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On the Relation Between Mechanisms for Single-Transverse-SpinAsymmetries

Description: Recent studies have shown that two widely-used mechanismsfor single-transverse-spin asymmetries based on either twist-threecontributions or on transverse-momentum-dependent (Sivers) partondistributions become identical in a kinematical regime of overlap. Thiswas demonstrated for the so-called soft-gluon-pole and hard-polecontributions to the asymmetry associated with a particular quark-gluoncorrelation function in the nucleon. In this paper, using semi-inclusivedeep inelastic scattering as an example, we extend the study to thecontributions by soft-fermion poles and by another independenttwist-three correlation function. We find that these additional termsorganize themselves in such a way as to maintain the mutual consistencyof the two mechanisms for single-spin asymmetries.
Date: November 5, 2007
Creator: Koike, Yuji; Vogelsang, Werner & Yuan, Feng
Partner: UNT Libraries Government Documents Department

Theoretical description of heavy quark production in DIS

Description: We present results from a new event-generator Monte Carlo program for semi- inclusive DIS heavy quark production computed in a composite 3-flavor/4-flavor scheme, which is applicable over a wider range of energy scales than existing calculations. We compare the semi-inclusive distributions in p{sub t}, Q{sup 2} and W at O ({alpha}{sup 1}{sub s}) with recent HERA results. We also compare the inclusive F{sup charm}{sub 2} with the data and the existing O ({alpha}{sup 2}{sub s}) 3-flavor scheme calculation. Both calculations agree will with current HERA data, but the resummed O ({alpha}{sup 1}{sub s}) composite scheme calculation is simpler and more efficient by an order of magnitude.
Date: July 1, 1998
Creator: Amundson, J., FERMI
Partner: UNT Libraries Government Documents Department

Determination of sin{superscript 2} theta {subscript W} in neutrino-nucleon scattering at the NuTeV

Description: We report the determination of sin{sup 2}{theta}{sub W} in {nu}-N deep inelastic scattering from the NuTeV experiment. Using separate neutrino and anti-neutrino beams, NuTeV is able to extract sin{sup 2}{theta}{sub W} with low systematic errors from the Paschos-Wolfenstein variable R{sup -}, a ratio of differences of neutrino and anti-neutrino neutral-current and charged-current cross-sections. NuTeV measures sin{sup 2}{theta}{sub W} {sup (on - shell)} = 0.2253 {+-} 0.0019(stat) {+-} 0.0010(syst), which implies M{sub W}= 80.26 {+-} 0.11 GeV.
Date: April 29, 1999
Creator: al., R. Bernstein et
Partner: UNT Libraries Government Documents Department

Note on Nuclear Shadowing at Low Q{sup 2} and the Extraction of sin{sup 2} theta{sub w}

Description: In the light of a recent claim that models of nuclear shadowing which incorporate a vector meson dominance component at low Q{sup 2} are incompatible with nuclear deep inelastic scattering data, we compare the predictions of such a model with high precision data on the Q{sup 2} dependence of nuclear shadowing. Contrary to this claim, we find that models which incorporate both vector meson and partonic mechanisms are indeed consistent with both the magnitude and the Q{sup 2} slope of the shadowing data.
Date: August 1, 2002
Creator: Melnitchouk, Wally & Thomas, A.W.
Partner: UNT Libraries Government Documents Department

Azimuthal Asymmetric Distribution of Hadrons Inside a Jet atHadron Collider

Description: We study the azimuthal asymmetric distribution of hadronsinside a high energy jet in the single transverse polarized proton protonscattering, coming from the Collins effect multiplied by the quarktransversity distribution. We argue that the Collins function in thisprocess is the same as that in the semi-inclusive deep inelasticscattering. The experimental study of this process will provide usimportant information on the quark transversity distribution and test theuniversality of the fragmentation functions.
Date: September 20, 2007
Creator: Yuan, Feng
Partner: UNT Libraries Government Documents Department

SOME NEWS ON SPIN PHYSICS.

