Please use this identifier to cite or link to this item: http://bura.brunel.ac.uk/handle/2438/19200
Title: Evidence for light-by-light scattering and searches for axion-like particles in ultraperipheral PbPb collisions at s<inf>NN</inf>=5.02TeV
Authors: Sirunyan, AM
Tumasyan, A
Adam, W
Ambrogi, F
Asilar, E
Bergauer, T
Brandstetter, J
Dragicevic, M
Erö, J
Escalante Del Valle, A
Flechl, M
Frühwirth, R
Ghete, VM
Hrubec, J
Jeitler, M
Krammer, N
Krätschmer, I
Liko, D
Madlener, T
Mikulec, I
Rad, N
Rohringer, H
Schieck, J
Schöfbeck, R
Spanring, M
Spitzbart, D
Taurok, A
Waltenberger, W
Wittmann, J
Wulz, CE
Zarucki, M
Chekhovsky, V
Mossolov, V
Suarez Gonzalez, J
De Wolf, EA
Di Croce, D
Janssen, X
Lauwers, J
Pieters, M
Van Haevermaet, H
Van Mechelen, P
Van Remortel, N
Abu Zeid, S
Blekman, F
D'Hondt, J
De Bruyn, I
De Clercq, J
Deroover, K
Flouris, G
Lontkovskyi, D
Lowette, S
Marchesini, I
Moortgat, S
Moreels, L
Python, Q
Skovpen, K
Tavernier, S
Van Doninck, W
Van Mulders, P
Van Parijs, I
Beghin, D
Bilin, B
Brun, H
Clerbaux, B
De Lentdecker, G
Delannoy, H
Dorney, B
Fasanella, G
Favart, L
Goldouzian, R
Grebenyuk, A
Kalsi, AK
Lenzi, T
Luetic, J
Postiau, N
Starling, E
Thomas, L
Vander Velde, C
Vanlaer, P
Vannerom, D
Wang, Q
Cornelis, T
Dobur, D
Fagot, A
Gul, M
Khvastunov, I
Poyraz, D
Roskas, C
Trocino, D
Tytgat, M
Verbeke, W
Vermassen, B
Vit, M
Zaganidis, N
Bakhshiansohi, H
Bondu, O
Brochet, S
Bruno, G
Caputo, C
David, P
Keywords: Light-by-light;CMS;UPC;Photoproduction;PbPb
Issue Date: 1-Aug-2019
Publisher: Elsevier
Citation: Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics, 2019, 797
Abstract: Evidence for the light-by-light scattering process, γγ → γγ , in ultraperipheral PbPb collisions at a centre-of-mass energy per nucleon pair of 5.02 TeV is reported. The analysis is conducted using a data sample corresponding to an integrated luminosity of 390 μb−1 recorded by the CMS experiment at the LHC. Light-by-light scattering processes are selected in events with two photons exclusively produced, each with transverse energy Eγ T > 2 GeV, pseudorapidity |ηγ | < 2.4, diphoton invariant mass mγγ > 5 GeV, diphoton transverse momentum pγγ T < 1 GeV, and diphoton acoplanarity below 0.01. After all selection criteria are applied, 14 events are observed, compared to expectations of 9.0 ± 0.9 (theo) events for the signal and 4.0 ± 1.2 (stat) for the background processes. The excess observed in data relative to the background-only expectation corresponds to a significance of 3.7 standard deviations, and has properties consistent with those expected for the light- by-light scattering signal. The measured fiducial light-by-light scattering cross section, σfid(γγ → γγ ) = 120±46 (stat)±28 (syst)±12 (theo) nb, is consistent with the standard model prediction. The mγγ distribution is used to set new exclusion limits on the production of pseudoscalar axion-like particles, via the γγ → a → γγ process, in the mass range ma = 5–90 GeV.
URI: http://bura.brunel.ac.uk/handle/2438/19200
DOI: http://dx.doi.org/10.1016/j.physletb.2019.134826
ISSN: 0370-2693
http://dx.doi.org/10.1016/j.physletb.2019.134826
Appears in Collections:Dept of Electronic and Computer Engineering Research Papers

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