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EMC effect

Description: A review is presented of data and theoretical interpretations of the nuclear dependence of quark and antiquark distributions as observed in the deep inelastic scattering of neutrinos and charged leptons from nuclei. After a summary of the experimental situation and a survey of the broad spectrum of proposed explanations, I concentrate on the Q/sup 2/-rescaling approach and on interpretations in terms of conventional nuclear physics. The review concludes with a list of desirable future experiments. 31 refs., 4 figs.
Date: June 1, 1986
Creator: Berger, E.L.
Partner: UNT Libraries Government Documents Department

Benchmark cross sections for bottom quark production

Description: A summary is presented of theoretical expectations for the total cross sections for bottom quark production, for longitudinal and transverse momentum distributions, and for b, /bar b/ momentum correlations at Fermilab fixed target and collider energies.
Date: January 7, 1988
Creator: Berger, E.L.
Partner: UNT Libraries Government Documents Department

Semi-inclusive inelastic electron scattering from nuclei

Description: A survey is presented of the physics of the electroproduction of hadrons from nuclear targets, eA ..-->.. e'hX. Variables and structure functions are specified. The parton model description of electroproduction is summarized; fragmentation functions are defined and their properties are listed. Specific measurements are suggested. Predictions of the pion exchange model are presented for the nuclear dependence of eA ..-->.. e'hX, including a discussion of the special subprocess e..pi.. ..-->.. e'..pi.. in which scattering occurs from the pion constituents of nuclei.
Date: April 30, 1987
Creator: Berger, E.L.
Partner: UNT Libraries Government Documents Department

Case studies in perturbative quantum chromodynamics

Description: A few aspects of QCD are discussed, beginning with a discussion of the ingredients of QCD and their observational basis. A pedagogical treatment of scaling violations is presented and the argument is presented that while entirely consistent with QCD, the phenomenological situation is clouded by the potentially crucial role of higher twist effects in the theory. Some explicit calculations of higher twist effects are presented.
Date: September 1, 1979
Creator: Berger, E.L.
Partner: UNT Libraries Government Documents Department

Important high-twist contribution to prompt single-photon production

Description: Quantitative predictions are presented for a specific hard-scattering reaction ..pi..N ..-->.. ..gamma..X in which both the incident meson and the produced prompt photon couple directly in the QCD amplitude. The process leads to a highly constrained class of events at large p/sub T/ in which the photon momentum is balanced by that of a recoil quark jet, with no spectator jet of final-state particles emerging along the beam axis. Normalized absolutely in terms of the electromagnetic form factor of the pion, F/sub ..pi../(Q/sup 2/), the cross section provides a lower bound on the total p/sub T//sup -6/ high twist contribution to the inclusive prompt-photon yield.
Date: February 1, 1982
Creator: Berger, E.L.
Partner: UNT Libraries Government Documents Department

Heavy quark production in hadron collisions

Description: Theoretical developments in the dynamics of heavy quark production in hadronic collisions as well as recent data are discussed. Focus is principally on bottom quark production. Extensive calculations of cross sections and production spectra for both collider and fixed target energies are presented. Available data are in excellent agreement with expectations of lowest order perturbative quantum chromodynamics. Uncertainties in the theoretical estimates are explored. The paper includes calculations and comments on charm and top quark production.
Date: January 1, 1987
Creator: Berger, E.L.
Partner: UNT Libraries Government Documents Department

Quark structure functions of mesons, fragmentation functions, higher-twist effects in QCD, deep inelastic scattering, and the Drell-Yan process. [Constituent binding in hadron wave function cross section azimuthal angular dependence]

Description: Inclusion of specific effects associated with constituent binding in hadronic wave functions is shown to lead to important nonscaling, nonfactorizing 1/Q/sup 2/ contributions to cross sections for semi-inclusive deep-inelastic scattering, the Drell-Yan process, and other hard scattering reactions. These 1/Q/sup 2/ higher-twist terms are predicted to be dominant in well defined kinematic regions such as large x and/or large z. They provide angular distributions typical of longitudinally polarized virtual photons and W's, including sin/sup 2/theta terms in meson induced Drell-Yan processes and in e/sup +/e/sup -/ ..-->.. ..pi..X, as well as unusual (1-y) terms in deep-inelastic scattering. Calculations are also presented of the quark structure functions of the pion q/sub ..pi../(x,Q/sup 2/) and for the quark to pion fragmentation function D/sub ..pi..(z,Q/sup 2/). Predictions are made for the azimuthal angle dependence of the cross sections for ..pi..N ..-->.. ..mu.. anti ..mu..X and lN ..-->.. l'..pi..X.
Date: July 1, 1979
Creator: Berger, E.L.
Partner: UNT Libraries Government Documents Department

