Speaker
Description
Muon pairs produced via two-photon scattering processes in hadronic Pb+Pb collisions provide a potentially sensitive electromagnetic probe of the quark gluon plasma. First measurements by ATLAS and STAR of dileptons produced via two-photon scattering in non-ultra-peripheral (non-UPC) nucleus-nucleus collisions showed an unexpected centrality-dependent broadening of the angular correlation between the two leptons and/or of the two-lepton $p_{\mathrm{T}}$ distribution. Recent measurements by ATLAS with significantly increased statistics have allowed new features to be observed in the data, both in the yields of the pairs as well as in their angular distributions. This talk will summarize the differential measurements of the dependence of the pair-distribution on the transverse-momentum and rapidity of the two muons, as well as the dependence on the event centrality. The possible physics implications will also be discussed.
