Shadowing Aspects of Nuclear Parton Distributions

Abstract

Various shadowing aspects of nuclear parton distributions are discussed in a parton-model framework. We explain existing $x$ dependent data of $F_2^A/F_2^D$, then the model is applied to a flavor asymmetry $\bar{u}-\bar{d}$ in a nucleus, to shadowing in valence-quark distributions, and to nuclear dependence of $Q^2$ evolution. First, we find that a finite nuclear $\bar{u}-\bar{d}$ distribution could be possible due to nuclear interactions even in the flavor symmetric case in the nucleon ($\bar{u}-\bar{d}$=0). Second, it is indicated that valence-quark shadowing could be used for discriminating among various shadowing models. Third, we find that nuclear dependence of $Q^2$ evolution $\partial [F_2^{Sn}/F_2^C]/\partial [\ln Q^2]$, which was found by NMC, is essentially understood by modification of parton distributions in nuclei. However, higher-twist effects in nuclear interactions could be tested by studying the details of the nuclear $Q^2$ evolution.

Comments: 10 pages, LATEX, 5 eps figures. Talk given at the Joint Japan-Australia Workshop on "Quarks, Hadrons, and Nuclei", Adelaide, Australia, Nov. 15 - 24, 1995. Complete postscript file including the figures is available at ftp://ftp.cc.saga-u.ac.jp/pub/paper/riko/quantum1/saga-he-95.ps.gz or at http://www.cc.saga-u.ac.jp/saga-u/riko/physics/quantum1/kumano.html Email: kumanos@cc.saga-u.ac.jp