Evidence for light-by-light scattering in ultraperipheral PbPb collisions at √sNN = 5.02 TeV

D'Enterria, David and Sirunyan, A. M. and Tumasyan, A. R. and Adam, Wolfgang and Ambrogi, Federico and Md. Ali, Mohd. Adli (2019) Evidence for light-by-light scattering in ultraperipheral PbPb collisions at √sNN = 5.02 TeV. Nuclear Physics A, 982. pp. 791-794. ISSN 0375-9474

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Abstract

Evidence for light-by-light (LbL) scattering, γγ → γγ, in ultraperipheral PbPb collisions at a nucleon-nucleon centerof-mass energy of 5.02 TeV is reported. LbL scattering processes are selected in events with just two photons produced, with transverse energy Eγ T > 2 GeV, pseudorapidity |ηγ| < 2.4; and diphoton invariant mass mγγ > 5 GeV, transverse momentum pγγ T < 1 GeV, and acoplanarity (1 − Δφγγ/π) < 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 4.1σ. The measured fiducial LbL scattering cross section, σfid(γγ → γγ) = 122 ± 46 (stat) ±29 (syst) ±4 (theo) nb is consistent with the standard model prediction

Item Type:	Article (Journal)
Additional Information:	7861/71952
Uncontrolled Keywords:	Light-by-light scattering, Heavy ions, Ultraperipheral collisions, CMS, LHC
Subjects:	Q Science > Q Science (General) Q Science > QC Physics
Kulliyyahs/Centres/Divisions/Institutes (Can select more than one option. Press CONTROL button):	Kulliyyah of Science Kulliyyah of Science > Department of Physics
Depositing User:	Dr Mohd Adli MD Ali
Date Deposited:	03 May 2019 09:55
Last Modified:	12 Jul 2019 10:08
URI:	http://irep.iium.edu.my/id/eprint/71952

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