Flavor Asymmetry of the Nucleon Sea: Consequences for Dilepton   Production
  Parton distributions derived from a chiral quark model that generates an excess of down quarks and antiquarks in the proton's sea satisfactorily describe the measured yields of muon pairs produced in proton-nucleus collisions. Comparison of dilepton yields from hydrogen and deuterium targets promises greater sensitivity to the predicted flavor asymmetry. 
Estia J. Eichten, Ian Hinchliffe, and Chris Quigg