Bound-free electron-positron pair creation in relativistic heavy-ion collisions as a charge-transfer process.

Abstract

Using a first-order distorted-wave Born approximation we examine the creation of bound-free electron-positron pairs in relativistic heavy-ion collisions. We consider this process as the transfer of a negative-energy electron in the Coulomb field of one of the colliding ions to a bound state of the other. We calculate differential and integral cross sections for various collision systems by employing exact relativistic single-electron wave functions in momentum space. Our results confirm the experimentally reported increase of cross sections with increasing collision energy and their unexpected strong dependence on the charge number of the ion which captures the electron. The calculated dependence on the charge number of the other colliding partner is, however, weaker than experimentally reported. A major conclusion of this investigation is that at least at moderate relativistic collision energies distortions of electronic states due to both Coulomb centers are important for this process. \textcopyright{} 1996 The American Physical Society.