Description: For many years now, spin physics has played a very prominent role in QCD. The field has been carried by the hugely successful experimental program of polarized deeply-inelastic lepton-nucleon scattering (DIS), and by a simultaneous tremendous progress in theory. This talk summarizes some of the interesting new developments in spin physics in the past roughly two years. As we will see, there have yet again been exciting new data from polarized lepton-nucleon scattering, but also from the world's first polarized pp collider, RHIC. There have been very significant advances in theory as well. It will not be possible to cover all developments. The author will select those topics that may be of particular interest to the attendees of a conference in the ''DIS'' series. The author briefly reviews some of the recent developments in QCD spin physics.
Date: September 29, 2003
Creator: VOGELSANG,W.
Partner: UNT Libraries Government Documents Department

Run II diffractive measurements at CDF

Description: We present results on hard diffraction obtained by the CDF Collaboration in Run II proton-antiproton collisions at the Fermilab Tevatron. Run I CDF results on hard diffraction are also reviewed.
Date: September 17, 2003
Creator: Terashi, K.
Partner: UNT Libraries Government Documents Department

Polarization of prompt J/{psi} and {Upsilon}(nS).

Description: We review predictions, based on the nonrelativistic QCD factorization framework, for the polarizations of prompt J={psi}'s and {Upsilon}(nS)'s produced at the Fermilab Tevatron. We also discuss the effect of relativistic corrections on the theoretical prediction for the polarization of prompt J={psi}'s at the Tevatron.
Date: July 16, 2002
Creator: Lee, J.
Partner: UNT Libraries Government Documents Department

Rapidity gaps in deep inelastic scattering

Description: A simple semiquantitative picture of diffractive electroproduction is described. Although the diffractive component of F{sub 2} is approximately independent of Q{sup 2} and W{sup 2}, this mechanism is ``soft,`` i.e. it depends upon large-distance physics and is not readily describable within perturbative QCD.
Date: December 31, 1995
Creator: Bjorken, J.D.
Partner: UNT Libraries Government Documents Department

Light-cone quantization and QCD phenomenology

Description: In principle, quantum chromodynamics provides a fundamental description of hadronic and nuclear structure and dynamics in terms of their elementary quark and gluon degrees of freedom. In practice, the direct application of QCD to reactions involving the structure of hadrons is extremely complex because of the interplay of nonperturbative effects such as color confinement and multi-quark coherence. A crucial tool in analyzing such phenomena is the use of relativistic light-cone quantum mechanics and Fock state methods to provide tractable and consistent treatments of relativistic many-body systems. In this article we present an overview of this formalism applied to QCD, focusing in particular on applications to the final states in deep inelastic lepton scattering that will be relevant for the proposed European Laboratory for Electrons (ELFE), HERMES, HERA, SLAC, and CEBAF. We begin with a brief introduction to light-cone field theory, stressing how it many allow the derivation of a constituent picture, analogous to the constituent quark model, from QCD. We then discuss several applications of the light-cone Fock state formalism to QCD phenomenology. The Fock state representation includes all quantum fluctuations of the hadron wavefunction, including far off-shell configurations such as intrinsic charm and, in the case of nuclei, hidden color. In some applications, such as exclusive processes at large momentum transfer, one can make first-principle predictions using factorization theorems which separate the hard perturbative dynamics from the nonpertubative physics associated with hadron binding. The Fock state components of the hadron with small transverse size, which dominate hard exclusive reactions, have small color dipole moments and thus diminished hadronic interactions. Thus QCD predicts minimal absorptive corrections, i.e., color transparency for quasi-elastic exclusive reactions in nuclear targets at large momentum transfer.
Date: December 1995
Creator: Brodsky, S. J. & Robertson, D. G.
Partner: UNT Libraries Government Documents Department

Determination of {alpha}{ sub s}} and Measurements of R{sub L}, k and |V{sub cs}| from {nu} - N DIS at CCFR

