qqq¯→qqq¯ and qq¯q¯→qq¯q¯ elastic scatterings and thermalization of quark matter and antiquark matter

Thermalization of quark matter and antiquark matter is studied with quark-quark-antiquark as well as quark-antiquark-antiquark elastic scatterings. Squared amplitudes of qqq¯→qqq¯ and qq¯q¯→qq¯q¯ at order αs4 are derived in perturbative QCD. Solved by a new technique, solutions of transport equations with the squared amplitudes indicate that the scatterings qqq¯→qqq¯ and qq¯q¯→qq¯q¯ shorten the thermalization time of quark matter and antiquark matter. It is emphasized that three-parton and other multi-parton scatterings become important at the high parton number density achieved in RHIC Au-Au collisions.