Hadroproduction of massive lepton pairs and tests of QCD. [Transverse momentum distribution dependence]

Description: Tests of quantum chromodynamics are proposed in the production of massive lepton pairs in hadronic collisions. Predictions are presented for the manner in which the transverse momentum distribution of the pair should change with changes in the mass and longitudinal momentum of the pair, and with changes in the overall energy of the collision. Data are shown to determine the average gluon momentum distribution in the nucleon. Lepton pair production in ..pi..N and anti p N processes provides a method to isolate a gluon jet. 20 references.
Date: August 1, 1978
Creator: Berger, E.L.
Partner: UNT Libraries Government Documents Department

Heavy flavor production

Description: Predictions are presented of total cross sections for charm and bottom quark production in /bar p/p, ..pi../sup /minus//p, and pp interactions at fixed target and collider energies. The calculations are done through next-to-leading order in QCD perturbation theory. The sensitivity is explored of results to the choices of renormalization/evolution scale, parton densities, ..lambda../sub QCD/, and heavy flavor masses. Comparisons with available data show that good agreement is obtained for reasonable values of charm and bottom quark masses and other parameters. Open issues in the interpretation of results are summarized including the large size of the next-to-leading order contributions, proper definition of the gluon density, the nuclear A dependence of charm cross sections, the role of final state interactions, and higher twist effects. 39 refs., 7 figs., 5 tabs.
Date: June 10, 1988
Creator: Berger, E.L.
Partner: UNT Libraries Government Documents Department

Hadronic production of massive lepton pairs

Description: A review is presented of recent experimental and theoretical progress in studies of the production of massive lepton pairs in hadronic collisions. I begin with the classical Drell-Yan annihilation model and its predictions. Subsequently, I discuss deviations from scaling, the status of the proofs of factorization in the parton model, higher-order terms in the perturbative QCD expansion, the discrepancy between measured and predicted yields (K factor), high-twist terms, soft gluon effects, transverse-momentum distributions, implications for weak vector boson (W/sup + -/ and Z/sup 0/) yields and production properties, nuclear A dependence effects, correlations of the lepton pair with hadrons in the final state, and angular distributions in the lepton-pair rest frame.
Date: December 1, 1982
Creator: Berger, E.L.
Partner: UNT Libraries Government Documents Department

Heavy flavor production at fixed target and collider energies

Description: A review is presented of heavy quark production in /bar p/p, p, and pp interactions at fixed target and collider energies. Calculations of total cross sections are described including contributions through next-to-leading order in QCD perturbation theory. Comparisons with available data on charm and bottom quark production show good agreement for reasonable values of charm and bottom quark masses and other parameters. Open issues in the interpretation of results are summarized. A discussion is presented of signatures, backgrounds, and expected event rates for top quark production. 19 refs., 4 figs.
Date: October 13, 1988
Creator: Berger, E.L.
Partner: UNT Libraries Government Documents Department

Massive lepton pair production in hadronic collisions. [Review, Drell-Yan quark annihilation, scaling violations]

Description: A review is presented of theoretical attempts to describe the massive lepton pair continuum produced in hadronic collisions. Beginning with the classical Drell-Yan quark-antiquark annihilation model, its expectations are compared with data. Scaling violations and corrections to the Drell-Yan pictured are discussed. Next, original work is presented bearing on the understanding of the transverse momentum distributions of the dileptons. In a parton model, the quark-gluon scattering graphs which provide scaling violations also endow the dileptons with relatively large (P/sub T/). Comparisons with available data support these QCD expectations; further tests of the QCD predictions are proposed. Implications are drawn for W production experiments, and predictions are presented for reactions initiated by antiprotons.
Date: January 1, 1978
Creator: Berger, E.L.
Partner: UNT Libraries Government Documents Department

Massive lepton pair production: what has QCD done to the classical Drell-Yan model

Description: A report is presented of recent experimental and theoretical progress in studies of the production of massive lepton pairs in hadronic collisions. Among the topics discussed are deviations from scaling, the status of the proofs of factorization in the parton model, higher-order terms in the QCD expansion, the discrepancy between measured and predicted yields (K factor), high-twist terms, soft gluon effects, and transverse momentum distributions.
Date: November 1, 1982
Creator: Berger, E.L.
Partner: UNT Libraries Government Documents Department

