Showing papers on "Parton published in 1985"
TL;DR: In this paper, the Weinberg-Salam model was generalized to include the massive W± and Z gauge bosons in the proton and the structure functions of both transversely and longitudinally polarized W's and Z's were derived.
273 citations
TL;DR: Elementary cross sections for the production of supersymmetric partners of the known constituents and gauge bosons in collisions of quarks and gluons are calculated in tree approximation using standard renormalization-group-improved parton-model methods.
Abstract: Elementary cross sections for the production of supersymmetric partners of the known constituents and gauge bosons in collisions of quarks and gluons are calculated in tree approximation. Standard renormalization-group-improved parton-model methods are then used to estimate differential and integrated production cross sections in proton-proton and proton-antiproton collisions. For completeness, some analogous results are presented for electron-positron collisions. Decay modes, experimental signatures, and bounds on masses of supersymmetric partners are surveyed, and prospects for future searches are discussed.
266 citations
TL;DR: In this paper, a detailed model for exclusive properties of initial state parton showers is presented, and a numerically efficient algorithm is obtained by tracing the parton shower backwards, i.e. start with the hard scattering partons and then successively reconstruct preceding branchings in falling sequence of spacelike virtualities Q2 and rising sequence of parton energies.
245 citations
TL;DR: In this article, the existence of a local correspondence between parton and hadron distributions in hard processes (local parton-hadron duality) is discussed and a comparison is made to check up local duality at modern energies.
Abstract: A possible existence of the local correspondence between parton and hadron distributions in hard processes (local parton-hadron duality) is discussed. First comparison is made to check up local duality at modern energies. It is shown, in particular, that an account of essential single-logarithmic corrections to leading double-logarithmic approximation proves sufficient to fit π± spectra ine+e− annihilation atW≳20GeV by theoretical perturbative spectra of QCD partons. Rapidity spectra versus the normalized rapidity appear to be similar for π,K, p. Further tests of local duality as well as effects of chromodynamical coherence are suggested.
231 citations
TL;DR: In this paper, it was shown that in hard processes with a single polarized particle contribution proportional to two-arguments distribution functions (parton correlation densities) can receive imaginary parts even from the Born subprocess, which results in large (not proportional to αs) single asymmetries.
230 citations
TL;DR: In this article, a special class of composite local operators of any twist whose matrix elements between hadronic states can be expressed in terms of the free parton matrix elements averaged with hadron correlation functions was constructed.
209 citations
TL;DR: In this paper, the parton distributions within real photons obtained from full solutions of the corresponding leading order evolution equations are modeled using Q2-dependent parametrizations, and the results differ appreciably from fits of the "asymptotic" solutions.
Abstract: We presentQ2-dependent parametrizations for the parton distributions within real photons obtained from full solutions of the corresponding leading order evolution equations. We show that our results differ appreciably from fits of the “asymptotic” solutions. Furthermore we discuss the production of heavy quarks as well as squarks and gluinos at the HERA collider using our parametrizations. The production rates are very promising especially in the case of gluino production.
105 citations
TL;DR: In this paper, the qualitative features for four-jet events arising from the QCD radiation process and from multi-parton scattering were compared at collider energies, and experimental tests discriminating between the two reaction mechanisms were presented.
80 citations
01 Jan 1985
TL;DR: In this paper, 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.
Abstract: Abstract The states obtained in hard high energy processes can, in a complementary way, be described in terms of partonic QCD language or in terms of a string-like confined force-field spanned by the partons. We define a surface characteristic of a confined force-field which breaks up into hadrons. 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. It reproduces the results of perturbative QCD in the kinematical regions where such results are relevant. It has simple mathematical properties, in particular it is factorizable and in that way generates a stochastic process.
52 citations
TL;DR: In this article, the authors present concise expressions for the two independent helicity amplitudes describing the subprocesses gg → q'q'q′ and gq → ggq′q′.
51 citations
TL;DR: The inclusion of a real part for the elastic amplitude, the removal of multiple diffraction zeros, and the behavior of the model up to the multi-TeV energy range (the Froissart bound is not saturated) are discussed.
Abstract: We study elastic diffraction in the pp and p-barp channels at high energies through an eikonal model, built in impact-parameter space out of QCD and parton-model concepts. The eikonal function is separated into two terms, a constant contribution from valence quarks and a gluon-fusion-initiated term. The latter is responsible for the whole energy dependence of the model at high energies. We discuss the inclusion of a real part for the elastic amplitude, the removal of multiple diffraction zeros, and the behavior of our model up to the multi-TeV energy range (the Froissart bound is not saturated). We find excellent agreement with a large body of experimental data.
