at left angle x{sub g} right angle ∼ 0.10, suggests that the gluon polarisation is positive in the measured x{sub g} range. (orig.)
Investigation of non-collinear spin states with scanning tunneling microscopy.
Wulfhekel, W; Gao, C L
2010-03-05
Most ferromagnetic and antiferromagnetic substances show a simple collinear arrangement of the local spins. Under certain circumstances, however, the spin configuration is non-collinear. Scanning tunneling microscopy with its potential atomic resolution is an ideal tool for investigating these complex spin structures. Non-collinearity can be due to topological frustration of the exchange interaction, due to relativistic spin-orbit coupling or can be found in excited states. Examples for all three cases are given, illustrating the capabilities of spin-polarized scanning tunneling microscopy.
Examination of evidence for collinear cluster tri-partition
Pyatkov, Yu. V.; Kamanin, D. V.; Alexandrov, A. A.; Alexandrova, I. A.; Goryainova, Z. I.; Malaza, V.; Mkaza, N.; Kuznetsova, E. A.; Strekalovsky, A. O.; Strekalovsky, O. V.; Zhuchko, V. E.
2017-12-01
Background: In a series of experiments at different time-of-flight spectrometers of heavy ions we have observed manifestations of a new at least ternary decay channel of low excited heavy nuclei. Due to specific features of the effect, it was called collinear cluster tri-partition (CCT). The obtained experimental results have initiated a number of theoretical articles dedicated to different aspects of the CCT. Special attention was paid to kinematics constraints and stability of collinearity. Purpose: To compare theoretical predictions with our experimental data, only partially published so far. To develop the model of one of the most populated CCT modes that gives rise to the so-called "Ni-bump." Method: The fission events under analysis form regular two-dimensional linear structures in the mass correlation distributions of the fission fragments. The structures were revealed both at a highly statistically reliable level but on the background substrate, and at the low statistics in almost noiseless distribution. The structures are bounded by the known magic fragments and were reproduced at different spectrometers. All this provides high reliability of our experimental findings. The model of the CCT proposed here is based on theoretical results, published recently, and the detailed analysis of all available experimental data. Results: Under our model, the CCT mode giving rise to the Ni bump occurs as a two-stage breakup of the initial three body chain like the nuclear configuration with an elongated central cluster. After the first scission at the touching point with one of the side clusters, the predominantly heavier one, the deformation energy of the central cluster allows the emission of up to four neutrons flying apart isotropically. The heavy side cluster and a dinuclear system, consisting of the light side cluster and the central one, relaxed to a less elongated shape, are accelerated in the mutual Coulomb field. The "tip" of the dinuclear system at the moment
χc charmonium - a tool to investigate gluon polarization
International Nuclear Information System (INIS)
Batunin, A.V.; Slabospitskij, S.R.
1986-01-01
Production of particles with a hidden charm Χ C in polarized parton beams (quarks or gluons) is studied. Parton polarization is shown to cause the changes of angular distributions of Χ C meson decay products, which allows one to investigate possible gluon polarization in hadrons
Accessing the distribution of linearly polarized gluons in unpolarized hadrons
Boer, Daniël; Brodsky, Stanley J.; Mulders, Piet J.; Pisano, Cristian
2011-01-01
Gluons inside unpolarized hadrons can be linearly polarized provided they have a nonzero transverse momentum. The simplest and theoretically safest way to probe this distribution of linearly polarized gluons is through cos(2 phi) asymmetries in heavy quark pair or dijet production in electron-hadron
Proton-proton elastic scattering with massive gluons
International Nuclear Information System (INIS)
Sauter, Werner K.; Ducati, M.B. Gay
2001-01-01
In this contribution different approaches to generate a gluon mass are discussed. More specially a recent result for the gluon propagator with a dynamical mass, proposal by Gorbar and Natale, is used in connection with the Landshoff-Nachtmann model for the Pomeron to describe the elastic differential cross section for pp scattering, with good agreement. (author)
Differences between quark and gluon jets as seen at LEP
International Nuclear Information System (INIS)
Tasevsky, M.
2001-01-01
The differences between quark and gluon jets are studied using LEP results on jet widths, scale dependent multiplicities, ratios of multiplicities, slopes and curvatures and fragmentation functions. It is emphasized that the observed differences stem primarily from the different quark and gluon colour factors
Differences between Quark and Gluon jets as seen at LEP
Tasevsky, Marek
2001-01-01
The differences between quark and gluon jets are studied using LEP results on jet widths, scale dependent multiplicities, ratios of multiplicities, slopes and curvatures and fragmentation functions. It is emphasized that the observed differences stem primarily from the different quark and gluon colour factors.
EXPLORING THE POLARIZATION OF GLUONS IN THE NUCLEON.
Energy Technology Data Exchange (ETDEWEB)
STRATMANN,M.; VOGELSANG,W.
2007-10-22
We give an overview of the current status of investigations of the polarization of gluons in the nucleon. We describe some of the physics of the spin-dependent gluon parton distribution and its phenomenology in high-energy polarized hadronic scattering. We also review the recent experimental results.
Regge behaviour of distribution functions and evolution of gluon ...
Indian Academy of Sciences (India)
work we solved DGLAP evolution equation for gluon distribution function at low-x in next-to-leading order (NLO) and the t and x-evolutions of gluon distribution function thus obtained have been compared with global MRST2004 and GRV98 parametrizations. In PQCD, since the higher-order terms in the leading logarithmic.
Linearly Polarized Gluons and the Higgs Transverse Momentum Distribution
Boer, Daniel; den Dunnen, Wilco J.; Pisano, Cristian; Schlegel, Marc; Vogelsang, Werner
2012-01-01
We study how gluons carrying linear polarization inside an unpolarized hadron contribute to the transverse momentum distribution of Higgs bosons produced in hadronic collisions. They modify the distribution produced by unpolarized gluons in a characteristic way that could be used to determine
Gluon condensate from lattice caculations: SU(3) pure gauge theory
International Nuclear Information System (INIS)
Kripfganz, J.
1981-01-01
A short distance expansion of Wilson loops is used to define and isolate vacuum expectation values of composite gluon operators. It is applied to available lattice Monte Carlo data for SU(3) pure gauge theory. The value obtained for the gluon condensate is consistent with the ITEP estimate. (author)
The Mixed Quark-Gluon Condensate from the Global Color Symmetry Model
Institute of Scientific and Technical Information of China (English)
ZONG Hong-Shi; PING Jia-Lun; LU Xiao-Fu; WANG Fan; ZHAO En-Guang
2002-01-01
The mixed quark-gluon condensate from the global color symmetry model is derived. It is shown that themixed quark-gluon condensate depends explicitly on the gluon propagator. This interesting feature may be regarded asan additional constraint on the model of gluon propagator. The values of the mixed quark-gluon condensate from someansatz for the gluon propagator are compared with those determined from QCD sum rules.
Equation of state of quasi-free gluon gas
International Nuclear Information System (INIS)
Chakrabarty, Somenath; Syam, Debapriyo
1993-01-01
The object of this work is to derive an equation of state for a system of gluons beyond the deconfining temperature (∼200 MeV) with phenomenological applications in mind. Our starting point is the relativistic virial theorem. We assume that the non-Abelian nature of QCD (especially the confirming gluon-gluon interaction), as far as the gluon gas is concerned, can be accounted for by postulating a bag pressure (B), while the residual interaction among the gluons can be treated as if the problem is Abelian. Near the 'critical' temperature the residual interactions are seen to play an important role. Also the Stefan-Boltzmann constant is required to be replaced by an effective constant having a somewhat smaller value. (Author)
Selection of Photon Gluon Fusion Events in DIS
International Nuclear Information System (INIS)
Kowalik, K.; Rondio, E.; Sulej, R.; Zaremba, K.
2001-01-01
A selection of the Photon Gluon Fusion (PGF) process with light quarks for deep inelastic scattering events is presented. This process is directly sensitive to gluon polarization and our goal is to find out the most effective selection on a sample of events simulated for the SMC experiment. We compare two general multi-class classification methods - Bayes method and neural network with a conventional selection procedure. The neural network algorithm presented here is a modification of method belonging to the family of directional minimization algorithms. This method is convenient and effective for photon gluon fusion selection and determination of gluon polarization. Finally we present the estimation for precision of gluon polarization for neural network method. (author)
Bound states of quarks and gluons and hadronic transitions
International Nuclear Information System (INIS)
Castro, Antonio Soares de.
1990-05-01
A potential which incorporates the concepts of confinement and asymptotic freedom, previously utilized in the description of the spectroscopy of mesons and baryons, is extended to the gluon sector. The mass spectroscopy of glueballs and hybrids is analyzed considering only pairwise potentials and massive constituent gluons. The mass spectrum of the color octet two-gluon system is adopted as a suitable description of the intermediate states of hadronic transitions, within the framework of the multipole expansion for quantum chromodynamics. The spin-dependent effects in the gluonium spectrum, associated with the Coulombian potential, are calculated through the inverted first Born approximation for the gluon-gluon scattering. (author). 102 refs, 1 fig, 13 tabs
The collinearly-improved Balitsky–Kovchegov equation
Energy Technology Data Exchange (ETDEWEB)
Iancu, E.; Madrigal, J.D. [Institut de Physique Théorique, CEA Saclay, CNRS UMR 3681, F-91191 Gif-sur-Yvette (France); Mueller, A.H. [Department of Physics, Columbia University, New York, NY 10027 (United States); Soyez, G. [Institut de Physique Théorique, CEA Saclay, CNRS UMR 3681, F-91191 Gif-sur-Yvette (France); Triantafyllopoulos, D.N. [European Centre for Theoretical Studies in Nuclear Physics and Related Areas ECT* and Fondazione Bruno Kessler, Strada delle Tabarelle 286, I-38123 Villazzano (Italy)
2016-12-15
The high-energy evolution in perturbative QCD suffers from a severe lack-of-convergence problem, due to higher order corrections enhanced by double and single transverse logarithms. We resum double logarithms to all orders within the non-linear Balitsky-Kovchegov equation, by taking into account successive soft gluon emissions strongly ordered in lifetime. We further resum single logarithms generated by the first non-singular part of the splitting functions and by the one-loop running of the coupling. The resummed BK equation admits stable solutions, which are used to successfully fit the HERA data at small x for physically acceptable initial conditions and reasonable values of the fit parameters.
International Nuclear Information System (INIS)
Ioffe, B.L.; Khoze, V.A.; Lipatov, L.N.
1984-01-01
Deep inelastic (hard) processes are now at the epicenter of modern high-energy physics. These processes are governed by short-distance dynamics, which reveals the intrinsic structure of elementary particles. The theory of deep inelastic processes is now sufficiently well settled. The authors' aim was to give an effective tool to theoreticians and experimentalists who are engaged in high-energy physics. This book is intended primarily for physicists who are only beginning to study the field. To read the book, one should be acquainted with the Feynman diagram technique and with some particular topics from elementary particle theory (symmetries, dispersion relations, Regge pole theory, etc.). Theoretical consideration of deep inelastic processes is now based on quantum chromodynamics (QCD). At the same time, analysis of relevant physical phenomena demands a synthesis of QCD notions (quarks, gluons) with certain empirical characteristics. Therefore, the phenomenological approaches presented are a necessary stage in a study of this range of phenomena which should undoubtedly be followed by a detailed description based on QCD and electroweak theory. The authors were naturally unable to dwell on experimental data accumulated during the past decade of intensive investigations. Priority was given to results which allow a direct comparison with theoretical predictions. (Auth.)
Hadron collisions and the fifth form factor
International Nuclear Information System (INIS)
Dokshitzer, Yu.L.; Marchesini, G.
2005-01-01
Logarithmically enhanced effects due to radiation of soft gluons at large angles in 2->2 QCD scattering processes are treated in terms of the ''fifth form factor'' that accompanies the four collinear singular Sudakov form factors attached to incoming and outgoing hard partons. Unexpected symmetry under exchange of internal and external variables of the problem is pointed out for the anomalous dimension that governs soft gluon effects in hard gluon-gluon scattering
Collinear resonant ionization laser spectroscopy of rare francium isotopes
Neyens, G; Flanagan, K; Rajabali, M M; Le blanc, F M; Ware, T; Procter, T J
2008-01-01
We propose a programme of collinear resonant ionization spectroscopy (CRIS) of the francium isotopes up to and including $^{201}$Fr and $^{218,219}$Fr. This work aims at answering questions on the ordering of quantum states, and effect of the ($\\pi s_{1/2}^{-1}$)1/2$^{+}$ intruder state, which is currently believed to be the ground state of $^{199}$Fr. This work will also study the edge of the region of reflection asymmetry through measurement of the moments and radii of $^{218,219}$Fr. This proposal forms the first part of a series of experiments that will study nuclei in this region of the nuclear chart. Based on the success of this initial proposal it is the intention of the collaboration to perform high resolution measurements on the isotopes of radium and radon that surround $^{201}$Fr and $^{218}$Fr and thus providing a comprehensive description of the ground state properties of this region of the nuclear chart. Recent in-source spectroscopy measurements of lead, bismuth and polonium have demonstrated a...
Magnon detection using a ferroic collinear multilayer spin valve.
Cramer, Joel; Fuhrmann, Felix; Ritzmann, Ulrike; Gall, Vanessa; Niizeki, Tomohiko; Ramos, Rafael; Qiu, Zhiyong; Hou, Dazhi; Kikkawa, Takashi; Sinova, Jairo; Nowak, Ulrich; Saitoh, Eiji; Kläui, Mathias
2018-03-14
Information transport and processing by pure magnonic spin currents in insulators is a promising alternative to conventional charge-current-driven spintronic devices. The absence of Joule heating and reduced spin wave damping in insulating ferromagnets have been suggested for implementing efficient logic devices. After the successful demonstration of a majority gate based on the superposition of spin waves, further components are required to perform complex logic operations. Here, we report on magnetization orientation-dependent spin current detection signals in collinear magnetic multilayers inspired by the functionality of a conventional spin valve. In Y 3 Fe 5 O 12 |CoO|Co, we find that the detection amplitude of spin currents emitted by ferromagnetic resonance spin pumping depends on the relative alignment of the Y 3 Fe 5 O 12 and Co magnetization. This yields a spin valve-like behavior with an amplitude change of 120% in our systems. We demonstrate the reliability of the effect and identify its origin by both temperature-dependent and power-dependent measurements.
Magnon spintronics in non-collinear magnetic insulator/metal heterostructures
Aqeel, Aisha
2017-01-01
The research presented in this thesis focuses on the growth of complex magnetic materials with unique magnetic properties and experimental investigation of fundamental spintronics phenomena in these magnetic insulators with magnetic orders varying from collinear to noncollinear chiral spin
Frustrated magnets : non-collinear spin textures, excitations and dynamics
Artyukhin, Sergey
2012-01-01
Moderne datacentra gebruiken magnetische harde schijven om gegevens op te slaan. De technologie voor het uitlezen van de opgeslagen magnetische informatie verbeterde aanzienlijk na de ontdekking van giant magnetoresistance, waarvoor in 2007 de Nobelprijs is toegekend. Het proefschrift van Sergey
Quarkonium decays: Testing the 3-gluon vertex
International Nuclear Information System (INIS)
Koller, K.; Walsh, T.F.; Zerwas, P.M.; Technische Hochschule Aachen
1980-12-01
We study the 3-jet decays of S and P-wave quarkonia with C = +. If observed, some of these will offer a way of seeing the 3G vertex of QCD via 1 Ssub(o), 3 Psub(o), 3 P 2 (Qanti Q) → GGG + Gqanti q → 3 jets. (As is well-known, cancellations reduce 3 P 1 (anti Q) → GGG.) We elaborate in detail the S-wave decay as it is expected to show all the characteristic features of orthoquarkonium decays into 4 jets, 3 S 1 (Qanti Q) → GGGG + GGqanti q → 4 jets which we will comment upon. These quarkonium decays offer a very clear signal for QCD as a non-abelian local gauge field theory with color-charged gluons. (orig.)
Very boosted Higgs in gluon fusion
Grojean, Christophe; Schlaffer, Matthias; Weiler, Andreas
2014-01-01
The Higgs production and decay rates offer a new way to probe new physics beyond the Standard Model. While dynamics aiming at alleviating the hierarchy problem generically predict deviations in the Higgs rates, the current experimental analyses cannot resolve the long- and short-distance contributions to the gluon fusion process and thus cannot access directly the coupling between the Higgs and the top quark. We investigate the production of a boosted Higgs in association with a high-transverse momentum jet as an alternative to the $t\\bar{t}h$ channel to pin down this crucial coupling. Presented first in the context of an effective field theory, our analysis is then applied to models of partial compositeness at the TeV scale and of natural supersymmetry.
Quark-gluon plasma: experimental signatures
International Nuclear Information System (INIS)
Drapier, O.
1995-01-01
The existence of a deconfining phase transition of nuclear matter is a clear prediction of lattice quantum chromodynamics calculations. The signatures of this quark-gluon plasma (QGP) have been searched for, since the first high energy ion beams became available at BNL and CERN in 1986, and gold and lead beams are now accelerated at 11 and 160 GeV per nucleon by the AGS and SPS. An overview of the main signatures expected in case of QGP formation is presented here. Although some recent results have been found in agreement with the predictions of the QGP scenario, no clear evidence for its formation has been observed at present. Nevertheless, new high statistics results are expected from CERN lead beams. In addition, future experiments are being prepared at RHIC and LHCC, providing an increase by two orders of magnitude of the c.m.s. energy within a few years. (author). 66 refs., 28 figs
Very boosted Higgs in gluon fusion
Energy Technology Data Exchange (ETDEWEB)
Grojean, C. [Univ. Autonoma de Barcelona, Bellaterra (Spain). ICREA at IFAE; Salvioni, E. [California Univ., Davis, CA (United States). Dept. of Physics; European Organization for Nuclear Research (CERN), Geneva (Switzerland); Padova Univ. (Italy). Dipt. di Fisica e Astronomica; INFN, Sezione di Padova (Italy); Schlaffer, M. [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany); Weiler, A. [European Organization for Nuclear Research (CERN), Geneva (Switzerland); Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany)
2013-12-15
The Higgs production and decay rates offer a new way to probe new physics beyond the Standard Model. While dynamics aiming at alleviating the hierarchy problem generically predict deviations in the Higgs rates, the current experimental analyses cannot resolve the long- and short-distance contributions to the gluon fusion process and thus cannot access directly the coupling between the Higgs and the top quark. We investigate the production of a boosted Higgs in association with a high-transverse momentum jet as an alternative to the t anti th channel to pin down this crucial coupling. Presented rst in the context of an effective field theory, our analysis is then applied to models of partial compositeness at the TeV scale and of natural supersymmetry.
Gluon Green functions free of quantum fluctuations
Directory of Open Access Journals (Sweden)
A. Athenodorou
2016-09-01
Full Text Available This letter reports on how the Wilson flow technique can efficaciously kill the short-distance quantum fluctuations of 2- and 3-gluon Green functions, remove the ΛQCD scale and destroy the transition from the confining non-perturbative to the asymptotically-free perturbative sector. After the Wilson flow, the behavior of the Green functions with momenta can be described in terms of the quasi-classical instanton background. The same behavior also occurs, before the Wilson flow, at low-momenta. This last result permits applications as, for instance, the detection of instanton phenomenological properties or a determination of the lattice spacing only from the gauge sector of the theory.
Energy Technology Data Exchange (ETDEWEB)
Castro, Antonio Soares de
1990-05-01
A potential which incorporates the concepts of confinement and asymptotic freedom, previously utilized in the description of the spectroscopy of mesons and baryons, is extended to the gluon sector. The mass spectroscopy of glueballs and hybrids is analyzed considering only pairwise potentials and massive constituent gluons. The mass spectrum of the color octet two-gluon system is adopted as a suitable description of the intermediate states of hadronic transitions, within the framework of the multipole expansion for quantum chromodynamics. The spin-dependent effects in the gluonium spectrum, associated with the Coulombian potential, are calculated through the inverted first Born approximation for the gluon-gluon scattering. (author). 102 refs, 1 fig, 13 tabs.
Improved hard-thermal-loop effective action for hot QED and QCD
International Nuclear Information System (INIS)
Flechsig, F.; Rebhan, A.K.
1995-01-01
The conventional results for hard thermal loops, which are the building blocks of resummed perturbation theory in thermal field theories, have collinear singularities when external momenta are light-like. It is shown that by taking into account asymptotic thermal masses these singularities are removed. The thus improved hard thermal loops can be summarized by compact gauge-invariant effective actions, generalizing the ones found by Taylor and Wong, and by Braaten and Pisarski. (orig.)
Baryonic hybrids: Gluons as beads on strings between quarks
International Nuclear Information System (INIS)
Cornwall, John M.
2005-01-01
In this paper we analyze the ground state of the heavy-quark qqqG system using standard principles of quark confinement and massive constituent gluons as established in the center-vortex picture. The known string tension K F and approximately-known gluon mass M lead to a precise specification of the long-range nonrelativistic part of the potential binding the gluon to the quarks with no undetermined phenomenological parameters, in the limit of large interquark separation R. Our major tool (also used earlier by Simonov) is the use of proper-time methods to describe gluon propagation within the quark system, along with some elementary group theory describing the gluon Wilson-line as a composite of colocated q and q lines. We show that (aside from color-Coulomb and similar terms) the gluon potential energy in the presence of quarks is accurately described (for small gluon fluctuations) via attaching these three strings to the gluon, which in equilibrium sits at the Steiner point of the Y-shaped string network joining the three quarks. The gluon undergoes small harmonic fluctuations that slightly stretch these strings and quasiconfine the gluon to the neighborhood of the Steiner point. To describe nonrelativistic ground-state gluonic fluctuations at large R we use the Schroedinger equation, ignoring mixing with l=2 states. Available lattice data and real-world hybrids require consideration of R values small enough for significant relativistic corrections, which we apply using a variational principle for the relativistic harmonic-oscillator. We also consider the role of color-Coulomb contributions. In terms of interquark separations R, we find leading nonrelativistic large-R terms in the gluon excitation energy of the form ε(R)→M+ξ[K F /(MR)] 1/2 -ζα c /R where ξ,ζ are calculable numerical coefficients and α c ≅ 0.15 is the color-Coulomb qq coupling. When the gluon is relativistic, ε∼(K F /R) 1/3 . We get an acceptable fit to lattice data with M=500 Me
Massive Boson Production at Small qT in Soft-Collinear Effective Theory
Becher, Thomas; Neubert, Matthias; Wilhelm, Daniel
2013-01-01
We study the differential cross sections for electroweak gauge-boson and Higgs production at small and very small transverse-momentum qT. Large logarithms are resummed using soft-collinear effective theory. The collinear anomaly generates a non-perturbative scale q*, which protects the processes from receiving large long-distance hadronic contributions. A numerical comparison of our predictions with data on the transverse-momentum distribution in Z-boson production at the Tevatron and LHC is given.
Rapidity distribution of photons from an anisotropic quark-gluon plasma
International Nuclear Information System (INIS)
Bhattacharya, Lusaka; Roy, Pradip
2010-01-01
We calculate rapidity distribution of photons due to Compton and annihilation processes from quark gluon plasma with pre-equilibrium momentum-space anisotropy. We also include contributions from hadronic matter with late-stage transverse expansion. A phenomenological model has been used for the time evolution of hard momentum scale, p hard (τ), and anisotropy parameter, ξ(τ). As a result of pre-equilibrium momentum-space anisotropy, we find significant modification of photons rapidity distribution. For example, with the fixed initial condition (FIC) free-streaming (δ=2) interpolating model we observe significant enhancement of photon rapidity distribution at fixed p T , where as for FIC collisionally broadened (δ=2/3) interpolating model the yield increases till y∼1. Beyond that suppression is observed. With fixed final multiplicity (FFM) free-streaming interpolating model we predict enhancement of photon yield which is less than the case of FIC. Suppression is always observed for FFM collisionally broadened interpolating model.
The proton-induced collinear deuteron breakup at 7.5 MeV
International Nuclear Information System (INIS)
Lekkas, P.
1985-01-01
The aim of the present thesis was to study the proton-induced deuteron breakup at an incident energy of 7.5 MeV in collinear geometry. In kinematically complete experiments in which two of the three particles of the exit channel are detected in coincidence we determined in equal kinematics the breakup cross section of the three-particle reactions 2 H(p,pp)n and 2 H(p,np)p. In both cases we observed in the region of the collinearity point an - indeed only weak - increasement of the cross section. The collinearity occurs in the neighbourhood of the QFS. Faddeev calculations with two different nucleon-nucleon interactions describe in the collinearity point the shape of the spectra well. Also the absolute quantity of the measured data in this point is well confirmed for the reaction 2 H(p,pp)n, less well however for the reaction 2 H(p,np)p. If in the theory three-nucleon forces are implemented their influence in the collinearity point is proved to be quantitatively weak. The collinear region is from the results of the present thesis especially because of the closely adjacent QFS little significant for three-body forces. (orig./HSI) [de
Phase space and jet definitions in soft-collinear effective theory
International Nuclear Information System (INIS)
Cheung, William Man-Yin; Luke, Michael; Zuberi, Saba
2009-01-01
We discuss consistent power counting for integrating soft and collinear degrees of freedom over arbitrary regions of phase space in the soft-collinear effective theory, and illustrate our results at one-loop with several jet algorithms: JADE, Sterman-Weinberg and k perpendicular . Consistently applying soft-collinear effective theory power counting in phase space, along with nontrivial zero-bin subtractions, prevents double counting of final states. The resulting phase space integrals over soft and collinear regions are individually ultraviolet divergent, but the phase space ultraviolet divergences cancel in the sum. Whether the soft and collinear contributions are individually infrared safe depends on the jet definition. We show that while this is true at one-loop for JADE and Sterman-Weinberg, the k perpendicular algorithm does not factorize into individually infrared safe soft and collinear pieces in dimensional regularization. We point out that this statement depends on the ultraviolet regulator, and that in a cutoff scheme the soft functions are infrared safe.
Shear and bulk viscosity of high-temperature gluon plasma
Zhang, Le; Hou, De-Fu
2018-05-01
We calculate the shear viscosity (η) and bulk viscosity (ζ) to entropy density (s) ratios η/s and ζ/s of a gluon plasma system in kinetic theory, including both the elastic {gg}≤ftrightarrow {gg} forward scattering and the inelastic soft gluon bremsstrahlung {gg}≤ftrightarrow {ggg} processes. Due to the suppressed contribution to η and ζ in the {gg}≤ftrightarrow {gg} forward scattering and the effective g≤ftrightarrow {gg} gluon splitting, Arnold, Moore and Yaffe (AMY) and Arnold, Dogan and Moore (ADM) have got the leading order computations for η and ζ in high-temperature QCD matter. In this paper, we calculate the correction to η and ζ in the soft gluon bremsstrahlung {gg}≤ftrightarrow {ggg} process with an analytic method. We find that the contribution of the collision term from the {gg}≤ftrightarrow {ggg} soft gluon bremsstrahlung process is just a small perturbation to the {gg}≤ftrightarrow {gg} scattering process and that the correction is at ∼5% level. Then, we obtain the bulk viscosity of the gluon plasma for the number-changing process. Furthermore, our leading-order result for bulk viscosity is the formula \\zeta \\propto \\tfrac{{α }s2{T}3}{ln}{α }s-1} in high-temperature gluon plasma. Supported by Ministry of Science and Technology of China (MSTC) under the “973” Project (2015CB856904(4)) and National Natural Science Foundation of China (11735007, 11521064)
Two-loop hard-thermal-loop thermodynamics with quarks
International Nuclear Information System (INIS)
Andersen, Jens O.; Petitgirard, Emmanuel; Strickland, Michael
2004-01-01
We calculate the quark contribution to the free energy of a hot quark-gluon plasma to two-loop order using hard-thermal-loop (HTL) perturbation theory. All ultraviolet divergences can be absorbed into renormalizations of the vacuum energy and the HTL quark and gluon mass parameters. The quark and gluon HTL mass parameters are determined self-consistently by a variational prescription. Combining the quark contribution with the two-loop HTL perturbation theory free energy for pure glue we obtain the total two-loop QCD free energy. Comparisons are made with lattice estimates of the free energy for N f =2 and with exact numerical results obtained in the large-N f limit
The SU(3) running coupling from lattice gluons
Energy Technology Data Exchange (ETDEWEB)
Parrinello, C. [Edinburgh Univ. (United Kingdom). Dept. of Phys. and Astron.; UKQCD Collaboration
1995-04-01
We provide numerical results for the running coupling in SU(3) Yang-Mills theory as determined from an analysis of lattice two and three-point gluon correlation functions. The coupling is evaluated directly, from first principles, by defining suitable renormalisation constants from the lattice triple gluon vertex and gluon propagator. For momenta larger than 2GeV, the coupling is found to run according to the 2-loop asymptotic formula. The influence of lattice artifacts on the results appears negligible within the precision of our measurements, although further work on this point is in progress. ((orig.)).
