Calculation of electron-positron production in supercritical uranium-uranium collisions near the Coulomb barrier

TL;DR

This study solves the time-dependent Dirac equation for uranium-uranium collisions near the Coulomb barrier to analyze electron-positron pair production and identify signatures of QED vacuum decay.

Contribution

It introduces a detailed computational approach to simulate pair production in supercritical heavy-ion collisions using a mapped Fourier grid method.

Findings

Observed signatures of spontaneous pair creation in supercritical U-U collisions.

Compared pair production spectra between subcritical and supercritical collisions.

Identified differences in electron-positron spectra related to nuclear sticking times.

Abstract

The time-dependent Dirac equation was solved for zero-impact-parameter bare U-U collisions in the monopole approximation using a mapped Fourier grid matrix representation. A total of 2048 states including bound, as well as positive- and negative-energy states for an N=1024 spatial grid were propagated to generate occupation amplitudes as a function of internuclear separation. From these amplitudes spectra were calculated for total inclusive positron and electron production, and also the correlated spectra for ($e^+,e^-$) pair production. These were analyzed as a function of nuclear sticking time in order to establish signatures of spontaneous pair creation, i.e., QED vacuum decay. Subcritical Fr-Fr and highly supercritical Db-Db collisions both at the Coulomb barrier were also studied and contrasted with the U-U results.