The influence of higher-order corrections on the production of heavy fermion pairs in ultrarelativistic heavy-ion collisions

The production of fermion pairs in ultrarelativistic heavy-ion collisions h as attracted renewed attention in the recent past. This was in part inspire d by the observation that at ultrarelativistic energies the underlying theo ry simplifies greatly. We briefly review the foundations for these simplifi cations and state the pair production amplitude exact in all orders perturb ation theory in the ultrarelativistic limit. The resulting impact parameter dependent cross section is derived in the Weizsacker-Williams approximatio n which is extended to include Coulomb corrections. The cross section shows deviations from the Born result, giving an enlarged total cross section fo r peripheral collisions. Accounting for the nuclear form factor we find an additional enhancement.