Description: We present recent QCD results in {nu}-N scattering at the Fermilab CCFR experiment. We present the latest Next-to-Next-to-Leading order strong coupling constant, {alpha}s , extracted from Gross-Llewellyn-Smith sum rule. The value of {alpha}s from this measurement, at the mass of Z boson, is {alpha}{sup NNLO}{sub s} (M{sup 2}{sub Z} ) = 0:114 {sup +0 : 009}{sub -0.012} Measurements of charged current neutrino and anti-neutrino nucleon interactions in the CCFR detector are used to extract the structure functions, F2, xF{sup {nu}}{sub 3} , xF{sup {anti{nu}}}{sub 3} and R(longitudinal) in the kinematic region 0:01 < x < 0:6 and 1 < Q 2 < 300 GeV{sup 2}. The new measurements of R in the x < 0:1 region provide a constraint on the level of the gluon distribution. The x and Q{sup 2} dependence of R is compared with a QCD based fit to previous data. The CKM matrix element jVcs j is extracted from a combined analysis of xF3 and dimuon data.
Date: October 1, 1998
Creator: al., Jae Yu et
Partner: UNT Libraries Government Documents Department

Superfluidity, Bose condensation and neutron scattering in liquid {sup 4}He

Description: The relation between superfluidity and Bose condensation in {sup 4}He provides lessons that may be valuable in understanding the strongly correlated electron system of high {Tc} superconductivity. Direct observation of a Bose condensate in the superfluid by deep inelastic neutron scattering measurements has been attempted over many years. But the impulse approximation, which relates momentum distributions to neutron scattering structure functions, is broadened by final state effects. Nevertheless, the excellent quantitative agreement between ab initio quantum many body theory and high precision neutron experiments provides confidence in the connection between superfluidity and Bose condensation.
Date: April 1, 1997
Creator: Silver, R.N.
Partner: UNT Libraries Government Documents Department

Strange sea and alpha {sub s} measurements from nu - N deep inelastic scattering at CCFR/NuTeV

Description: We present the latest Next-to-Next-Leading order strong coupling constant, {alpha}{sub s}, extracted from Gross-Llewellyn-Smith sum rule. The value of {alpha}{sub s} from this measurement, at the mass of Z boson, is {alpha}{sub s}{sup NNLO} (M{sup 2}{sub Z}) = 0.114{sup +0.009}{sub -0.012}. We discuss the previous strange sea quark measurement from the CCFR experiment and the prospects for improvements of the measurement in the NuTeV experiment.
Date: August 1, 1998
Creator: Yu, J. & Collaboration, CCFR /NuTeV
Partner: UNT Libraries Government Documents Department

The Pomeron beyond BFKL

Description: Conformally invariant reggeon interactions derived from t-channel unitarity are discussed and progress towards understanding the {open_quotes}physical Pomeron{close_quotes}, via massless quark reggeon interactions, is briefly out-lined.
Date: May 12, 1997
Creator: White, A. R.
Partner: UNT Libraries Government Documents Department

Open charm production in deep inelastic scattering at next-to-leading order at HERA.

Description: An introduction and overview of charm production in deep inelastic scattering at HERA is given. The existing next-to-leading order perturbative QCD calculations are then reviewed, and key results are summarized. Finally, comparisons are made with the most recent HERA data, and unresolved issues are highlighted.
Date: September 20, 1999
Creator: Harris, B. W.
Partner: UNT Libraries Government Documents Department

Probing the structure of nucleons in the resonance region

Description: Status, open questions, and future prospects of the physics of excited nucleons are discussed. Emphasis is on the study of the structure of nucleons via measurements of their electromagnetic transition form factors, the search for ''missing'' resonances, the spin structure of the nucleon in the resonance region, and connections between the resonance and the deep-inelastic regimes.
Date: May 1, 2000
Creator: Burkert, Volker D.
Partner: UNT Libraries Government Documents Department

Transversity Single Spin Asymmetries.