Searching for top, Higgs, and supersymmetry: the minimum invariant mass technique

Description: Supersymmetric particls, Higgs mesons, the top quark and other heavy objects are expected to decay frequently into three or more body final states in which at least one particle, such a neutrino or photino, is non-interacting. A method is described for obtaining an excellent estimate of both the mass and the longitudinal momentum of the parent state. The probable longitudinal momenta of the non-interacting particle and of the parent, and the minimum invariant mass of the parent are derived from a minimization procedure. The distributions in these variables are shown to peak sharply at their true values.
Date: March 5, 1984
Creator: Berger, E.L.
Partner: UNT Libraries Government Documents Department

Phenomenology of heavy flavor production

Description: A review is presented of heavy quark in /bar p/p, p, and pp interactions at fixed target and collider energies. Calculations of total cross sections are described, including contributions through next-to-leading order in QCD perturbation theory. Comparisons with available data on charm and bottom quark production show good agreement for reasonable values of charm and bottom quark masses and other parameters. Open issues in the interpretation of results are summarized. A discussion is presented of signatures, backgrounds, and expected event rates for top quark production. 19 refs., 4 figs.
Date: October 13, 1988
Creator: Berger, E.L.
Partner: UNT Libraries Government Documents Department

Deep-inelastic lepton scattering by nuclei. The pion-exchange model

Description: Quark constituents of nucleons were discovered in deep-inelastic electron scattering. It is not surprising therefore that the nuclear effects in deep-inelastic lepton scattering first observed by the European Muon Collaboration (EMC) have spawned many suggestions of revolutionary changes in our views of nuclear structure. Perhaps quarks play a far more active role in nuclear dynamics than the conventional theory provides. Before following the natural appeal of radical conclusions we believe it is important to examine in quantitative detail the consequences of the conventional nuclear model, in which the nucleon-nucleon potential features a one-pion exchange tail at large distances, an intermediate range attraction dominated by two-pion exchange and a strong short-range phenomenological repulsion. For this purpose let us assume that quarks are strictly confined to single hadrons, and that the quark structure of the hadrons in a nucleus is not affected by their environment. These assumptions allow a consistent description of deep-inelastic lepton-nucleus scattering, and the quantitative consequences agree well with available data. 15 refs.
Date: January 1, 1985
Creator: Coester, F. & Berger, E.L.
Partner: UNT Libraries Government Documents Department

Nuclear dependence of structure functions in the shadowing region of deep inelastic scattering

Description: A discussion of nuclear shadowing in deep inelastic lepton scattering is presented. We show that the parton recombination model suggests that shadowing should begin to occur at larger values of Bjorken x as A increases. This expectation as well as that of weak dependence on Q/sup 2/, and the trend of the x dependence of the shadowing phenomenon are consistent with recent data. Shadowing at small x is combined with nuclear bound state effects, responsible for nuclear dependence at larger x, to provide description of the A dependence of the structure function for the entire range of x. 21 refs., 5 figs.
Date: July 27, 1988
Creator: Berger, E.L. & Qiu, Jianwei
Partner: UNT Libraries Government Documents Department

Threshold resummation of soft gluons in hadronic reactions - an introduction.

Description: The authors discuss the motivation for resummation of the effects of initial-state soft gluon radiation, to all orders in the strong coupling strength, for processes in which the near-threshold region in the partonic subenergy is important. The author summarizes the method of perturbative resummation and its application to the calculation of the total cross section for top quark production at hadron colliders. Comments are included on the differences between the treatment of subleading logarithmic terms in this method and in other approaches.
Date: February 17, 1998
Creator: Berger, E. L.
Partner: UNT Libraries Government Documents Department

Higher twist QCD terms in high-p/sub T/ pion production

Description: The higher twist subprocesses qG ..-->.. q..pi../sup + -/ and q anti q ..-->.. G..pi../sup + -/ in the framework of perturbative Quantum Chromodynamics (QCD) are investigated. Cross sections for these processes are compared with the minimum twist QCD results for q anti q ..-->.. q anti q and qG ..-->.. qG. The higher twist terms give sizeable corrections to the inclusive pion yields, particularly for q anti q initial states. The effects of higher twist QCD terms for the charge ratio, N(..pi../sup -/N ..-->.. ..pi../sup -/X)/N(..pi../sup -/N ..-->.. ..pi../sup +/X) are examined.
Date: August 1, 1980
Creator: Berger, E.L.; Gottschalk, T. & Sivers, D.
Partner: UNT Libraries Government Documents Department