  Dilepton production provides a unique probe of the strong electromagnetic
field produced in heavy-ion collisions. To map out the behavior of its
transverse momentum broadening, we present a theoretical model based on the
equivalent photon approximation, and then we update it to make direct
comparisons with the recent experimental measurements. We find that the model
calculations can describe well, not only the average transverse momentum
squared of $e^{+}e^{-}$ pairs in Au--Au collisions at $\sqrt{s_{\rm NN}}=200$
GeV, but also the acoplanarity of $\mu^{+}\mu^{-}$ pairs in Pb--Pb collisions
at$\sqrt{s_{\rm NN}}=5.02$ TeV. Furthermore, the model predictions are also
able to reproduce the measured dependencies of the pair mass and the transverse
momentum squared.
