Publication: Evidence for light-by-light scattering in ultraperipheral PbPb collisions at root S-NN=5.02 TeV
Дата
2019
Авторы
d'Enterria, D.
Sirunyan, A. M.
Tumasyan, A.
Adam, W.
Matveev, V.
Chadeeva, M.
Parygin, P.
Philippov, D.
Polikarpov, S.
Popova, E.
Journal Title
Journal ISSN
Volume Title
Издатель
Аннотация
Evidence for light-by-light (LbL) scattering, gamma gamma -> gamma gamma, in ultraperipheral PbPb collisions at a nucleon-nucleon center of-mass energy of 5.02 TeV is reported. LbL scattering processes are selected in events with just two photons produced, with transverse energy E-T(gamma) > 2 GeV, pseudorapidity vertical bar eta(gamma)vertical bar < 2.4; and diphoton invariant mass m(gamma gamma) > 5 GeV, transverse momentum p(T)(gamma gamma) < 1 GeV, and acoplanarity (1 - Delta phi(gamma gamma)/pi) < 0.01. After all selection criteria, 14 events are observed, compared to 11.1 +/- 1.1 (theo) and 3.8 +/- 1.3 (stat) events expected for signal and background processes respectively. The significance of the signal excess over the background-only hypothesis is 4.10 sigma. The measured fiducial LbL scattering cross section, sigma(fid)(gamma gamma -> gamma gamma) = 122 +/- 46 (stat) +/- 29 (syst) +/- 4 (theo) nb is consistent with the standard model prediction.
Описание
Ключевые слова
Цитирование
Evidence for light-by-light scattering in ultraperipheral PbPb collisions at root S-NN=5.02 TeV / d'Enterria, D [et al.] // NUCLEAR PHYSICS A. - 2019. - 982. - P. 791-794. - 10.1016/j.nuclphysa.2018.10.018