Parton Distribution of Proton in a Simple Statistical Model

Taking proton as an ensemble of quark-gluon Fock states and using the principle of detailed balance, we construct a simple statistical model for parton distribution of proton. The recent observed Bjorken-x dependent light flavor sea quark asymmetry d̄(x) − ū(x) can be well reproduced by Monte Carlo simulation as a pure statistical effect. PACS: 12.40.Ee, 12.38.Lg, 14.20.Dh, 14.65.Bt Proton is the simplest system in which the three colors of QCD neutralize into a colorless object, but its internal quark-gluon structure is still not well understood. The complication comes from the presence of sea quarks in the proton. In all global analyses of parton distribution in nucleons before 1990, a symmetric light-quark (ū, d̄) sea was assumed, based on the usual assumption that the sea of quark-antiquark pairs is produced perturbatively from gluon splitting[1]. However, a surprisingly large asymmetry between the ū and d̄ sea quark distributions in the proton has been observed in recent deep inelastic scattering[2, 3] and Drell-Yan experiments[4, 5, 6]. There have been many theoretical attempts[7, 8, 9, 10, 11] trying to find the origins for this asymmetry. It is believed[1, 6] that the asymmetry cannot be produced from perturbative QCD and mesonic degrees of freedom play an important role for the effect. [email protected] [email protected]