Showing papers on "Parton published in 1986"
TL;DR: In this article, the authors compared 2nd-order QCD calculations with 3-and 4-jet models in the energy range of 14.0-46.7 GeV and showed that the observed excess of spherical events can partially be explained by the production of multi-parton events expected from higher order QCD contributions.
Abstract: Hadronic jet production bye+e−-annihilation has been studied in the energy range of 14.0–46.7 GeV. The data have been analysed in terms of a cluster algorithm and other topological quantities. The results are compared with 2nd order QCD calculations which incorporate models for the fragmentation of quarks and gluons into hadrons. At the higher energies we observe more spherical and 4-jet like events than predicted by these calculations. We cannot achieve a simultaneous description of the observed 3- and 4-jet production by adjusting the strong coupling constant αs or the fragmentation parameters of the 2nd order QCD models. The observed excess of spherical events can partially be explained by the production of multi-parton events expected from higher order QCD contributions. Consequences of the presented results for the value of αs, determined in previous analyses, are discussed. QCD parton shower models, including soft gluon interference, are able to describe the observed number of spherical events.
292 citations
TL;DR: In this article, the matrix elements squared for all (2 → 2) and (2→ 3) parton scattering subprocesses calculated at O(αs3) were presented in n dimensions to regulate singularities due to the emission of soft or collinear radiation.
254 citations
TL;DR: In this article, the angular distribution of muon pairs obtained in a high-statistics experiment using a 194-GeV/c π- impinging on a tungsten target is presented.
Abstract: We present the angular distributions of muon pairs obtained in a high-statistics experiment using a 194-GeV/c π- impinging on a tungsten target. Our results are based on the analysis of 145,000 events with positive Feynmanx and mass above 4.07 GeV/c2, excluding the ϒ region. Simple first-order QCD relations allow us to determine the ratio of annihilation with hard-gluon emission to the sum of annihilation with hard-gluon emission and hard-gluon Compton scattering, which is found to be about 58% to 75%. We determine the parton square intrinsic transverse momenta to be of the order of 0.6 (GeV/c)2, and about 30% larger in the pion than in the nucleon. At largex1, our data agree with the higher-twist hypothesis, and support the interpretation of the relevant scale parameter as the dimuon square transverse momentum.
142 citations
TL;DR: In this paper, the problem of computing the cross section for producing heavy strongly interacting particles (quarks, gluinos, squarks) in high-energy hadron collisions was considered.
128 citations
TL;DR: Based on perturbative QCD, the parton fragmentation picture of hadronic interactions is reviewed in this paper, where the authors propose a perturbation-based QCD-based model of the hadronic interaction.
Abstract: Based on perturbative QCD, the parton fragmentation picture of hadronic interactions is reviewed. (AIP)
127 citations
TL;DR: In this paper, a systematic calculation of the evolution of parton distribution functions including the effects of heavy-quark masses is presented, which involves the use of a special renormalization scheme which ensures ordinary massless evolution with the correct number of active quark flavors at all stages, and specifies appropriate matching conditions at thresholds.
111 citations
TL;DR: In this article, the results of two-loop calculations of the O( α s 2 ) corrections to the first nonsinglet moments of the deep inelastic scattering structure functions for polarized and unpolarized targets are presented.
95 citations
TL;DR: In this article, the Faddeev-Kulish approach of asymptotic dynamics is used to construct the QCD coherent states at the level of leading and first sub-leading infrared singularities.
88 citations
CERN1
TL;DR: In this paper, the authors derived the helicity amplitudes of the four-gluon-twogluino subprocess 4g2q using the improved CALKUL method.
86 citations
TL;DR: In this article, a parton model description for transverse spin effects in hadronic interactions is presented, and the Q 2 dependence of the various structure functions involved (corresponding to operators of both twist two and three) is evaluated to leading-logarithmic order via the ladder-diagram summation technique.