Infra-red ghost contribution to the gluon Green's functions
International Nuclear Information System (INIS)
Paccanoni, F.
1985-01-01
The Schwinger-Dyson equations for the ghost propagator and the ghost-ghost-gluon vertex function are studied in the Landau gauge. A confining infra-red singularity is assumed for the gluon propagator and a suitable approximation is devised for the solution of the integral equations. It is found that the bare values of the ghost propagator and coupling cannot be a consistent solution of either equation. It is determined a possible behaviour of the correction factor for the ghost propagator in the small-momentum limit and discussed the consistency of the approximation schemes for the gluon propagator that neglet Faddeev-Popov ghost
Heavy Flavour Production as Probe of Gluon Sivers Function
International Nuclear Information System (INIS)
Godbole, Rohini M.; Kaushik, Abhiram; Misra, Anuradha; Rawoot, Vaibhav; Sonawane, Bipin
2017-01-01
Heavy flavour production like J/ψ and D-meson production in scattering of electrons/unpolarized protons off polarized proton target offer promising probes to investigate gluon Sivers function. In this talk, I will summarize our recent work on transverse single spin asymmetry in J/ψ-production and D-meson production in pp↑ scattering using a generalized parton model approach. We compare predictions obtained using different models of gluon Sivers function within this approach and then, taking into account the transverse momentum dependent evolution of the unpolarized parton distribution functions and gluon Sivers function, we study the effect of evolution on asymmetry. (author)
Quark and gluon propagators in the spherical bag model
Energy Technology Data Exchange (ETDEWEB)
Kulish, Yu V [AN Ukrainskoj SSR, Fiziko-Tekhnicheskij Inst., Kharkov
1983-12-01
The quark and gluon propagators in a spherical cavity have been obtained by summation of the quark field modes (J-1/2, J is the total moment) and gluon field modes (J=1). The requirements for the spatial components of the gluon propagator Gsub(ik)(x, x') and the quark propagator S(x, x') to be Green functions of the wave equations result in the coincidence of directions for anti x and anti x' vectors. Relations have been derived which allow verification of the self-consistency of approximations used to calculate dynamic values.
Quark and gluon propagators in the spherical bag model
International Nuclear Information System (INIS)
Kulish, Yu.V.
1983-01-01
The quark and gluon propagators in a spherical cavity have been obtained by summation of the quark field modes (J-1/2, J is the total moment) and gluon field modes (J=1). The requirements for the spatial components of the gluon propagator Gsub(ik)(x, x') and the quark propagator S(x, x') to be Green functions of the wave equations result in the coincidence of directions for anti x and anti x' vectors. Relations have been derived which allow verification of the self-consistency of approximations used to calculate dynamic values
The gluon distribution at small x - a phenomenological analysis
International Nuclear Information System (INIS)
Harriman, P.N.; Martin, A.D.; Stirling, W.J.; Roberts, R.G.
1990-03-01
The size of the gluon distribution at small χ has important implications for phenomenology at future high energy hadron-hadron and lepton-hadron colliders. We extend a recent global parton distribution fit to investigate the constraints on the gluon from deep inelastic and prompt photon data. In particular, we estimate a band of allowed gluon distributions with qualitatively small-χ behaviour and study the implications of these on a variety of cross sections at high energy pp and ep colliders. (author)
Quark-gluon mixing in pseudoscalar and tensor mesons
International Nuclear Information System (INIS)
Eremyan, Sh.S.; Nazaryan, A.E.
1986-01-01
A mixing model of quark-antiquark ang gluonium states in η, η', i(1440) pseudoscalar and f, f', Θ(1690) tensor mesons is considered. Description of and predictions for 68 two-particle decays with these particles taking part in them are obtained. It is shown that i(1440) by 85% consists of gluonium and Θ(1690) is a pure gluonic state. The quark-gluon and gluon-gluon couplings in the pseudoscalar sector are obtained to be stronger as compared to the corresponding ones in the tensor case
Rapidity evolution of gluon TMD from low to moderate x
International Nuclear Information System (INIS)
Balitsky, I.
2016-01-01
I discuss how the rapidity evolution of gluon transverse momentum dependent distribution (TMD) changes from nonlinear evolution at small x << 1 to linear evolution at moderate x ∼ 1. I have described the rapidity evolution of gluon TMD in the whole range of Bjorken x B and the whole range of transverse momentum. It should be emphasized that with our definition of rapidity cutoff the leading-order matrix elements of TMD operators are UV-finite so the rapidity evolution is the only evolution and it describes all the dynamics of gluon TMDs in the leading-log approximation
Collinear laser spectroscopy on radioactive praseodymium ions and cadmium ions
International Nuclear Information System (INIS)
Froemmgen, Nadja
2013-01-01
Collinear laser spectroscopy is a tool for the model independent determination of spins, charge radii and electromagnetic moments of nuclei in ground and long-lived isomeric states. In the context of this thesis a new offline ion source for high evaporating temperatures and an ion beam analysis system were implemented at the TRIGA-LASER Experiment at the Institute for Nuclear Chemistry at the University of Mainz. The main part of the thesis deals with the determination of the properties of radioactive praseodymium and cadmium isotopes by collinear laser spectroscopy at ISOLDE/CERN. The necessary test measurements for the spectroscopy of praseodymium ions have been conducted with the aforementioned offline ion source at the TRIGA-LASER experiment. The spectroscopy of the praseodymium ions was motivated by the observation of a modulation of the electron capture decay rates of hydrogen-like 140 Pr 58+ . The nuclear magnetic moment of the nucleus is, among others, required for the explanation of the so-called GSI Oscillations and has not been studied experimentally before. Additionally, the determined electron capture decay constant of hydrogen-like 140 Pr 58+ is lower than the one of helium-like 140 Pr 57+ . The explanation of this phenomenon requires a positive magnetic moment. During the experiment at the COLLAPS apparatus the magnetic moments of the neutron-deficient isotopes 135 Pr, 136 Pr and 137 Pr could be determined for the first time. Unfortunately, due to a too low production yield the desired isotope 140 Pr could not be studied.The systematic study of cadmium isotopes was motivated by nuclear physics in the tin region. With Z=48 two protons are missing for the shell closure and the isotopes extend from the magic neutron number N=50 to the magic neutron number N=82. The extracted nuclear properties allow tests of different nuclear models in this region. In this thesis the obtained results of the spectroscopy of the cadmium isotopes 106-124,126 Cd and their
Open heavy flavor and other hard probes in ultra-relativistic heavy-ion collisions
Uphoff, Jan
2014-01-01
In this thesis hard probes are studied in the partonic transport model BAMPS (Boltzmann Approach to MultiParton Scatterings). Employing Monte Carlo techniques, this model describes the 3+1 dimensional evolution of the quark gluon plasma phase in ultra-relativistic heavy-ion collisions by propagating all particles in space and time and carrying out their collisions according to the Boltzmann equation. Since hard probes are produced in hard processes with a large momentum transfer, the value of...
The very hot soup of quarks and gluons; La tres chaude soupe de quarks et de gluons
Energy Technology Data Exchange (ETDEWEB)
Ter Minassian, V.
2010-05-15
The Phenix collaboration at the RHIC collider (Usa) has measured directly, for the first time, the temperature just after 2 gold nuclei have collided. All the experimental conditions were taken to assure that the temperature measured was that of the quark-gluon plasma. The value of this temperature is 4000*10{sup 9} K, which is 1.20 as high as the theoretical temperature threshold for the existence of the quark-gluon plasma. It is a proof that the quark-gluon plasma can be created within the operating conditions of the RHIC. (A.C.)
Role of the QCD induced gluon-gluon coupling to gauge boson pairs in the multitev region
International Nuclear Information System (INIS)
Ametller, L.; Gava, E.; Paver, N.; Treleani, D.
1985-02-01
We discuss the production of γγ and Zsup(O)γ pairs induced by the gluon-gluon fusion mechanism at typical supercollider energies. Due to the large flux of gluons with small fractional momenta, it is found that in certain kinematical configurations that subprocess, although of order (αsub(S)/π) 2 with respect to the leading quark annihilation, can give an appreciable contribution to the cross-section for Zsup(O)γ and even a larger one for the γγ production. (author)
Hard processes in hadronic interactions
International Nuclear Information System (INIS)
Satz, H.; Wang, X.N.
1995-01-01
Quantum chromodynamics is today accepted as the fundamental theory of strong interactions, even though most hadronic collisions lead to final states for which quantitative QCD predictions are still lacking. It therefore seems worthwhile to take stock of where we stand today and to what extent the presently available data on hard processes in hadronic collisions can be accounted for in terms of QCD. This is one reason for this work. The second reason - and in fact its original trigger - is the search for the quark-gluon plasma in high energy nuclear collisions. The hard processes to be considered here are the production of prompt photons, Drell-Yan dileptons, open charm, quarkonium states, and hard jets. For each of these, we discuss the present theoretical understanding, compare the resulting predictions to available data, and then show what behaviour it leads to at RHIC and LHC energies. All of these processes have the structure mentioned above: they contain a hard partonic interaction, calculable perturbatively, but also the non-perturbative parton distribution within a hadron. These parton distributions, however, can be studied theoretically in terms of counting rule arguments, and they can be checked independently by measurements of the parton structure functions in deep inelastic lepton-hadron scattering. The present volume is the work of Hard Probe Collaboration, a group of theorists who are interested in the problem and were willing to dedicate a considerable amount of their time and work on it. The necessary preparation, planning and coordination of the project were carried out in two workshops of two weeks' duration each, in February 1994 at CERn in Geneva andin July 1994 at LBL in Berkeley
Strangeness and the quark-gluon plasma: An experimenter's perspective
International Nuclear Information System (INIS)
Odyniec, G.
1994-02-01
Current status of experimental results on strange particle production in relativistic nucleus-nucleus collisions is reviewed. Emphasis is placed on the relevance to the hypothetical quark-gluon plasma formation and the origin of the Universe
The LPM effect in sequential bremsstrahlung: 4-gluon vertices
Energy Technology Data Exchange (ETDEWEB)
Arnold, Peter; Chang, Han-Chih [Department of Physics, University of Virginia,382 McCormick Road, Charlottesville, Virginia 22904-4714 (United States); Iqbal, Shahin [National Centre for Physics, Quaid-i-Azam University Campus, Islamabad, 45320 (Pakistan)
2016-10-24
The splitting processes of bremsstrahlung and pair production in a medium are coherent over large distances in the very high energy limit, which leads to a suppression known as the Landau-Pomeranchuk-Migdal (LPM) effect. In this paper, we continue study of the case when the coherence lengths of two consecutive splitting processes overlap (which is important for understanding corrections to standard treatments of the LPM effect in QCD), avoiding soft-gluon approximations. In particular, this paper completes the calculation of the rate for real double gluon bremsstrahlung from an initial gluon with various simplifying assumptions (thick media; q̂ approximation; and large N{sub c}) by now including processes involving 4-gluon vertices.
Resummation and the gluon damping rate in hot QCD
International Nuclear Information System (INIS)
Pisarski, R.D.
1990-08-01
At high temperature a consistent perturbative expansion requires the resummation of an infinite subset of loop corrections into an effective expansion. This effective exansion is used to compute the gluon damping rate at leading order. 25 refs
The gluon condensation at high energy hadron collisions
Energy Technology Data Exchange (ETDEWEB)
Zhu, Wei, E-mail: weizhu@mail.ecnu.edu.cn [Department of Physics, East China Normal University, Shanghai 200241 (China); Lan, Jiangshan [Institute of Modern Physics, Chinese Academy of Sciences, Lanzhou 730000 (China)
2017-03-15
We report that the saturation/CGC model of gluon distribution is unstable under action of the chaotic solution in a nonlinear QCD evolution equation, and it evolves to the distribution with a sharp peak at the critical momentum. We find that this gluon condensation is caused by a new kind of shadowing–antishadowing effects, and it leads to a series of unexpected effects in high energy hadron collisions including astrophysical events. For example, the extremely intense fluctuations in the transverse-momentum and rapidity distributions of the gluon jets present the gluon-jet bursts; a sudden increase of the proton–proton cross sections may fill the GZK suppression; the blocking QCD evolution will restrict the maximum available energy of the hadron–hadron colliders.
Differences between quark and gluon jets at LEP1
Boutemeur, Madjid
1997-01-01
A report is ven here on the differences between quark and gluon initiated jets as measured in LEPl. Various measurements, agree qualitatively on the differences between quark and gluon jets. However a direct quantitative comparison among the measurements as well as comparisons between the measurements and analytical calculations are difficult. This is due to the dependence of the results on the selected event topologies and used jet finding algorithms. Topology dependence of the charged particle multiplicity in quark and gluon jets is studied by ALEPH and transverse momentum-like scales are proposed to account for it. OPAL produced the first quantitative test of QCD analytic prediction for the ratio of the mean particle multiplicity between gluon and quark jets valid, at least, for 39 GeV jets.
A new method for computing the quark-gluon vertex
International Nuclear Information System (INIS)
Aguilar, A C
2015-01-01
In this talk we present a new method for determining the nonperturbative quark-gluon vertex, which constitutes a crucial ingredient for a variety of theoretical and phenomenological studies. This new method relies heavily on the exact all-order relation connecting the conventional quark-gluon vertex with the corresponding vertex of the background field method, which is Abelian-like. The longitudinal part of this latter quantity is fixed using the standard gauge technique, whereas the transverse is estimated with the help of the so-called transverse Ward identities. This method allows the approximate determination of the nonperturbative behavior of all twelve form factors comprising the quark-gluon vertex, for arbitrary values of the momenta. Numerical results are presented for the form factors in three special kinematical configurations (soft gluon and quark symmetric limit, zero quark momentum), and compared with the corresponding lattice data. (paper)
Time evolution of the quark-gluon plasma
International Nuclear Information System (INIS)
Cooper, F.; New Hampshire Univ., Durham, NH
1993-01-01
We review progress in our understanding the production and time evolution of the quark gluon plasma starting with boost invariant initial conditions in a filed theory model based on the Schwinger mechanism of particle production via tunneling
On the application of gluon to heavy quarkonium fragmentation function
International Nuclear Information System (INIS)
Qi Wei; Wang Jianxiong
2007-01-01
We analyze the uncertainties induced by different definitions of the momentum fraction z in the application of gluon to heavy quarkonium fragmentation function. We numerically calculate the initial g→J/ψ fragmentation functions by using the non-covariant definitions of z with finite gluon momentum and find that these fragmentation functions have strong dependence on the gluon momentum k. As |k|→∞, these fragmentation functions approach to the fragmentation function in the light-cone definition. We find that when |k| is small (for instance in the typical energy scale (about 4-20GeV) of the gluon production at the hadron colliders, such as Tevatron and LHC), large uncertainty remains while the in-covariant definitions of z are employed in the application of the fragmentation functions. (authors)
Calculation of parton fragmentation functions from jet calculus: gluon applications
International Nuclear Information System (INIS)
Lassila, K.E.; Ng, A.
1985-01-01
A method is presented for calculation of general parton fragmentation functions based on jet calculus plus meson and baryon wave functions. Results for gluon fragmentation into mesons and baryons are discussed and related to recent information on upsilon decay into gluons. The expressions derived can be used directly in e + e - cross section predictions and will need to be folded in with baryon parton distribution functions when used in p-barp collisions. (author)
Strangeness Production in a Chemically Equilibrating Quark-Gluon Plasma
Institute of Scientific and Technical Information of China (English)
HE Ze-Jun; LONG Jia-Li; MA Yu-Gang; MA Guo-Liang
2004-01-01
@@ We study the strangeness of a chemically equilibrating quark-gluon plasma at finite baryon density based on the and will accelerate with the change of the initial system from a chemically non-equilibrated to an equilibrated system. We also find that the calculated strangeness is very different from the one in the thermodynamic equilibrium system. This study may be helpful to understand the formation of quark-gluon plasma via a chemically non-equilibrated evolution framework.
Phenomenological Evidence for Gluon Depletion in pA Collisions
Hwa, R. C.; Pisut, J.; Pisutova, N.
2000-01-01
The data of J/psi suppression at large x_F in pA collisions are used to infer the existence of gluon depletion as the projectile proton traverses the nucleus. The modification of the gluon distribution is studied by use of a convolution equation whose non-perturbative splitting function is determined phenomenologically. The depletion factor at x_1=0.8 is found to be about 25% at A=100.
Gluon asymmetries in the leptoproduction of J/Ψ
International Nuclear Information System (INIS)
Godbole, R.M.; Gupta, S.; Sridhar, K.
1990-07-01
We study J/Ψ production, in deep inelastic scattering experiments with polarised beams and polarised targets. The spin asymmetries are seen to depend strongly on the particular form of the spin dependent gluon distributions used. Therefore, it should be possible in these experiments, to discriminate between different parametrizations of polarised gluon distributions, and hence between the distinctly different physical pictures of the proton spin underlying these parametrizations. (author). 18 refs, 4 figs, 1 tab
The five-gluon amplitude and one-loop integrals
International Nuclear Information System (INIS)
Bern, Z.; Dixon, L.; Kosower, D.A.
1992-12-01
We review the conventional field theory description of the string motivated technique. This technique is applied to the one-loop five-gluon amplitude. To evaluate the amplitude a general method for computing dimensionally regulated one-loop integrals is outlined including results for one-loop integrals required for the pentagon diagram and beyond. Finally, two five-gluon helicity amplitudes are given
Krieger, A.; Catherall, R.; Hochschulz, F.; Kramer, J.; Neugart, R.; Rosendahl, S.; Schipper, J.; Siesling, E.; Weinheimer, Ch.; Yordanov, D.T.; Nortershauser, W.
2011-01-01
A high-voltage divider with accuracy at the ppm level and collinear laser spectroscopy were used to calibrate the highvoltage installation at the radioactive ion beam facility ISOLDE at CERN. The accurate knowledge of this voltage is particularly important for collinear laser spectroscopy measurements. Beam velocity measurements using frequencycomb based collinear laser spectroscopy agree with the new calibration. Applying this, one obtains consistent results for isotope shifts of stable magnesium isotopes measured using collinear spectroscopy and laser spectroscopy on laser-cooled ions in a trap. The long-term stability and the transient behavior during recovery from a voltage dropout were investigated for the different power supplies currently applied at ISOLDE.
Subleading terms in the collinear limit of Yang–Mills amplitudes
Directory of Open Access Journals (Sweden)
Stephan Stieberger
2015-11-01
Full Text Available For two massless particles i and j, the collinear limit is a special kinematic configuration in which the particles propagate with parallel four-momentum vectors, with the total momentum P distributed as pi=xP and pj=(1−xP, so that sij≡(pi+pj2=P2=0. In Yang–Mills theory, if i and j are among N gauge bosons participating in a scattering process, it is well known that the partial amplitudes associated to the (single trace group factors with adjacent i and j are singular in the collinear limit and factorize at the leading order into (N−1-particle amplitudes times the universal, x-dependent Altarelli–Parisi factors. We give a precise definition of the collinear limit and show that at the tree level, the subleading, non-singular terms are related to the amplitudes with a single graviton inserted instead of two collinear gauge bosons. To that end, we argue that in one-graviton Einstein–Yang–Mills amplitudes, the graviton with momentum P can be replaced by a pair of collinear gauge bosons carrying arbitrary momentum fractions xP and (1−xP.
International Nuclear Information System (INIS)
Martinez, E.; Vega, A.; Robles, R.; Vazquez de Parga, A.L.
2005-01-01
We present a theoretical study of the magnetic properties of thin Mn films of 6 and 7 monolayers supported on Fe(001). The ab-initio tight binding linear muffin tin orbital (TB-LMTO) method was used to investigate the competition between ferromagnetic (F) and antiferromagnetic (AF) couplings within the system. We found several collinear magnetic solutions that may coexist at room temperature. The most stable configurations are characterized by AF coupling between the surface and subsurface Mn layers together with F coupling between Mn and Fe at the interface. The ground state arrangements for the 6 and 7 Mn films display opposite sign of the surface magnetic moment relative to the Fe substrate. The implications of these results in the possible onset of non-collinear magnetism when a step is present at the interface are discussed in comparison with Cr/Fe systems where non-collinear magnetism has been recently reported
Hall effect driven by non-collinear magnetic polarons in diluted magnetic semiconductors
Denisov, K. S.; Averkiev, N. S.
2018-04-01
In this letter, we develop the theory of Hall effect driven by non-collinear magnetic textures (topological Hall effect—THE) in diluted magnetic semiconductors (DMSs). We show that a carrier spin-orbit interaction induces a chiral magnetic ordering inside a bound magnetic polaron (BMP). The inner structure of non-collinear BMP is controlled by the type of spin-orbit coupling, allowing us to create skyrmion- (Rashba) or antiskyrmion-like (Dresselhaus) configurations. The asymmetric scattering of itinerant carriers on polarons leads to the Hall response which exists in weak external magnetic fields and at low temperatures. We point out that DMS-based systems allow one to investigate experimentally the dependence of THE both on a carrier spin polarization and on a non-collinear magnetic texture shape.
Deep inelastic scattering near the endpoint in soft-collinear effective theory
International Nuclear Information System (INIS)
Chay, Junegone; Kim, Chul
2007-01-01
We apply the soft-collinear effective theory to deep inelastic scattering near the endpoint region. The forward scattering amplitude and the structure functions are shown to factorize as a convolution of the Wilson coefficients, the jet functions, and the parton distribution functions. The behavior of the parton distribution functions near the endpoint region is considered. It turns out that it evolves with the Altarelli-Parisi kernel even in the endpoint region, and the parton distribution function can be factorized further into a collinear part and the soft Wilson line. The factorized form for the structure functions is obtained by the two-step matching, and the radiative corrections or the evolution for each factorized part can be computed in perturbation theory. We present the radiative corrections of each factorized part to leading order in α s , including the zero-bin subtraction for the collinear part
International Nuclear Information System (INIS)
Fuhrer, Andreas; Manohar, Aneesh V.; Waalewijn, Wouter J.
2011-01-01
Soft-collinear effective theory (SCET) is applied to compute electroweak radiative corrections to Higgs production via gauge boson fusion, qq→qqH. There are several novel features which make this process an interesting application of SCET: The amplitude is proportional to the Higgs vacuum expectation value, and so is not a gauge singlet amplitude. Standard resummation methods require a gauge singlet operator and do not apply here. The SCET analysis requires operators with both collinear and soft external fields, with the Higgs vacuum expectation value being described by an external soft φ field. There is a scalar soft-collinear transition operator in the SCET Lagrangian which contributes to the scattering amplitude, and is derived here.
American Society for Testing and Materials. Philadelphia
2007-01-01
1.1 Conversion Table 1 presents data in the Rockwell C hardness range on the relationship among Brinell hardness, Vickers hardness, Rockwell hardness, Rockwell superficial hardness, Knoop hardness, and Scleroscope hardness of non-austenitic steels including carbon, alloy, and tool steels in the as-forged, annealed, normalized, and quenched and tempered conditions provided that they are homogeneous. 1.2 Conversion Table 2 presents data in the Rockwell B hardness range on the relationship among Brinell hardness, Vickers hardness, Rockwell hardness, Rockwell superficial hardness, Knoop hardness, and Scleroscope hardness of non-austenitic steels including carbon, alloy, and tool steels in the as-forged, annealed, normalized, and quenched and tempered conditions provided that they are homogeneous. 1.3 Conversion Table 3 presents data on the relationship among Brinell hardness, Vickers hardness, Rockwell hardness, Rockwell superficial hardness, and Knoop hardness of nickel and high-nickel alloys (nickel content o...
International Nuclear Information System (INIS)
Dan, J.P.; Boving, H.J.; Hintermann, H.E.
1993-01-01
Hard, wear resistant and low friction coatings are presently produced on a world-wide basis, by different processes such as electrochemical or electroless methods, spray technologies, thermochemical, CVD and PVD. Some of the most advanced processes, especially those dedicated to thin film depositions, basically belong to CVD or PVD technologies, and will be looked at in more detail. The hard coatings mainly consist of oxides, nitrides, carbides, borides or carbon. Over the years, many processes have been developed which are variations and/or combinations of the basic CVD and PVD methods. The main difference between these two families of deposition techniques is that the CVD is an elevated temperature process (≥ 700 C), while the PVD on the contrary, is rather a low temperature process (≤ 500 C); this of course influences the choice of substrates and properties of the coating/substrate systems. Fundamental aspects of the vapor phase deposition techniques and some of their influences on coating properties will be discussed, as well as the very important interactions between deposit and substrate: diffusions, internal stress, etc. Advantages and limitations of CVD and PVD respectively will briefly be reviewed and examples of applications of the layers will be given. Parallel to the development and permanent updating of surface modification technologies, an effort was made to create novel characterisation methods. A close look will be given to the coating adherence control by means of the scratch test, at the coating hardness measurement by means of nanoindentation, at the coating wear resistance by means of a pin-on-disc tribometer, and at the surface quality evaluation by Atomic Force Microscopy (AFM). Finally, main important trends will be highlighted. (orig.)
Kaluza-Klein gluon + jets associated production at the Large Hadron Collider
Iyer, A.M.; Manglani, N.; Sridhar, K.
2016-08-10
The Kaluza-Klein excitations of gluons offer the exciting possibility of probing bulk Randall-Sundrum (RS) models. In these bulk models either a custodial symmetry or a deformation of the metric away from AdS is invoked in order to deal with electroweak precision tests. Addressing both these models, we suggest a new channel in which to study the production of KK-gluons ($g_{KK}$): one where it is produced in association with one or more hard jets. The cross-section for the $g_{KK}+$ jets channel is significant because of several contributing sub-processes. In particular, the 1-jet and the 2-jet associated processes are important because at these orders in QCD the $qg$ and the $gg$ initial states respectively come into play. We have performed a hadron-level simulation of the signal and present strategies to effectively extract the signal from what could potentially be a huge background. We present results for the kinematic reach of the LHC Run-II for different $g_{KK}$ masses in bulk-RS models.
International Nuclear Information System (INIS)
Gao Zhiwen; Zhou Youhe; Lee, Kang Yong
2010-01-01
The interaction of two collinear cracks is obtained for a type-II superconducting under electromagnetic force. Fracture analysis is performed by means of finite element method and the magnetic behavior of superconductor is described by the critical-state Bean model. The stress intensity factors at the crack tips can be obtained and discussed for decreasing field after zero-field cooling. It is revealed that the stress intensity factor decreases as applied field increases. The crack-tip stress intensity factors decrease when the distance between the two collinear cracks increases and the superconductors with smaller crack has more remarkable shielding effect than those with larger cracks.
Diffractive hard scattering at ep and p antip colliders
International Nuclear Information System (INIS)
Bruni, P.; Ingelman, G.; Uppsala Univ.
1993-12-01
Models for diffractive scattering based on the exchange of a pomeron with a parton structure are analysed in terms of hard scattering processes and the resulting characteristics of the final state. Diffractive deep inelastic ep scattering is considered in connection with the recently observed rapidity gap events at HERA. Heavy flavour and W, Z production in p anti p interactions are interesting measures of the gluon and quark component, respectively, in the pomeron. (orig.)
Evidence of ghost suppression in gluon mass scale dynamics
Aguilar, A. C.; Binosi, D.; Figueiredo, C. T.; Papavassiliou, J.
2018-03-01
In this work we study the impact that the ghost sector of pure Yang-Mills theories may have on the generation of a dynamical gauge boson mass scale, which hinges on the appearance of massless poles in the fundamental vertices of the theory, and the subsequent realization of the well-known Schwinger mechanism. The process responsible for the formation of such structures is itself dynamical in nature, and is governed by a set of Bethe-Salpeter type of integral equations. While in previous studies the presence of massless poles was assumed to be exclusively associated with the background-gauge three-gluon vertex, in the present analysis we allow them to appear also in the corresponding ghost-gluon vertex. The full analysis of the resulting Bethe-Salpeter system reveals that the contribution of the poles associated with the ghost-gluon vertex are particularly suppressed, their sole discernible effect being a slight modification in the running of the gluon mass scale, for momenta larger than a few GeV. In addition, we examine the behavior of the (background-gauge) ghost-gluon vertex in the limit of vanishing ghost momentum, and derive the corresponding version of Taylor's theorem. These considerations, together with a suitable Ansatz, permit us the full reconstruction of the pole sector of the two vertices involved.
