506 research outputs found
Parton distribution functions in nuclei
Optimum nuclear parton distributions are determined by an analysis of muon
and electron deep inelastic scattering data. Assuming simple A dependence and
polynomial functions of x and 1-x for nuclear modification of parton
distributions, we determine the initial distributions by a chi^2 analysis.
Although valence-quark distributions are relatively well determined except for
the small-x region, antiquark distributions cannot be fixed at medium and large
x. It is also difficult to fix gluon distributions.Comment: 1+4 pages, LaTeX2e, ws-p8-50x6-00.cls, 4 eps figures. Talk given at
the 9th International Workshop on Deep Inelastic Scattering, Bologna, Italy,
April 27 - May 1, 2001. To be published in proceedings. Computer codes for
the nuclear parton distributions could be obtained from
http://hs.phys.saga-u.ac.jp Email: [email protected],
[email protected], [email protected]
Determination of polarized parton distribution functions
We study parametrization of polarized parton distribution functions in the
\alpha_s leading order (LO) and in the next-to-leading order (NLO). From \chi^2
fitting to the experimental data on A_1, optimum polarized distribution
functions are determined. The quark spin content \Delta\Sigma is very sensitive
to the small-x behavior of antiquark distributions which suggests that small-x
data are needed for precise determination of \Delta\Sigma. We propose three
sets of distributions and also provide FORTRAN library for our distributions.Comment: 1+5 pages, LATEX, aipproc.sty, 4 eps figures. Talk given at the 14th
International Spin Physics Symposium, Osaka, Japan, October 16-21, 200
Transversity distributions and Drell-Yan spin asymmetries
We discuss transversity distributions and Drell-Yan transverse double spin
asymmetries. First, the antiquark flavor asymmetry is discussed by using two different descriptions, a
meson-cloud model and a Pauli exclusion model. We find that both calculations
produce a significant excess over .
Next, we study its effects on the transverse spin asymmetry and on
the Drell-Yan proton-deuteron asymmetry . We find that the ratio is very useful for investigating the flavor asymmetry
effect.Comment: 1+3 pages, LATEX with npb.sty, 2 eps figures. Talk given at the 7th
International Workshop on Deep Inelastic Scattering and QCD, DESY Zeuthen,
Germany, April 29 -- 23,1999, to be published in Nuclear Physics B. Complete
postscript file including the figures is available at
http://www2.cc.saga-u.ac.jp/saga-u/riko/physics/quantum1/structure.html
Email: [email protected]
Parametrization of nuclear parton distributions
Optimum nuclear parton distributions are obtained by analyzing available
experimental data on electron and muon deep inelastic scattering (DIS). The
distributions are given at Q^2=1 GeV^2 with a number of parameters, which are
determined by a chi^2 analysis of the data. Valence-quark distributions are
relatively well determined at medium x, but they are slightly dependent on the
assumed parametrization form particularly at small x. Although antiquark
distributions are shadowed at small x, their behavior is not obvious at medium
x from the F_2 data. The gluon distributions could not be restricted well by
the inclusive DIS data; however, the analysis tends to support the gluon
shadowing at small x. We provide analytical expressions and computer
subroutines for calculating the nuclear parton distributions, so that other
researchers could use them for applications to other high-energy nuclear
reactions.Comment: 1+11 pages, LaTeX, amsmath.sty, wrapfig.sty, graphicx.sty, ias.cls,
ias.sty, pramana.sty, pmana10.sty, pbib.sty, times.sty, 9 eps figures.
Invited talk given at the International Symposium on Nuclear Physics, Mumbai,
India, Dec. 18-22, 2000, to be published in proceedings. Complete postscript
file is available at http://www-hs.phys.saga-u.ac.jp Email:
[email protected], [email protected],
[email protected]
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