Index
Determination of parton distribution functions in nuclei is important for calculating nuclear corrections in oscillation experiments, from which detailed information should be extracted on neutrino properties. First, nuclear parton distributions are discussed for explaining high-energy nuclear reaction data. Possible nuclear modification is explained for valence-quark and antiquark distributions. It is rather difficult to determine gluon distributions in nuclei. Next, reversing the topic, we discuss structure functions which could be investigated by neutrino reactions. Determination of polarized parton distributions in the nucleon is discussed in polarized neutrino reactions. In addition, neutrino reactions should be important for finding nuclear modification of valence-quark distributions at small x if structure function ratios F_3^A/F_3^D are measured for various nuclei.
We discuss possible studies of parton distribution functions (PDFs) in the nucleon and nuclei at the Japan Hadron Facility (JHF). First, the PDFs could be investigated by the 50 GeV primary proton facility. The distributions at medium x are determined, for example, by Drell-Yan measurements. Second, there are feasibility studies to propose a neutrino factory within the 50 GeV proton ring. If such an intensive high-energy neutrino facility is built, neutrino reactions should be able to provide valuable information on the PDFs, whereas the current structure functions have been measured mainly for neutrino-iron reactions.
The NuTeV collaboration reported anomalously large weak mixing angle sin^2 theta_W in comparison with the standard model prediction. Neutrino and antineutrino charged- and neutral-current events are analyzed for extracting sin^2 theta_W. Although the Paschos-Wolfenstein relation is not directly used in the analysis, it plays an important role in the determination. Noting that the target nucleus, iron, is not an isoscalar nucleus, we derive a leading-order expression for a modified Paschos-Wolfenstein relation for nuclei, which may have neutron excess. Then, using charge and baryon-number conservations for nuclei, we discuss an important nuclear correction in the sin^2 theta_W determination. It is noteworthy that nuclear modifications are different between valence up- and down-quark distributions. We find that this difference effect could be of the order of the NuTeV sin^2 theta_W deviation.
We report recent studies on a chi^2 analysis of nuclear DIS and Drell-Yan data for obtaining optimum nuclear parton distribution functions. The initial distributions at Q^2=1 GeV^2 are expressed by a number of parameters, which are then determined by minimizing chi^2 in comparison with the data. Obtained distributions are discussed, and possible studies at a neutrino factory are suggested.
The parallel sessions of the working group 3 were devoted to the discussions of short-baseline neutrino physics program at neutrino factories. First, possible studies of parton distribution functions (PDFs), in particular nuclear and polarized PDFs, are discussed in this summary. Second, the extractions of alpha_s from sum rules and structure functions of deep-inelastic neutrino-nucleon scattering, higher-order perturbative QCD corrections and estimates of high-twist effects are summarized. Third, the situation of the observed NuTeV sin^2 theta_W anomaly is discussed.
We investigate the nuclear effects on the transverse and longitudinal responses in the deep inelastic region due to the nuclear binding and nucleon Fermi motion. We display the role of the transverse-longitudinal admixture due to the transverse nucleon momentum. The mixing effect is appreciable at small Q^2 values, and gradually disappears at large Q^2 values. The nuclear modification is then dominated by the binding and Fermi-motion effects which are contained in the spectral function.