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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


Description: Calculational procedures oriented toward computer application are preserted to evaluate the neutron inelastic scattering cross section in the incoherent approximation for a simple cubic Bravais lattice. The differential scattering cross section, the scattering law, or inelastic scattering matrices and transport cross sections for multigroup calculations are evaluated using the contributions of 25 phonons. The inelastic scattering cross section for graphite is calculated as an example of polycrystalline media where the phonon-frequency distribution is dependent on the direction of polarization. (H.D.R.)
Date: September 1, 1962
Creator: Jankus, V.Z.
Partner: UNT Libraries Government Documents Department


Description: BS>Graphs were prepared as basic inelastic neutron data requested for neutron age calculations to be made using the compositions NaF-ZrF/sub 4/, BeF/ sub 2/, LiF-BeF/sub 2/, and ZrH. Nuclear temperature as a function of incident neutron energy was obtained for F, Be, and Zr. (W.D.M.)
Date: June 1, 1956
Creator: Copenhaver, C.M.
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

Nuclear structure studies with the inelastic neutron scattering rection and gamma-ray detection

Description: The (<i>n</i>, <i>n</i>´(gamma)) reaction has been used at the University of Kentucky accelerator facility to examine the detailed structure of a number of nuclei. The advantages of this method are reviewed, and recent developments are described. Examples of unique nuclear structure studies that have been carried out with this method are presented.
Date: December 10, 1998
Creator: Garrett, P. E.; Warr, N. & Yates, S. W.
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

Nuclear effects at HERA

Description: The development of a nuclear beam facility at HERA would allow the study of fundamental features of quark and gluon interactions in QCD. I briefly review the physics underlying nuclear shadowing and anti-shadowing as well as other diffractive and jet fragmentation processes that can be studies in high energy electron-nucleus collisions.
Date: July 1, 1996
Creator: Brodsky, S.J.
Partner: UNT Libraries Government Documents Department

How well do we know the neutron structure function?

Description: We present a detailed analysis of the uncertainty in the neutron F{sub 2}n structure function extracted from inclusive deuteron and proton deep-inelastic scattering data. The analysis includes experimental uncertainties as well as uncertainties associated with the deuteron wave function, nuclear smearing, and nucleon off-shell corrections. Consistently accounting for the Q{sup 2} dependence of the data and calculations, and restricting the nuclear corrections to microscopic models of the deuteron, we find significantly smaller uncertainty in the extracted F{sub 2}n/F{sub 2}p ratio than in previous analyses. In addition to yielding an improved extraction of the neutron structure function, this analysis also provides an important baseline that will allow future, model-independent extractions of neutron structure to be used to examine nuclear medium effects in the the deuteron.
Date: June 1, 2012
Creator: J. Arrington, J. G. Rubin, W. Melnitchouk
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


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
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&quot;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

Quasi-zero dimensional CuB2O4: a resonant inelastic X-ray scattering case study

Description: We explore the general phenomenology of resonant inelastic scattering (RIXS) using CuB{sub 2}O{sub 4}, a network of CuO{sub 4} plaquettes electronically isolated by B{sup +3} ions. Spectra show a small number of well-separated features, and we exploit the simple electronic structure to explore RIXS phenomenology by developing a calculation which allows for intermediate-state effects ignored in standard approaches. These effects are found to be non-negligible and good correspondence between our model and experiment leads to a simple picture of such phenomenology as the genesis of d {yields} d excitations at the K edge and intermediate-state interference effects.
Date: April 29, 2010
Creator: Hancock, J.N.
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