Determination of the ratior v =d v u v of the valence quark distributions in the proton from neutrino and antineutrino reactions on hydrogen and deuterium

Abstract

Based on a QCD analysis of the parton momentum distributions in the proton, the ratior v =d v /u v of thed andu valence quark distributions is determined as function ofx in the range 0.01<x<0.7. The analysis uses data from neutrino and antineutrino charged current interactions on hydrogen and deuterium, obtained with BEBC in the (anti)neutrino wideband beam of the CERN SPS. Since v mainly depends on the deuterium/hydrogen ratios of the normalisedx-y-Q2-distributions many systematic effects cancel. It is found thatr v decreases with increasingx, and drops below the naiveSU(6) expectation of 0.5 forx≳0.3. An extrapolation ofr v tox=1 is consistent with the hypothesisr v (1)=0.