Speaker
Description
Ultra-relativistic heavy-ion collisions are expected to produce some of the strongest magnetic fields ($10^{13}$ $-$ $10^{16}$ Tesla) in the universe. The initial strong electromagnetic fields have been proposed as a source of linearly-polarized, quasi-real photons that can interact via the Breit-Wheeler process to produce electron-positron pairs. The energy and momentum distribution of the produced electron-positron pairs provides precise information about the strength and spatial distribution of the colliding electromagnetic fields and the underlying nuclear charge distribution.
In this talk, we will present the lowest-order QED prediction for collision energy dependence of the cross section and the transverse momentum distribution of dielectrons from the Breit-Wheeler process in heavy-ion collisions, which are compared with STAR measurements and found to be sensitive to the nuclear charge distribution and the infrared-divergence of the ultra-Lorentz boosted Coulomb field. Following this approach we demonstrate that the experimental measurements of the Breit-Wheeler process in ultrarelativistic heavy-ion collisions can be used to quantitatively constrain the nuclear charge radius and map the magnetic fields. 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.
