On the shape of the d ˉ ? u ˉ asymmetry

摘要

Using data from a recent reanalysis of neutron structure functions extracted from inclusive proton and deuteron deep-inelastic scattering (DIS), we re-examine the constraints on the shape of thedˉ?uˉasymmetry in the proton at large parton momentum fractionsx. A global analysis of the proton–neutron structure function difference from BCDMS, NMC, SLAC and Jefferson Lab DIS measurements, and of Fermilab Drell-Yan lepton-pair production cross sections, suggests that existing data can be well described withdˉ>uˉfor all values ofxcurrently accessible. We compare the shape of the fitteddˉ?uˉdistributions with expectations from nonperturbative models based on chiral symmetry breaking, which can be tested by upcoming Drell-Yan data from the SeaQuest experiment at larger values ofx.