TL;DR: In this paper, the effect of the intrinsic parton may be disentangled from the perturbative contribution, and the aplanarity distribution characteristic of 3 jet events is investigated.
Abstract: We calculateO(α s ) corrections to largepT double photon production in hadronic collisions We find that these corrections to the basic\(q\bar q \to \gamma \gamma \) subprocess are important, preventing to describe double photon production on the basis of the leading logarithm approximation only We give a phenomenological discussion of the results obtained at SPS, ISR and\(Sp\bar pS\) energies In particular, we investigate how the effect of the intrinsic parton may be disentangled from the perturbative contribution We also calculate the aplanarity distribution characteristic of 3 jet events
TL;DR: In this paper, the role of multiple parton interactions in the production of multijets at the Collider and Tevatron energies is discussed and the kinematics of double parton collisions are analyzed.
Abstract: We discuss the role of multiple parton interactions in the production of multijets at Collider and Tevatron energies and we analize in detail the kinematics of double parton collisions. We make also some remarks on the combined parton distributions and some qualitative estimates on the total rate of events to be expected.
TL;DR: In this paper, the authors measured the momenta of charged particles produced in inelastic αα, αp, andpp collisions using the Split-Field-Magnet detector at the CERN Intersecting Storage Rings.
Abstract: Momenta of charged particles produced in inelastic αα, αp, andpp collisions were measured using the Split-Field-Magnet detector at the CERN Intersecting Storage Rings. Inclusive and semi-in-clusive spectra are presented as a function of rapidityy, Feynman-x, and transverse momentumpT. The inclusivey distributions agree well with predictions of the dual parton model; the highest particle densities are reached aty≃0 and the momenta of leading protons decrease significantly for increasing total multiplicity. ‘Temperatures’ are equal in αα, αp, andpp interactions. ThepT distributions depend weakly on the multiplicity.
TL;DR: In this article, three currently used fragmentation models are tested by studying the distribution of particles between jet axes in the 3-jet events of e+e− annihilation, using data collected by the Time Projection Chamber at PEP.
Abstract: Three currently used fragmentation models are tested by studying the distribution of particles between jet axes in the 3-jet events ofe+e− annihilation, using data collected by the Time Projection Chamber at PEP. These three models — the Lund String model, the Webber Cluster model and an Independent Fragmentation model (IF) — each implement different Lorentz-frame structures for the fragmentation process of quarks and gluons into hadrons. The Lund model provides a good description of the data, while the IF model does not. The Webber model, which is untuned, does not describe the absolute particle densities between jets, but correctly predicts the ratios of those densities, which are less sensitive to the tuning.
TL;DR: In this article, the relative yield of high transverse momentum protons measured in the CERN ISR was calculated in the framework of simple parton models and the hypothesis of diquark scattering provided a quantitative understanding of the measured dependences on transverse velocity, polar angle, and centre-of-mass energy.
Abstract: The relative yield of high transverse momentum protons measured inpp interctions at the CERN ISR is calculated in the framework of simple parton models Whereas models based exclusively on quark and gluon scattering fail to describe the data, the hypothesis of diquark scattering provides a quantitative understanding of the measured dependences on transverse momentum, polar angle, and centre-of-mass energy Different assumptions on diquark structure functions are tested
TL;DR: In this paper, the authors considered all available data on the production of Drell-Yan pairs by high energy proton beams and showed that the lepton pair cross sections and q T distributions are correctly described by QCD using the known distributions of partons in the proton and acceptable values of the QCD scale Λ.
TL;DR: In this paper, the structure of high-energy inclusive hadron-hadron scattering in the Feynman gauge was analyzed and it was shown that final-state interactions cancel on a graph-by-graph basis after a sum over final states.
TL;DR: In this paper, the fragmentation functions of u-quarks into positive and negative pions were determined from an analysis of identified pions produced in deep inelastic muon-deuterium scattering.
TL;DR: In this paper, the distribution of particles in three-jet events from e+e− → hadrons are compared with different fragmentation schemes, i.e., the Lund string model, independent parton fragmentation and QCD shower models.
TL;DR: The distribution of particles in three-jet events is compared with the predictions of three fragmentation models currently in use: the Lund string model, the Webber cluster model, and an independent fragmentation model and the results provide evidence that the sources of hadrons are Lorentz boosted with respect to the overall c.m.
Abstract: The distribution of particles in three-jet events is compared with the predictions of three fragmentation models currently in use: the Lund string model, the Webber cluster model, and an independent fragmentation model. The Lund model and, to a certain extent, the Webber model provide reasonable descriptions of the data. The independent fragmentation model does not describe the distribution of particles at large angles with respect to the jet axes. The results provide evidence that the sources of hadrons are Lorentz boosted with respect to the overall c.m.
