Flavor asymmetry of polarized and unpolarized sea quark distributions in the large-N_c limit

Abstract

We summarize recent attempts to calculate the flavor asymmetry of the nucleon's sea quark distributions in the large-$N_c$ limit, where the nucleon can be described as a soliton of an effective chiral theory. We discuss the leading-twist longitudinally polarized and transversity antiquark distributions, $\hat{I}”\bar{u}(x)-\hat{I}”\bar{d}(x)$ and $\hat{I}´\bar{u}(x)-\hat{I}´\bar{d}(x)$, as well as the unpolarized one, $\bar{u}(x)-\bar{d}(x)$, which appears only in the next-to-leading order of the $1/N_c$-expansion. Results for $\bar{u}(x)-\bar{d}(x)$ are in good agreement with the recent Drell-Yan data from the FNAL E866 experiment. The longitudinally polarized antiquark asymmetry, $\hat{I}”\bar{u}(x)-\hat{I}”\bar{d}(x)$, is found to be larger than the unpolarized one.

12 pages, LaTeX, 3 figures included using epsf. Part of Plenary Talk given by C. Weiss at the XI International Conference ``Problems of Quantum Field Theory'' (In Memory of D.I. Blokhintsev), Dubna, July 13-17, 1998