Electromagnetic processes with quasireal photons in Pb plus Pb collisions: QED, QCD, and the QGP

Authors：Steinberg Peter; Aaboud M; Aad G; Abbott B; Abdinov O; Abeloos B; Abhayasinghe D K; Abidi S H; AbouZeid O S; Abraham N L; Abramowicz H; Abreu H; Abulaiti Y; Acharya B S; Adachi S; Adam L; Adamczyk L; Adelman J; Adersberger M; Adiguzel A; Adye T; Affolder A A; Afik Y; Agheorghiesei C; Aguilar Saavedra J A; Ahmadov F; Aielli G; Akatsuka S; Akesson T P A; Akilli E; Akimov A V; Alberghi G L; Albert J; Albicocco P; Alconada Verzini M J; Alderweireldt S; Aleksa M; Aleksandrov I N; Alexa C

Source：Nuclear Physics A, 2019, 982: 259-262.

DOI：10.1016/j.nuclphysa.2018.10.087

Electromagnetic processes, both photon-photon and photon-nucleus, are shown to be useful in studying aspects of QED, QCD, and potentially the QGP. Using lead-lead collisions at root s(NN) = 5.02 TeV, the ATLAS detector has performed measurements of exclusive dimuon production, light-by-light scattering (via exclusive diphoton production), and photo-nuclear dijet production. These are all important examples of ultraperipheral collisions, where the nuclei do not interact hadronically. A recent study of the opening angles of dimuons produced in hadronic heavy-ion collisions, after subtracting heavy-flavor backgrounds, demonstrates that the dimuons carry information correlated with the overlap geometry, potentially about the density of charges in the QGP itself.

• Institution
  中国科学院; 上海交通大学; 山东大学; 清华大学; 香港大学; 香港科技大学; 香港理工大学; 香港中文大学; 中国地震局; 南京大学