Observation of centrality-dependent acoplanarity for muon pairs produced via two-photon scattering in Pb+Pb collisions at $\sqrt{s_{\mathrm{NN}}}=5.02$ TeV with the ATLAS detector

Understand

This Letter presents a measurement of $\gamma \gamma \rightarrow \mu^{+} \mu^{-}$ production in Pb+Pb collisions recorded by the ATLAS detector at the Large Hadron Collider at $\sqrt{s_{\mathrm{NN}}}=5.02$ TeV with an integrated luminosity of 0.49 nb$^{-1}$.

• The azimuthal angle and transverse momentum correlations between the muons are measured as a function of collision centrality.
• The muon pairs are produced from $\gamma \gamma$ through the interaction of the large electromagnetic fields of the nuclei.
• The contribution from background sources of muon pairs is removed using a template fit method.