Measurements of the structure of quark and gluon jets in hadronic Z decays
Barate, R; Décamp, D; Ghez, P; Goy, C; Lees, J P; Lucotte, A; Merle, E; Minard, M N; Nief, J Y; Pietrzyk, B; Alemany, R; Boix, G; Casado, M P; Chmeissani, M; Crespo, J M; Delfino, M C; Fernández, E; Fernández-Bosman, M; Garrido, L; Graugès-Pous, E; Juste, A; Martínez, M; Merino, G; Miquel, R; Mir, L M; Park, I C; Pascual, A; Perlas, J A; Riu, I; Sánchez, F; Colaleo, A; Creanza, D; De Palma, M; Gelao, G; Iaselli, Giuseppe; Maggi, G; Maggi, M; Nuzzo, S; Ranieri, A; Raso, G; Ruggieri, F; Selvaggi, G; Silvestris, L; Tempesta, P; Tricomi, A; Zito, G; Huang, X; Lin, J; Ouyang, Q; Wang, T; Xie, Y; Xu, R; Xue, S; Zhang, J; Zhang, L; Zhao, W; Abbaneo, D; Becker, U; Bright-Thomas, P G; Casper, David William; Cattaneo, M; Ciulli, V; Dissertori, G; Drevermann, H; Forty, Roger W; Frank, M; Hagelberg, R; Hansen, J B; Harvey, J; Janot, P; Jost, B; Lehraus, Ivan; Mato, P; Minten, Adolf G; Moneta, L; Pacheco, A; Pusztaszeri, J F; Ranjard, F; Rolandi, Luigi; Rousseau, D; Schlatter, W D; Schmitt, M; Schneider, O; Tejessy, W; Teubert, F; Tomalin, I R; Wachsmuth, H W; Wagner, A; Ajaltouni, Ziad J; Badaud, F; Chazelle, G; Deschamps, O; Falvard, A; Ferdi, C; Gay, P; Guicheney, C; Henrard, P; Jousset, J; Michel, B; Monteil, S; Montret, J C; Pallin, D; Perret, P; Podlyski, F; Proriol, J; Rosnet, P; Hansen, J D; Hansen, J R; Hansen, P H; Nilsson, B S; Rensch, B; Wäänänen, A; Daskalakis, G; Kyriakis, A; Markou, C; Simopoulou, Errietta; Siotis, I; Vayaki, Anna; Blondel, A; Bonneaud, G R; Brient, J C; Bourdon, P; Rougé, A; Rumpf, M; Valassi, Andrea; Verderi, M; Videau, H L; Focardi, E; Parrini, G; Zachariadou, K; Corden, M; Georgiopoulos, C H; Jaffe, D E; Antonelli, A; Bencivenni, G; Bologna, G; Bossi, F; Campana, P; Capon, G; Cerutti, F; Chiarella, V; Felici, G; Laurelli, P; Mannocchi, G; Murtas, F; Murtas, G P; Passalacqua, L; Pepé-Altarelli, M; Curtis, L; Halley, A W; Lynch, J G; Negus, P; O'Shea, V; Raine, C; Scarr, J M; Smith, K; Teixeira-Dias, P; Thompson, A S; Thomson, E; Buchmüller, O L; Dhamotharan, S; Geweniger, C; Graefe, G; Hanke, P; Hansper, G; Hepp, V; Kluge, E E; Putzer, A; Sommer, J; Tittel, K; Werner, S; Wunsch, M; Beuselinck, R; Binnie, David M; Cameron, W; Dornan, Peter J; Girone, M; Goodsir, S M; Martin, E B; Marinelli, N; Moutoussi, A; Nash, J; Sedgbeer, J K; Spagnolo, P; Williams, M D; Ghete, V M; Girtler, P; Kneringer, E; Kuhn, D; Rudolph, G; Betteridge, A P; Bowdery, C K; Buck, P G; Colrain, P; Crawford, G; Finch, A J; Foster, F; Hughes, G; Jones, R W L; Williams, M I; Giehl, I; Greene, A M; Hoffmann, C; Jakobs, K; Kleinknecht, K; Quast, G; Renk, B; Rohne, E; Sander, H G; Van Gemmeren, P; Zeitnitz, C; Aubert, Jean-Jacques; Benchouk, C; Bonissent, A; Bujosa, G; Carr, J; Coyle, P; Etienne, F; Leroy, O; Motsch, F; Payre, P; Talby, M; Sadouki, A; Thulasidas, M; Trabelsi, K; Aleppo, M; Antonelli, M; Ragusa, F; Berlich, R; Blum, Walter; Büscher, V; Dietl, H; Ganis, G; Kroha, H; Lütjens, G; Mannert, C; Männer, W; Moser, H G; Schael, S; Settles, Ronald; Seywerd, H C J; Stenzel, H; Wiedenmann, W; Wolf, G; Boucrot, J; Callot, O; Chen, S; Cordier, A; Davier, M; Duflot, L; Grivaz, J F; Heusse, P; Höcker, A; Jacholkowska, A; Kim, D W; Le Diberder, F R; Lefrançois, J; Lutz, A M; Schune, M H; Tournefier, E; Veillet, J J; Videau, I; Zerwas, D; Azzurri, P; Bagliesi, G; Batignani, G; Bettarini, S; Boccali, T; Bozzi, C; Calderini, G; Carpinelli, M; Ciocci, M A; Dell'Orso, R; Fantechi, R; Ferrante, I; Foà, L; Forti, F; Giassi, A; Giorgi, M A; Gregorio, A; Ligabue, F; Lusiani, A; Marrocchesi, P S; Messineo, A; Palla, Fabrizio; Rizzo, G; Sanguinetti, G; Sciabà, A; Tenchini, Roberto; Tonelli, G; Vannini, C; Venturi, A; Verdini, P G; Blair, G A; Bryant, L M; Chambers, J T; Green, M G; Medcalf, T; Perrodo, P; Strong, J A; Von Wimmersperg-Töller, J H; Botterill, David R; Clifft, R W; Edgecock, T R; Haywood, S; Norton, P R; Thompson, J C; Wright, A E; Bloch-Devaux, B; Colas, P; Emery, S; Kozanecki, Witold; Lançon, E; Lemaire, M C; Locci, E; Pérez, P; Rander, J; Renardy, J F; Roussarie, A; Schuller, J P; Schwindling, J; Trabelsi, A; Vallage, B; Black, S N; Dann, J H; Johnson, R P; Kim, H Y; Konstantinidis, N P; Litke, A M; McNeil, M A; Taylor, G; Booth, C N; Brew, C A J; Cartwright, S L; Combley, F; Kelly, M S; Lehto, M H; Reeve, J; Thompson, L F; Affholderbach, K; Böhrer, A; Brandt, S; Cowan, G D; Grupen, Claus; Saraiva, P; Smolik, L; Stephan, F; Apollonio, M; Bosisio, L; Della Marina, R; Giannini, G; Gobbo, B; Musolino, G; Rothberg, J E; Wasserbaech, S R; Armstrong, S R; Charles, E; Elmer, P; Ferguson, D P S; Gao, Y; González, S; Greening, T C; Hayes, O J; Hu, H; Jin, S; McNamara, P A; Nachtman, J M; Nielsen, J; Orejudos, W; Pan, Y B; Saadi, Y; Scott, I J; Walsh, J; Wu Sau Lan; Wu, X; Zobernig, G
2000-01-01
An experimental investigation of the structure of identified quark and gluon jets is presented. Observables related to both the global and internal structure of jets are measured; this allows for tests of QCD over a wide range of transverse momentum scales. The observables include distributions of jet-shape variables, the mean and standard deviation of the subjet multiplicity distribution and the fragmentation function for charged particles. The data are compared with predictions of perturbative QCD as well as QCD-based Monte Carlo models. In certain kinematic regions the measurements are sensitive mainly to perturbatively calculable effects, allowing for a test of QCD. The comparisons are also extended into regions where nonperturbative effects become large, and in this way the transition from hard to soft QCD is investigated. It is found that by including leading and next-to-leading logarithmic contributions in the QCD predictions, the agreement with the data can be extended to lower transverse momentum sca...
Infrared Behavior of Gluon and Ghost Propagators in Landau Gauge QCD
International Nuclear Information System (INIS)
von Smekal, L.; Hauck, A.; Alkofer, R.
1997-01-01
A truncation scheme for the Dyson-Schwinger equations of Euclidean QCD in Landau gauge is presented. It implements the Slavnov-Taylor identities for the three-gluon and ghost-gluon vertices, whereas irreducible four-gluon couplings as well as the gluon-ghost and ghost-ghost scattering kernels are neglected. The infrared behavior of gluon and ghost propagators is obtained analytically: The gluon propagator vanishes for small momenta, whereas the ghost propagator diverges strongly. The numerical solutions are compared with recent lattice results. The running coupling approaches a fixed point, α c ≅9.5 , in the infrared. copyright 1997 The American Physical Society
Gluon and quark jets in a recursive model motivated by quantum chromodynamics
International Nuclear Information System (INIS)
Sukhatme, U.P.
1979-01-01
We compute observable quantities like the multiplicity and momentum distributions of hadrons in gluon and quark jets in the framework of a recursive cascade model, which is strongly motivated by the fundamental interactions of QCD. Fragmentation occurs via 3 types of breakups: quark → meson + quark, gluon → meson + gluon, gluon → quark + antiquark. In our model gluon jets are softer than quark jets. The ratio of gluon jet to quark jet multiplicity is found to be 2 asymptotically, but much less at lower energies. Some phenomenological consequences for γ decay are discussed. (orig.)
Energy Technology Data Exchange (ETDEWEB)
Kang, Hyejoo
2002-01-30
We present production measurements of the charged hadrons {pi}{sup {+-}}, K{sup {+-}} and p/{bar p} in e{sup +}e{sup -} interactions at the Z{sup 0} pole. The excellent particle identification capability of the SLC Large Detector (SLD) at the Stanford Linear Collider (SLC) are used. In addition to studies over a wide momentum range in hadronic Z{sup 0} events of all five flavors, we have made the most precise measurements in light (uds), c and b flavor events separately. Unambiguous flavor dependencies have been observed, and the results have been compared with the predictions of several QCD fragmentation models. We have also exploited the unique feature of electron beam polarization in our experiment to compare hadron production separately in quark and antiquark jets. Direct evidence that higher momentum hadrons are more likely to contain the primary quark and antiquark is seen, with precision sufficient to provide new model tests. Finally, we have studied hard gluon jets in detail. We have confirmed that gluon jets have a higher multiplicity of softer particles than light quark jets, and found this enhancement to be the same for {pi}{sup {+-}}, K{sup {+-}} and p/{bar p} at the few percent level at all momenta. Any overall difference in the hadron fractions is limited to 0.018 at the 95% confidence level, indicating that there are no differences at the hadronization stage in jet formation between gluons and quarks.
Imaginary part of the next-to-leading-order static gluon self-energy in an anisotropic plasma
International Nuclear Information System (INIS)
Carrington, M. E.; Rebhan, A.
2009-01-01
Using hard-loop (HL) effective theory for an anisotropic non-Abelian plasma, which even in the static limit involves nonvanishing HL vertices, we calculate the imaginary part of the static next-to-leading-order gluon self-energy in the limit of a small anisotropy and with external momentum parallel to the anisotropy direction. At leading order, the static propagator has spacelike poles corresponding to plasma instabilities. On the basis of a calculation using bare vertices, it has been conjectured that, at next-to-leading order, the static gluon self-energy acquires an imaginary part which regulates these spacelike poles. We find that the one-loop resummed expression taken over naively from the imaginary-time formalism does yield a nonvanishing imaginary part even after including all HL vertices. However, this result is not correct. Starting from the real-time formalism, which is required in a nonequilibrium situation, we construct a resummed retarded HL propagator with correct causality properties and show that the static limit of the retarded one-loop-resummed gluon self-energy is real. This result is also required for the time-ordered propagator to exist at next-to-leading order.
Collective phenomena in the non-equilibrium quark-gluon plasma
Energy Technology Data Exchange (ETDEWEB)
Schenke, Bjoern Peter
2008-07-03
In this work we study the non-equilibrium dynamics of a quark-gluon plasma, as created in heavy-ion collisions. We investigate how big of a role plasma instabilities can play in the isotropization and equilibration of a quark-gluon plasma. In particular, we determine, among other things, how much collisions between the particles can reduce the growth rate of unstable modes. This is done both in a model calculation using the hard-loop approximation, as well as in a real-time lattice simulation combining both classical Yang-Mills-fields as well as inter-particle collisions. The new extended version of the simulation is also used to investigate jet transport in isotropic media, leading to a cutoff-independent result for the transport coefficient q. The precise determination of such transport coefficients is essential, since they can provide important information about the medium created in heavy ion collisions. In anisotropic media, the effect of instabilities on jet transport is studied, leading to a possible explanation for the experimental observation that high-energy jets traversing the plasma perpendicular to the beam axis experience much stronger broadening in rapidity than in azimuth. The investigation of collective modes in the hard-loop limit is extended to fermionic modes, which are shown to be all stable. Finally, we study the possibility of using high energy photon production as a tool to experimentally determine the anisotropy of the created system. Knowledge of the degree of local momentum-space anisotropy reached in a heavy-ion collision is essential for the study of instabilities and their role for isotropization and thermalization, because their growth rate depends strongly on the anisotropy. (orig.)
Transport quasiparticles and transverse interactions in quark-gluon plasmas
International Nuclear Information System (INIS)
Baym, Gordon
1996-01-01
Calculations of the properties of interacting quark-gluon plasmas are beset by infrared divergences associated with the fact that magnetic interactions, i.e., those occurring through exchange of transverse gluons, are, in the absence of a 'magnetic mass''in QCD, not screened. In this lecture we discuss the effects of magnetic interactions on the transport coefficients and the quasiparticle structure of quark-gluon plasmas. We describe how inclusion of dynamical screening effects - corresponding to Landau damping of the virtual quanta exchanged - leads to finite transport scattering rates. In the weak coupling limit, dynamical screening effects dominate over a magnetic mass. We illustrate the breakdown of the quasi particle structure of degenerate plasmas caused by long-ranged magnetic interactions, describe the structure of fermion quasiparticles in hot relativistic plasmas, and touch briefly on the problem of the lifetime of quasiparticle in the presence of long-ranged magnetic interactions. (author)
Quark and gluon tagging in dijet mass resonance search
Kellermann, Edgar
2013-01-01
Several models beyond the Standard Model predict new phenomena in particle physics, which would appear as resonant signals in dijet mass distributions. An example for such a resonance is the excited quark q, which is a consequence of Compositeness Models postulating that quarks and leptons are build by more fundamental particles. The main signature of an excited quark would be a dijet event, originated from the radiation of a gluon from the original excited quark when going back to its non-excited state, leading to a quark and a gluon in the final state (with a branching ratio of 83%) . Other examples are the heavy vector bosonsW0 decaying to two quarks and colour octet scalar S8 decaying to two gluons.
Worldline calculation of the three-gluon vertex
International Nuclear Information System (INIS)
Ahmadiniaz, N.; Schubert, C.
2012-01-01
The three-gluon vertex is a basic object of interest in nonabelian gauge theory. At the one-loop level, it has been calculated and analyzed by a number of authors. Here we use the worldline formalism to unify the calculations of the scalar, spinor and gluon loop contributions to the one-loop vertex, leading to an extremely compact representation in terms of field strength tensors. We verify its equivalence with previously obtained representations, and explain the relation of its structure to the low-energy effective action. The sum rule found by Binger and Brodsky for the scalar, spinor and gluon loop contributions in the present approach relates to worldline supersymmetry.
The gluon Reggeization in perturbative QCD at NLO
Energy Technology Data Exchange (ETDEWEB)
Fadin, V.S. [Novosibirsk State Univ., Institute for Nuclear Physics (Russian Federation)
2005-07-01
The gluon Reggeization is one of the outstanding properties of QCD. It is extremely important for description of high energy processes. In particular, it appears as the basis of the BFKL approach to summation of the terms strengthened by powers of log(1/x). The hypothesis is extremely powerful, since all scattering amplitudes are expressed in terms of the gluon trajectory and several Reggeon vertices. Now the hypothesis is proved in NLA (next-to leading approximation). The proof is based on bootstrap relations. It is shown that an infinite number of these relations is reduced to several bootstrap conditions on the gluon trajectory and the Reggeon vertices. It is shown that fulfillment of these conditions means a proof of the Reggeization hypothesis. All bootstraps conditions are formulated explicitly and are proved to be fulfilled.
Study of gluon condensates using the Bogolyubov transformation
International Nuclear Information System (INIS)
Iracane, Daniel
1985-01-01
We describe the ground state of non-perturbative QCD as a gluon condensate. In the framework of the Coulomb gauge Hamiltonian, we introduce an effective interaction between infrared gluons by removing high-momentum gluons. The Bogoliubov transformation provides us with our variational space. The minimisation over this Fock subspace leads to a non-perturbative vacuum and its excitations. The minimum functional space for a boson dynamic is a distribution set. We find two kinds of condensation. The first one occurs only for zero-momentum states and looks like the Bose Condensation. In the second one, the quasiparticle spectrum shows a finite gap and the vacuum is a superconducting state. We give constraints on the interaction so that the superconducting phase is more bounded than the Bose one. (author) [fr
Non-perturbative power corrections to ghost and gluon propagators
International Nuclear Information System (INIS)
Boucaud, Philippe; Leroy, Jean-Pierre; Yaouanc, Alain Le; Lokhov, Alexey; Micheli, Jacques; Pene, Olivier; RodrIguez-Quintero, Jose; Roiesnel, Claude
2006-01-01
We study the dominant non-perturbative power corrections to the ghost and gluon propagators in Landau gauge pure Yang-Mills theory using OPE and lattice simulations. The leading order Wilson coefficients are proven to be the same for both propagators. The ratio of the ghost and gluon propagators is thus free from this dominant power correction. Indeed, a purely perturbative fit of this ratio gives smaller value ( ≅ 270MeV) of Λ M-barS-bar than the one obtained from the propagators separately( ≅ 320MeV). This argues in favour of significant non-perturbative ∼ 1/q 2 power corrections in the ghost and gluon propagators. We check the self-consistency of the method
Low-momentum ghost dressing function and the gluon mass
International Nuclear Information System (INIS)
Boucaud, Ph.; Leroy, J. P.; Le Yaouanc, A.; Micheli, J.; Pene, O.; Gomez, M. E.; Rodriguez-Quintero, J.
2010-01-01
We study the low-momentum ghost propagator Dyson-Schwinger equation in the Landau gauge, assuming for the truncation a constant ghost-gluon vertex, as it is extensively done, and a simple model for a massive gluon propagator. Then, regular Dyson-Schwinger equation solutions (the zero-momentum ghost dressing function not diverging) appear to emerge, and we show the ghost propagator to be described by an asymptotic expression reliable up to the order O(q 2 ). That expression, depending on the gluon mass and the zero-momentum Taylor-scheme effective charge, is proven to fit pretty well some low-momentum ghost propagator data [I. L. Bogolubsky, E. M. Ilgenfritz, M. Muller-Preussker, and A. Sternbeck, Phys. Lett. B 676, 69 (2009); Proc. Sci., LAT2007 (2007) 290] from big-volume lattice simulations where the so-called ''simulated annealing algorithm'' is applied to fix the Landau gauge.
In search of the quark-gluon plasma
International Nuclear Information System (INIS)
Schutz, Y.; Delagrange, H.
2002-01-01
This article describes in a very pedagogical manner the ultimate state of matter when quarks are no longer confined in hadrons. This state is called quark and gluon plasma, its existence is suspected through 4 facts: 1) a quark and gluon plasma that has just been created from a high energy ion-collision is mainly made up of light quarks (up and down), then this plasma should evolve towards other quarks (particularly strange quarks) because of the Pauli exclusion principle. This fact has been experimentally confirmed: at the CERN accelerator physicists have detected a higher production of strange hadrons when the energy of the collision increases; 2) some particles like ρ 0 mesons, that are made up of 2 quarks, are massively produced in ion collisions, their mass has been measured at the moment of the collision and later in the quark and gluon plasma, 2 different values have been found so it confirms the theory that predicts that free quarks have a mass that decreases as energy increases; 3) J/Ψ mesons are made up of a charmed quark combined with its anti-quark, physicists have noticed that less J/Ψ mesons are detected when the energy of the collision rises, this result agrees with the fact that in quark gluon plasma where quarks are free and of different colours and flavors, it is highly unlikely that a charmed quark combines with its anti-quark to form a J/Ψ meson; and 4) the theory of the formation of quark gluon plasma predicts that its electromagnetic radiation has a thermal radiation specificity, physicists have studied the radiation spectra emitted in the core of a ion collision, they have shown that it is a thermal radiation and that the temperature of the emitter corresponds to the temperature of a quark gluon plasma. (A.C.)
Prediction equations of forced oscillation technique: the insidious role of collinearity.
Narchi, Hassib; AlBlooshi, Afaf
2018-03-27
Many studies have reported reference data for forced oscillation technique (FOT) in healthy children. The prediction equation of FOT parameters were derived from a multivariable regression model examining the effect of age, gender, weight and height on each parameter. As many of these variables are likely to be correlated, collinearity might have affected the accuracy of the model, potentially resulting in misleading, erroneous or difficult to interpret conclusions.The aim of this work was: To review all FOT publications in children since 2005 to analyze whether collinearity was considered in the construction of the published prediction equations. Then to compare these prediction equations with our own study. And to analyse, in our study, how collinearity between the explanatory variables might affect the predicted equations if it was not considered in the model. The results showed that none of the ten reviewed studies had stated whether collinearity was checked for. Half of the reports had also included in their equations variables which are physiologically correlated, such as age, weight and height. The predicted resistance varied by up to 28% amongst these studies. And in our study, multicollinearity was identified between the explanatory variables initially considered for the regression model (age, weight and height). Ignoring it would have resulted in inaccuracies in the coefficients of the equation, their signs (positive or negative), their 95% confidence intervals, their significance level and the model goodness of fit. In Conclusion with inaccurately constructed and improperly reported models, understanding the results and reproducing the models for future research might be compromised.
Can, Seda; van de Schoot, Rens|info:eu-repo/dai/nl/304833207; Hox, Joop|info:eu-repo/dai/nl/073351431
2015-01-01
Because variables may be correlated in the social and behavioral sciences, multicollinearity might be problematic. This study investigates the effect of collinearity manipulated in within and between levels of a two-level confirmatory factor analysis by Monte Carlo simulation. Furthermore, the
Non-collinear upconversion of incoherent light: designing infrared spectrometers and imaging systems
DEFF Research Database (Denmark)
Dam, Jeppe Seidelin; Hu, Qi; Pedersen, Christian
2014-01-01
for each angle of propagation. Non-collinear phase matching has been an area of limited attention for many years due to inherent incompatibility with tightly focused laser beams typically used for most second order processes in order to achieve acceptable conversion efficiency. The development...
Collinear laser spectroscopy on In isotopes from heavy ion fusion reactions
International Nuclear Information System (INIS)
Ulm, G.
1984-07-01
Indium isotopes 107-111 were produced by 16 O-fusion reactions and investigated in a collinear laser geometry. The hyperfine structure and isotopic shifts are measured and the deduced magnetic dipole moments are in agreement with shell model calculations. The nuclear charge radii are determined from the isotopic shifts. (WL)
Cancellation of infrared and collinear singularities in relativistic thermal field theories. Pt. 2
International Nuclear Information System (INIS)
Le Bellac, M.; Reynaud, P.
1992-01-01
We study the infrared and collinear divergences of a renormalizable scalar field theory at finite temperature. We give the final results of an investigation undertaken in a previous work by showing the complete cancellation of all divergences at two-loop order in a physical process. This result makes the validity of the Kinoshita-Lee-Nauenberg theorem at finite temperature extremely plausible. (orig.)
Coalescence model of two collinear cracks existing in steam generator tubes
International Nuclear Information System (INIS)
Moon, S.-I.; Chang, Y.-S.; Kim, Y.-J.; Park, Y.-W.; Song, M.-H.; Choi, Y.-H.; Lee, J.-H.
2005-01-01
The 40% of wall thickness criterion has been used as a plugging rule of steam generator tubes but it can be applicable just to a single-cracked tubes. In the previous studies preformed by the authors, a total of 10 local failure prediction models were introduced to estimate the coalescence load of two adjacent collinear through-wall cracks existing in thin plates, and the reaction force model and plastic zone contact model were selected as optimum models among them. The objective of this study is to verify the applicability of the proposed optimum local failure prediction models to the tubes with two collinear through-wall cracks. For this, a series of plastic collapse tests and finite element analyses were carried out using the tubes containing two collinear through-wall cracks. It has been shown that the proposed optimum failure models can predict the local failure behavior of two collinear through-wall cracks existing in tubes well. And a coalescence evaluation diagram was developed which can be used to determine whether the adjacent cracks detected by NED coalsece or not. (authors)
Effects of Perturbations on the Location of Collinear Points In The ...
African Journals Online (AJOL)
In this paper, the effect of small perturbations in the coriolis and the centrifugal forces on the location of collinear points in the restricted three-body problem has been examined when both primaries are triaxial rigid bodies with one of the axes as the axis of symmetry and its equatorial plane coinciding with the plane of ...
Soft Probes of the Quark-Gluon Plasma in ATLAS
Wozniak, K W; The ATLAS collaboration
2014-01-01
Measurements of low-$p_{_{\\rm T}}$ ($<$ 5 GeV) particles in Pb+Pb collisions at the LHC provide valuable insight in the production and evolution of the quark-gluon plasma. In particular, measurements of the elliptic and higher order collective flow imprinted on the azimuthal angle distributions of low-$p_{T}$ particles directly probe the strongly-coupled dynamics of the quark gluon plasma and test hydrodynamic model descriptions of its evolution. The large acceptance of detectors like ATLAS makes it possible to measure flow event-by-event and to determine the correlations between different event planes and different flow harmonics.
A gauge quantum field theory of confined quarks and gluons
International Nuclear Information System (INIS)
Voelkel, A.H.
1983-01-01
A SU(3)-gauge quantum field theory with a quark triplet, an antiquark triplet and a self-conjugate gluon octet as basic fields is investigated. In virtue of a non trivial coupling between the representation of the translation group and the SU(3)-colour charge of the basic fields it is proved: (i) The basic quark, antiquark and gluon fields are confined. (ii) Every statevector of the physical Hilbert space is a SU(3)-colour singlet state. (iii) Poincare invariance holds in the physical Hilbert space. (orig.)
Evidence for a spin 1 gluon in three jet events
International Nuclear Information System (INIS)
Brandelik, R.; Braunschweig, W.; Gather, K.; Kadansky, V.; Kirschfink, F.J.; Luebelsmeyer, K.; Martyn, H.U.; Peise, G.; Rimkus, J.; Sander, H.G.
1980-08-01
High energy e + e - annihilation events obtained in the TASSO detector at PETRA have been used to determine the spin of the gluon in the reaction e + e - → q anti qg. We analyzed angular correlations between the 3 jet axes. While vector gluons are consistent with the data (55% confidence limit), scalar fluons are disfavored by 3.8 standard deviations, corresponding to a confidence level of about 10 -4 . Our conclusion is free of possible biases due to uncertainties in the fragmentation process or in determining the q anti qg kinematic from the observed hadrons. (orig.)
A gluon cluster solution of effective Yang-Mills theory
Pavlovsky, O V
2001-01-01
A classical solution of the effective Yang-Mills (YM) theory with a finite energy and nonstandard Lagrangian was obtained. Influence of vacuum polarization on gluon cluster formation was discussed. Appearance of cluster solutions in the theory of non-Abelian fields can take place only if the result goes beyond the framework of pure YM theory. It is shown that account of quantum effects of polarized vacuum in the presence of a classical gluon field can also result in formation of the solutions. Solutions with the finite intrinsic energy are provided. Besides, fields of colour groups SU(2) were studied
Check of the bootstrap conditions for the gluon Reggeization
International Nuclear Information System (INIS)
Papa, A.
2000-01-01
The property of gluon Reggeization plays an essential role in the derivation of the Balitsky-Fadin-Kuraev-Lipatov (BFKL) equation for the cross sections at high energy √s in perturbative QCD. This property has been proved to all orders of perturbation theory in the leading logarithmic approximation and it is assumed to be valid also in the next-to-leading logarithmic approximation, where it has been checked only to the first three orders of perturbation theory. From s-channel unitarity, however, very stringent 'bootstrap' conditions can be derived which, if fulfilled, leave no doubts that gluon Reggeization holds
'' Ideal Gas '' gluon plasma with medium dependent dispersion relation
International Nuclear Information System (INIS)
Gorenstein, M.I.
