Drell-Yan Study of Sea Isospin Symmetry

The purpose of the experiment is to study the isospin symmetry in the light quark sea of the proton. Its violation is one possible explanation of recent unexpected muon deep inelastic scattering experimental results which disagree with the Gottfried sum rule. \\ \\ The experiment makes use of the large acceptance muon spectrometer used previously by NA10 and NA38. It detects muon pairs produced by the Drell-Yan mechanism in p-p and p-d reactions. A beam of 450 GeV/c protons impinges on alternating liquid hydrogen and deuterium targets. \\ \\ The aim is to measure the cross-section ratio :USERDOC. .nameit symbol=bp size=9 text='p-p' .nameit symbol=bd size=9 text='p-d' .nameit symbol=DY size=8 text='DY' .namef symbol=nom fpart='sigma .adj(u 6 r 2) bp .adj(d 6 l 10) DY .adj(l 5)' .namef symbol=denom fpart='sigma .adj(u 6 r 2) bd .adj(d 6 l 10) DY .adj(l 4)' $ nom / denom 'at':eF. dimuon masses above 4 GeV/$c ^{2} $, :USERDOC. which is a sensitive probe of the relative content of light antiquarks $ u bar $ and $ d bar $ in the proton sea.