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Committee for collaboration of Czech Republic

with Joint Institute for Nuclear Research in Dubna Login
Evidence for light-by-light scattering in ultraperipheral PbPb collisions at root S-NN=5.02 TeV

Author
Sirunyan A.M. Yerevan Physics Institute, Armenia
Finger Miroslav, prof. Ing. DrSc. Faculty of Mathematics and Physics, Charles University in Prague
Finger Michael, M.Sc. CSc. Faculty of Mathematics and Physics, Charles University in Prague, JINR Dubna
Korenkov V. JINR
et al.  different institutions

Year
2019

Scientific journal
NUCLEAR PHYSICS A 982 791-794

Web


Abstract
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.

Cite article as:
A. Sirunyan, M. Finger, M. Finger, V. Korenkov, . et al., "Evidence for light-by-light scattering in ultraperipheral PbPb collisions at root S-NN=5.02 TeV ", NUCLEAR PHYSICS A 982 791-794 (2019)