1995-01-01
An '' ideal gas '' model with temperature dependent particle mass is constructed for the gluon plasma equation of state. This simple model gives us an example of a system with temperature dependent effective Hamiltonian. To satisfy thermodynamical relations in these systems, standard statistical mechanics formulas have to be supplemented by special requirements which are considered in details. A self-consistent '' ideal gas '' formulation is used to describe Monte Carlo lattice data for the thermodynamical functions of SU(2) and SU(3) gluon plasma. 14 refs., 8 figs
Plaquette expectation value and gluon condensate in three dimensions
International Nuclear Information System (INIS)
Hietanen, Ari; Kajantie, Keijo; Schroeder, York; Laine, Mikko; Rummukainen, Kari
2005-01-01
In three dimensions, the gluon condensate of pure SU(3) gauge theory has ultraviolet divergences up to 4-loop level only. By subtracting the corresponding terms from lattice measurements of the plaquette expectation value and extrapolating to the continuum limit, we extract the finite part of the gluon condensate in lattice regularization. Through a change of regularization scheme to MS-bar and (inverse) dimensional reduction, this result would determine the first non-perturbative coefficient in the weak-coupling expansion of hot QCD pressure. (author)
Nielsen's identity and gluon condensation at finite temperature
International Nuclear Information System (INIS)
Skalozub, V.V.
1992-11-01
The gauge dependence problem of the gluon field zero component condensate, A 0 =const, is investigated in finite temperature SU(3) gluodynamics. The two-loop effective action W(A 0 ,ξ) is recalculated in the background R ξ gauge. The obtained result somewhat differs from that of other authors. By straightforward calculation it is shown that W(A 0 ,ξ) satisfies the Nielsen (the Ward type) identity. Thus, the gauge invariance of the gluon condensation phenomenon is proved. (author). 14 refs
Plaquette expectation value and gluon condensate in three dimensions
Hietanen, A; Laine, Mikko; Rummukainen, K; Schröder, Y
2005-01-01
In three dimensions, the gluon condensate of pure SU(3) gauge theory has ultraviolet divergences up to 4-loop level only. By subtracting the corresponding terms from lattice measurements of the plaquette expectation value and extrapolating to the continuum limit, we extract the finite part of the gluon condensate in lattice regularization. Through a change of regularization scheme to MSbar and (inverse) dimensional reduction, this result would determine the first non-perturbative coefficient in the weak-coupling expansion of hot QCD pressure.
Mechanism of J/PSI production: determining gluon distributions
International Nuclear Information System (INIS)
Nandi, S.; Schneider, H.R.
1978-01-01
Assuming a generalised Drell-Yan type mechanism for hadronic PSI-production, the relative importance of the different possible contributions is estimated from the data. We find that about 80% of the pp → PSI X cross-section is due to gluons. Therefore, these data give some information on the gluon distribution G(x) in the proton. Assuming xG(x) approximately (1-x)sup(n), data restrict n to 4... 6, in agreement with dimensional counting rules. The energy dependence of sigma(anti p p → PSI X)/sigma(pp → PSIX) is predicted. (orig.) [de
Kovchegov, Yuri V.; Skokov, Vladimir V.
2018-05-01
We show that, in the saturation/color glass condensate framework, odd azimuthal harmonics of the two-gluon correlation function with a long-range separation in rapidity are generated by the higher-order saturation corrections in the interactions with the projectile and the target. At the very least, the odd harmonics require three scatterings in the projectile and three scatterings in the target. We derive the leading-order expression for the two-gluon production cross section which generates odd harmonics: the expression includes all-order interactions with the target and three interactions with the projectile. We evaluate the obtained expression both analytically and numerically, confirming that the odd-harmonics contribution to the two-gluon production in the saturation framework is nonzero.
Renormalization group approach to soft gluon resummation
International Nuclear Information System (INIS)
Forte, Stefano; Ridolfi, Giovanni
2003-01-01
We present a simple proof of the all-order exponentiation of soft logarithmic corrections to hard processes in perturbative QCD. Our argument is based on proving that all large logs in the soft limit can be expressed in terms of a single dimensionful variable, and then using the renormalization group to resum them. Beyond the next-to-leading log level, our result is somewhat less predictive than previous all-order resummation formulae, but it does not rely on non-standard factorization, and it is thus possibly more general. We use our result to settle issues of convergence of the resummed series, we discuss scheme dependence at the resummed level, and we provide explicit resummed expressions in various factorization schemes
QCD corrections for two jet production in photon-photon collisions
International Nuclear Information System (INIS)
Gastmans, R.; Berends, F.A.; Kunszt, Z.
1980-09-01
We present the calculation of the first order QCD corrections to the process γγ → q anti q, including virtual gluons and bremsstrahlung of soft and hard collinear gluons. The obtained cross section is then used to calculate the αsub(s) corrections to the process e + e - → e + e - + 2 jets. The numerical importance of hard acollinear gluons is also discussed. (orig.)
Developmental efforts of RF collinear load for 10 MeV, 6 kW travelling wave Linac
International Nuclear Information System (INIS)
Kumar, Pankaj; Kumar, Harish; Soni, R.K.; Dwivedi, Jishnu; Thakurta, A.C.; Wanmode, Y.D.; Pareek, Prashant; Senthil Kumar, S; Shinde, R.S.
2015-01-01
RRCAT is developing a 10 MeV, 6 kW Travelling Wave Electron Linac for radiation processing applications. The remnant RF power from the Linac structure is taken out by output RF coupler and absorbed by the waveguide load. RF collinear load is an improved technique for absorption of the remnant RF power. It replaces the output RF coupler, RF window and waveguide load leading to reduction in size of magnetic elements and less transverse beam instabilities. In addition, it uses the remnant RF power to increase the electron beam energy. The collinear load consists of a number of copper cavities coated with microwave absorbing material at inner surfaces and brazed to the Linac structure at the end. Development of the collinear load has been started at RRCAT and a prototype low power collinear load using Kanthal (FeCrAl alloy) coating has been developed. Further works are going on the development of high power collinear load using FeSiAl alloy. The paper describes the development of the Kanthal based prototype low power collinear load as well as the works for the development of FeSiAl alloy based high power collinear load. (author)
Dong, Bo-Wen; Cramer, Joel; Ganzhorn, Kathrin; Yuan, H Y; Guo, Er-Jia; Goennenwein, Sebastian T B; Kläui, Mathias
2018-01-24
We investigate the spin Hall magnetoresistance (SMR) in a gadolinium iron garnet (GdIG)/platinum (Pt) heterostructure by angular dependent magnetoresistance measurements. The magnetic structure of the ferromagnetic insulator GdIG is non-collinear near the compensation temperature, while it is collinear far from the compensation temperature. In the collinear regime, the SMR signal in GdIG is consistent with the usual [Formula: see text] relation well established in the collinear magnet yttrium iron garnet, with [Formula: see text] the angle between magnetization and spin Hall spin polarization direction. In the non-collinear regime, both an SMR signal with inverted sign and a more complex angular dependence with four maxima are observed within one sweep cycle. The number of maxima as well as the relative strength of different maxima depend strongly on temperature and field strength. Our results evidence a complex SMR behavior in the non-collinear magnetic regime that goes beyond the conventional formalism developed for collinear magnetic structures.
Quark-gluon plasma and the little bang
International Nuclear Information System (INIS)
McLerran, L.
1981-06-01
A space-time picture of the fragmentation and central regions is presented for extremely high energy head-on heavy nucleus collisions. The energy densities of the matter produced in such collisions are estimated. Speculations concerning the possible formation of a quark-gluon plasma are discussed, as are possible experimental signals for analyzing such a plasma
Bounds on the gluon mass from nucleon decay
Energy Technology Data Exchange (ETDEWEB)
Avila, M.A. [Universidad Autonoma del Estado de Morelos, Morelos (Mexico)
2001-04-01
Permanent confinement of quarks is assumed to hold in QCD. However, if the gluon has a small mass it is possible to produce-quarks in hadron decays, high-energy reactions or in the early-universe. This situation is modelled by a quark-diquark potential composed of a linear (or harmonic) plus a Yukawa term. We compare our prediction for the proton decay with the experimental lower bound on its life-time, and obtain an upper bound on the gluon mass. [Spanish] Se supone se cumple el confinamiento permanente de quarks en cromodinamica cuantica. Si el gluon tiene masa pequena es posible producir quarks libres en decaimiento hadronicos, reacciones de altas energias o en el universo temprano. Esta situacion es modelada por un potencial quark-diquark, compuesto de un termino lineal (o armonico) mas un termino Yukawa. Comparamos nuestra prediccion para el decaimiento del proton con la cota inferior experimental de su vida media y obtenemos una cota superior sobre la masa del gluon.
Universal Regge slope α' from QCD gluon propagator
International Nuclear Information System (INIS)
Nielsen, H.B.; Ninomiya, M.
1980-02-01
An effective gluon propagator is estimated in the presence of a fluctuating color magnetic field in vacuum. Using the dual honeycomb diagram tlhe universal slope is estimated to yield Λsub(p) = 0.34 GeV when corrected by instanton, for α' = 0.88 GeV -2 . (Auth.)
Direct Probes of Linearly Polarized Gluons inside Unpolarized Hadrons
Boer, D.; Brodsky, S. J.; Mulders, P.J.G.; Pisano, C.
2011-01-01
We show that linearly polarized gluons inside unpolarized hadrons can be directly probed in jet or heavy quark pair production in electron-hadron collisions. We discuss the simplest cos2 asymmetries and estimate their maximal value, concluding that measurements of the unknown linearly polarized
Screening in an expanding quark-gluon plasma
International Nuclear Information System (INIS)
Broniowski, W.
1988-12-01
Effects of expansion on the Debye length in quark-gluon plasma are calculated in an abelian, boost invariant model. It is found that for early times the screening is significantly more efficient than what follows from naive static considerations. 11 refs., 1 fig., 1 tab. (author)
The quark gluon plasma: Lattice computations put to experimental test
Indian Academy of Sciences (India)
I describe how lattice computations are being used to extract experimentally relevant features of the quark gluon plasma. I deal speciﬁcally with relaxation times, photon emissivity, strangeness yields, event-by-event ﬂuctuations of conserved quantities and hydrodynamic ﬂow. Finally I give evidence that the plasma is rather ...
The angular ordering in soft-gluon emission
International Nuclear Information System (INIS)
Tesima, K.
1987-01-01
The way to evaluate multi-parton cross-sections systematically is discussed. In the leading-double-log approximation in QCD, the successive emission of soft gluons is at successively smaller angles. The angular ordering, however, is violated in the next-to-leading order
Experiments to measure the gluon helicity distribution in protons
International Nuclear Information System (INIS)
Spinka, H.; Beddo, M.E.; Underwood, D.G.
1993-01-01
Several experiments are described that could obtain information about the gluon helicity distribution in protons. These experiments include inclusive direct-γ, direct-γ + jet, jet, and jet + jet production with colliding beams of longitudinally-polarized protons. Some rates and kinematics are also discussed
How Resummation Depresses the Gluon at Small x
Forte, Stefano; Ball, Richard D.; Forte, Stefano; Altarelli, Guido; Ball, Richard D.
2006-01-01
We summarize recent progress in the resummation of perturbative evolution at small x. We show that the problem of incorporating BFKL small x logs in GLAP evolution is now completely solved, and that the main effect of small x resummation is to reduce the growth of the gluon at small x in the HERA and LHC regions.
Nonperturbative quark-gluon thermodynamics at finite density
Andreichikov, M. A.; Lukashov, M. S.; Simonov, Yu. A.
2018-03-01
Thermodynamics of the quark-gluon plasma at finite density is studied in the framework of the Field Correlator Method, where thermodynamical effects of Polyakov loops and color magnetic confinement are taken into account. Having found good agreement with numerical lattice data for zero density, we calculate pressure P(T,μ), for 0 confinement.
Strangeness and quark gluon plasma: Aspects of theory and experiment
International Nuclear Information System (INIS)
Eggers, H.C.; Rafelski, J.
1990-07-01
A survey of our current understanding of the strange particle signature of quark gluon plasma is presented. Emphasis is placed on the theory of strangeness production in the plasma and recent pertinent experimental results. Useful results on spectra of thermal particles are given. (orig.)
Two theoretical treatments of the quark-gluon plasma
International Nuclear Information System (INIS)
Carrington, M.E.
1989-01-01
The study of the quark-gluon plasma is of direct relevance to questions about the confinement properties of QCD and the validity of the standard theory of QCD in a different physical regime. Part 1 of this work contains a brief discussion of the theoretical and numerical evidence for the existence of the quark-gluon plasma. In the next two sections, two different approaches are discussed. In Part 2, the problem is presented in the general framework of kinetic theory. A definition of the Wigner distribution operator is introduced for quarks and a set of kinetic equations are derived for the momentum moments of this operator. A Wigner distribution operator is defined for gluons and the momentum of this operator are calculated and related to physical quantities. In Part 3, a calculation of linear response functions in a hot gluon plasma is presented. Problems related to gauge invariance and to the definition of a thermal ensemble in the presence of unphysical degrees of freedom are discussed. Results in different gauges and with different ensembles are compared, and the implications of the results for plasma oscillations are discussed
Quark-gluon plasma: Status of heavy ion physics
Indian Academy of Sciences (India)
Lattice quantum chromodynamics (QCD), deﬁned on a discrete space–time lattice, leads to a spectacular non-perturbative prediction of a new state of matter, called quark-gluon plasma (QGP), at sufﬁciently high temperatures or equivalently large energy densities. The experimental programs of CERN, Geneva and BNL, ...
Gluon condensation and modelling of quark confinement in QCD-motivated Nambu-Jona-Lasinio model
International Nuclear Information System (INIS)
Bel'kov, A.A.; Ebert, D.; Emel'yanenko, A.V.
1992-01-01
The possibility of modelling of a quark propagator without poles realizing quark confinement is considered on the basis of a nonperturbative gluon propagator including gluon condensation and a dynamical gluon mass. The property of spontaneous chiral symmetry breaking is retained providing us with a reasonable pattern of low-lying meson properties. 2 figs.; 1 tab
Collinear and Regge behavior of 2{yields}4 MHV amplitude in N=4 super Yang-Mills theory
Energy Technology Data Exchange (ETDEWEB)
Bartels, J.; Prygarin, A. [Hamburg Univ. (Germany). 2. Inst. fuer Theoretische Physik; Lipatov, L.N. [Hamburg Univ. (Germany). 2. Inst. fuer Theoretische Physik; St. Petersburg Nuclear Physics Institute (Russian Federation)
2011-04-15
We investigate the collinear and Regge behavior of the 2{yields}4 MHV amplitude in N=4 super Yang-Mills theory in the BFKL approach. The expression for the remainder function in the collinear kinematics proposed by Alday, Gaiotto, Maldacena, Sever and Vieira is analytically continued to the Mandelstam region. The result of the continuation in the Regge kinematics shows an agreement with the BFKL approach up to to five-loop level. We present the Regge theory interpretation of the obtained results and discuss some issues related to a possible nonmultiplicative renormalization of the remainder function in the collinear limit. (orig.)
Thermal gluons beyond pure perturbation theory
International Nuclear Information System (INIS)
Reinbach, J.
2000-01-01
The perturbative treatment of non-abelian gauge theory at high temperature leads to a threshold in calculation because of chromomagnetic effects. Infinitely many terms of the same order of magnitude arise. The numerical series to be summed is contained in the part of the theory reduced on 3D, which was recently treated non-perturbative as 2+1D Yang-Mills theory at T=0 by Karabali, Kim and Nair. In the thesis in question the exact 3D results are combined with the thermal 4D diagrammatic. In particular the splitting of the space-part of the transverse self-energy in the static limit is treated. As expected, the 3D subsystem can separate as regularized 3D Yang-Mills theory from the 4D structure. In 1-loop order the regulators are received explicit. For 2-loop order it can be shown amongst other things, that the generic contribution with hard inner momenta vanishes. It is examined, how the magnetic mass could follow. Under pressure it is possible to separate the 3D part in 1- and 2-loop order and to receive regulators [de
Studies of semi-inclusive and hard exclusive processes at Jlab
International Nuclear Information System (INIS)
Harutyun Avagyan
2008-01-01
The main goal of experiments proposed for the CLAS12 detector in conjunction with the 12-GeV CEBAF accelerator is the study of the nucleon through hard exclusive, semi-inclusive, and inclusive processes. This will provide new insights into nucleon dynamics at the elementary quark and gluon level. In this contribution we provide an overview of ongoing studies of the structure of nucleon in terms of quark and gluon degrees of freedom and future physics program planned with CLAS and CLAS12
Improving the simulation of quark and gluon jets with Herwig 7
Energy Technology Data Exchange (ETDEWEB)
Reichelt, Daniel [Technische Universitaet Dresden, Institut fuer Kern- und Teilchenphysik, Dresden (Germany); Richardson, Peter [CERN, Theory Department, Geneva (Switzerland); Durham University, Department of Physics, IPPP, Durham (United Kingdom); Siodmok, Andrzej [Polish Academy of Sciences, Institute of Nuclear Physics, Krakow (Poland)
2017-12-15
The properties of quark and gluon jets, and the differences between them, are increasingly important at the LHC. However, Monte Carlo event generators are normally tuned to data from e{sup +}e{sup -} collisions which are primarily sensitive to quark-initiated jets. In order to improve the description of gluon jets we make improvements to the perturbative and the non-perturbative modelling of gluon jets and include data with gluon-initiated jets in the tuning for the first time. The resultant tunes significantly improve the description of gluon jets and are now the default in Herwig 7.1. (orig.)
Gluon saturation and baryon stopping in the SPS, RHIC, and LHC energy regions
International Nuclear Information System (INIS)
Li Shuang; Feng Shengqin
2012-01-01
A new geometrical scaling method with a gluon saturation rapidity limit is proposed to study the gluon saturation feature of the central rapidity region of relativistic nuclear collisions. The net-baryon number is essentially transported by valence quarks that probe the saturation regime in the target by multiple scattering. We take advantage of the gluon saturation model with geometric scaling of the rapidity limit to investigate net baryon distributions, nuclear stopping power and gluon saturation features in the SPS and RHIC energy regions. Predictions for net baryon rapidity distributions, mean rapidity loss and gluon saturation feature in central Pb + Pb collisions at the LHC are made in this paper. (authors)
Quark and gluon jet properties in symmetric three-jet events
Buskulic, Damir; De Bonis, I; Décamp, D; Ghez, P; Goy, C; Lees, J P; Lucotte, A; Minard, M N; Odier, P; Pietrzyk, B; Chmeissani, M; Crespo, J M; Efthymiopoulos, I; Fernández, E; Fernández-Bosman, M; Garrido, L; Juste, A; Martínez, M; Orteu, S; Pacheco, A; Padilla, C; Palla, Fabrizio; Pascual, A; Perlas, J A; Riu, I; Sánchez, F; Teubert, F; Colaleo, A; Creanza, D; De Palma, M; Farilla, A; Gelao, G; Girone, M; Iaselli, Giuseppe; Maggi, G; Maggi, M; Marinelli, N; Natali, S; Nuzzo, S; Ranieri, A; Raso, G; Romano, F; Ruggieri, F; Selvaggi, G; Silvestris, L; Tempesta, P; Zito, G; Huang, X; Lin, J; Ouyang, Q; Wang, T; Xie, Y; Xu, R; Xue, S; Zhang, J; Zhang, L; Zhao, W; Alemany, R; Bazarko, A O; Bonvicini, G; Cattaneo, M; Comas, P; Coyle, P; Drevermann, H; Forty, Roger W; Frank, M; Hagelberg, R; Harvey, J; Jacobsen, R; Janot, P; Jost, B; Kneringer, E; Knobloch, J; Lehraus, Ivan; Martin, E B; Mato, P; Minten, Adolf G; Miquel, R; Mir, L M; Moneta, L; Oest, T; Palazzi, P; Pater, J R; Pusztaszeri, J F; Ranjard, F; Rensing, P E; Rolandi, Luigi; Schlatter, W D; Schmelling, M; Schneider, O; Tejessy, W; Tomalin, I R; Venturi, A; Wachsmuth, H W; Wildish, T; Witzeling, W; Wotschack, J; Ajaltouni, Ziad J; Barrès, A; Boyer, C; Falvard, A; Gay, P; Guicheney, C; Henrard, P; Jousset, J; Michel, B; Monteil, S; Montret, J C; Pallin, D; Perret, P; Podlyski, F; Proriol, J; Rossignol, J M; Fearnley, Tom; Hansen, J B; Hansen, J D; Hansen, J R; Hansen, P H; Nilsson, B S; Wäänänen, A; Kyriakis, A; Markou, C; Simopoulou, Errietta; Siotis, I; Vayaki, Anna; Zachariadou, K; Blondel, A; Bonneaud, G R; Brient, J C; Bourdon, P; Rougé, A; Rumpf, M; Tanaka, R; Valassi, Andrea; Verderi, M; Videau, H L; Candlin, D J; Parsons, M I; Focardi, E; Parrini, G; Corden, M; Delfino, M C; Georgiopoulos, C H; Jaffe, D E; Antonelli, A; Bencivenni, G; Bologna, G; Bossi, F; Campana, P; Capon, G; Chiarella, V; Felici, G; Laurelli, P; Mannocchi, G; Murtas, F; Murtas, G P; Passalacqua, L; Pepé-Altarelli, M; Curtis, L; Dorris, S J; Halley, A W; Knowles, I G; Lynch, J G; O'Shea, V; Raine, C; Reeves, P; Scarr, J M; Smith, K; Thompson, A S; Thomson, F; Thorn, S; Turnbull, R M; Becker, U; Braun, O; Geweniger, C; Graefe, G; Hanke, P; Hepp, V; Kluge, E E; Putzer, A; Rensch, B; Schmidt, M; Sommer, J; Stenzel, H; Tittel, K; Werner, S; Wunsch, M; Abbaneo, D; Beuselinck, R; Binnie, David M; Cameron, W; Colling, D J; Dornan, Peter J; Moutoussi, A; Nash, J; San Martin, G; Sedgbeer, J K; Stacey, A M; Dissertori, G; Girtler, P; Kuhn, D; Rudolph, G; Bowdery, C K; Brodbeck, T J; Colrain, P; Crawford, G; Finch, A J; Foster, F; Hughes, G; Sloan, Terence; Whelan, E P; Williams, M I; Galla, A; Greene, A M; Kleinknecht, K; Quast, G; Renk, B; Rohne, E; Sander, H G; Van Gemmeren, P; Zeitnitz, C; Aubert, Jean-Jacques; Bencheikh, A M; Benchouk, C; Bonissent, A; Bujosa, G; Calvet, D; Carr, J; Diaconu, C A; Etienne, F; Konstantinidis, N P; Nicod, D; Payre, P; Rousseau, D; Talby, M; Sadouki, A; Thulasidas, M; Trabelsi, K; Abt, I; Assmann, R W; Bauer, C; Blum, Walter; Brown, D; Dietl, H; Dydak, Friedrich; Ganis, G; Gotzhein, C; Jakobs, K; Kroha, H; Lütjens, G; Lutz, Gerhard; Männer, W; Moser, H G; Richter, R H; Rosado-Schlosser, A; Schael, S; Settles, Ronald; Seywerd, H C J; Saint-Denis, R; Wiedenmann, W; Wolf, G; Boucrot, J; Callot, O; Cordier, A; Davier, M; Duflot, L; Grivaz, J F; Heusse, P; Jacquet, M; Kim, D W; Le Diberder, F R; Lefrançois, J; Lutz, A M; Nikolic, I A; Park, H J; Park, I C; Schune, M H; Simion, S; Veillet, J J; Videau, I; Azzurri, P; Bagliesi, G; Batignani, G; Bettarini, S; Bozzi, C; Calderini, G; Carpinelli, M; Ciocci, M A; Ciulli, V; Dell'Orso, R; Fantechi, R; Ferrante, I; Foà, L; Forti, F; Giassi, A; Giorgi, M A; Gregorio, A; Ligabue, F; Lusiani, A; Marrocchesi, P S; Messineo, A; Rizzo, G; Sanguinetti, G; Sciabà, A; Spagnolo, P; Steinberger, Jack; Tenchini, Roberto; Tonelli, G; Vannini, C; Verdini, P G; Walsh, J; Betteridge, A P; Blair, G A; Bryant, L M; Cerutti, F; Chambers, J T; Gao, Y; Green, M G; Johnson, D L; Medcalf, T; Perrodo, P; Strong, J A; Von Wimmersperg-Töller, J H; Botterill, David R; Clifft, R W; Edgecock, T R; Haywood, S; Edwards, M; Maley, P; Norton, P R; Thompson, J C; Bloch-Devaux, B; Colas, P; Emery, S; Kozanecki, Witold; Lançon, E; Lemaire, M C; Locci, E; Marx, B; Pérez, P; Rander, J; Renardy, J F; Roussarie, A; Schuller, J P; Schwindling, J; Trabelsi, A; Vallage, B; Johnson, R P; Kim, H Y; Litke, A M; McNeil, M A; Taylor, G; Beddall, A; Booth, C N; Boswell, R; Brew, C A J; Cartwright, S L; Combley, F; Köksal, A; Letho, M; Newton, W M; Rankin, C; Reeve, J; Thompson, L F; Böhrer, A; Brandt, S; Cowan, G D; Feigl, E; Grupen, Claus; Lutters, G; Minguet-Rodríguez, J A; Rivera, F; Saraiva, P; Smolik, L; Stephan, F; Apollonio, M; Bosisio, L; Della Marina, R; Giannini, G; Gobbo, B; Musolino, G; Ragusa, F; Rothberg, J E; Wasserbaech, S R; Armstrong, S R; Bellantoni, L; Elmer, P; Feng, Z; Ferguson, D P S; Gao, Y S; González, S; Grahl, J; Greening, T C; Harton, J L; Hayes, O J; Hu, H; McNamara, P A; Nachtman, J M; Orejudos, W; Pan, Y B; Saadi, Y; Schmitt, M; Scott, I J; Sharma, V; Turk, J; Walsh, A M; Wu Sau Lan; Wu, X; Yamartino, J M; Zheng, M; Zobernig, G
1996-01-01
Quark and gluon jets with the same energy, 24GeV, are compared in symmetric three-jet configurations from hadronic Z decays observed by the ALEPH detector. Jets are defined using the Durham algorithm. Gluon jets are identified using an anti-tag on b jets, based on either a track impact parameter method or a high transverse momentum lepton tag. The comparison of gluon and mixed flavour quark jets shows that gluon jets have a softer fragmentation function, a larger angular width and a higher particle multiplicity. Evidence is also presented which shows that the corresponding differences between gluon and heavy flavour jets are significantly smaller.
Improving the Simulation of Quark and Gluon Jets with Herwig 7 arXiv
Reichelt, Daniel; Siodmok, Andrzej
2017-12-16
The properties of quark and gluon jets, and the differences between them, are increasingly important at the LHC. However, Monte Carlo event generators are normally tuned to data from $e^+e^-$ collisions which are primarily sensitive to quark-initiated jets. In order to improve the description of gluon jets we make improvements to the perturbative and the non-perturbative modelling of gluon jets and include data with gluon-initiated jets in the tuning for the first time. The resultant tunes significantly improve the description of gluon jets and are now the default in Herwig 7.1.
International Nuclear Information System (INIS)
Anon.
1995-01-01
-production. The pioneer experiment was UA8 at CERN, which found events with a ''nearly elastic'' antiproton in which the proton was excited to a massive state containing jets (March 1992, page 4). Interpreted as evidence for quark or gluon constituents in the pomeron (as suggested by Gunnar Ingelman and Peter Schlein), a ''hard'' pomeron structure was favoured, one in which nearly all the pomeron momentum is often carried by a single gluon or quark
Research on the Collinear Equation Model of Visual Positioning Based on Visible Light Communication
Directory of Open Access Journals (Sweden)
Wang Yuqi
2015-01-01
Full Text Available A positioning method based on visible light communication is proposed, which receiving visible light information by low-resolution photodiode array and receiving visual information by the front camera of mobile phone. The terminal position is determined by matching spot information provided by photodiode array with visual information and position information provided by visible light communication. A collinear equation model is derived which based on mobile phone front camera. A hardware-in-loop simulation has been conducted to verify the collinear equation. The three-dimensional positioning error is on the level of decimeter. Moreover, the main factors which affect the positioning accuracy are analyzed in order to further improve the positioning accuracy.