Description: The theoretical aspects of two leading twist transversity single spin asymmetries, one arising from the Collins effect and one from the interference fragmentation functions, are reviewed. Issues of factorization, evolution and Sudakov factors for the relevant observables are discussed. These theoretical considerations pinpoint the most realistic scenarios towards measurements of transversity.
Date: April 27, 2001
Creator: Boer, D.
Partner: UNT Libraries Government Documents Department

x-dependent polarized parton distributions

Description: Using QCD motivated and phenomenological considerations, they construct x- dependent polarized parton distributions, which evolve under GLAP evolution, satisfy DIS data and are within positivity constraints. Each flavor is done separately and the overall set can be used to predict polarization asymmetries for various processes. They perform their NLO analysis strictly in x space, avoiding difficulties in moment inversion. Small-x results and other physical considerations are discussed.
Date: March 1, 1998
Creator: Gordon, Lionel E.; Goshtasbpour, Mehrdad & Ramsey, Gordon P.
Partner: UNT Libraries Government Documents Department

Moments of the proton F{sub 2} structure function at low Q{sup 2}

Description: The authors review the status of inclusive electron-proton scattering F{sub 2} structure function data in both the nucleon resonance region and the deep inelastic region, at momentum transfers below 5 (GeV/c){sup 2}. From these data they construct moments of F{sub 2}, down to momentum transfers of Q{sup 2}{approx}0.1(GeV/c){sup 2}. The second moment is only slowly varying with Q{sup 2} down to Q{sup 2}{approx}1, which is a reflection of duality. Below Q{sup 2} of 1 (GeV/c){sup 2}, the Q{sup 2} dependence of the moments is predominantly governed by the elastic contribution, whereas the inelastic channels still seem governed by local duality.
Date: May 1, 2000
Creator: Armstrong, C.S.; Ent, R.; Keppel, C.E.; Liuti, S.; Niculescu, G. & Niculescu, I.
Partner: UNT Libraries Government Documents Department

Recent QCD results in {nu} - N deep-inelastic-scattering at CCFR/NUTEV

Description: We present recent QCD results in {nu}-N scattering at the Fermilab CCFR/NuTeV experiments. We present the latest Next-to-Next-Leading order strong coupling constant, {alpha}{sub s}, extracted from Gross-Llewellyn-Smith sum rule. The value of {alpha}{sub s} from this measurement, at the mass of Z boson, is {alpha}{sub s}{sup NNLO}(M{sub Z}{sup 2})=0.114{sub -0.012}{sup +0.009}. We also present a preliminary result of the CCFR F{sub 2} at large-x. This measurement of F{sub 2} is compared to other experiments and various models that provide nuclear effects. We discuss the previous strange sea quark measurement from the CCFR experiment and the prospects for improvements of the measurement in the NuTeV experiment.
Date: August 1, 1998
Creator: Yu, Jaehoon
Partner: UNT Libraries Government Documents Department

Polarized lepton-nucleon scattering

Description: Deep inelastic polarized lepton-nucleon scattering is reviewed in three lectures. The first lecture covers the polarized deep inelastic scattering formalism and foundational theoretical work. The second lecture describes the nucleon spin structure function experiments that have been performed up through 1993. The third lecture discusses implication of the results and future experiments aimed at high-precision measurements of the nucleon spin structure functions.
Date: February 1, 1994
Creator: Hughes, E.
Partner: UNT Libraries Government Documents Department

Probing hard color singlet exchange at D Zero

Description: We present latest preliminary results on hard color-singlet exchange in proton-antiproton collisions. The fraction of dijet events produced via color-singlet exchange is measured as a function of jet transverse energy, dijet pseudorapidity separation, and proton-antiproton center-of-mass energy. The results favour a color-singlet fraction that increases with increasing quark-initiated processes.
Date: June 1, 1998
Creator: Goussiou, A.
Partner: UNT Libraries Government Documents Department