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.
Digital Object Identifier (DOI)
This work was supported in part by the National Science Council of the Republic of China and the U.S. Department of Energy under contact Nos. DE-AC02-98CH10886 and DE-FG05-84ER40154, and the National Science Foundation under grant Nos. PHY-0969739 and PHY-1316617.
Peng, Jen-Chieh; Chang, Wen-Chen; Cheng, Hai-Yang; Hou, Tie-Jiun; Liu, Keh-Fei; and Qiu, Jian-Wei, "On the Momentum Dependence of the Flavor Structure of the Nucleon Sea" (2014). Physics and Astronomy Faculty Publications. 351.