Collinear laser spectroscopy of manganese isotopes using optical pumping in ISCOOL
Marsh, B A; Neyens, G; Flanagan, K; Rajabali, M M; Reponen, M; Campbell, P; Procter, T J
Recently, optical pumping of ions has been achieved inside an ion beam cooler-buncher. By illuminating the central axis of the cooler with laser light, subsequent decay populates selected ionic metastable states. This population enhancement is retained as the ion beam is delivered to an experimental station. In the case of collinear laser spectroscopy, transitions can then be excited from a preferred metastable level, rather than the ground-state. This proposal seeks to establish and develop the technique for ISCOOL. As a test of efficiency, this will be applied to the study of $^{55-66}$Mn isotopes using collinear laser spectroscopy-expanding an earlier study where the benefit of the technique was demonstrated. This will provide nuclear spins, magnetic-dipole and electric-quadrupole moments and changes in mean-square charge radii across N = 40 shell closure candidate and into a region where an onset of deformation, and a new "island of inversion" is predicted.
RFQ beam cooler and buncher for collinear laser spectroscopy of rare isotopes
Barquest, B. R.; Bollen, G.; Mantica, P. F.; Minamisono, K.; Ringle, R.; Schwarz, S.; Sumithrarachchi, C. S.
2017-09-01
A radiofrequency quadrupole (RFQ) ion beam cooler and buncher has been developed to deliver bunched beams with low transverse emittance, energy spread, and time spread to the BECOLA collinear laser spectroscopy system at the National Superconducting Cyclotron Laboratory (NSCL) at Michigan State University. The beam cooler and buncher contains new features which enhance performance, especially for high count rate beams, as well as simplifying construction, maintenance, and operation. The transverse emittance, energy spread, and time spread of the bunched beam, as well as buncher efficiency are reported, showcasing the capabilities of the BECOLA facility to perform collinear laser spectroscopy measurements with bunched rare isotope beams at NSCL and at the future Facility for Rare Isotope Beams (FRIB).
Renormalization of dijet operators at order 1 /Q 2 in soft-collinear effective theory
Goerke, Raymond; Inglis-Whalen, Matthew
2018-05-01
We make progress towards resummation of power-suppressed logarithms in dijet event shapes such as thrust, which have the potential to improve high-precision fits for the value of the strong coupling constant. Using a newly developed formalism for Soft-Collinear Effective Theory (SCET), we identify and compute the anomalous dimensions of all the operators that contribute to event shapes at order 1 /Q 2. These anomalous dimensions are necessary to resum power-suppressed logarithms in dijet event shape distributions, although an additional matching step and running of observable-dependent soft functions will be necessary to complete the resummation. In contrast to standard SCET, the new formalism does not make reference to modes or λ-scaling. Since the formalism does not distinguish between collinear and ultrasoft degrees of freedom at the matching scale, fewer subleading operators are required when compared to recent similar work. We demonstrate how the overlap subtraction prescription extends to these subleading operators.
All-phosphorus flexible devices with non-collinear electrodes: a first principles study.
Li, Junjun; Ruan, Lufeng; Wu, Zewen; Zhang, Guiling; Wang, Yin
2018-03-07
With the continuous expansion of the family of two-dimensional (2D) materials, flexible electronics based on 2D materials have quickly emerged. Theoretically, predicting the transport properties of the flexible devices made up of 2D materials using first principles is of great importance. Using density functional theory combined with the non-equilibrium Green's function formalism, we calculated the transport properties of all-phosphorus flexible devices with non-collinear electrodes, and the results predicted that the device with compressed metallic phosphorene electrodes sandwiching a P-type semiconducting phosphorene shows a better and robust conducting behavior against the bending of the semiconducting region when the angle between the two electrodes is less than 45°, which indicates that this system is very promising for flexible electronics. The calculation of a quantum transport system with non-collinear electrodes demonstrated in this work will provide more interesting information on mesoscopic material systems and related devices.
Magnetic response of magnetic molecules with non-collinear local d-tensors
Directory of Open Access Journals (Sweden)
J. Schnack
2009-01-01
Full Text Available Investigations of molecular magnets are driven both by prospective applications in future storage technology or quantum computing as well as by fundamental questions. Nowadays numerical simulation techniques and computer capabilities make it possible to investigate spin Hamiltonians with realistic arrangements of local anisotropy tensors. In this contribution I will discuss the magnetic response of a small spin system with special emphasis on non-collinear alignments of the local anisotropy axes.
Shell structure and level migrations in zinc studied using collinear laser spectroscopy
Tungate, G; De rydt, M A E; Flanagan, K; Rajabali, M M; Hammen, M; Blaum, K; Froemmgen, N E; Kowalska, M; Campbell, P; Neugart, R; Kreim, K D; Stroke, H H; Krieger, A R; Procter, T J
We propose to perform collinear laser spectroscopy of zinc isotopes to measure the nuclear spin, magnetic dipole moment, electric quadrupole moment and mean-square charge radius. The yield database indicates that measurements of the isotopes $^{60-81}$Zn will be feasible. These measurements will cross the N = 50 shell closure and provide nuclear moments in a region where an inversion of ground-state spin has been identified in neighbouring chains.
Integration of collinear-type doubly unresolved counterterms in NNLO jet cross sections
Del Duca, Vittorio; Somogyi, Gábor; Trócsányi, Zoltán
2013-06-01
In the context of a subtraction method for jet cross sections at NNLO accuracy in the strong coupling, we perform the integration over the two-particle factorised phase space of the collinear-type contributions to the doubly unresolved counterterms. We present the final result as a convolution in colour space of the Born cross section and of an insertion operator, which is written in terms of master integrals that we expand in the dimensional regularisation parameter.
Separation of soft and collinear infrared limits of QCD squared matrix elements
Nagy, Zoltan; Trócsányi, Z L; Trocsanyi, Zoltan; Somogyi, Gabor; Trocsanyi, Zoltan
2007-01-01
We present a simple way of separating the overlap between the soft and collinear factorization formulae of QCD squared matrix elements. We check its validity explicitly for single and double unresolved emissions of tree-level processes. The new method makes possible the definition of helicity-dependent subtraction terms for regularizing the real contributions in computing radiative corrections to QCD jet cross sections. This implies application of Monte Carlo helicity summation in computing higher order corrections.
Integration of collinear-type doubly unresolved counterterms in NNLO jet cross sections
Del Duca, Vittorio; Trocsanyi, Zoltan
2013-01-01
In the context of a subtraction method for jet cross sections at NNLO accuracy in the strong coupling, we perform the integration over the two-particle factorised phase space of the collinear-type contributions to the doubly unresolved counterterms. We present the final result as a convolution in colour space of the Born cross section and of an insertion operator, which is written in terms of master integrals that we expand in the dimensional regularisation parameter.
Xu, Lu; Yu, Lianghong; Liang, Xiaoyan
2016-04-01
We present for the first time a scheme to amplify a Laguerre-Gaussian vortex beam based on non-collinear optical parametric chirped pulse amplification (OPCPA). In addition, a three-dimensional numerical model of non-collinear optical parametric amplification was deduced in the frequency domain, in which the effects of non-collinear configuration, temporal and spatial walk-off, group-velocity dispersion and diffraction were also taken into account, to trace the dynamics of the Laguerre-Gaussian vortex beam and investigate its critical parameters in the non-collinear OPCPA process. Based on the numerical simulation results, the scheme shows promise for implementation in a relativistic twisted laser pulse system, which will diversify the light-matter interaction field.
Energy Technology Data Exchange (ETDEWEB)
Krieger, A., E-mail: kriegea@uni-mainz.d [Institut fuer Kernchemie, Johannes Gutenberg, Universitaet Mainz, Fritz-Strassmann-Weg 2, 55128 Mainz (Germany); Geppert, Ch. [Institut fuer Kernchemie, Johannes Gutenberg, Universitaet Mainz, Fritz-Strassmann-Weg 2, 55128 Mainz (Germany); GSI Helmholtzzentrum fuer Schwerionenforschung, 64291 Darmstadt (Germany); Catherall, R. [CERN, CH-1211 Geneve 23 (Switzerland); Hochschulz, F. [Institut fuer Kernphysik, Universitaet Muenster, 48149 Muenster (Germany); Kraemer, J.; Neugart, R. [Institut fuer Kernchemie, Johannes Gutenberg, Universitaet Mainz, Fritz-Strassmann-Weg 2, 55128 Mainz (Germany); Rosendahl, S. [Institut fuer Kernphysik, Universitaet Muenster, 48149 Muenster (Germany); Schipper, J.; Siesling, E. [CERN, CH-1211 Geneve 23 (Switzerland); Weinheimer, Ch. [Institut fuer Kernphysik, Universitaet Muenster, 48149 Muenster (Germany); Yordanov, D.T. [Max-Planck-Institut fuer Kernphysik, 69117 Heidelberg (Germany); Noertershaeuser, W. [Institut fuer Kernchemie, Johannes Gutenberg, Universitaet Mainz, Fritz-Strassmann-Weg 2, 55128 Mainz (Germany); GSI Helmholtzzentrum fuer Schwerionenforschung, 64291 Darmstadt (Germany)
2011-03-11
A high-voltage divider with accuracy at the ppm level and collinear laser spectroscopy were used to calibrate the high-voltage installation at the radioactive ion beam facility ISOLDE at CERN. The accurate knowledge of this voltage is particularly important for collinear laser spectroscopy measurements. Beam velocity measurements using frequency-comb based collinear laser spectroscopy agree with the new calibration. Applying this, one obtains consistent results for isotope shifts of stable magnesium isotopes measured using collinear spectroscopy and laser spectroscopy on laser-cooled ions in a trap. The long-term stability and the transient behavior during recovery from a voltage dropout were investigated for the different power supplies currently applied at ISOLDE.
Monte Carlo evidence for the gluon-chain model of QCD string formation
International Nuclear Information System (INIS)
Greensite, J.; San Francisco State Univ., CA
1988-08-01
The Monte Carlo method is used to calculate the overlaps string vertical stroken gluons>, where Ψ string [A] is the Yang-Mills wavefunctional due to a static quark-antiquark pair, and vertical stroken gluons > are orthogonal trial states containing n=0, 1, or 2 gluon operators multiplying the true ground state. The calculation is carried out for SU(2) lattice gauge theory in Coulomb gauge, in D=4 dimensions. It is found that the string state is dominated, at small qanti q separations, by the vacuum ('no-gluon') state, at larger separations by the 1-gluon state, and, at the largest separations attempted, the 2-gluon state begins to dominate. This behavior is in qualitative agreement with the gluon-chain model, which is a large-N colors motivated theory of QCD string formation. (orig.)
Selection rules for single-chain-magnet behaviour in non-collinear Ising systems
Energy Technology Data Exchange (ETDEWEB)
Vindigni, Alessandro [Laboratorium fuer Festkoerperphysik, ETH Zuerich, CH-8093 Zuerich (Switzerland); Pini, Maria Gloria [Istituto dei Sistemi Complessi, Consiglio Nazionale delle Ricerche, Via Madonna del Piano 10, I-50019 Sesto Fiorentino (Italy)], E-mail: vindigni@phys.ethz.ch
2009-06-10
The magnetic behaviour of molecular single-chain magnets is investigated in the framework of a one-dimensional Ising model with single spin-flip Glauber dynamics. Opportune modifications to the original theory are required in order to account for non-collinearity of local anisotropy axes between themselves and with respect to the crystallographic (laboratory) frame. The extension of Glauber's theory to the case of a collinear Ising ferrimagnetic chain is also discussed. Within this formalism, both the dynamics of magnetization reversal in zero field and the response of the system to a weak magnetic field, oscillating in time, are studied. Depending on the experimental geometry, selection rules are found for the occurrence of slow relaxation of the magnetization at low temperatures, as well as for resonant behaviour of the a.c. susceptibility as a function of temperature at low frequencies. The present theory applies successfully to some real systems, namely Mn-, Dy- and Co-based molecular magnetic chains, showing that single-chain-magnet behaviour is not only a feature of collinear ferro- and ferrimagnetic, but also of canted antiferromagnetic chains.
Real-space imaging of non-collinear antiferromagnetic order with a single-spin magnetometer
Gross, I.; Akhtar, W.; Garcia, V.; Martínez, L. J.; Chouaieb, S.; Garcia, K.; Carrétéro, C.; Barthélémy, A.; Appel, P.; Maletinsky, P.; Kim, J.-V.; Chauleau, J. Y.; Jaouen, N.; Viret, M.; Bibes, M.; Fusil, S.; Jacques, V.
2017-09-01
Although ferromagnets have many applications, their large magnetization and the resulting energy cost for switching magnetic moments bring into question their suitability for reliable low-power spintronic devices. Non-collinear antiferromagnetic systems do not suffer from this problem, and often have extra functionalities: non-collinear spin order may break space-inversion symmetry and thus allow electric-field control of magnetism, or may produce emergent spin-orbit effects that enable efficient spin-charge interconversion. To harness these traits for next-generation spintronics, the nanoscale control and imaging capabilities that are now routine for ferromagnets must be developed for antiferromagnetic systems. Here, using a non-invasive, scanning single-spin magnetometer based on a nitrogen-vacancy defect in diamond, we demonstrate real-space visualization of non-collinear antiferromagnetic order in a magnetic thin film at room temperature. We image the spin cycloid of a multiferroic bismuth ferrite (BiFeO3) thin film and extract a period of about 70 nanometres, consistent with values determined by macroscopic diffraction. In addition, we take advantage of the magnetoelectric coupling present in BiFeO3 to manipulate the cycloid propagation direction by an electric field. Besides highlighting the potential of nitrogen-vacancy magnetometry for imaging complex antiferromagnetic orders at the nanoscale, these results demonstrate how BiFeO3 can be used in the design of reconfigurable nanoscale spin textures.
Collinear facilitation and contour integration in autism: evidence for atypical visual integration.
Jachim, Stephen; Warren, Paul A; McLoughlin, Niall; Gowen, Emma
2015-01-01
Autism spectrum disorder (ASD) is a neurodevelopmental disorder characterized by impaired social interaction, atypical communication and a restricted repertoire of interests and activities. Altered sensory and perceptual experiences are also common, and a notable perceptual difference between individuals with ASD and controls is their superior performance in visual tasks where it may be beneficial to ignore global context. This superiority may be the result of atypical integrative processing. To explore this claim we investigated visual integration in adults with ASD (diagnosed with Asperger's Syndrome) using two psychophysical tasks thought to rely on integrative processing-collinear facilitation and contour integration. We measured collinear facilitation at different flanker orientation offsets and contour integration for both open and closed contours. Our results indicate that compared to matched controls, ASD participants show (i) reduced collinear facilitation, despite equivalent performance without flankers; and (ii) less benefit from closed contours in contour integration. These results indicate weaker visuospatial integration in adults with ASD and suggest that further studies using these types of paradigms would provide knowledge on how contextual processing is altered in ASD.
Collinear facilitation and contour integration in autism: evidence for atypical visual integration
Directory of Open Access Journals (Sweden)
Stephen eJachim
2015-03-01
Full Text Available Autism spectrum disorder (ASD is a neurodevelopmental disorder characterized by impaired social interaction, atypical communication and a restricted repertoire of interests and activities. Altered sensory and perceptual experiences are also common, and a notable perceptual difference between individuals with ASD and controls is their superior performance in visual tasks where it may be beneficial to ignore global context. This superiority may be the result of atypical integrative processing. To explore this claim we investigated visual integration in adults with ASD (diagnosed with Asperger’s Syndrome using two psychophysical tasks thought to rely on integrative processing - collinear facilitation and contour integration. We measured collinear facilitation at different flanker orientation offsets and contour integration for both open and closed contours. Our results indicate that compared to matched controls, ASD participants show (i reduced collinear facilitation, despite equivalent performance without flankers and (ii less benefit from closed contours in contour integration. These results indicate weaker visuospatial integration in adults with ASD and suggest that further studies using these types of paradigms would provide knowledge on how contextual processing is altered in ASD.
Collinearity analysis of Brassica A and C genomes based on an updated inferred unigene order
Directory of Open Access Journals (Sweden)
Ian Bancroft
2015-06-01
Full Text Available This data article includes SNP scoring across lines of the Brassica napus TNDH population based on Illumina sequencing of mRNA, expanded to 75 lines. The 21, 323 mapped markers defined 887 recombination bins, representing an updated genetic linkage map for the species. Based on this new map, 5 genome sequence scaffolds were split and the order and orientation of scaffolds updated to establish a new pseudomolecule specification. The order of unigenes and SNP array probes within these pseudomolecules was determined. Unigenes were assessed for sequence similarity to the A and C genomes. The 57, 246 that mapped to both enabled the collinearity of the A and C genomes to be illustrated graphically. Although the great majority was in collinear positions, some were not. Analyses of 60 such instances are presented, suggesting that the breakdown in collinearity was largely due to either the absence of the homoeologue on one genome (resulting in sequence match to a paralogue or multiple similar sequences being present. The mRNAseq datasets for the TNDH lines are available from the SRA repository (ERA283648; the remaining datasets are supplied with this article.
Collinear masking effect in visual search is independent of perceptual salience.
Jingling, Li; Lu, Yi-Hui; Cheng, Miao; Tseng, Chia-Huei
2017-07-01
Searching for a target in a salient region should be easier than looking for one in a nonsalient region. However, we previously discovered a contradictory phenomenon in which a local target in a salient structure was more difficult to find than one in the background. The salient structure was constructed of orientation singletons aligned to each other to form a collinear structure. In the present study, we undertake to determine whether such a masking effect was a result of salience competition between a global structure and the local target. In the first 3 experiments, we increased the salience value of the local target with the hope of adding to its competitive advantage and eventually eliminating the masking effect; nevertheless, the masking effect persisted. In an additional 2 experiments, we reduced salience of the global collinear structure by altering the orientation of the background bars and the masking effect still emerged. Our salience manipulations were validated by a controlled condition in which the global structure was grouped noncollinearly. In this case, local target salience increase (e.g., onset) or global distractor salience reduction (e.g., randomized flanking orientations) effectively removed the facilitation effect of the noncollinear structure. Our data suggest that salience competition is unlikely to explain the collinear masking effect, and other mechanisms such as contour integration, border formation, or the crowding effect may be prospective candidates for further investigation.
Selection rules for single-chain-magnet behaviour in non-collinear Ising systems
International Nuclear Information System (INIS)
Vindigni, Alessandro; Pini, Maria Gloria
2009-01-01
The magnetic behaviour of molecular single-chain magnets is investigated in the framework of a one-dimensional Ising model with single spin-flip Glauber dynamics. Opportune modifications to the original theory are required in order to account for non-collinearity of local anisotropy axes between themselves and with respect to the crystallographic (laboratory) frame. The extension of Glauber's theory to the case of a collinear Ising ferrimagnetic chain is also discussed. Within this formalism, both the dynamics of magnetization reversal in zero field and the response of the system to a weak magnetic field, oscillating in time, are studied. Depending on the experimental geometry, selection rules are found for the occurrence of slow relaxation of the magnetization at low temperatures, as well as for resonant behaviour of the a.c. susceptibility as a function of temperature at low frequencies. The present theory applies successfully to some real systems, namely Mn-, Dy- and Co-based molecular magnetic chains, showing that single-chain-magnet behaviour is not only a feature of collinear ferro- and ferrimagnetic, but also of canted antiferromagnetic chains.
A simulation study on Bayesian Ridge regression models for several collinearity levels
Efendi, Achmad; Effrihan
2017-12-01
When analyzing data with multiple regression model if there are collinearities, then one or several predictor variables are usually omitted from the model. However, there sometimes some reasons, for instance medical or economic reasons, the predictors are all important and should be included in the model. Ridge regression model is not uncommon in some researches to use to cope with collinearity. Through this modeling, weights for predictor variables are used for estimating parameters. The next estimation process could follow the concept of likelihood. Furthermore, for the estimation nowadays the Bayesian version could be an alternative. This estimation method does not match likelihood one in terms of popularity due to some difficulties; computation and so forth. Nevertheless, with the growing improvement of computational methodology recently, this caveat should not at the moment become a problem. This paper discusses about simulation process for evaluating the characteristic of Bayesian Ridge regression parameter estimates. There are several simulation settings based on variety of collinearity levels and sample sizes. The results show that Bayesian method gives better performance for relatively small sample sizes, and for other settings the method does perform relatively similar to the likelihood method.
Quark-number susceptibility, thermodynamic sum rule, and the hard thermal loop approximation
International Nuclear Information System (INIS)
Chakraborty, Purnendu; Mustafa, Munshi G.; Thoma, Markus H.
2003-01-01
The quark number susceptibility, associated with the conserved quark number density, is closely related to the baryon and charge fluctuations in the quark-gluon plasma, which might serve as signature for the quark-gluon plasma formation in ultrarelativistic heavy-ion collisions. In addition to QCD lattice simulations, the quark number susceptibility has been calculated recently using a resummed perturbation theory (hard thermal loop resummation). In the present work we show, based on general arguments, that the computation of this quantity neglecting hard thermal loop vertices contradicts the Ward identity and violates the thermodynamic sum rule following from quark number conservation. We further show that the hard thermal loop perturbation theory is consistent with the thermodynamic sum rule
Medium-induced gluon radiation beyond the eikonal approximation
Apolinário, Liliana; Milhano, Guilherme; Salgado, Carlos A
2014-01-01
In this work we improve existing calculations of radiative energy loss by computing corrections that implement energy-momentum conservation, previously only implemented a posteriori, in a rigorous way. Using the path-integral formalism, we compute in-medium splittings allowing transverse motion of all particles in the emission process, thus relaxing the assumption that only the softest particle is permitted such movement. This work constitutes the extension of the computation carried out for x$\\rightarrow$1 in Phys. Lett. B718 (2012) 160-168, to all values of x, the momentum fraction of the energy of the parent parton carried by the emitted gluon. In order to accomplish a general description of the whole in-medium showering process, in this work we allow for arbitrary formation times for the emitted gluon. We provide general expressions and their realisation in the path integral formalism within the harmonic oscillator approximation.
Quark-Gluon Soup -- The Perfectly Liquid Phase of QCD
Heinz, Ulrich
2015-03-01
At temperatures above about 150 MeV and energy densities exceeding 500 MeV/fm3, quarks and gluons exist in the form of a plasma of free color charges that is about 1000 times hotter and a billion times denser than any other plasma ever created in the laboratory. This quark-gluon plasma (QGP) turns out to be strongly coupled, flowing like a liquid. About 35 years ago, the nuclear physics community started a program of relativistic heavy-ion collisions with the goal of producing and studying QGP under controlled laboratory conditions. This article recounts the story of its successful creation in collider experiments at Brookhaven National Laboratory and CERN and the subsequent discovery of its almost perfectly liquid nature, and reports on the recent quantitatively precise determination of its thermodynamic and transport properties.
Singular gauge potentials and the gluon condensate at zero temperature
International Nuclear Information System (INIS)
Langfeld, K.; Ilgenfritz, E.-M.; Reinhardt, H.; Schaefke, A.
2002-01-01
We consider a new cooling procedure which separates gluon degrees of freedom from singular center vortices in SU(2) LGT in a gauge invariant way. Restricted by a cooling scale κ 4 /σ 2 fixing the residual SO(3) gluonic action relative to the string tension, the procedure is RG invariant. In the limit κ → 0 a pure Z(2) vortex texture is left. This minimal vortex content does not contribute to the string tension. It reproduces, however, the lowest glueball states. With an action density scaling like a 4 with β, it defines a finite contribution to the action density at T = 0 in the continuum limit. We propose to interpret this a mass dimension 4 condensate related to the gluon condensate. Similarly, this vortex texture is revealed in the Landau gauge
Recursive Neural Networks in Quark/Gluon Tagging
CERN. Geneva
2018-01-01
Vidyo contribution Based on the natural tree-like structure of jet sequential clustering, the recursive neural networks (RecNNs) embed jet clustering history recursively as in natural language processing. We explore the performance of RecNN in quark/gluon discrimination. The results show that RecNNs work better than the baseline BDT by a few percent in gluon rejection at the working point of 50\\% quark acceptance. We also experimented on some relevant aspects which might influence the performance of networks. It shows that even only particle flow identification as input feature without any extra information on momentum or angular position is already giving a fairly good result, which indicates that most of the information for q/g discrimination is already included in the tree-structure itself.
Running coupling corrections to high energy inclusive gluon production
International Nuclear Information System (INIS)
Horowitz, W.A.; Kovchegov, Yuri V.
2011-01-01
We calculate running coupling corrections for the lowest-order gluon production cross section in high energy hadronic and nuclear scattering using the BLM scale-setting prescription. In the final answer for the cross section the three powers of fixed coupling are replaced by seven factors of running coupling, five in the numerator and two in the denominator, forming a 'septumvirate' of running couplings, analogous to the 'triumvirate' of running couplings found earlier for the small-x BFKL/BK/JIMWLK evolution equations. It is interesting to note that the two running couplings in the denominator of the 'septumvirate' run with complex-valued momentum scales, which are complex conjugates of each other, such that the production cross section is indeed real. We use our lowest-order result to conjecture how running coupling corrections may enter the full fixed-coupling k T -factorization formula for gluon production which includes nonlinear small-x evolution.
Quark/gluon jet discrimination: a reproducible analysis using R
CERN. Geneva
2017-01-01
The power to discriminate between light-quark jets and gluon jets would have a huge impact on many searches for new physics at CERN and beyond. This talk will present a walk-through of the development of a prototype machine learning classifier for differentiating between quark and gluon jets at experiments like those at the Large Hadron Collider at CERN. A new fast feature selection method that combines information theory and graph analytics will be outlined. This method has found new variables that promise significant improvements in discrimination power. The prototype jet tagger is simple, interpretable, parsimonious, and computationally extremely cheap, and therefore might be suitable for use in trigger systems for real-time data processing. Nested stratified k-fold cross validation was used to generate robust estimates of model performance. The data analysis was performed entirely in the R statistical programming language, and is fully reproducible. The entire analysis workflow is data-driven, automated a...
Quark-gluon plasma in strong magnetic fields
International Nuclear Information System (INIS)
Kalaydzhyan, Tigran
2013-04-01
One of the fundamental problems in subatomic physics is the determination of properties of matter at extreme temperatures, densities and electromagnetic fields. The modern ultrarelativistic heavy-ion experiments are able to study such states (the quark-gluon plasma) and indicate that the physics at extreme conditions differs drastically from what is known from the conventional observations. Also the theoretical methods developed mostly within the perturbative framework face various conceptual problems and need to be replaced by a nonperturbative approach. In this thesis we study the physics of the strongly-coupled quark-gluon plasma in external magnetic fields as well as general electromagnetic and topological properties of the QCD and QCD-like systems. We develop and apply various nonperturbative techniques, based on e.g. gauge-gravity correspondence, lattice QCD simulations, relativistic hydrodynamics and condensed-matter-inspired models.
Quark-gluon plasma in strong magnetic fields
Energy Technology Data Exchange (ETDEWEB)
Kalaydzhyan, Tigran
2013-04-15
One of the fundamental problems in subatomic physics is the determination of properties of matter at extreme temperatures, densities and electromagnetic fields. The modern ultrarelativistic heavy-ion experiments are able to study such states (the quark-gluon plasma) and indicate that the physics at extreme conditions differs drastically from what is known from the conventional observations. Also the theoretical methods developed mostly within the perturbative framework face various conceptual problems and need to be replaced by a nonperturbative approach. In this thesis we study the physics of the strongly-coupled quark-gluon plasma in external magnetic fields as well as general electromagnetic and topological properties of the QCD and QCD-like systems. We develop and apply various nonperturbative techniques, based on e.g. gauge-gravity correspondence, lattice QCD simulations, relativistic hydrodynamics and condensed-matter-inspired models.
The strongly coupled quark-gluon plasma created at RHIC
Heinz, Ulrich W
2009-01-01
The Relativistic Heavy Ion Collider (RHIC) was built to re-create and study in the laboratory the extremely hot and dense matter that filled our entire universe during its first few microseconds. Its operation since June 2000 has been extremely successful, and the four large RHIC experiments have produced an impressive body of data which indeed provide compelling evidence for the formation of thermally equilibrated matter at unprecedented temperatures and energy densities -- a "quark-gluon plasma (QGP)". A surprise has been the discovery that this plasma behaves like an almost perfect fluid, with extremely low viscosity. Theorists had expected a weakly interacting gas of quarks and gluons, but instead we seem to have created a strongly coupled plasma liquid. The experimental evidence strongly relies on a feature called "elliptic flow" in off-central collisions, with additional support from other observations. This article explains how we probe the strongly coupled QGP, describes the ideas and measurements whi...
