  The collision energy dependence of the cross section and the transverse
momentum distribution of dielectrons from the Breit-Wheeler process in
heavy-ion collisions are computed in the lowest-order QED and found to be
sensitive to the nuclear charge distribution and the infrared-divergence of the
ultra-Lorentz boosted Coulomb field. Within a given experimental kinematic
acceptance, the cross section is found to increase while the pair transverse
momentum ($\sqrt{\langle p_{T}^{2} \rangle}$) decreases with increasing beam
energy. We demonstrate that the transverse-momentum component of
Weizsacker-Williams photons is due to the finite extent of the charge source
and electric field component in the longitudinal direction. We further clarify
the connection between the nuclear charge distribution and the kinematics of
produced $e^+e^-$ from the Breit-Wheeler process, and propose a criterion for
the validity of the Breit-Wheeler process in relativistic heavy-ion collisions.
Following this approach we demonstrate that the experimental measurements of
the Breit-Wheeler process in ultra-relativistic heavy-ion collisions can be
used to quantitatively constrain the nuclear charge radius. The extracted
parameters show sensitivity to the impact parameter dependence, and can be used
to study the initial-state and final-state effects in hadronic interactions.

Nuclear Theory;High Energy Physics - Phenomenology;Nuclear Experiment