  The heavy ion cross section for continuum e+ e- pair production has been
calculated to all orders in Z alpha. Comparison is made with available CERN SPS
and RHIC STAR data. Computed cross sections are found to be reduced from
perturbation theory with increasing charge of the colliding heavy ions and for
all energy and momentum regions investigated. Au or Pb total cross sections are
reduced by 28% (SPS), 17% (RHIC),and 11% (LHC). For very high energy (E_e+,
E_e- > 3 GeV) forward pairs at LHC the reduction from perturbation theory is a
bit larger (17%). Use of zero degree calorimeter triggering (and thus small
impact parameter weighting) makes impact parameter representation of exact pair
production useful. Preliminary exact calculations in the zero impact parameter
limit show a much larger reduction from perturbation theory (about 40%) at both
RHIC and LHC.
