Asymmetry of strange sea in nucleons

Based on the finite-temperature field theory, we evaluate the medium effects in nucleon which can induce an asymmetry between quarks and antiquarks of the strange sea. The short-distance effects determined by the weak interaction can give rise to δm ≡ ∆ms −∆ms where ∆ms(s) is the medium-induced mass of strange quark by a few KeV at most, but the long-distance effects by strong interaction are sizable. Our numerical results show that there exists an obvious mass difference between strange and anti-strange quarks, as large as 10− 100 MeV. PACS numbers: 11.10.Wx, 11.30.Na, 12.40.-y, 14.20.Dh To be published in Phys. Rev. D.