On the zero crossing of the three-gluon vertex
Energy Technology Data Exchange (ETDEWEB)
Athenodorou, A. [Department of Physics, University of Cyprus, POB 20537, 1678 Nicosia (Cyprus); Binosi, D., E-mail: binosi@ectstar.eu [European Centre for Theoretical Studies in Nuclear Physics and Related Areas - ECT* and Fondazione Bruno Kessler, Villa Tambosi, Strada delle Tabarelle 286, I-38050 Villazzano (Italy); Boucaud, Ph. [Laboratoire de Physique Théorique (UMR8627), CNRS, Univ. Paris-Sud, Université Paris-Saclay, 91405 Orsay (France); De Soto, F. [Dpto. Sistemas Físicos, Químicos y Naturales, Univ. Pablo de Olavide, 41013 Sevilla (Spain); Papavassiliou, J. [Department of Theoretical Physics and IFIC, University of Valencia-CSIC, E-46100, Valencia (Spain); Rodríguez-Quintero, J. [Department of Integrated Sciences, University of Huelva, E-21071 Huelva (Spain); Zafeiropoulos, S. [Institut für Theoretische Physik, Goethe-Universität Frankfurt, Max-von-Laue-Str. 1, 60438 Frankfurt am Main (Germany)
2016-10-10
We report on new results on the infrared behavior of the three-gluon vertex in quenched Quantum Chromodynamics, obtained from large-volume lattice simulations. The main focus of our study is the appearance of the characteristic infrared feature known as ‘zero crossing’, the origin of which is intimately connected with the nonperturbative masslessness of the Faddeev–Popov ghost. The appearance of this effect is clearly visible in one of the two kinematic configurations analyzed, and its theoretical origin is discussed in the framework of Schwinger–Dyson equations. The effective coupling in the momentum subtraction scheme that corresponds to the three-gluon vertex is constructed, revealing the vanishing of the effective interaction at the exact location of the zero crossing.
Baryonic decay of the J/psi and gluon spin
International Nuclear Information System (INIS)
Pallin, D.
1985-04-01
A study of the J/psi state of the charmomium (c antic state) was performed at the D.C.I. collider in Orsay with the DM2 detector. 9 millions of J/psi have been produced, corresponding to more than one half of the actual world statistics. The very simple mecanism of the e +- annihilation into baryon-antibaryon via the J/psi state, allows measurements of the gluon spin through the emitted baryon angular distribution. The analyse of the channels J/psi → p antip and Λ antiΛ, permits to obtain parameters for the angular distributions. These experimental values favour very clearly a vectorial gluon hypothesis, as postulated by the quantum Chromodynamics [fr
RHIC and the pursuit of the quark-gluon plasma
International Nuclear Information System (INIS)
Mitchell, J.T.
2001-01-01
There is a fugitive on the loose. Its name is Quark-Gluon Plasma, alias the QGP. The QGP is a known informant with knowledge about the fundamental building blocks of nature that we wish to extract. This briefing will outline the status of the pursuit of the elusive QGP. We will cover what makes the QGP tick, its modus operandi, details on how we plan to hunt the fugitive down, and our level of success thus far
Superconvergent gluon propagator and the quark-antiquark potential
International Nuclear Information System (INIS)
Oehme, R.; Chicago Univ., IL; Chicago Univ., IL
1989-01-01
Superconvergence of the gluon propagator, together with the asymptotically negative sign of the discontinuity, imply that the structure function has a representation which corresponds to an approximately linear quark-antiquark potential, provided the number of flavors is less than ten. For more than ten flavors, there is no indication for a linear potential within this framework. The connection with metric confinement is emphasized. Possible dipole terms are considered briefly. (orig.)
On the scattering of gluons in the GKP string
International Nuclear Information System (INIS)
Bianchi, Lorenzo; Hamburg Univ.; Bianchi, Marco S.
2015-11-01
We compute the one-loop S-matrix for the light bosonic excitations of the GKP string at strong coupling. These correspond, on the gauge theory side, to gluon insertions in the GKP vacuum. We perform the calculation by Feynman diagrams in the worldsheet theory and we compare the result to the integrability prediction, finding perfect agreement for the scheme independent part. For scheme dependent rational terms we test different schemes and find that a recent proposal reproduces exactly the integrability prediction.
Gluon and charm content of the η' meson and instantons
International Nuclear Information System (INIS)
Shuryak, E.V.; Zhitnitsky, A.R.
1998-01-01
Motivated by recent CLEO measurements of the B→η ' 'K decay, we evaluate the gluon and charm content of the η ' ' meson using the interacting instanton liquid model of the QCD vacuum. Our main result is left-angle 0|g 3 f abc G μν a G να b G αμ c |η ' 'right-angle=-(2
Q2 evolution of a soft gluon distribution function
International Nuclear Information System (INIS)
Enkovskij, L.L.; Kotikov, A.V.; Pakkanoni, F.
1992-01-01
Model parameter dependence refferring to the function of gluon distribution linked with the exchange of a dipole pomeron from Q 2 is calculated within the framework of the Gribov-Lipatov-Altarelli-Parisi evolution equation (GLAP) both in the leading logarithm approximation and in the double logarithmic approximation. The behaviour of logarithmic parametrization ∼ (ln(1/x)) b appears to be unstable in relation to perturbative calculations
Cold quark-gluon plasma. Theoretical and experimental perspectives
Energy Technology Data Exchange (ETDEWEB)
Mandzhavidze, I [Institute of Physics, Tbilisi (Georgia); Sisakyan, A N [Bogolyubov Laboratory of Theoretical Physics, Joint Institute for Nuclear Research, Dubna (Russian Federation)
1998-12-01
The arguments that extremely high-multiplicity hadron interactions at high energies are the source of cold, dense quark-gluon plasma (CQGP) created by the QCD heavy jets are offered. The possibility of calorimetric triggering and measurements of CQGP is considered. The space-time local thermodynamical formalism is adopted for field-theoretical description of such measurements. The valid phenomena in the CQGP are discussed (qualitatively) from theoretical and experimental points of view 62 refs.
Enhanced J/psi suppression due to gluon depletion
Hwa, R. C.; Pisut, J.; Pisutova, N.
1997-01-01
The nonlinear effect of gluon depletion in the collision of large nuclei can be large. It is due to multiple scatterings among comoving partons initiated by primary scattering of partons in the colliding nuclei. The effect can give rise to substantial suppression of $J/\\psi$ production in very large nuclei, even if the linear depletion effect is insignificant for the collisions of nuclei of smaller sizes. This mechanism offers a natural explanation of the enhanced suppression in the Pb-Pb dat...
Tree-level gluon amplitudes on the celestial sphere
Schreiber, Anders Ø.; Volovich, Anastasia; Zlotnikov, Michael
2018-06-01
Pasterski, Shao and Strominger have recently proposed that massless scattering amplitudes can be mapped to correlators on the celestial sphere at infinity via a Mellin transform. We apply this prescription to arbitrary n-point tree-level gluon amplitudes. The Mellin transforms of MHV amplitudes are given by generalized hypergeometric functions on the Grassmannian Gr (4 , n), while generic non-MHV amplitudes are given by more complicated Gelfand A-hypergeometric functions.
Debye's length in expanding quark-gluon plasma
International Nuclear Information System (INIS)
Bialas, A.
1988-06-01
The screening properties of an abelian quark-gluon plasma and boost invariantly expanding in a given direction, are discussed. The expansion results in anisotropic screening. At early stages of the process, the Debye length along the direction of the expansion is reduced by a factor of about 2, relative to static calculations. This may have important consequences for the J/ψ production rate. 12 refs., 2 figs., 1 tab. (author)
Phenomenological Review on Quark-Gluon Plasma: Concepts vs. Observations
Czech Academy of Sciences Publication Activity Database
Pasechnik, R.; Šumbera, Michal
2017-01-01
Roč. 3, č. 1 (2017), č. článku 7. ISSN 2218-1997 R&D Projects: GA MŠk(CZ) LG13031; GA ČR GA13-20841S Institutional support: RVO:61389005 Keywords : extreme states of matter * heavy ion collisions * QCD critical point * quark-gluon plasma * saturation phenomena * QCD vacuum Subject RIV: BF - Elementary Particles and High Energy Physics OBOR OECD: Particles and field physics
Evolution of gluon TMDs from small to moderate x
Energy Technology Data Exchange (ETDEWEB)
Tarasov, Andrey [Thomas Jefferson National Accelerator Facility (TJNAF), Newport News, VA (United States)
2016-05-01
Recently we obtained an evolution equation of gluon TMDs, which addresses a problem of unification of different kinematic regimes. It describes evolution in the whole range of Bjorken $x_B$ and the whole range of transverse momentum $k_\\perp$. In this notes I study different limits of this evolution equation and show how it yields several well-known and some previously unknown results.
From quarks and gluons to baryon form factors.
Eichmann, Gernot
2012-04-01
I briefly summarize recent results for nucleon and [Formula: see text] electromagnetic, axial and transition form factors in the Dyson-Schwinger approach. The calculation of the current diagrams from the quark-gluon level enables a transparent discussion of common features such as: the implications of dynamical chiral symmetry breaking and quark orbital angular momentum, the timelike structure of the form factors, and their interpretation in terms of missing pion-cloud effects.
Dynamical gluon masses in perturbative calculations at the loop level
International Nuclear Information System (INIS)
Machado, Fatima A.; Natale, Adriano A.
2013-01-01
Full text: In the phenomenology of strong interactions one always has to deal at some extent with the interplay between perturbative and non-perturbative QCD. On one hand, the former has quite developed tools, yielded by asymptotic freedom. On the other, concerning the latter, we nowadays envisage the following scenario: 1) There are strong evidences for a dynamically massive gluon propagator and infrared finite coupling constant; 2) There is an extensive and successful use of an infrared finite coupling constant in phenomenological calculations at tree level; 3) The infrared finite coupling improves the perturbative series convergence; 4) The dynamical gluon mass provides a natural infrared cutoff in the physical processes at the tree level. Considering this scenario it is natural to ask how these non-perturbative results can be used in perturbative calculations of physical observables at the loop level. Recent papers discuss how off-shell gauge and renormalization group invariant Green functions can be computed with the use of the Pinch Technique (PT), with IR divergences removed by the dynamical gluon mass, and using a well defined effective charge. In this work we improve the former results by the authors, which evaluate 1-loop corrections to some two- and three-point functions of SU(3) pure Yang-Mills, investigating the dressing of quantities that could account for an extension of loop calculations to the infrared domain of the theory, in a way applicable to phenomenological calculations. One of these improvements is maintaining the gluon propagator transverse in such a scheme. (author)
Soft probes of the quark gluon plasma in ATLAS
Wozniak, K W; The ATLAS collaboration
2014-01-01
Measurements of low-$p_{T}$ (< 5 GeV) particle production have provided valuable insight on the production and evolution of the quark-gluon plasma in Pb+Pb collisions at the LHC. In particular, measurements of elliptic and higher order collective flow imprinted on the azimuthal angle distributions of low-$p_{T}$ particles directly probe the strongly-coupled dynamics of the quark gluon plasma and test hydrodynamic model descriptions of its evolution. The large acceptance of detectors like ATLAS have made it possible to measure flow event-by-event and to determine the correlations between different harmonics. Recent measurements of low-$p_{T}$ particle production and multi-particle correlations in proton-lead collisions have shown features similar to the collective flow observed in Pb+Pb collisions. Results will be presented from a variety of single and multi-particle measurements in Pb+Pb and proton-Pb collisions that probe the collective dynamics of the quark gluon plasma and possibly provide evidence for ...
Quarks and gluons in nuclear and particle physics
International Nuclear Information System (INIS)
Van Hove, L.
1988-01-01
This paper provides a broad overview of strong interactions, or nuclear forces, as ones understanding has expanded over the past 25 years. The major particles and models are briefly touched upon. The author expands upon the field theories which have evolved to explain the experimental work, and the present model of quarks and gluons which form the components of hadrons. The standard model has been very successful in explaining much of the newly acquired experimental data. But the property of confinement, where the partons, (quarks and gluons), are not observed seperately has precluded observation of these particles. He touches on the manifestation of these particles in high energy physics, where they model the observed particles and resonances, and are responsible for the production of hadronic jets. However in nuclear physics, one does not need to postulate the existance of these particles to explain the properties of nuclei, until one deals with interaction energies in the range of GeV. The author then touches on the area of ultra-relativistic nuclear physics, where the partons must play a role in the effects which are observed. In particular he discusses deep inelastic lepton scattering on nuclei, the Drell-Yan process in nuclei, and ultra-relativistic nuclear collisions. Finally he gives a brief discussion of the quark-gluon plasma, which is postulated to form during very high energy collisions, manifesting itself as a brief deconfinement of the partons into an equilibrium plasma
The gluon momentum fraction of the nucleon from lattice QCD
International Nuclear Information System (INIS)
Alexandrou, Constantia; Hadjiyiannakou, Kyriakos; Constantinou, Martha; Jansen, Karl; Wiese, Christian; Panagopoulos, Haralambos
2016-01-01
We perform a direct calculation of the gluon momentum fraction of the nucleon using maximally twisted mass fermion ensembles with N_f=2+1+1 flavors at a pion mass of about 370 MeV and a lattice spacing of a∼0.082 fm and with N_f=2 flavors at the physical pion mass and a lattice spacing of a∼0.093 fm. In the definition of the gluon operator we employ stout smearing to obtain a statistically significant result for the bare matrix elements. In addition, we perform a lattice perturbative calculation including 2 levels of stout smearing to carry out the mixing and the renormalization of the quark and gluon operators. We find, after conversion to the MS scheme at a scale of 2 GeV: left angle x right angle "R_g=0.284(23)(23) for pion mass of about 370 MeV and left angle x right angle "R_g=0.283(23)(15) for the physical pion mass.
Physics and astrophysics of quark-gluon plasma
Energy Technology Data Exchange (ETDEWEB)
Anon.
1993-06-15
The quark gluon plasma - matter too hot or dense for quarks to crystallize into particles - played a vital role in the formation of the Universe. Efforts to recreate and understand this type of matter are forefront physics and astrophysics, and progress was highlighted in the Second International Conference on Physics and Astrophysics of Quark Gluon Plasma (ICPA-QGP 93), held in Calcutta from 19-23 January. (The first conference in the series was held in Bombay in February 1988). Although primarily motivated towards enlightening the Indian physics community in this new and rapidly evolving area, in which India now plays an important role, the conference also catered for an international audience. Particular emphasis was placed on the role of quark gluon plasma in astrophysics and cosmology. While Charles Alcock of Lawrence Livermore looked at a less conventional picture giving inhomogeneous ('clumpy') nucleosynthesis, David Schramm (Chicago) covered standard big bang nucleosynthesis. The abundances of very light elements do not differ appreciably for these contrasting scenarios; the crucial difference between them shows up for heavier elements like lithium-7 and -8 and boron-11. Richard Boyd (Ohio State) highlighted the importance of accurate measurements of the primordial abundances of these elements for clues to the cosmic quark hadron phase transition. B. Banerjee (Bombay) argued, on the basis of lattice calculations, for only slight supercooling in the cosmic quark phase transition - an assertion which runs counter to the inhomogeneous nucleosynthesis scenario.
Physics and astrophysics of quark-gluon plasma
International Nuclear Information System (INIS)
Anon.
1993-01-01
The quark gluon plasma - matter too hot or dense for quarks to crystallize into particles - played a vital role in the formation of the Universe. Efforts to recreate and understand this type of matter are forefront physics and astrophysics, and progress was highlighted in the Second International Conference on Physics and Astrophysics of Quark Gluon Plasma (ICPA-QGP 93), held in Calcutta from 19-23 January. (The first conference in the series was held in Bombay in February 1988). Although primarily motivated towards enlightening the Indian physics community in this new and rapidly evolving area, in which India now plays an important role, the conference also catered for an international audience. Particular emphasis was placed on the role of quark gluon plasma in astrophysics and cosmology. While Charles Alcock of Lawrence Livermore looked at a less conventional picture giving inhomogeneous ('clumpy') nucleosynthesis, David Schramm (Chicago) covered standard big bang nucleosynthesis. The abundances of very light elements do not differ appreciably for these contrasting scenarios; the crucial difference between them shows up for heavier elements like lithium-7 and -8 and boron-11. Richard Boyd (Ohio State) highlighted the importance of accurate measurements of the primordial abundances of these elements for clues to the cosmic quark hadron phase transition. B. Banerjee (Bombay) argued, on the basis of lattice calculations, for only slight supercooling in the cosmic quark phase transition - an assertion which runs counter to the inhomogeneous nucleosynthesis scenario
Gluon density determination from open charm events at HERA
International Nuclear Information System (INIS)
Woudenberg, R. van; Ould-Saada, F.; Eisenberg, Y.; Glasman, C.; Karshon, U.; Montag, A.; Egli, S.
1992-01-01
We study some prospects of measuring the gluon density in the proton using charm events at HERA for the ep center of mass energy √s = 314 GeV. We invoke the QCD-improved boson-gluon fusion model and find the following cross-section: σ(ep → ecanti cX) ≅ O(0.6 μb). This cross-section would provide O(10 8 ) events/year, for an integrated luminosity of 100 pb -1 . We have investigated two traditional methods for tagging of charm, namely, D *± reconstruction using the process D *± → D 0 π ± → (K -+ π ± )π ± , and dileptonic decays of charmed hadrons (canti c → l + l - X). The inclusive cross-sections after full detector simulation are 10 3 pb and 10 2 pb, respectively. In both cases the background was strongly reduced. By using these events, the gluon distribution in the proton can be measured in the range 10 -3 ≤ x g ≤ 10 -1 . We conclude that an adequate discrimination among the present theoretical parametrizations can be achieved at HERA. (orig.)
Experimental study of rapidity gaps in gluon jets
Gary, J W
2003-01-01
Gluon jets are selected from hadronic Z/sup 0/ decay events produced in e/sup +/e/sup -/ annihilations, collected with the OPAL detector at LEP. A subsample of these jets is identified which exhibit a large gap in the rapidity distribution of particles within the jet. These jets are observed to demonstrate a high degree of sensitivity to the presence of color reconnection, i.e. higher order QCD processes affecting the underlying color structure. We test two QCD Monte Carlo programs which implement color reconnection: one in the Ariadne Monte Carlo and the other by Rathsman in the Pythia Monte Carlo. We find these models can describe our gluon jet measurements only if very large values are used for the cutoff parameters which serve to terminate the parton showers, and conclude that color reconnection as implemented in these models is disfavored. Further, we use our data on gluon jets with a rapidity gap to search for glueball-like objects in the leading part of those jets. We do not find any clear evidence for...
Hard exclusive meson production to constrain GPDs
Energy Technology Data Exchange (ETDEWEB)
Wolbeek, Johannes ter; Fischer, Horst; Gorzellik, Matthias; Gross, Arne; Joerg, Philipp; Koenigsmann, Kay; Malm, Pasquale; Regali, Christopher; Schmidt, Katharina; Sirtl, Stefan; Szameitat, Tobias [Physikalisches Institut, Albert-Ludwigs-Universitaet Freiburg, Freiburg im Breisgau (Germany); Collaboration: COMPASS Collaboration
2014-07-01
The concept of Generalized Parton Distributions (GPDs) combines the two-dimensional spatial information, given by form factors, with the longitudinal momentum information from the PDFs. Thus, GPDs provide a three-dimensional 'tomography' of the nucleon. Furthermore, according to Ji's sum rule, the GPDs H and E enable access to the total angular momenta of quarks, antiquarks and gluons. While H can be approached using electroproduction cross section, hard exclusive meson production off a transversely polarized target can help to constrain the GPD E. At the COMPASS experiment at CERN, two periods of data taking were performed in 2007 and 2010, using a longitudinally polarized 160 GeV/c muon beam and a transversely polarized NH{sub 3} target. This talk introduces the data analysis of the process μ + p → μ' + p' + V, and recent results are presented.
Quantum Simulations of Strongly Coupled Quark-Gluon Plasma
International Nuclear Information System (INIS)
Filinov, V.S.; Bonitz, M.; Ivanov, Yu.B.
2013-01-01
In recent years, there has been an increasing interest in dynamics and thermodynamics of non-Abelian plasmas at both very high temperature and density. It is expected that a specific state of matter with unconfined quarks and gluons - the so called quark - gluon plasma (QGP) - can exist. The most fundamental way to compute properties of the strongly interacting matter is provided by the lattice QCD. Interpretation of these very complicated computations requires application of various QCD motivated, albeit schematic, models simulating various aspects of the full theory. Moreover, such models are needed in cases when the lattice QCD fails, e.g. at large baryon chemical potentials and out of equilibrium. A semi-classical approximation, based on a point like quasi-particle picture has been recently introduced in literature. It is expected that it allows to treat soft processes in the QGP which are not accessible by the perturbative means and the main features of non-Abelian plasmas can be understood in simple semi-classical terms without the difficulties inherent to a full quantum field theoretical analysis. Here we propose stochastic simulation of thermodynamics and kinetic properties for QGP in semi-classical approximation in the wide region of temperature, density and quasi-particles masses. We extend previous classical nonrelativistic simulations based on a color Coulomb interaction to the quantum regime and take into account the Fermi (Bose) statistics of quarks (gluons) and quantum degeneracy self-consistently. In grand canonical ensemble for finite and zero baryon chemical potential we use the direct quantum path integral Monte Carlo method (PIMC) developed for finite temperature within Feynman formulation of quantum mechanics to do calculations of internal energy, pressure and pair correlation functions. The QGP quasi-particles representing dressed quarks, antiquarks and gluons interact via color quantum Kelbg pseudopotential rigorously derived in for Coulomb
arXiv Soft photon and two hard jets forward production in proton-nucleus collisions
Altinoluk, Tolga; Kovner, Alex; Lublinsky, Michael; Petreska, Elena
2018-04-11
We calculate the cross section for production of a soft photon and two hard jets in the forward rapidity region in proton-nucleus collisions at high energies. The calculation is performed within the hybrid formalism. The hardness of the final particles is defined with respect to the saturation scale of the nucleus. We consider both the correlation limit of small momentum imbalance and the dilute target limit where the momentum imbalance is of the order of the hardness of the jets. The results depend on the first two transversemomentum-dependent (TMD) gluon distributions of the nucleus.
Implications of confining force field structures in hard hadronic processes
International Nuclear Information System (INIS)
Bengtsson, H.-U.
1983-04-01
This thesis is centered on the study of confining force field structures in hard scattering processes. Perturbative QCD provides the means of calculating any process on the parton level, but to be able accurately to describe the actual outcome of an event, one still needs a phenomenological model for how quarks and gluons transform into observable hadrons. One such model is based on the assumption that the particles are produced by the confining fields stretched between the partons. The actual particle distributions will then depend on the topology of the confining fields. We have developed a Monte Carlo program to simulate complete events in hard scattering, and we use this to study the properties of the confining field in different trigger situations. We further look at the amount of hard processes that can be expected in experiments that trigger on transverse energy sum (calorimeter experiments). Finally, we investigate charm production within our model. (author)
Hard Diffraction - from Blois 1985 to 2005
Energy Technology Data Exchange (ETDEWEB)
Gunnar, Ingelman [Uppsala Univ., High Energy Physics (Sweden)
2005-07-01
The idea of diffractive processes with a hard scale involved, to resolve the underlying parton dynamics, was presented at the first Blois conference in 1985 and experimentally verified a few years later. Today hard diffraction is an attractive research field with high-quality data and new theoretical models. The trend from Regge-based pomeron models to QCD-based parton level models has given insights on QCD dynamics involving perturbative gluon exchange mechanisms. In the new QCD-based models, the pomeron is not part of the proton wave function, but diffraction is an effect of the scattering process. Models based on interactions with a colour background field provide an interesting approach which avoids conceptual problems of pomeron-based models, such as the pomeron flux, and provide a basis for common theoretical framework for all final states, diffractive gap events as well as non-diffractive events. Finally, the new process of gaps between jets provides strong evidence for the BFKL dynamics as predicted since long by QCD, but so far hard to establish experimentally.
On a possible test of the hard-Pomeron theory
International Nuclear Information System (INIS)
Ioffe, B.L.
1992-01-01
In the last few years there have been discussions of the fact that the Pomeron-the Regge pole responsible for high-energy scattering-has in reality a double role: a soft Pomeron built of multiperipheral hadron exchange and a hard Pomeron described by gluon exchanges in QCD. Recently, Bjorken emphasized the need to distinguish these two forms of the Pomeron. The question arises of whether it is possible to distinguish the hard and soft Pomeron experimentally. According to the hard-Pomeron concept, the hadron-hadron total cross section is determined by the imaginary part of the forward scattering amplitude corresponding to two-gluon exchange with ladder corrections. This mechanism dominates in the case of scattering of particles built from heavy quarks (a good example is γγ scattering) and also in the case of virtual-particle scattering (for example, virtual photons, where quark pairs must also be included in the ladder). These processes are hard (γ virt γ virt scattering) or impossible (γγ scattering) to observe experimentally. Bjorken suggested another process whose cross section is determined by hard-Pomeron exchange - double diffractional hadron-hadron (e.g., pp) scattering at high energies with jet production in the projectile and target fragmentation regions. If the momentum transfer from the projectile to the target is in the intermediate region, |t|∼1 GeV, and events are selected with a rapidity gap in the rapidity distribution of produced particles between the two fragmentation regions, then, according to Bjorken, a process determined by the hard Pomeron will be observed. The author addresses this proposal
Structural Failure Sites in Anterior Vaginal Wall Prolapse: Identification of a Collinear Triad.
Chen, Luyun; Lisse, Sean; Larson, Kindra; Berger, Mitchell B; Ashton-Miller, James A; DeLancey, John O L
2016-10-01
To test the null hypothesis that six factors representing potential fascial and muscular failure sites contribute equally to the presence and size of a cystocele: two vaginal attachment factors (apical support and paravaginal defects), two vaginal wall factors (vaginal length and width), and two levator ani factors (hiatus size and levator ani defects). Thirty women with anterior-predominant prolapse (women in a case group) and 30 women in a control group underwent three-dimensional stress magnetic resonance imaging. The location of the anterior vaginal wall at maximal Valsalva was identified with the modified Pelvic Inclination Coordinate System and the six factors measured. Analysis included repeated-measure analysis of variance, logistic regression, and stepwise linear regression. We identified a collinear triad consisting of apical location, paravaginal location, and hiatus size that were not only the strongest predictors of cystocele size, but were also highly correlated with one another (r=0.84-0.89, P<.001) for the presence and size of the prolapse. Together they explain up to 83% of the variation in cystocele size. Among the less significant vaginal factors, vaginal length explained 19% of the variation in cystocele size, but no significant difference in vaginal width existed. Women in the case group were more likely to have abnormalities in collinear triad factors (up to 80%) than vaginal wall factors (up to 23.3%). Combining the strongest collinear triad with the vaginal factors, the model explained 92.5% of the variation in cystocele size. Apical location, paravaginal location, and hiatus size are highly correlated and are strong predictors of cystocele presence and size.
Numerical estimates of the evolution of quark and gluon populations inside QCD jets
International Nuclear Information System (INIS)
Garetto, M.
1980-01-01
The system of first order differential equations for the probabilities of producing nsub(g) gluons and nsub(q) quarks in a single gluon or quark jet are solved numerically for a convenient choice of the parameters A, A-tilde, B. Relevant branching ratios as the evolution parameter Y increases are shown. The different behaviour of the distributions in the quark- and in the gluon-jet is discussed. (author)
Structure functions and pair correlations of the quark-gluon plasma
International Nuclear Information System (INIS)
Thoma, Markus H.
2005-01-01
Recent experiments at RHIC and theoretical considerations indicate that the quark-gluon plasma, present in the fireball of relativistic heavy-ion collisions, might be in a liquid phase. The liquid state can be identified by characteristic correlation and structure functions. Here definitions of the structure functions and pair correlations of the quark-gluon plasma are presented as well as perturbative results. These definitions might be useful for verifying the quark-gluon-plasma liquid in QCD lattice calculations
Regge behaviour of structure function and gluon distribution at low-x in leading order
International Nuclear Information System (INIS)
Sarma, J.K.
2000-01-01
We present a method to find the gluon distribution from the F 2 proton structure function data at low-x assuming the Regge behaviour of the gluon distribution function at this limit. We use the leading order (LO) Altarelli-Parisi (AP) evolution equation in our analysis and compare our result with those of other authors. We also discuss the limitations of the Taylor expansion method in extracting the gluon distribution from the F 2 structure function used by those authors. (orig.)
