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

Transversity distributions and Drell-Yan spin asymmetries

We discuss transversity distributions and Drell-Yan transverse double spin asymmetries. First, the antiquark flavor asymmetry $\Delta_{_T} \bar u/\Delta_{_T} \bar d$ is discussed by using two different descriptions, a meson-cloud model and a Pauli exclusion model. We find that both calculations produce a significant $\Delta_{_T} \bar d$ excess over $\Delta_{_T} \bar u$. Next, we study its effects on the transverse spin asymmetry $A_{_{TT}}$ and on the Drell-Yan proton-deuteron asymmetry $\Delta_{_T}\sigma^{pd}/2 \Delta_{_T}\sigma^{pp}$. We find that the ratio $\Delta_{_T}\sigma^{pd}/2 \Delta_{_T}\sigma^{pp}$ 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]

Nuclear Shadowing in the Structure Function F3(x)F_3(x)

Nuclear modification of the structure function $F_3$ is investigated. Although it could be estimated in the medium and large $x$ regions from the nuclear structure function $F_2^A$, it is essentially unknown at small $x$. The nuclear structure function $F_3^A$ at small $x$ is investigated in two different theoretical models: a parton-recombination model with $Q^2$ rescaling and an aligned-jet model. We find that these models predict completely different behavior at small $x$: {\it antishadowing} in the first parton model and {\it shadowing} in the aligned-jet model. Therefore, studies of the ratio $F_3^A/F_3^D$ at small $x$ could be useful in discriminating among different models, which produce similar shadowing behavior in the structure function $F_2$. We also estimate currently acceptable nuclear modification of $F_3$ at small $x$ by using $F_2^A/F_2^D$ experimental data and baryon-number conservation.Comment: 10 pages, Latex, Figs.1 and 2 are not included, Complete postscript file including the figures is available at ftp://ftp.cc.saga-u.ac.jp/pub/paper/riko/quantum1/saga-he-78.ps.gz or at http://www.cc.saga-u.ac.jp/saga-u/riko/physics/quantum1/structure.htm