The quark–antiquark asymmetry of the strange sea of the nucleon

The strange sea of the proton is generally assumed to have quark–antiquark symmetry. However, it has been known for some time that non-perturbative processes involving the meson cloud of the proton may break this symmetry. Recently this has been of interest as it affects the analysis of the so-called ‘NuTeV anomaly’, and could explain the large discrepancy between the NuTeV measurement of sin2θW and the currently accepted value. In this Letter we re-examine strange–anti-strange asymmetry using the meson cloud model. We calculate contributions to the strange sea arising from fluctuations in the proton wavefunction to states containing either Lambda or Sigma hyperons together with either Kaons or pseudovector K∗ mesons. We find that we should not ignore fluctuations involving K∗ mesons in this picture. The strange sea asymmetry is found to be small, and is unlikely to affect the analysis of the Llewellyn–Smith cross section ratios or the Paschos–Wolfenstein relationship.