A QCD derivation of the additive quark model from two and three gluon exchanges
International Nuclear Information System (INIS)
Lipkin, H.J.
1982-06-01
The contributions to the Pomeron from two and three gluon exchanges are shown to give the correct combinatorial factors for the additive quark model relation between meson and baryon Pomeron couplings, even though two-quark and three-quark operators are involved. Similar results hold for the contributions to hadron masses from three-gluon vertices as well as one-gluon exchange. The color algebra reduces the multiquark couplings to a linear function of quark number. (author)
Transverse gluon contributions to the thermal static potential of heavy quarkonium
International Nuclear Information System (INIS)
Zhu, Jia-Qing; Li, Yun-De
2015-01-01
The transverse gluon contributions to the thermal static potentials of heavy quarkonia in isotropic medium are studied. Using the resummation of the damping rates method developed by Hou and Li, the infrared divergence that appeared in the effective potential calculations of transverse gluon is avoided. The comparisons between the transverse and the longitudinal contributions for heavy quarkonia are discussed. The results show that the dissociation scales of quarkonia in thermal medium are decreased by the transverse gluon contributions
Polarized triple-collinear splitting functions at NLO for processes with photons
International Nuclear Information System (INIS)
Sborlini, Germán F.R.; Florian, Daniel de; Rodrigo, Germán
2015-01-01
We compute the polarized splitting functions in the triple collinear limit at next-to-leading order accuracy (NLO) in the strong coupling α_S, for the splitting processes γ→qq-barγ, γ→qq-barg and g→qq-barγ. The divergent structure of each splitting function was compared to the predicted behaviour according to Catani’s formula. The results obtained in this paper are compatible with the unpolarized splitting functions computed in a previous article. Explicit results for NLO corrections are presented in the context of conventional dimensional regularization (CDR).
Polarized triple-collinear splitting functions at NLO for processes with photons
Energy Technology Data Exchange (ETDEWEB)
Sborlini, Germán F.R. [Departamento de Física and IFIBA, FCEyN, Universidad de Buenos Aires (1428) Pabellón 1 Ciudad Universitaria, Capital Federal (Argentina); Instituto de Física Corpuscular, Universitat de València,Consejo Superior de Investigaciones Científicas,Parc Científic, E-46980 Paterna, Valencia (Spain); Florian, Daniel de [Departamento de Física and IFIBA, FCEyN, Universidad de Buenos Aires (1428) Pabellón 1 Ciudad Universitaria, Capital Federal (Argentina); Rodrigo, Germán [Instituto de Física Corpuscular, Universitat de València,Consejo Superior de Investigaciones Científicas,Parc Científic, E-46980 Paterna, Valencia (Spain)
2015-03-04
We compute the polarized splitting functions in the triple collinear limit at next-to-leading order accuracy (NLO) in the strong coupling α{sub S}, for the splitting processes γ→qq-barγ, γ→qq-barg and g→qq-barγ. The divergent structure of each splitting function was compared to the predicted behaviour according to Catani’s formula. The results obtained in this paper are compatible with the unpolarized splitting functions computed in a previous article. Explicit results for NLO corrections are presented in the context of conventional dimensional regularization (CDR).
On the libration collinear points in the restricted three – body problem
Directory of Open Access Journals (Sweden)
Alzahrani F.
2017-03-01
Full Text Available In the restricted problem of three bodies when the primaries are triaxial rigid bodies, the necessary and sufficient conditions to find the locations of the three libration collinear points are stated. In addition, the Linear stability of these points is studied for the case of the Euler angles of rotational motion being θi = 0, ψi + φi = π/2, i = 1, 2 accordingly. We underline that the model studied in this paper has special importance in space dynamics when the third body moves in gravitational fields of planetary systems and particularly in a Jupiter model or a problem including an irregular asteroid.
Arisholm, Gunnar
2007-05-14
Group velocity mismatch (GVM) is a major concern in the design of optical parametric amplifiers (OPAs) and generators (OPGs) for pulses shorter than a few picoseconds. By simplifying the coupled propagation equations and exploiting their scaling properties, the number of free parameters for a collinear OPA is reduced to a level where the parameter space can be studied systematically by simulations. The resulting set of figures show the combinations of material parameters and pulse lengths for which high performance can be achieved, and they can serve as a basis for a design.
Hard scattering processes in high energy γ-induced reactions
International Nuclear Information System (INIS)
D'Agostini, G.
1994-09-01
Recent results from photoproduction and γγ collisions are reviewed, with special focus on hard interactions, featuring the jets as the best evidence, as manifestation of parton-parton and photon-parton scattering. The experimental results are in good agreement with perturbative QCD expectations and the data are going to have the appropriate accuracy to discriminate between the available parameterizations of the photon structure functions. In particular, the combination of F 2 γ measured in γγ and the jet cross sections measured in γγ and γp will probably constrain in the near future the gluon content of the photon. (orig.)
Regge meets collinear in strongly-coupled N=4 super Yang-Mills
Energy Technology Data Exchange (ETDEWEB)
Sprenger, Martin [Institut für Theoretische Physik, Eidgenössische Technische Hochschule Zürich,Wolfgang-Pauli-Strasse 27, 8093 Zürich (Switzerland)
2017-01-10
We revisit the calculation of the six-gluon remainder function in planar N=4 super Yang-Mills theory from the strong coupling TBA in the multi-Regge limit and identify an infinite set of kinematically subleading terms. These new terms can be compared to the strong coupling limit of the finite-coupling expressions for the impact factor and the BFKL eigenvalue proposed by Basso et al. in https://www.doi.org/10.1007/JHEP01(2015)027, which were obtained from an analytic continuation of the Wilson loop OPE. After comparing the results order by order in those subleading terms, we show that it is possible to precisely map both formalisms onto each other. A similar calculation can be carried out for the seven-gluon amplitude, the result of which shows that the central emission vertex does not become trivial at strong coupling.
Inclusive gluon production in deep inelastic scattering at high parton density
International Nuclear Information System (INIS)
Kovchegov, Yuri V.; Tuchin, Kirill
2002-01-01
We calculate the cross section of single inclusive gluon production in deep inelastic scattering at very high energies in the saturation regime, where the parton densities inside hadrons and nuclei are large and the evolution of structure functions with energy is nonlinear. The expression we obtain for the inclusive gluon production cross section is generated by this nonlinear evolution. We analyze the rapidity distribution of the produced gluons as well as their transverse momentum spectrum given by the derived expression for the inclusive cross section. We propose an ansatz for the multiplicity distribution of gluons produced in nuclear collisions which includes the effects of nonlinear evolution in both colliding nuclei
Semirelativistic potential model for low-lying three-gluon glueballs
International Nuclear Information System (INIS)
Mathieu, Vincent; Semay, Claude; Silvestre-Brac, Bernard
2006-01-01
The three-gluon glueball states are studied with the generalization of a semirelativistic potential model giving good results for two-gluon glueballs. The Hamiltonian depends only on 3 parameters fixed on two-gluon glueball spectra: the strong coupling constant, the string tension, and a gluon size which removes singularities in the potential. The Casimir scaling determines the structure of the confinement. Low-lying J PC states are computed and compared with recent lattice calculations. A good agreement is found for 1 -- and 3 -- states, but our model predicts a 2 -- state much higher in energy than the lattice result. The 0 -+ mass is also computed
High energy production of gluons in a quasi-multi-Regge kinematics
International Nuclear Information System (INIS)
Fadin, V.S.; Lipatov, L.N.
1989-01-01
Inelastic gluon-gluon scattering amplitudes in the Born approximation for the quasi-multi-Regge kinematics are calculated, starting with the Veneziano-type expression for the inelastic amplitude of the gluon-tachyon scattering with its subsequent simplification in the region of large energies and the Regge slope α'→0. Results obtained allow one to determine the high order corrections to the gluon Regge trajectory, the reggeon-particle vertices and to the integral kernel of the Bethe-Salpeter equation for the vacuum t-channel partial waves. 10 refs.; 7 figs
Looking at the gluon moment of the nucleon with dynamical twisted mass fermions
International Nuclear Information System (INIS)
Alexandrou, Constantia; Cyprus Institute, Nicosia; Drach, Vincent; Wiese, Christian; Hadjiyiannakou, Kyriakos; Jansen, Karl; Deutsches Elektronen-Synchrotron; Kostrzewa, Bartosz
2013-11-01
To understand the structure of hadrons it is important to know the PDF of their constituents, the quarks and gluons. In our work we aim to compute the first moment of the gluon PDF left angle x right angle g for the nucleon. We follow two possible approaches in order to extract the gluon moment: the Feynman-Hellmann theorem and a direct method with smearing of the gluon operator. We present preliminary results computed on 24 3 x 48 lattices for the case where the Feynman-Hellman theorem is used and 32 3 x 64 lattices for the direct method, employing N f =2+1+1 maximally twisted mass fermions.
Heavy ion collisions, the quark-gluon plasma and antinucleon annihilation
International Nuclear Information System (INIS)
Sarma, Nataraja
1985-01-01
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)
Threshold region for Higgs boson production in gluon fusion.
Bonvini, Marco; Forte, Stefano; Ridolfi, Giovanni
2012-09-07
We provide a quantitative determination of the effective partonic kinematics for Higgs boson production in gluon fusion in terms of the collider energy at the LHC. We use the result to assess, as a function of the Higgs boson mass, whether the large m(t) approximation is adequate and Sudakov resummation advantageous. We argue that our results hold to all perturbative orders. Based on our results, we conclude that the full inclusion of finite top mass corrections is likely to be important for accurate phenomenology for a light Higgs boson with m(H)~125 GeV at the LHC with √s=14 TeV.
Probing Quark-Gluon Interactions with Transverse Polarized Scattering
International Nuclear Information System (INIS)
Rondon, Oscar A.
2011-01-01
Transverse polarized inelastic scattering extends the power of the electromagnetic interaction as a probe of nucleon dynamics beyond the leading order regime explored with longitudinally polarized DIS. In transverse polarized scattering, the twist-3 g 2 spin structure function contributes at the same order as the longitudinal, twist-2, g 1 , so interactions between quarks and gluons can be studied, opening a window on the mechanisms of confinement. This talk reports the results of Jefferson Lab's Resonances Spin Structure experiment measurement of g 2 and the d 2 twist-3 quark matrix element at a four-momentum transfer of 1.3 GeV 2 .
Singular gauge potentials and the gluon condensate at zero temperature
Langfeld, K.; Ilgenfritz, E. -M.; Reinhardt, H.; Schäfke, A.
2001-01-01
We consider a new cooling procedure which separates gluon degrees of freedom from singular center vortices in SU(2) LGT in a gauge invariant way. Restricted by a cooling scale $\\kappa^4/\\sigma^2$ fixing the residual SO(3) gluonic action relative to the string tension, the procedure is RG invariant. In the limit $\\kappa \\to 0$ a pure Z(2) vortex texture is left. This {\\it minimal} vortex content does not contribute to the string tension. It reproduces, however, the lowest glueball states. With...
Very high energy probes of the quark-gluon plasma
International Nuclear Information System (INIS)
Ludlam, T.; Paige, F.; Madansky, L.
1984-01-01
Among the penetrating probes of nuclear matter the most frequently discussed have been those which involve the detection of photons or leptons with m/sub T/ approx. = P/sub T/ < 3 GeV. This is the expected range of emission from a hot, thermalized plasma of quarks and gluons. The suggestion has been made that in very high energy collisions of nuclei the properties of high P/sub T/ jets may also reflect the characteristics of the nuclear medium through which the parent partons have propagated just after the collision. In this note we expand on the possible uses of such a probe
Viscosities in the Gluon-Plasma within a Quasiparticle Model
Bluhm, M; Redlich, K
2009-01-01
A phenomenological quasiparticle model, featuring dynamically generated self-energies of excitation modes, successfully describes lattice QCD results relevant for the QCD equation of state and related quantities both at zero and non-zero net baryon density. Here, this model is extended to study bulk and shear viscosities of the gluon-plasma within an effective kinetic theory approach. In this way, the compatibility of the employed quasiparticle ansatz with the apparent low viscosities of the strongly coupled deconfined gluonic medium is shown.
Finite size effects in quark-gluon plasma formation
International Nuclear Information System (INIS)
Gopie, Andy; Ogilvie, Michael C.
1999-01-01
Using lattice simulations of quenched QCD we estimate the finite size effects present when a gluon plasma equilibrates in a slab geometry, i.e., finite width but large transverse dimensions. Significant differences are observed in the free energy density for the slab when compared with bulk behavior. A small shift in the critical temperature is also seen. The free energy required to liberate heavy quarks relative to bulk is measured using Polyakov loops; the additional free energy required is on the order of 30 - 40 MeV at 2 - 3 T c
Quark-gluon plasma searches: today and tomorrow
International Nuclear Information System (INIS)
Geist, W.M.
1991-01-01
Selected recent data from ion collisions at high energy are discussed in the frame-work of Quark-Gluon Plasma (QGP) searches. The purpose of these experiments is to measure the volume where a high temperature QGP may have been formed, determine its characteristic temperature, verify chemical equilibrium, establish deconfinement of this phase of matter, and/or find anything that differs from natural extrapolations from pp and pA collisions. Refined methods and new theoretical ideas for future experiments with heavier beams and/or at higher energies are briefly outlined. (G.P.) 49 refs., 28 figs
Gluon ladders in pp (pp-bar) collisions
International Nuclear Information System (INIS)
Machado, Magno Valerio Trindade; Ducati, Maria Beatriz Gay
2000-01-01
Full text follows: We study the contribution of a finite sum of gluon ladders to the hadronic processes showing that a reliable description is obtained using two order on perturbation theory. The pp(pp-bar) total cross sections are described with good agreement, consistent with unitarity bound. We also calculate the elastic scattering amplitude at non zero momentum transfer t, introducing two distinct Ansatz for the proton impact factor. As a by product the elastic differential cross section is obtained at small t approximation and compared with the data. (author)
Effects of magnetic fields on the quark–gluon plasma
Energy Technology Data Exchange (ETDEWEB)
Bali, G.S. [Institute for Theoretical Physics, Universität Regensburg, D-93040 Regensburg (Germany); Tata Institute of Fundamental Research, Homi Bhabha Road, Mumbai 400005 (India); Bruckmann, F. [Institute for Theoretical Physics, Universität Regensburg, D-93040 Regensburg (Germany); Endrődi, G., E-mail: gergely.endrodi@physik.uni-r.de [Institute for Theoretical Physics, Universität Regensburg, D-93040 Regensburg (Germany); Fodor, Z. [Eötvös University, Theoretical Physics, Pázmány P. s 1/A, H-1117, Budapest (Hungary); Bergische Universität Wuppertal, Theoretical Physics, 42119 Wuppertal (Germany); Jülich Supercomputing Centre, Forschungszentrum Jülich, D-52425 Jülich (Germany); Katz, S.D. [Eötvös University, Theoretical Physics, Pázmány P. s 1/A, H-1117, Budapest (Hungary); MTA-ELTE Lendület Lattice Gauge Theory Research Group (Hungary); Schäfer, A. [Institute for Theoretical Physics, Universität Regensburg, D-93040 Regensburg (Germany)
2014-11-15
In this talk, the response of the thermal QCD medium to external (electro)magnetic fields is studied using continuum extrapolated lattice results at physical quark masses. The magnetic susceptibility of QCD is calculated, revealing a strong paramagnetic response at high temperatures. This paramagnetism is shown to result in an anisotropic squeezing of the quark–gluon plasma in non-central heavy-ion collisions, implying a sizeable contribution to the elliptic flow. Another aspect is the magnetic response of topologically non-trivial domains to the magnetic field. We quantify this effect on the lattice and compare the results to a simple model estimate.
Interactions of quarks and gluons with nuclei at intermediate energies
Energy Technology Data Exchange (ETDEWEB)
Mueller, A.H. [Columbia Univ., New York, NY (United States)
1994-04-01
Some processes involving the interaction of medium energy quarks and gluons with nuclear matter are described. Possible mechanisms for the A-dependence of the energy loss of leading protons produced in proton-nucleus collisions are given, and an experiment which may help to distinguish these mechanisms is described. A possible color transparency experiment at CEBAF is described. Experiments to measure energy loss of quarks in nuclear matter and the formation time of hadrons are discussed along with the possibilities of measuring {sigma}{sub J}/{psi} and {sigma}{sub {psi}{prime}} at CEBAF.
Attractive Casimir effect in an infrared modified gluon bag model
International Nuclear Information System (INIS)
Oxman, L.E.; Amaral, R.L.P.G.; Svaiter, N.F.
2005-01-01
In this work, we are motivated by previous attempts to derive the vacuum contribution to the bag energy in terms of familiar Casimir energy calculations for spherical geometries. A simple infrared modified model is introduced which allows studying the effects of the analytic structure as well as the geometry in a clear manner. In this context, we show that if a class of infrared vanishing effective gluon propagators is considered, then the renormalized vacuum energy for a spherical bag is attractive, as required by the bag model to adjust hadron spectroscopy
Gluon cascades and amplitudes in light-front perturbation theory
International Nuclear Information System (INIS)
Cruz-Santiago, C.A.; Staśto, A.M.
2013-01-01
We construct the gluon wave functions, fragmentation functions and scattering amplitudes within the light-front perturbation theory. Recursion relations on the light-front are constructed for the wave functions and fragmentation functions, which in the latter case are the light-front analogs of the Berends–Giele recursion relations. Using general relations between wave functions and scattering amplitudes it is demonstrated how to obtain the maximally-helicity violating amplitudes, and explicit verification of the results is based on simple examples.
Astrophysical Aspects of Neutrino Dynamics in Ultradegenerate Quark Gluon Plasma
Directory of Open Access Journals (Sweden)
Souvik Priyam Adhya
2017-01-01
Full Text Available The cardinal focus of the present review is to explore the role of neutrinos originating from the ultradense core of neutron stars composed of quark gluon plasma in the astrophysical scenario. The collective excitations of the quarks involving the neutrinos through the different kinematical processes have been studied. The cooling of the neutron stars as well as pulsar kicks due to asymmetric neutrino emission has been discussed in detail. Results involving calculation of relevant physical quantities like neutrino mean free path and emissivity have been presented in the framework of non-Fermi liquid behavior as applicable to ultradegenerate plasma.
Meson interferometry and the quest for quark-gluon matter
International Nuclear Information System (INIS)
Soff, Sven
2001-01-01
We point out what we may learn from the investigation of identical two-particle interferometry in ultrarelativistic heavy ion collisions if we assume a particular model scenario by the formation of a thermalized quark-gluon plasma hadronizing via a first-order phase transition to an interacting hadron gas. The bulk properties of the two-pion correlation functions are dominated by these late and soft resonance gas rescattering processes. However, we show that kaons at large transverse momenta have several advantages and a bigger sensitivity to the QCD phase transition parameters
Heavy quarks and squarks from W-gluon fusion
International Nuclear Information System (INIS)
Lindfors, J.
1986-05-01
We discuss Wg-fusion as a source of heavy quark and squark pairs at very high energy hadron colliders. Effective W approximation is used to calculate the cross-sections analytically in the forward scattering configuration; good agreement is obtained with exact numerical calculations. W-gluon fusion is found to be not nearly as important a production mechanism of heavy squarks as it is of heavy quarks. This is especially true when the mass-splitting within the SU(2) L doublet is small
International Nuclear Information System (INIS)
Greiner, M.; Hofmann, C.; Schaefer, A.; Soff, G.
1994-08-01
The photon-gluon fusion process into a pair of heavy quarks is studied for peripheral Pb+Pb collisions at LHC energies. The double differential cross section with respect to the invariant mass and the rapidity of the produced quark pair at zero rapidity is directly proportional to the gluon distribution in the nuclear medium. Differential cross sections for the b-quark production lie well in the μbarn/GeV regime which will allow the deduction of the gluon distribution at low x. Rapidity cuts for the actual detectors are also considered. (orig.)
Central configurations of the collinear three-body problem and singular surfaces in the mass space
Energy Technology Data Exchange (ETDEWEB)
Xie, Zhifu, E-mail: zxie@vsu.edu [Department of Mathematics and Computer Science, Virginia State University, Petersburg, VA 23806 (United States)
2011-09-12
This Letter is to provide a new approach to study the phenomena of degeneracy of the number of the collinear central configurations under geometric equivalence. A direct and simple explicit parametric expression of the singular surface H{sub 3} is constructed in the mass space (m{sub 1},m{sub 2},m{sub 3}) element of (R{sup +}){sup 3}. The construction of H{sub 3} is from an inverse respective, that is, by specifying positions for the bodies and then determining the masses that are possible to yield a central configuration. It reveals the relationship between the phenomena of degeneracy and the inverse problem of central configurations. We prove that the number of central configurations is decreased to 3!/2-1=2, m{sub 1}, m{sub 2}, and m{sub 3} are mutually distinct if m element of H{sub 3}. Moreover, we know not only the number of central configurations but also what the nonequivalent central configurations are. -- Highlights: → Provide a new method to study the degeneracy of number of CC. → Results advanced the understanding of number of central configurations. → Singular mass surface H{sub 3} is given by a direct and simple parametric expression. → The proof only requires some basic knowledge of linear algebra. → The method can be applied to some other collinear n-body problem.
Closed-form solution for piezoelectric layer with two collinear cracks parallel to the boundaries
Directory of Open Access Journals (Sweden)
B. M. Singh
2006-01-01
Full Text Available We consider the problem of determining the stress distribution in an infinitely long piezoelectric layer of finite width, with two collinear cracks of equal length and parallel to the layer boundaries. Within the framework of reigning piezoelectric theory under mode III, the cracked piezoelectric layer subjected to combined electromechanical loading is analyzed. The faces of the layers are subjected to electromechanical loading. The collinear cracks are located at the middle plane of the layer parallel to its face. By the use of Fourier transforms we reduce the problem to solving a set of triple integral equations with cosine kernel and a weight function. The triple integral equations are solved exactly. Closed form analytical expressions for stress intensity factors, electric displacement intensity factors, and shape of crack and energy release rate are derived. As the limiting case, the solution of the problem with one crack in the layer is derived. Some numerical results for the physical quantities are obtained and displayed graphically.
International Nuclear Information System (INIS)
Lantzsch, J.; Bushaw, B. A.; Bystrow, V. A.; Herrmann, G.; Kluge, H.-J.; Niess, S.; Otten, E. W.; Passler, G.; Schwalbach, R.; Schwarz, M.; Stenner, J.; Trautmann, N.; Wendt, K.; Yushkevich, Y. V.; Zimmer, K.
1995-01-01
Collinear resonance ionization spectroscopy has been developed as a sensitive technique for fast trace detection of 90 Sr and 89 Sr in the environment. A detection limit for 90 Sr of 10 7 atoms in the presence of 10 17 atoms in the presence of 10 17 atoms of stable Strontium has been achieved, while the applicability of the method has been demonstrated on real world samples. After collection and chemical separation, strontium is surface ionized, accelerated to 33keV and mass separated. The ions are neutralized and the emerging fast atoms interact with an argon ion laser beam (γ=364 nm) in a quasi-collinear geometry. Optical excitation starts from the long-lived 5s4d 3 D2 state of strontium, which is populated in the charge exchange process, and the fast atoms are selectively excited into the high-lying 5s23f 3 F3 Rydberg state. The Rydberg-atoms are subsequently field-ionized and detected by a channeltron detector after energy selection. The described method was successfully used to determine the 90 Sr-content in air samples collected near Munich during the Chernobyl reactor accident in April 1986
International Nuclear Information System (INIS)
Mantry, Sonny; Petriello, Frank
2010-01-01
We derive a factorization theorem for the Higgs boson transverse momentum (p T ) and rapidity (Y) distributions at hadron colliders, using the soft-collinear effective theory (SCET), for m h >>p T >>Λ QCD , where m h denotes the Higgs mass. In addition to the factorization of the various scales involved, the perturbative physics at the p T scale is further factorized into two collinear impact-parameter beam functions (IBFs) and an inverse soft function (ISF). These newly defined functions are of a universal nature for the study of differential distributions at hadron colliders. The additional factorization of the p T -scale physics simplifies the implementation of higher order radiative corrections in α s (p T ). We derive formulas for factorization in both momentum and impact parameter space and discuss the relationship between them. Large logarithms of the relevant scales in the problem are summed using the renormalization group equations of the effective theories. Power corrections to the factorization theorem in p T /m h and Λ QCD /p T can be systematically derived. We perform multiple consistency checks on our factorization theorem including a comparison with known fixed-order QCD results. We compare the SCET factorization theorem with the Collins-Soper-Sterman approach to low-p T resummation.
Soft gluon approach for diffractive photoproduction of J/ψ
International Nuclear Information System (INIS)
Ma, J.P.; Xu Jiasheng
2002-01-01
We study diffractive photoproduction of J/ψ by taking the charm quark as a heavy quark. A description of nonperturbative effect related to J/ψ can be made by using NRQCD. In the forward region of the kinematics, the interaction between the cc-bar-pair and the initial hadron is due to exchange of soft gluons. The effect of the exchange can be studied by using the expansion in the inverse of the quark mass m c . At the leading order we find that the nonperturbative effect related to the initial hadron is represented by a matrix element of field strength operators, which are separated in the moving direction of J/ψ in the spacetime. The S-matrix element is then obtained without using perturbative QCD and the results are not based on any model. Corrections to the results can be systematically added. Keeping the dominant contribution of the S-matrix element in the large energy limit we find that the imaginary part of the S-matrix element is related to the gluon distribution for x→0 with a reasonable assumption, the real part can be obtained with another approximation or with dispersion relation. Our approach is different than previous approaches and also our results are different than those in these approaches. The differences are discussed in detail. A comparison with experiment is also made and a qualitative agreement is found. (author)
Resummation improved rapidity spectrum for gluon fusion Higgs production
International Nuclear Information System (INIS)
Ebert, Markus A.; Tackmann, Frank J.; Michel, Johannes K.L.; Muenster Univ.
2017-02-01
Gluon-induced processes such as Higgs production typically exhibit large perturbative corrections. These partially arise from large virtual corrections to the gluon form factor, which at timelike momentum transfer contains Sudakov logarithms evaluated at negative arguments ln 2 (-1)=-π 2 . It has been observed that resumming these terms in the timelike form factor leads to a much improved perturbative convergence for the total cross section. We discuss how to consistently incorporate the resummed form factor into the perturbative predictions for generic cross sections differential in the Born kinematics, including in particular the Higgs rapidity spectrum. We verify that this indeed improves the perturbative convergence, leading to smaller and more reliable perturbative uncertainties, and that this is not affected by cancellations between resummed and unresummed contributions. Combining both fixed-order and resummation uncertainties, the perturbative uncertainty for the total cross section at N 3 LO+N 3 LL φ ' is about a factor of two smaller than at N 3 LO. The perturbative uncertainty of the rapidity spectrum at NNLO+NNLL φ ' is similarly reduced compared to NNLO. We also study the analogous resummation for quark-induced processes, namely Higgs production through bottom quark annihilation and the Drell-Yan rapidity spectrum. For the former the resummation leads to a small improvement, while for the latter it confirms the already small uncertainties of the fixed-order predictions.
Two-gluon correlations in heavy–light ion collisions
International Nuclear Information System (INIS)
Wertepny, Douglas E.
