Index
We discuss nuclear structure functions in lepton scattering including neutrino reactions. First, the determination of nuclear parton distribution functions is explained by using the data of electron and muon deep inelastic scattering and those of Drell-Yan processes. Second, NuTeV sin^2 theta_W anomaly is discussed by focusing on nuclear corrections in the iron target. Third, we show that the HERMES effect, which indicates nuclear modification of the longitudinal-transverse structure function ratio, should exist at large x with small Q^2 in spite of recent experimental denials at small x.
Neutrino scattering physics is discussed for investigating internal structure of the nucleon and nuclei at future neutrino facilities. We explain structure functions in neutrino scattering. In particular, there are new polarized functions g_3, g_4, and g_5, and they should provide us important information for determining internal nucleon spin structure. Next, nuclear structure functions are discussed. From F_3 structure function measurements, valence-quark shadowing should be clarified. Nuclear effects on the NuTeV sin^2\theta_W anomaly are explained. We also comment on low-energy neutrino scattering, which is relevant to current long-baseline neutrino oscillation experiments.
We investigate the polarized parton distribution functions (PDFs) and their uncertainties by using the world data on the spin asymmetry A_1. The uncertainties of the polarized PDFs are estimated by the Hessian method. The up and down valence-quark distributions are determined well. However, the antiquark distributions have large uncertainties at this stage, and it is particularly difficult to fix the gluon distribution. The \chi^2 analysis produces a positively polarized gluon distribution, but even \Delta g(x)=0 could be allowed according to our uncertainty estimation. In comparison with the previous AAC (Asymmetry Analysis Collaboration) parameterization in 2000, accurate SLAC-E155 proton data are added to the analysis. We find that the E155 data improve the determination of the polarized PDFs, especially the polarized antiquark distributions. In addition, the gluon-distribution uncertainties are reduced due to the correlation with the antiquark distributions. We also show the global analysis results with the condition \Delta g(x)=0 at the initial scale, Q^2=1 GeV^2, for clarifying the error correlation effects with the gluon distribution.