445 Matching Results

Search Results

Advanced search parameters have been applied.

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

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

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

Recent results in DIS from Jefferson Lab

Description: Recent results in Deep Inelastic processes measured at Jefferson Lab are presented. In addition to the inclusive reactions typically discussed in the context of Deep Inelastic (electron) Scattering, particular emphasis is given to Deep Exclusive and semi#19;inclusive reactions. Jefferson Lab has made significant contributions to the understanding of the partonic structure of the nucleon at large x, and with its first dedicated measurements is already providing important contributions to understanding the three-dimensional structure of the nucleon via constraints on Generalized Parton Distributions (GPDs) and Transverse Momentum Distributions (TMDs).
Date: April 1, 2010
Creator: Gaskell, David
Partner: UNT Libraries Government Documents Department

Hyperon Polarization in Unpolarized Scattering Processes

Description: Transverse polarization in the Hyperon (\Lambda) production in the unpolarizeddeep inelastic scattering and pp collisions is studied in the twist-three approach, considering the contribution from the quark-gluon-antiquark correlation distribution in nucleon. We further compare our results for deep inelastic scattering to a transverse momentum dependent factorization approach, and find consistency between the two approaches in the intermediate transverse momentum region. We also find that in pp collisions, there are only derivative terms contributions, and the non-derivative terms vanish.
Date: August 27, 2008
Creator: Zhou, Jian; Yuan, Feng & Liang, Zuo-Tang
Partner: UNT Libraries Government Documents Department

SINGLE SPIN ASYMMETRIES OF IDENTIFIED HADRONS IN p +p AT SQUARE ROOT S = 62.4 AND 200 GeV.

Description: Measurements of x{sub F}-dependent single spin asymmetries of identified charged hadrons, {pi}{sup {+-}}, K{sup {+-}}, p, and {bar p}, from transversely polarized proton collisions at {radical}s = 200 and 62.4 GeV at RHIC are presented. The energy and flavor dependent asymmetry measurements bring new insight into the fundamental mechanisms of transverse spin asymmetries and Quantum Chromodynamical description of hadronic structure.
Date: April 16, 2007
Creator: LEE,J.H.; VIDEBAEK, F. & COLLABORATION), (FOR THE BRAHMS
Partner: UNT Libraries Government Documents Department

The SISCone and anti-k_t jet algorithms

Description: We illustrate how the midpoint and iterative cone (with progressive removal) algorithms fail to satisfy the fundamental requirements of infrared and collinear safety, causing divergences in the perturbative expansion. We introduce SISCone and the anti-k{sub t} algorithms as respective replacements that do not have those failures without any cost at the experimental level.
Date: April 7, 2008
Creator: Soyez,G.
Partner: UNT Libraries Government Documents Department

Test of the Universality of Naive-time-reversal-odd Fragmentation Functions

Description: We investigate the"spontaneous'' hyperon transverse polarization in e+e- annihilation and semi-inclusive deep inelastic scattering processes as a test of the universality of the naive-time-reversal-odd transverse momentum dependent fragmentation functions. We find that universality implies definite sign relations among various observables. This provides a unique opportunity to study initial/final state interaction effects in the fragmentation process and test the associated factorization.
Date: August 23, 2010
Creator: Boer, Daniel; Kang, Zhong-Bo; Vogelsang, Werner & Yuan, Feng
Partner: UNT Libraries Government Documents Department

kt-factorization for Hard Processes in Nuclei

Description: Two widely proposed kt-dependent gluon distributions in the small-x saturation regime are investigated using two particle back-to-back correlations in high energy scattering processes. The Weizsacker-Williams gluon distribution, interpreted as the number density of gluon inside the nucleus, is studied in the quark-antiquark jet correlation in deep inelastic scattering. On the other hand, the unintegrated gluon distribution, defined as the Fourier transform of the color-dipole cross section, is probed in the direct photon-jet correlation in pA collisions. Dijet-correlation in pA collisions depends on both gluon distributions through combination and convolution in the large Nc limit. We calculate these processes in two approaches: the transverse momentum dependent factorization approach and the color-dipole/color glass condensate formalism, and they agree with each other completely.
Date: September 13, 2010
Creator: Dominguez, Fabio; Xiao, Bo-Wen & Yuan, Feng
Partner: UNT Libraries Government Documents Department