2014-01-01
We derive the cross-section for two-gluon production in heavy–light ion collisions in the saturation/Color Glass Condensate framework. This calculation includes saturation effects to all orders in one of the nuclei (heavy ion) along with a single saturation correction in the projectile (light ion). The calculation of the correlation function predicts (qualitatively) two identical ridge-like correlations, near- and away-side. This prediction was later supported by experimental findings in p + A collisions at the LHC. Concentrating on the energy and geometry dependence of the correlation functions we find that the correlation function is nearly center-of-mass energy independent. The geometry dependence of the correlation function leads to an enhancement of near- and away-side correlations for the tip-on-tip U + U collisions when compared with side-on-side U + U collisions, an exactly opposite behavior from the correlations generated by the elliptic flow of the quark–gluon plasma
The strongly coupled quark-gluon plasma created at RHIC
International Nuclear Information System (INIS)
Heinz, Ulrich
2009-01-01
The relativistic heavy-ion collider (RHIC) was built to re-create and study in the laboratory the extremely hot and dense matter that filled our entire universe during its first few microseconds. Its operation since June 2000 has been extremely successful, and the four large RHIC experiments have produced an impressive body of data which indeed provide compelling evidence for the formation of thermally equilibrated matter at unprecedented temperatures and energy densities-a 'quark-gluon plasma (QGP)'. A surprise has been the discovery that this plasma behaves like an almost perfect fluid, with extremely low viscosity. Theorists had expected a weakly interacting gas of quarks and gluons, but instead we seem to have created a strongly coupled plasma liquid. The experimental evidence strongly relies on a feature called 'elliptic flow' in off-central collisions, with additional support from other observations. This paper explains how we probe the strongly coupled QGP, describes the ideas and measurements which led to the conclusion that the QGP is an almost perfect liquid, and shows how they tie relativistic heavy-ion physics into other burgeoning fields of modern physics, such as strongly coupled Coulomb plasmas, ultracold systems of trapped atoms and superstring theory
Chemical Evolution of Strongly Interacting Quark-Gluon Plasma
International Nuclear Information System (INIS)
Pan, Ying-Hua; Zhang, Wei-Ning
2014-01-01
At very initial stage of relativistic heavy ion collisions a wave of quark-gluon matter is produced from the break-up of the strong color electric field and then thermalizes at a short time scale (~1 fm/c). However, the quark-gluon plasma (QGP) system is far out of chemical equilibrium, especially for the heavy quarks which are supposed to reach chemical equilibrium much late. In this paper a continuing quark production picture for strongly interacting QGP system is derived, using the quark number susceptibilities and the equation of state; both of them are from the results calculated by the Wuppertal-Budapest lattice QCD collaboration. We find that the densities of light quarks increase by 75% from the temperature T=400 MeV to T=150 MeV, while the density of strange quark annihilates by 18% in the temperature region. We also offer a discussion on how this late production of quarks affects the final charge-charge correlations
New signals of quark-gluon-hadron mixed phase formation
Energy Technology Data Exchange (ETDEWEB)
Bugaev, K.A.; Sagun, V.V.; Ivanytskyi, A.I.; Zinovjev, G.M. [Bogolyubov Institute for Theoretical Physics, Kiev (Ukraine); Oliinychenko, D.R. [Bogolyubov Institute for Theoretical Physics, Kiev (Ukraine); Goethe University, FIAS, Frankfurt am Main (Germany); Ilgenfritz, E.M. [JINR, Bogoliubov Laboratory of Theoretical Physics, Dubna (Russian Federation); Nikonov, E.G. [JINR, Laboratory for Information Technologies, Dubna (Russian Federation); Taranenko, A.V. [Moscow Engineering Physics Institute, National Research Nuclear University ' ' MEPhI' ' , Moscow (Russian Federation)
2016-08-15
Here we present several remarkable irregularities at chemical freeze-out which are found using an advanced version of the hadron resonance gas model. The most prominent of them are the sharp peak of the trace anomaly existing at chemical freeze-out at the center-of-mass energy 4.9 GeV and two sets of highly correlated quasi-plateaus in the collision energy dependence of the entropy per baryon, total pion number per baryon, and thermal pion number per baryon which we found at the center-of-mass energies 3.8-4.9 GeV and 7.6-10 GeV. The low-energy set of quasi-plateaus was predicted a long time ago. On the basis of the generalized shock-adiabat model we demonstrate that the low-energy correlated quasi-plateaus give evidence for the anomalous thermodynamic properties inside the quark-gluon-hadron mixed phase. It is also shown that the trace anomaly sharp peak at chemical freeze-out corresponds to the trace anomaly peak at the boundary between the mixed phase and quark gluon plasma. We argue that the high-energy correlated quasi-plateaus may correspond to a second phase transition and discuss its possible origin and location. Besides we suggest two new observables which may serve as clear signals of these phase transformations. (orig.)
Field-induced non-collinear magnetic structures in amorphous Co80-xDy xB20 alloys
International Nuclear Information System (INIS)
Annouar, F.; Roky, K.; Lassri, H.; Elmoussaoui, A.; Driouch, L.; Ayadi, M.; Omri, M.; Krishnan, R.
2005-01-01
Amorphous Co 80-x Dy x B 20 alloys have been prepared by melt spinning technique and their magnetic properties have been studied. The mean field theory has been used to explain the temperature dependence of the magnetization. High-field magnetization studies performed at 4.2 K in magnetic fields up to 38 T have revealed, for samples with stoichiometry close to that of a compensated ferrimagnet, a magnetic behavior that is characteristic of a non-collinear magnetic structure of the Dy and Co sublattices. From the non-collinear regime the exchange interactions between the Co and Dy magnetic sublattices and the magnetic anisotropy constants have been evaluated
Certain exclusive processes in QCD taking into account two-gluon states
International Nuclear Information System (INIS)
Baier, V.N.; Grozin, A.G.
1982-01-01
The wave functions and evolution equations for mesons are classified completely taking into account two-gluon states and then are compared to the Altarelli-Parisi evolution equations. The form factors of completely neutral mesons and the probabilities for exclusive decays of quarkonium states are found taking into account two-gluon states
Multiplicity distributions of gluon and quark jets and a test of QCD analytic calculations
International Nuclear Information System (INIS)
Gary, J. William
1999-01-01
Gluon jets are identified in e + e - hadronic annihilation events by tagging two quark jets in the same hemisphere of an event. The gluon jet is defined inclusively as all the particles in the opposite hemisphere. Gluon jets defined in this manner have a close correspondence to gluon jets as they are defined for analytic calculations, and are almost independent of a jet finding algorithm. The mean and first few higher moments of the gluon jet charged particle multiplicity distribution are compared to the analogous results found for light quark (uds) jets, also defined inclusively. Large differences are observed between the mean, skew and curtosis values of the gluon and quark jets, but not between their dispersions. The cumulant factorial moments of the distributions are also measured, and are used to test the predictions of QCD analytic calculations. A calculation which includes next-to-next-to-leading order corrections and energy conservation is observed to provide a much improved description of the separated gluon and quark jet cumulant moments compared to a next-to-leading order calculation without energy conservation. There is good quantitative agreement between the data and calculations for the ratios of the cumulant moments between gluon and quark jets. The data sample used is the LEP-1 sample of the OPAL experiment at LEP
Multiplicity distributions of gluon and quark jets and a test of QCD analytic calculations
Energy Technology Data Exchange (ETDEWEB)
Gary, J. William
1999-03-01
Gluon jets are identified in e{sup +}e{sup -} hadronic annihilation events by tagging two quark jets in the same hemisphere of an event. The gluon jet is defined inclusively as all the particles in the opposite hemisphere. Gluon jets defined in this manner have a close correspondence to gluon jets as they are defined for analytic calculations, and are almost independent of a jet finding algorithm. The mean and first few higher moments of the gluon jet charged particle multiplicity distribution are compared to the analogous results found for light quark (uds) jets, also defined inclusively. Large differences are observed between the mean, skew and curtosis values of the gluon and quark jets, but not between their dispersions. The cumulant factorial moments of the distributions are also measured, and are used to test the predictions of QCD analytic calculations. A calculation which includes next-to-next-to-leading order corrections and energy conservation is observed to provide a much improved description of the separated gluon and quark jet cumulant moments compared to a next-to-leading order calculation without energy conservation. There is good quantitative agreement between the data and calculations for the ratios of the cumulant moments between gluon and quark jets. The data sample used is the LEP-1 sample of the OPAL experiment at LEP.
Multiplicity distributions of gluon and quark jets and a test of QCD analytic calculations
Energy Technology Data Exchange (ETDEWEB)
Gary, J.W. [California Univ., Riverside, CA (United States). Dept. of Physics
1999-03-01
Gluon jets are identified in e{sup +}e{sup -} hadronic annihilation events by tagging two quark jets in the same hemisphere of an event. The gluon jet is defined inclusively as all the particles in the opposite hemisphere. Gluon jets defined in this manner have a close correspondence to gluon jets as they are defined for analytic calculations, and are almost independent of a jet finding algorithm. The mean and first few higher moments of the gluon jet charged particle multiplicity distribution are compared to the analogous results found for light quark (uds) jets, also defined inclusively. Large differences are observed between the mean, skew and curtosis values of the gluon and quark jets, but not between their dispersions. The cumulant factorial moments of the distributions are also measured, and are used to test the predictions of QCD analytic calculations. A calculation which includes next-to-next-to-leading order corrections and energy conservation is observed to provide a much improved description of the separated gluon and quark jet cumulant moments compared to a next-to-leading order calculation without energy conservation. There is good quantitative agreement between the data and calculations for the ratios of the cumulant moments between gluon and quark jets. The data sample used is the LEP-1 sample of the OPAL experiment at LEP. (orig.) 6 refs.
Multiplicity distributions of gluon and quark jets and a test of QCD analytic calculations
International Nuclear Information System (INIS)
Gary, J.W.
1999-01-01
Gluon jets are identified in e + e - hadronic annihilation events by tagging two quark jets in the same hemisphere of an event. The gluon jet is defined inclusively as all the particles in the opposite hemisphere. Gluon jets defined in this manner have a close correspondence to gluon jets as they are defined for analytic calculations, and are almost independent of a jet finding algorithm. The mean and first few higher moments of the gluon jet charged particle multiplicity distribution are compared to the analogous results found for light quark (uds) jets, also defined inclusively. Large differences are observed between the mean, skew and curtosis values of the gluon and quark jets, but not between their dispersions. The cumulant factorial moments of the distributions are also measured, and are used to test the predictions of QCD analytic calculations. A calculation which includes next-to-next-to-leading order corrections and energy conservation is observed to provide a much improved description of the separated gluon and quark jet cumulant moments compared to a next-to-leading order calculation without energy conservation. There is good quantitative agreement between the data and calculations for the ratios of the cumulant moments between gluon and quark jets. The data sample used is the LEP-1 sample of the OPAL experiment at LEP. (orig.)
Multiplicity distributions of gluon and quark jets and a test of QCD analytic calculations
Gary, J. William
1999-03-01
Gluon jets are identified in e +e - hadronic annihilation events by tagging two quark jets in the same hemisphere of an event. The gluon jet is defined inclusively as all the particles in the opposite hemisphere. Gluon hets defined in this manner have a close correspondence to gluon jets as they are defined for analytic calculations, and are almost independent of a jet finding algorithm. The mean and first few higher moments of the gluon jet charged particle multiplicity distribution are compared to the analogous results found for light quark (uds) jets, also defined inclusively. Large differences are observed between the mean, skew and curtosis values of the gluon and quark jets, but not between their dispersions. The cumulant factorial moments of the distributions are also measured, and are used to test the predictions of QCD analytic calculations. A calculation which includes next-to-next-to-leading order corrections and energy conservation is observed to provide a much improved description of the separated gluon and quark jet cumulant moments compared to a next-to-leading order calculation without energy conservation. There is good quantitative agreement between the data and calculations for the ratios of the cumulant moments between gluon and quark jets. The data sample used is the LEP-1 sample of the OPAL experiment at LEP.
Renormalizability of a quark-gluon model with soft BRST breaking in the infrared region
Baulieu, L; Gomez, A J; Lemes, V E R; Sobreiro, R F; Sorella, S P
2010-01-01
We prove the renormalizability of a quark-gluon model with a soft breaking of the BRST symmetry, which accounts for the modification of the large distance behavior of the quark and gluon correlation functions. The proof is valid to all orders of perturbation theory, by making use of softly broken Ward identities.
A solution of the DGLAP equation for gluon at low x
Indian Academy of Sciences (India)
We obtain a solution of the DGLAP equation for the gluon at low ﬁrst by expanding the gluon in a Taylor series and then using the method of characteristics. We test its validity by comparing it with that of Glück, Reya and Vogt. The convergence criteria of the approximation used are also discussed. We also calculate ...
A solution of the DGLAP equation for gluon at low x
Indian Academy of Sciences (India)
Using (43) we will estimate the logarithmic slope of the structure function from the proposed gluon distribution at several points of expansion and compare with data [19] at. Q2 =20 GeV2 where the data on the slope are available. 3. Results and discussion. In the present paper, we have obtained a new description of gluon ...
Low-energy behavior of gluons and gravitons from gauge invariance
DEFF Research Database (Denmark)
di Vecchia, Paolo; Bern, Zvi; Davies, Scott
2014-01-01
We show that at tree level, on-shell gauge invariance can be used to fully determine the first subleading soft-gluon behavior and the first two subleading soft-graviton behaviors. Our proofs of the behaviors for n-gluon and n-graviton tree amplitudes are valid in D dimensions and are similar to Low...
Gluon structure function for deeply inelastic scattering with nucleus in QCD
Energy Technology Data Exchange (ETDEWEB)
Ayala Filho, Alvaro L; Ducati, M.B. Gay [Rio Grande do Sul Univ., Porto Alegre, RS (Brazil). Inst. de Fisica; Levin, Eugene [Centro Brasileiro de Pesquisas Fisicas (CBPF), Rio de Janeiro, RJ (Brazil); [Petersburg Nuclear Physics Institute, Gatchina (Russian Federation). Theory Dept.
1995-06-01
In this talk we present the first calculation of the gluon structure function for nucleus in QCD. We discuss the Glauber formula for the gluon structure function and the violation of this simple approach that we anticipate in QCD. (author). 10 refs, 4 figs.
Quark and gluon fragmentation in high energy e+e- annihilation
International Nuclear Information System (INIS)
Saxon, D.H.
1986-07-01
The paper on quark and gluon fragmentation in high energy e + e - annihilation is based on lectures given at the International School of High Energy Physics, Yugoslavia, 1986. Fragmentation Models, charged particle multiplicity, Bose-Einstein correlations, single particle inclusive distributions, hadrons in jets, leading particle effects, baryon production, comparison of quark and gluon jets, and the string effect, are all discussed. (UK)
A two-loop four-gluon helicity amplitude in QCD
Energy Technology Data Exchange (ETDEWEB)
Dixon, L.
2000-01-06
The authors present the two-loop pure gauge contribution to the gluon-gluon scattering amplitude with maximal helicity violation. The construction of the amplitude does not rely directly on Feynman diagrams, but instead uses its analytic properties 4--2{epsilon} dimensions. The authors evaluate the loop integrals appearing in the amplitude through order({epsilon}{sup 0})in terms of polylogarithms.
The quark and gluon condensates in the Nambu-Jona-Lasinio model
International Nuclear Information System (INIS)
Ebert, D.; Volkov, M.K.
1991-10-01
Systematic study of the role of the nonperturbative gluon condensate arising in a QCD motivated NJL model is presented. The effects of the gluon condensate on meson coupling constants, the pion decay constant, quark condensate and mass formulae are investigated. An interesting result is the decrease of the scale Λ of chiral symmetry breaking. (author). 21 refs
Dilepton production from quark gluon plasma using non-equilibrium thermodynamics
International Nuclear Information System (INIS)
Sinha, B.
1984-01-01
The importance of the approach phase to the thermodynamic equilibrium has been investigated for dilepton production from quark-gluon plasma - an effective temperature for the quarks as Brounian particle in a heat bath of gluons has been suggested. The spectrum for low invariant mass is, as a consequence, sharper
Introduction to quantum chromo transport theory for quark-gluon plasmas
International Nuclear Information System (INIS)
Gyulassy, M.; Elze, H.Th.; Iwazaki, A.; Vasak, D.
1986-08-01
Upcoming heavy ion experiments at the AGS and SPS are aimed at producing and diagnosing a primordial form of matter, the quark-gluon plasma. In these lectures some recent developments on formulating a quantum transport theory for quark-gluon plasmas are introduced. 46 refs
Flavour equilibration studies of quark-gluon plasma with non-zero ...
Indian Academy of Sciences (India)
Abstract. Flavour equilibration for a thermally equilibrated but chemically non- equilibrated quark-gluon plasma is presented. Flavour equilibration is studied enforcing baryon number conservation. In addition to the usual processes like single additional gluon production gg ⇌ ggg and its reverse and quark–antiquark pair ...
Quark Loop Effects on Dressed Gluon Propagator in Framework of Global Color Symmetry Model
Institute of Scientific and Technical Information of China (English)
ZONG Hong-Shi; SUN Wei-Min
2006-01-01
Based on the global color symmetry model (GCM), a method for obtaining the quark loop effects on the dressed gluon propagator in GCM is developed. In the chiral limit, it is found that the dressed gluon propagator containing the quark loop effects in the Nambu-Goldstone and Wigner phases are quite different. In solving the quark self-energy functions in the two different phases and subsequent study of bag constant one should use the above dressed gluon propagator as input. The above approach for obtaining the current quark mass effects on the dressed gluon propagator is quite general and can also be used to calculate the chemical potential dependence of the dressed gluon propagator.
Shadowing of gluons in perturbative QCD: A comparison of different models
International Nuclear Information System (INIS)
Jalilian-Marian, Jamal; Wang, Xin-Nian
2001-01-01
We investigate the different perturbative QCD-based models for nuclear shadowing of gluons. We show that, in the kinematic region appropriate to the BNL relativistic heavy ion collider experiment, all models give similar estimates for the magnitude of gluon shadowing. At scales relevant to CERN large hadron collider (LHC), there is a sizable difference between the predictions of the different models. However, the uncertainties in gluon shadowing coming from a different parametrization of the gluon distribution in nucleons, are larger than those due to different perturbative QCD models of gluon shadowing. We also investigate the effect of initial nonperturbative shadowing on the magnitude of perturbative shadowing and show that the magnitudes of perturbative and nonperturbative shadowing are comparable at RHIC but perturbative shadowing dominates over nonperturbative shadowing at smaller values of x reached at LHC
Forward gluon production in hadron-hadron scattering with Pomeron loops
International Nuclear Information System (INIS)
Iancu, E.
2006-01-01
We discuss new physical phenomena expected in particle production in hadron-hadron collisions at high energy, as a consequence of Pomerons loop effects in the evolution equations for the Color Glass Condensate. We focus on gluon production in asymmetric, 'dilute-dense', collisions: a dilute projectile scatters off a dense hadronic target, whose gluon distribution is highly evolved. This situation is representative for particle production in proton-proton collisions at forward rapidities (say, at LHC) and admits a dipole factorization similar to that of deep inelastic scattering (DIS). We show that at sufficiently large forward rapidities, where the Pomerons loop effects become important in the evolution of the target wavefunction, gluon production is dominated by 'black spots' (saturated gluon configurations) up to very large values of the transverse momentum, well above the average saturation momentum in the target. In this regime, the produced gluon spectrum exhibits diffusive scaling, so like DIS at sufficiently high energy. (authors)
Quark and gluon jet properties in symmetric three-jet events
Buskulic, D.; Casper, D.; de Bonis, I.; Decamp, D.; Ghez, P.; Goy, C.; Lees, J.-P.; Lucotte, A.; Minard, M.-N.; Odier, P.; Pietrzyk, B.; Chmeissani, M.; Crespo, J. M.; Efthymiopoulos, I.; Fernandez, E.; Fernandez-Bosman, M.; Garrido, Ll.; Juste, A.; Martinez, M.; Orteu, S.; Pacheco, A.; Padilla, C.; Palla, F.; Pascual, A.; Perlas, J. A.; Riu, I.; Sanchez, F.; Teubert, F.; Colaleo, A.; Creanza, D.; de Palma, M.; Farilla, A.; Gelao, G.; Girone, M.; Iaselli, G.; Maggi, G.; Maggi, M.; Marinelli, N.; Natali, S.; Nuzzo, S.; Ranieri, A.; Raso, G.; Romano, F.; Ruggieri, F.; Selvaggi, G.; Silvestris, L.; Tempesta, P.; Zito, G.; Huang, X.; Lin, J.; Ouyang, Q.; Wang, T.; Xie, Y.; Xu, R.; Xue, S.; Zhang, J.; Zhang, L.; Zhao, W.; Alemany, R.; Bazarko, A. O.; Bonvicini, G.; Cattaneo, M.; Comas, P.; Coyle, P.; Drevermann, H.; Forty, R. W.; Frank, M.; Hagelberg, R.; Harvey, J.; Jacobsen, R.; Janot, P.; Jost, B.; Kneringer, E.; Knobloch, J.; Lehraus, I.; Martin, E. B.; Mato, P.; Minten, A.; Miquel, R.; Mir, Ll. M.; Moneta, L.; Oest, T.; Palazzi, P.; Pater, J. R.; Pusztaszeri, J.-F.; Ranjard, F.; Rensing, P.; Rolandi, L.; Schlatter, D.; Schmelling, M.; Schneider, O.; Tejessy, W.; Tomalin, I. R.; Venturi, A.; Wachsmuth, H.; Wildish, T.; Witzeling, W.; Wotschack, J.; Ajaltouni, Z.; Barrès, A.; Boyer, C.; Falvard, A.; Gay, P.; Guicheney, C.; Henrard, P.; Jousset, J.; Michel, B.; Monteil, S.; Montret, J.-C.; Pallin, D.; Perret, P.; Podlyski, F.; Proriol, J.; Rossignol, J.-M.; Fearnley, T.; Hansen, J. B.; Hansen, J. D.; Hansen, J. R.; Hansen, P. H.; Nilsson, B. S.; Wäänänen, A.; Kyriakis, A.; Markou, C.; Simopoulou, E.; Siotis, I.; Vayaki, A.; Zachariadou, K.; Blondel, A.; Bonneaud, G.; Brient, J. C.; Bourdon, P.; Rougé, A.; Rumpf, M.; Tanaka, R.; Valassi, A.; Verderi, M.; Videau, H.; Candlin, D. J.; Parsons, M. I.; Focardi, E.; Parrini, G.; Corden, M.; Delfino, M.; Georgiopoulos, C.; Jaffe, D. E.; Antonelli, A.; Bencivenni, G.; Bologna, G.; Bossi, F.; Campana, P.; Capon, G.; Chiarella, V.; Felici, G.; Laurelli, P.; Mannocchi, G.; Murtas, F.; Murtas, G. P.; Passalacqua, L.; Pepe-Altarelli, M.; Curtis, L.; Dorris, S. J.; Halley, A. W.; Knowles, I. G.; Lynch, J. G.; O'Shea, V.; Raine, C.; Reeves, P.; Scarr, J. M.; Smith, K.; Thompson, A. S.; Thomson, F.; Thorn, S.; Turnbull, R. M.; Becker, U.; Braun, O.; Geweniger, C.; Graefe, G.; Hanke, P.; Hepp, V.; Kluge, E. E.; Putzer, A.; Rensch, B.; Schmidt, M.; Sommer, J.; Stenzel, H.; Tittel, K.; Werner, S.; Wunsch, M.; Abbaneo, D.; Beuselinck, R.; Binnie, D. M.; Cameron, W.; Colling, D. J.; Dornan, P. J.; Moutoussi, A.; Nash, J.; San Martin, G.; Sedgbeer, J. K.; Stacey, A. M.; Dissertori, G.; Girtler, P.; Kuhn, D.; Rudolph, G.; Bowdery, C. K.; Brodbeck, T. J.; Colrain, P.; Crawford, G.; Finch, A. J.; Foster, F.; Hughes, G.; Sloan, T.; Whelan, E. P.; Williams, M. I.; Galla, A.; Greene, A. M.; Kleinknecht, K.; Quast, G.; Renk, B.; Rohne, E.; Sander, H.-G.; van Gemmeren, P.; Zeitnitz, C.; Aubert, J. J.; Bencheikh, A. M.; Benchouk, C.; Bonissent, A.; Bujosa, G.; Calvet, D.; Carr, J.; Diaconu, C.; Etienne, F.; Konstantinidis, N.; Nicod, D.; Payre, P.; Rousseau, D.; Talby, M.; Sadouki, A.; Thulasidas, M.; Trabelsi, K.; Abt, I.; Assmann, R.; Bauer, C.; Blum, W.; Brown, D.; Dietl, H.; Dydak, F.; Ganis, G.; Gotzhein, C.; Jakobs, K.; Kroha, H.; Lütjens, G.; Lutz, G.; Männer, W.; Moser, H.-G.; Richter, R.; Rosado-Schlosser, A.; Schael, S.; Settles, R.; Seywerd, H.; Denis, R. St.; Wiedenmann, W.; Wolf, G.; Boucrot, J.; Callot, O.; Cordier, A.; Davier, M.; Duflot, L.; Grivaz, J.-F.; Heusse, Ph.; Jacquet, M.; Kim, D. W.; Le Diberder, F.; Lefrançois, J.; Lutz, A.-M.; Nikolic, I.; Park, H. J.; Park, I. C.; Schune, M.-H.; Simion, S.; Veillet, J.-J.; Videau, I.; Azzurri, P.; Bagliesi, G.; Batignani, G.; Bettarini, S.; Bozzi, C.; Calderini, G.; Carpinelli, M.; Ciocci, M. A.; Ciulli, V.; Dell'Orso, R.; Fantechi, R.; Ferrante, I.; Foà, L.; Forti, F.; Giassi, A.; Giorgi, M. A.; Gregorio, A.; Ligabue, F.; Lusiani, A.; Marrocchesi, P. S.; Messineo, A.; Rizzo, G.; Sanguinetti, G.; Sciabà, A.; Spagnolo, P.; Steinberger, J.; Tenchini, R.; Tonelli, G.; Vannini, C.; Verdini, P. G.; Walsh, J.; Betteridge, A. P.; Blair, G. A.; Bryant, L. M.; Cerutti, F.; Chambers, J. T.; Gao, Y.; Green, M. G.; Johnson, D. L.; Medcalf, T.; Perrodo, P.; Strong, J. A.; von Wimmersperg-Toeller, J. H.; Botterill, D. R.; Clifft, R. W.; Edgecock, T. R.; Haywood, S.; Edwards, M.; Maley, P.; Norton, P. R.; Thompson, J. C.; Bloch-Devaux, B.; Colas, P.; Emery, S.; Kozanecki, W.; Lançon, E.; Lemaire, M. C.; Locci, E.; Marx, B.; Perez, P.; Rander, J.; Renardy, J.-F.; Roussarie, A.; Schuller, J.-P.; Schwindling, J.; Trabelsi, A.; Vallage, B.; Johnson, R. P.; Kim, H. Y.; Litke, A. M.; McNeil, M. A.; Taylor, G.; Beddall, A.; Booth, C. N.; Boswell, R.; Brew, C. A. J.; Cartwright, S.; Combley, F.; Koksal, A.; Letho, M.; Newton, W. M.; Rankin, C.; Reeve, J.; Thompson, L. F.; Böhrer, A.; Brandt, S.; Cowan, G.; Feigl, E.; Grupen, C.; Lutters, G.; Minguet-Rodriguez, J.; Rivera, F.; Saraiva, P.; Smolik, L.; Stephan, F.; Apollonio, M.; Bosisio, L.; Della Marina, R.; Giannini, G.; Gobbo, B.; Musolino, G.; Ragusa, F.; Rothberg, J.; Wasserbaech, S.; Armstrong, S. R.; Bellantoni, L.; Elmer, P.; Feng, Z.; Ferguson, D. P. S.; Gao, Y. S.; González, S.; Grahl, J.; Greening, T. C.; Harton, J. L.; Hayes, O. J.; Hu, H.; McNamara, P. A.; Nachtman, J. M.; Orejudos, W.; Pan, Y. B.; Saadi, Y.; Schmitt, M.; Scott, I. J.; Sharma, V.; Turk, J. D.; Walsh, A. M.; Wu, Sau Lan; Wu, X.; Yamartino, J. M.; Zheng, M.; Zobernig, G.; Aleph Collaboration
1996-02-01
Quark and gluon jets with the same energy, 24 GeV, are compared in symmetric three-jet configurations from hadronic Z decays observed by the ALEPH detector. Jets are defined using the Durham algorithm. Gluon jets are identified using an anti-tag on b jets, based on a track impact parameter method. The comparison of gluon and mixed flavour quark jets shows that gluon jets have a softer fragmentation function, a larger angular width and a higher particle multiplicity, Evidence is presented which shows that the corresponding differences between gluon and b jets are significantly smaller. In a statistically limited comparison the multiplicity in c jets was found to be comparable with that observed for the jets of mixed quark flavour.
From the multifragmentation to the quark-gluon plasma
International Nuclear Information System (INIS)
Boisgard, R.
1988-01-01
Multifragmentation and quark de-confinement phenomena are discussed. A scenario for studying the stability of a hot and compressed nuclei is developed. The thermalization of the nuclei generated in heavy ion reactions is described by a pre-equilibrium model. A hydrodynamical approach and a percolation model are applied for determining the stability of the nucleus. The conditions for the nuclear fragmentation process and the cross sections for various systems at different energies are calculated. The experiments were carried out in ultrarelativistic interactions at CERN. The results are different from those obtained at lower energies and in proton reactions. The formation of a quark-gluon plasma is described by means of an aggregation model. The results are similar to those obtained with sophisticated methods. The differences between the macroscopical systems and the studied one (small number of particles) are stressed [fr