On the Momentum Dependence of the Flavor Structure of the Nucleon Sea

Abstract

Difference between the $\bar{u}$ and $\bar{d}$ sea quark distributions in the proton was first observed in the violation of the Gottfried sum rule in deep-inelastic scattering (DIS) experiments. The parton momentum fraction $x$ dependence of this difference has been measured over the region $0.02<x<0.35$ from Drell-Yan and semi-inclusive DIS experiments. The Drell-Yan data suggested a possible sign-change for $\bar{d}(x)-\bar{u}(x)$ near $x\sim 0.3$, which has not yet been explained by existing theoretical models. We present an independent evidence for the $\bar{d}(x)-\bar{u}(x)$ sign-change at $x\sim 0.3$ from an analysis of the DIS data. We further discuss the $x$-dependence of $\bar{d}(x)-\bar{u}(x)$ in the context of meson cloud model and the lattice QCD formulation.

Comments: 5 pages, 5 figures, final version