Investigating $^{238}$U Deformation via Dilepton Production in Relativistic Heavy-Ion Collisions

TL;DR

This study shows that dilepton production in uranium-uranium collisions at high energy is linearly related to nuclear deformation, offering a new way to measure the shape of the nucleus using relativistic heavy-ion collision data.

Contribution

It introduces a modified transport model to connect dilepton yields with nuclear deformation, revealing a linear dependence and greater sensitivity in the intermediate-mass region.

Findings

Dilepton yields depend linearly on deformation parameter $eta_2^2$.

Higher sensitivity of dileptons to deformation in the intermediate-mass region.

Potential for using dilepton measurements to determine nuclear deformation.

Abstract

Due to their weak coupling to the strongly interacting matter produced in relativistic heavy-ion collisions, dileptons serve as a sensitive probe of the initial geometry of the colliding nuclei. In this study, we investigate the influence of initial nuclear quadrupole deformation, characterized by the parameter $\beta_2$, on dilepton production in $U+U$ collisions at $\sqrt{s_{NN}}=196$ GeV. The analysis is varried out using a modified multiphase transport model in which partonic interactions are described by the Nambu-Jona-Lasinio model. We observe a clear linear dependence of dilepton yields on $\beta_2^2$ in both the low-mass region (LMR, $<1 GeV/c^2$) and intermediate-mass region (IMR, $1-3 GeV/c^2$) of the dilepton spectrum for the most central collisions. Also, dilepton production in the IMR region exhibits a stronger sensitivity to nuclear deformation than in the LMR, reflecting the dominance of earlier partonic processes in this mass range. These results suggest that precise measurements of dilepton yields in relativistic heavy-ion collisions can provide a viable means to determine the deformation parameter $\beta_2$ of $^{238}$U.