79 citations
TL;DR: In this paper, the contribution of QCD jets to the rise with energy of the inelastic cross section is discussed quantitatively and found to be large and the dependence of this yield upon the rapidity cuts, the choice of parton densities, the QCD scale Q 2 and the transverse momentum cutoff p cut are examined.
TL;DR: In this article, the authors define a surface characteristic of a confined force-field which breaks up into hadrons, and the negative exponential of this surface multiplied by the appropriate phase-space defines a measure on the QCD states which is everywhere finite and infrared stable.
TL;DR: In this article, a Monte Carlo model for initial state parton showers is presented, which allows the incorporation of exact kinematic constraints at all stages of the phase transition process.
TL;DR: In this paper, it was shown that parton branhing equations for the probability P mn of m quarks and n gluons have exact solutions which violate KNO scaling.
TL;DR: In this paper, the role of multiple parton scattering in the production of four-jet events at the SppS Collider is discussed, and it is found that such a mechanism can contribute to the Pout distribution appreciably enough to be differentiated from the leading perturbative QCD.
TL;DR: The problem of thermalization of quarks and gluons in relativistic nuclear collisions is considered in a way that minimizes the explicit dependence on the details of the soft QCD interaction.
Abstract: The problem of thermalization of quarks and gluons in relativistic nuclear collisions is considered in a way that minimizes the explicit dependence on the details of the soft QCD interaction. With nuclear transparency and distributed contraction as essential inputs, it is found that, when the collision energy is asymptotically high, the average initial temperature is in the range 300--500 MeV and the thermalization time has a lower bound of order 0.15 fm/c.
TL;DR: In this paper, the leading log part of the perturbatively calculable F POINT-LIKE 2 was found to be independent of ∧ at all orders in α s. At experimentally relevant Q 2 values non-leading log terms are important, QCD corrections to the naive QPM prediction are small and the sensitivity of F γ 2 to ∧ is weak.
TL;DR: In this article, the authors review the experimental techniques of neutrino physics, traces the main developments, summarises the present status of the field and gives some hints on future activities.
Abstract: High energy neutrino physics has been an active field of research at all proton accelerators over the last two decades and has played a key role in the development and verification of the standard model. The author reviews the experimental techniques of neutrino physics, traces the main developments, summarises the present status of the field and gives some hints on future activities. The author concentrates on those fields of physics where neutrino experiments have made unique contributions, namely the structure of the charged and neutral weak currents, the verification of the quark parton model and the determination of the quark and gluon distributions in the nucleon including their scaling violations, and the study of new particle production in neutrino interactions.
CERN1
TL;DR: In this article, the magnetic moment of the weak boson W was measured at the Tevatron collider with a 2TeV energy √s = 2.5TeV by applying experimentally feasible cuts.
[...]
TL;DR: The Drell-Yan process is better suited than antineutrino scattering to determine the nuclear ocean distributions, and may be studied in an experimentally accessible kinematic region in which a quark from the projectile annihilates with a nuclear antiquark.
Abstract: We study the different explanations of the European Muon Collaboration effect. Although the theoretical models are very sensitive to input free-nucleon structure functions, we find that each has distinctive testable traits. Therefore, we examine different reactions to see which can distinguish the models. Deep-inelastic (anti)neutrino-nucleus scattering data are examined, but we find that the model differences to be exposed by this process are small. J/\ensuremath{\psi} production in lepton-nucleus collision is, in principle, capable of determining the nuclear gluon distribution, but there are too many difficulties to successfully separate the different models. We find that the Drell-Yan process is better suited than antineutrino scattering to determine the nuclear ocean distributions. These may be studied in an experimentally accessible kinematic region in which a quark from the projectile annihilates with a nuclear antiquark.
TL;DR: In this article, the wave functions of multihadron systems are calculated in terms of the wave function of the hadrons in them in the case when these hadrons are sufficiently well separated from each other (and from the partons) in the phase space.
