SU(2)-Flavor-Symmetry Breaking in Nuclear Antiquark Distributions

SU(2)-flavor-symmetry breaking in antiquark distributions of the nucleon was suggested by the New Muon Collaboration (NMC) in deep inelastic muon scattering. As an independent test, Drell-Yan data for the tungsten target have been used for examining the asymmetry. We investigate whether there exists significant modification of the ū− d̄ distribution in nuclei in a parton recombination model. It should be noted that a finite ū− d̄ distribution is theoretically possible in nuclei even if the sea is SU(2)f symmetric in the nucleon. In neutron-excess nuclei such as the tungsten, there exist more d-valence quarks than u-valence quarks, so that more d̄-quarks are lost than ū-quarks are due to parton recombinations in the small x region. Our results suggest that the nuclear modification in the tungsten is a 2–10 % effect on the ū − d̄ distribution suggested by the NMC data. Nuclear effects on the flavor asymmetric distribution could be an interesting topic for future theoretical and experimental investigations. ∗ Email: [email protected]. submitted for publication