62 Matching Results

Search Results

Advanced search parameters have been applied.

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

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

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

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

Calculation of the cross section for top quark production

Description: The authors summarize calculations of the cross section for top quark production at hadron colliders within the context of perturbative quantum chromodynamics, including resummation of the effects of initial-state soft gluon radiation to all orders in the strong coupling strength. In their approach they resume the universal leading-logarithm contributions, and they restrict the calculation to the region of phase space that is demonstrably perturbative. They compare the approach with other methods. They present predictions of the physical cross section as a function of the top quark mass in proton-antiproton reactions at center-of-mass energies of 1.8 and 2.0 TeV, and they discuss estimated uncertainties.
Date: June 21, 1996
Creator: Berger, E.L. & Contopanagos, H.
Partner: UNT Libraries Government Documents Department

Constraints on the gluon density from lepton pair production

Description: The hadroproduction of lepton pairs with mass Q and finite transverse momentum Q{sub T} is described in perturbative QCD by the same partonic subprocesses as prompt photon production. The authors demonstrate that, like prompt photon production, lepton pair production is dominated by quark-gluon scattering in the region Q{sub T} > Q/2. This feature leads to sensitivity to the gluon density in kinematical regimes accessible in collider and fixed target experiments, and it provides a new independent method for constraining the gluon density.
Date: February 4, 2000
Creator: Berger, E. L. & Klasen, M.
Partner: UNT Libraries Government Documents Department

Top quark production dynamics in QCD

Description: A calculation of the total cross section for top quark production in hadron-hadron collisions is presented based on an all-orders perturbative resummation of initial-state gluon radiative contributions to the basic quantum chromodynamics subprocesses. Principal-value resummation is used to evaluate all relevant large threshold contributions. In this method there are no arbitrary infrared cutoffs, and the perturbative regime of applicability is well defined, two attributes that significantly reduce the estimated uncertainty of the results. For p{bar p} collisions at center-of-mass energy {radical}s = 1.8 TeV and a top mass of 175 GeV, we obtain {sigma}(t{bar t}) = 5.52{sup +0.07}{sub {minus}0.45}pb, in agreement with experiment. Predicted cross sections are provided as a function of top mass in p{bar p} collisions at {radical}s = 2.0 TeV and in pp at CERN LHC energies.
Date: December 31, 1995
Creator: Berger, E.L. & Contopanagos, H.
Partner: UNT Libraries Government Documents Department

The perturbative resummed series for top production

Description: Our calculation of the total cross section for inclusive production of t{bar t} pairs in hadron collisions is summarized. Principal ingredient of this calculation is resummation of the universal leading-logarithm effect of gluon radiation to all orders in the quantum chromodynamics coupling strength, restricted to the region of phase space that is manifestly perturbative. We present predictions of the physical cross section as a function of top quark mass in proton-antiproton reactions at center-of-mass energies of 1.8 and 2.0 TeV. 7 refs., 3 figs., 2 tabs.
Date: May 2, 1996
Creator: Berger, E.L. & Contopanagos, H.
Partner: UNT Libraries Government Documents Department

Resummation of gluon radiation and the top quark production cross section

Description: A calculation of the total cross section for top quark production in hadron-hadron collisions is presented based on an all-orders perturbative resummation of initial-state gluon radiative contributions to the basic quantum chromodynamics subprocesses. For p{anti p} collisions at center-of-mass energy {radical}s = 1.8 TeV and a top mass of 175 GeV, the authors obtain {sigma}(t{anti t}) = 5.52 {sub {minus}0.45}{sup +0.07} pb. Cross sections are provided as a function of top mass at CERN LHC energies.
Date: October 23, 1995
Creator: Berger, E.L. & Contopanagos, H.
Partner: UNT Libraries Government Documents Department

Perturbative resummation of gluon radiation for top-quark production

Description: We present a calculation of the total cross section for top quark production based on a new perturbative resummation of gluon radiative corrections to the basic QCD subprocesses. We use Principal Value Resummation to calculate all relevant large threshold corrections. Advantages of this method include its independence from arbitrary infrared cutoffs and specification of the perturbative regime of applicability. For p{bar p} collisions at center-of-mass energy {radical}s = 1.8TeV and a top mass of 175 GeV, we compute {sigma}(t{bar t}) = 5.52{sub -0.45}{sup +0.07}pb.
Date: December 1, 1995
Creator: Contopanagos, H. & Berger, E.L.
Partner: UNT Libraries Government Documents Department

Low mass lepton pair production in hadron collisions.

Description: The hadroproduction of lepton pairs with mass Q and transverse momentum Q{sub T} can be described in perturbative QCD by the same partonic subprocesses as prompt photon production. They demonstrate that, like prompt photon production, lepton pair production is dominated by quark-gluon scattering in the region Q{sub T} > Q/2. This leads to sensitivity to the gluon density in kinematical regimes that are accessible both at collider and fixed target experiments while eliminating the theoretical and experimental uncertainties present in prompt photon production.
Date: June 29, 1999
Creator: Berger, E. L. & Klasen, M.
Partner: UNT Libraries Government Documents Department

Physics landscape-fixed target energies

Description: An introductory review is presented of physics issues and opportunities at Fermilab fixed-target energies. Included are discussions of precision electroweak studies; deep inelastic lepton scattering; heavy quark production, spectroscopy, and decays; perturbative QCD; prompt photon production; massive lepton production; and spin dependence. 79 refs., 7 figs.
Date: October 1, 1989
Creator: Berger, E.L.
Partner: UNT Libraries Government Documents Department

Phenomenology of heavy quark production

Description: A review is presented of heavy quark production in {bar p}p, {pi}{sup -}p, and pp interactions at fixed target and collider energies. Calculations of total cross sections and of single quark inclusive differential cross sections d{sup 2}{omega}/dk{sub T}dy 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 the charm and bottom quark masses and other parameters. Predictions and open issues in the interpretation of results are summarized. A brief discussion is presented of signatures, backgrounds, and expected event rates for top quark production. 24 refs., 6 figs.
Date: January 1, 1989
Creator: Berger, E.L.
Partner: UNT Libraries Government Documents Department

B production in hadron collisions: Theory

Description: A review is presented of heavy quark production in {bar p}p, {pi}{sup -}p, and pp interactions at fixed target and collider energies. Calculations of total cross sections and of single quark inclusive differential cross sections d{sup 2}{sigma}/dk{sub T}dy 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 the charm and bottom quark masses and other parameters. Predictions and open issues in the interpretation of results are summarized. 20 refs., 5 figs.
Date: September 28, 1989
Creator: Berger, E.L.
Partner: UNT Libraries Government Documents Department

Diffractive hard scattering

Description: I discuss events in high energy hadron collisions that contain a hard scattering, in the sense that very heavy quarks or high P/sub T/ jets are produced, yet are diffractive, in the sense that one of the incident hadrons is scattered with only a small energy loss. 8 refs.
Date: March 1, 1986
Creator: Berger, E.L.; Collins, J.C.; Soper, D.E. & Sterman, G.
Partner: UNT Libraries Government Documents Department

Diffractive hard scattering and the SSC

Description: Events in high energy hadron collisions are discussed that contain a hard scattering, in the sense that very heavy quarks or high P/sub T/ jets are produced, yet are diffractive, in the sense that one of the incident hadrons is scattered with only a small energy loss. 12 refs., 6 figs.
Date: January 1, 1986
Creator: Berger, E.L.; Collins, J.C.; Soper, D.E. & Sterman, G.
Partner: UNT Libraries Government Documents Department