Detailed Balance and Sea-Quark Flavor Asymmetry of Proton

In this study, the proton is taken as an ensemble of quark-gluon Fock states. Using the principle of detailed balance, the probabilities of finding every Fock states of the proton are obtained without any parameter. A new origin of the light flavor sea quark asymmetry, i.e., $\bar{u} \not= \bar{d}$, is given as a pure statistical effect. It is found that $\bar{d}-\bar{u} \approx 0.124$, which is in surprisingly agreement with the experimental observation.