d'Enterria, D;
Sirunyan, AM;
Tumasyan, A;
Adam, W;
Ambrogi, F;
Asilar, E;
Bergauer, T;
... Woods, N; + view all
(2019)
Evidence for light-by-light scattering in ultraperipheral PbPb collisions at root S-NN=5.02 TeV.
Nuclear Physics A
, 982
pp. 791-794.
10.1016/j.nuclphysa.2018.10.018.
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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.
| Type: | Article |
|---|---|
| Title: | Evidence for light-by-light scattering in ultraperipheral PbPb collisions at root S-NN=5.02 TeV |
| Open access status: | An open access version is available from UCL Discovery |
| DOI: | 10.1016/j.nuclphysa.2018.10.018 |
| Publisher version: | https://doi.org/10.1016/j.nuclphysa.2018.10.018 |
| Language: | English |
| Additional information: | © 2018 The Authors. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/). |
| Keywords: | Light-by-light scattering, Heavy ions, Ultraperipheral collisions, CMS, LHC |
| UCL classification: | UCL UCL > Provost and Vice Provost Offices > UCL BEAMS UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences |
| URI: | https://discovery-pp.ucl.ac.uk/id/eprint/10070616 |
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