On the momentum dependence of the flavor structure of the nucleon sea

Abstract

Difference between the u¯ and 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 d¯(x)−u¯(x) near x∼0.3, which has not yet been explained by existing theoretical models. We present an independent evidence for the d¯(x)−u¯(x) sign-change at x∼0.3 from an analysis of the DIS data. We further discuss the x-dependence of d¯−u¯ in the context of meson cloud model and the lattice QCD formulation.

Keywords

• Parton distributions
• Sea quark
• d¯(x)−u¯(x)
• Lattice QCD