Production of $e^{+}e^{-}$ from U+U collisions at $\sqrt{s_{NN}}$ = 193 GeV and Au+Au collisions at $\sqrt{s_{NN}}$ = 19.6, 27, 39, 62.4, and 200 GeV as measured by STAR

TL;DR

This paper reports measurements of electron-positron pairs produced in U+U and Au+Au collisions at various energies, analyzing their spectra and yields to understand the properties and lifetime of the quark-gluon plasma formed.

Contribution

It provides new invariant mass spectra and continuum measurements across multiple collision energies, enhancing understanding of electromagnetic radiation in heavy-ion collisions.

Findings

Observation of $e^{+}e^{-}$ excess yields correlated with collision centrality.

Invariant mass spectra analyzed for different energies and collision systems.

Discussion of the relationship between $e^{+}e^{-}$ yields and fireball lifetime.

Abstract

We present STAR's measurement of the $e^{+}e^{-}$ continuum as a function of centrality, invariant mass, and transverse momentum for U+U collisions at $\sqrt{s_{NN}}$ = 193 GeV. Also reported are the acceptance-corrected $e^{+}e^{-}$ invariant mass spectra for minimum-bias Au+Au collisions at $\sqrt{s_{NN}}$ = 27, 39, and 62.4 GeV and U+U collisions at $\sqrt{s_{NN}}$ = 193 GeV. The connection between the integrated $e^{+}e^{-}$ excess yields normalized by charge particle multiplicity ($dN_{ch}/dy$) at mid-rapidity and the lifetime of the fireball is discussed.