TL;DR: It is shown that any simple two-component cluster model can represent the European Muon Collaboration data reasonably well; thus the model is not sensitive to the data.
Abstract: We show that any simple two-component cluster model can represent the European Muon Collaboration data reasonably well; thus the model is not sensitive to the data.
TL;DR: In this article, the authors discuss some interesting features expected in high-energy hadronic collisions producing three large p T jets, and show that the main departure from this simple behavior is a significant predicted asymmetry arising solely from qg → 3J, which would confirm the existence of two distinct parton types.
TL;DR: In this paper, it was shown that highp T K− mesons and their associated jets are produced by hard scattering and subsequent fragmentation of flavour neutral partons with a rather soft structure function.
Abstract: Events obtained by triggering on a single particle with high transverse momentump T show a four-jet structure. The two transverse jets are due to the fragmentation of point-like scattered partons. Experimental evidence is presented that highp T K− mesons and their associated jets are produced by hard scattering and subsequent fragmentation of flavour neutral partons with a rather soft structure function. Hence, gluons are a natural source of highp T K− mesons which do not share any valence quark with the incoming protons. The analysis is based upon measurements of short-range quantum number correlations within the trigger jet and of long-range correlations between different jets. The data were obtained at\(\sqrt s\)=62 GeV GeV with the Split Field Magnet Detector (SFM) at the CERN ISR.
TL;DR: In this article, the spectra of secondary antibaryons in non-annihilation inelastic interactions were calculated in the dual parton model and it was shown that the number of antibaryon in the backward hemisphere in the center-of-mass frame can grow with the atomic number of the nucleus.
Abstract: In the framework of the dual parton model we calculate the spectra of secondary antibaryons in\(\bar p\)-nucleus non-annihilation inelastic interactions. We find that the number of antibaryons in the backward hemisphere in the\(\bar p\)-nucleon centre-of-mass frame can grow with the atomic number of the nucleus.
CERN1
TL;DR: In this article, the influence of the vacuum structure of QCD has been taken into account by including a correlation in spin and colour for the partons that initiate a hard scattering process.
Abstract: We comment on an unconventional factorization scheme which has been recently proposed by Nachtmann and Reiter. These authors propose to take into account the influence of the vacuum structure of QCD by including a correlation in spin and colour for the partons that initiate a hard scattering process. We show on a specific example that such a factorization is either trivial in colour or spoiled by leading twist infrared divergences.
TL;DR: In this paper, it was shown that the differences between leading and higher order QCD predictions for F 2 γ (x, Q2) are too small to be distinguished by present experiments.
Abstract: It is demonstrated that the differences between leading and higher order QCD predictions forF 2 γ (x, Q2) are too small to be distinguished by present experiments. Similarly to the well known case of deep inelastic lepton-nucleon scattering, the hadronic (non-perturbative) photonic input parton distributions atQ2=Q 0 2 have to be different for the LO and HO calculations.
TL;DR: A variation of the QCD parton model is proposed in which the partons are identified with nearly degenerate quark-gluon states and this relies only on the Kinoshita-Lee-Nauenberg theorem to cancel infrared singularities.
Abstract: A variation of the QCD parton model is proposed in which the partons are identified with nearly degenerate quark-gluon states. This relies only on the Kinoshita-Lee-Nauenberg theorem to cancel infrared singularities. In deep-inelastic scattering, incoming quark states are replaced by degenerate ''jet'' states and the Bjorken x variable is reinterpreted to be the momentum fraction of a ''jet'' in a hadron. Calculations of the full O(..cap alpha../sub s/) corrections are then done for the nonsinglet structure functions and for the associated nonsinglet operator matrix elements. In both quantities, the soft infrared singularities cancel and the collinear singularities cancel. Thus the proposal has been implemented. By the operator-product expansion the associated coefficient function is obtained and it is the usual one.
TL;DR: In this paper, the consequences of dynamic rescaling for reactions where the parton distributions in nuclei are a crucial ingredient are investigated, and a number of predictions are made, some of which can very soon be compared with experiment.
Abstract: We investigate the consequences of dynamic rescaling—i.e. the simpleQ2 shift relating nuclear and nucleon structure functions—for reactions where the parton distributions in nuclei are a crucial ingredient. A number of predictions are made, some of which can very soon be compared with experiment. We discuss ways of testing dynamical rescaling for valence quarks, sea quarks and gluons separately.