Coherent lepton pair production in hadronic heavy ion collisions

Abstract

Recently, significant enhancements of $e^{+} e^{-}$ pair production at very low transverse momentum ($p_{T} < 0.15$ GeV/c) were observed by the STAR collaboration in peripheral hadronic A+A collisions. This excesses can not be described by the QGP thermal radiation and $\rho$ in-medium broadening calculations. This is a sign of coherent photon-photon interactions, which were conventionally studied only in ultra-peripheral collisions. In this article, we present calculations of lepton pair ($e^{+}e^{-}$ and $\mu^{+}\mu^{-}$) production from coherent photon-photon interactions in hadronic A+A collisions at RHIC and LHC energies within the STAR and ALICE acceptance.