Collins Asymmetry at Hadron Colliders

Description: We study the Collins effect in the azimuthal asymmetricdistribution of hadrons inside a high energy jet in the single transversepolarized proton proton scattering. From the detailed analysis ofone-gluon and two-gluon exchange diagrams contributions, the Collinsfunction is found the same as that in the semi-inclusive deep inelasticscattering and e+e- annihilations. The eikonal propagators in thesediagrams do not contribute to the phase needed for the Collins-typesingle spin asymmetry, and the universality is derived as a result of theWard identity. We argue that this conclusion depends on the momentum flowof the exchanged gluon and the kinematic constraints in the fragmentationprocess, and is generic and model-independent.
Date: January 17, 2008
Creator: Yuan, Feng
Partner: UNT Libraries Government Documents Department

FastNLO: Fast pQCD calculations for PDF fits

Description: We present a method for very fast repeated computations of higher-order cross sections in hadron-induced processes for arbitrary parton density functions. A full implementation of the method for computations of jet cross sections in Deep-Inelastic Scattering and in Hadron-Hadron Collisions is offered by the ''fastNLO'' project.
Date: September 1, 2006
Creator: Kluge, T.; /DESY; Rabbertz, K.; U., /Karlsruhe; Wobisch, M. & /Fermilab
Partner: UNT Libraries Government Documents Department

Hadronic Final States and QCD: Summary

Description: A summary of new experimental results and recent theoretical developments discussed in the 'Hadronic Final States and QCD' working group is presented.
Date: August 1, 2008
Creator: Gehrmann, Thomas; U., /Zurich; Grindhammer, Guenter; /Munich, Max Planck Inst.; O'Dell, Vivian; /Fermilab et al.
Partner: UNT Libraries Government Documents Department

NLO evolution of color dipoles

Description: The small-x deep inelastic scattering in the saturation region is governed by the non-linear evolution of Wilson-lines operators. In the leading logarithmic approximation it is given by the BK equation for the evolution of color dipoles. In the next-to-leaing order the BK equation gets contributions from quark and gluon loops as well as from the tree gluon diagrams with quadratic and cubic nonlinearities. We calculate the gluon contribution to small-x evolution of Wilson lines (the quark part was obtained earlier).
Date: January 1, 2008
Creator: Balitsky, Ian & Chirilli, Giovanni
Partner: UNT Libraries Government Documents Department

Collins Fragmentation and the Single Transverse Spin Asymmetry

Description: We study the Collins mechanism for the single transverse spin asymmetry in the collinear factorization approach. The correspondent twist-three fragmentation function is identified. We show that the Collins function calculated in this approach is universal.We further examine its contribution to the single transverse spin asymmetry of semi-inclusive hadron production in deep inelastic scattering and demonstrate that the transverse momentum dependent and twist-three collinear approaches are consistent in the intermediate transverse momentum region where both apply.
Date: March 26, 2009
Creator: Yuan, Feng & Zhou, Jian
Partner: UNT Libraries Government Documents Department

Semi-inclusive Deep Inelastic Scattering at Small-x

Description: We study the semi-inclusive hadron production in deep inelastic scattering at small-x.A transverse momentum dependent factorization is found consistent with the resultscalculated in the color-dipole framework in the appropriate kinematic region. The transverse momentum dependent quark distribution can be studied in this processas a probe for the small-x saturation physics. Especially, the ratio of the quark distributions as functions of transverse momentum at different x demonstrates strong dependence on the saturation scale. The Q2 dependence of the same ratio is also studied by applying the Collins-Soper-Sterman resummation method.
Date: May 29, 2009
Creator: Marquet, C.; Xiao, B.-W. & Yuan, Feng
Partner: UNT Libraries Government Documents Department

Neutrino physics

Description: The field of neutrino physics has expanded greatly in recent years with the discovery that neutrinos change flavor and therefore have mass. Although there are many neutrino physics results since the last DIS workshop, these proceedings concentrate on recent neutrino physics results that either add to or depend on the understanding of Deep Inelastic Scattering. They also describe the short and longer term future of neutrino DIS experiments.
Date: September 1, 2008
Creator: Harris, Deborah A.
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