Abstract: One- and two-particle wave functions of systems of several hadrons (and, possibly, partons) that determine the amplitudes for the production of such systems in hard processes in the case when the invariant mass of the system is much less than the characteristic momentum transfer are introduced. The wave functions of multihadron systems are calculated in terms of the wave functions of the hadrons in them in the case when these hadrons are sufficiently well separated from each other (and from the partons) in the phase space.
RWTH Aachen University1, University of Bonn2, University of Bristol3, University of Hamburg4, Imperial College London5, Autonomous University of Madrid6, University of Oxford7, Queen Mary University of London8, Rutherford Appleton Laboratory9, Weizmann Institute of Science10, University of Wisconsin-Madison11
TL;DR: In this article, the photon structure function was determined at an average q2 of 23 (GeV/c)2 with statistical and systematic uncertainties, where the errors include statistical, systematic, and higher order corrections.
Abstract: We have measured the processe
+
e
−→e
+
e
−+hadrons, where one of the scattered electrons was detected at large angles, withQ
2 ranging from 7 to 70 (VeV/c)2. The photon structure functionF
2
γ
(x, Q2) was determined at an averageQ
2 of 23 (GeV/c)2. The measurements were compared to theoretical predictions of the Quark Parton Model and Quantum Chromodynamics. In both models a hadronic part was added. Within the errors the data are in agreement with the QPM using quark masses of 300 MeV/c2 for the light quarks. The data also agree with a QCD calculation including higher order corrections. A fit yielded a
$$\Lambda _{\overline {MS} } $$
value of 140
−65
+190
MeV, where the errors include statistical and systematic uncertainties.
TL;DR: In this paper, the predictions of perturbative QCD for the evolution of quark and gluon distributions for polarized hadrons, in general, and for polarized protons, in particular, are developed.
TL;DR: In this paper, the production of lepton pairs and intermediate vector bosons in hadron interactions is reviewed in terms of the parton model and structure functions, cross sections, and scale breaking are considered.
Abstract: The production of lepton pairs and intermediate vector bosons in hadron interactions is reviewed. Structure functions, cross sections, and scale breaking are considered in terms of the parton model. (AIP)
TL;DR: In this paper, it was shown that the final states produced in single diffractive dissociation at fixed mass M are identical to those in non-diffractive inelastic π p collisions at √ s = M.
TL;DR: The origin of transverse momenta in minimum-bias events is investigated within the framework of the dual parton model to obtain the multiplicity dependence of the average transverse momentum.
Abstract: The origin of transverse momenta in minimum-bias events is investigated within the framework of the dual parton model. A Monte Carlo code nicely reproduces almost all available data in a purely soft framework. However, to obtain the multiplicity dependence of the average transverse momentum, it is necessary to attribute transverse momenta to the initial partons which exceed soft values. Without drastically changing the general picture of particle production, the scattering process has to contain a sizable ''semihard'' component.
CERN1
TL;DR: In this paper, the universal behaviour of parton scattering subprocesses was examined for four-jet production at hadron colliders given by QCD (2 → 4) sub-processes.
TL;DR: In this article, the quark interchange contribution to deuteron electromagnetic form factors is examined in the non-relativistic harmonic-oscillator model and in the light-cone parton model.
Journal Article•
CERN1
TL;DR: In this article, the universal behaviour of parton scattering subprocesses was examined for four-jet production at hadron colliders given by QCD (2 → 4) sub-processes.
TL;DR: In this paper, meson and baryon operators on the light cone are studied which reproduce the well-known parton distribution amplitudes as matrix elements between the vacuum and an one-meson (baryon) state.
Abstract: Meson and baryon operators on the light cone are studied which reproduce the well-known parton distribution amplitudes as matrix elements between the vacuum and an one-meson (baryon) state We extent our previous results to the case of the quark-gluon mixing which is relevan for the description of a flavour-singlet meson The anomalous dimensions of the considered nonlocal light-cone operators are calculated explicity in the one-loop approximation We thus recover the evolution kernels for meson and baryon wave functions derived earlier by other authors using different methods