Structure functions in polarized proton-deuteron Drell-Yan processes

Polarized proton-deuteron (pd) Drell-Yan processes are investigated for studying new spin structure of a spin-1 hadron. Our formalism indicates that there exist many structure functions: 108 in general and 22 in the \vec Q_T-integrated case. A naive parton model suggests that at least one of them should be related to the tensor polarized distributions, which have not been measured at all. There are some experimental possibilities at FNAL, HERA, and RHIC to study the polarized pd reactions.Comment: 1+3 pages, LaTeX, espcrc2.sty. Talk at the 7th international workshop on Deep Inelastic Scattering and QCD, Zeuthen, Germany, April 19-23, 1999. To be published in Nucl. Phys. B. Complete postscript file is available at http://www2.cc.saga-u.ac.jp/saga-u/riko/physics/quantum1/structure.html Email: [email protected]

Studies of parton distributions at a neutrino factory

The determination of parton distribution functions in the nucleon and nuclei is important for obtaining precise hadron-reaction cross sections, from which any new exotic signature could be found. We show that a future neutrino factory could provide important information on the parton distributions. First, a recent effort concerning the parametrization of nuclear parton distributions is explained. It suggests that the factory should be important for determining unknown behavior of valence-quark distributions in nuclei at small $x$. Second, the facility could be used for understanding nucleon spin structure and isospin violation in the parton distributions.Comment: 1+3 pages, LaTeX2e, elsart.cls, wrapfig.sty, 1 eps figure. Talk given at the Third International Workshop on Neutrino Factories based on Muon Storage Rings (NuFACT'01), May 24 - 30, 2001, Tsukuba, Japan. To be published in proceedings. Email: [email protected], WWW: http://hs.phys.saga-u.ac.j

Shadowing Aspects of Nuclear Parton Distributions

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.Comment: 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: [email protected]