e+e- pair production in ultrarelativistic heavy-ion collisions at   intermediate impact parameters
  Using the quasiclassical Green's function in the Coulomb field, we analyze the probabilities of single and multiple $e^+e^-$-pair production at fixed impact parameter $b$ between colliding ultrarelativistic heavy nuclei. We perform calculations in the Born approximation with respect to the parameter $Z_B\alpha$, and exactly in $Z_A\alpha$, $Z_{A}$ and $Z_{B}$ are the charge numbers of the corresponding nuclei. We also obtain the approximate formulas for the probabilities valid for $Z_A\alpha, Z_B\alpha\lesssim 1$. 
R.N. Lee and A.I. Milstein