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https://hdl.handle.net/11147/8500
Title: | Evidence for Light-By Scattering and Searches for Axion-Like Particles in Ultraperipheral Pbpb Collisions at Snn=5.02tev |
Authors: | Sirunyan, A.M. Tumasyan, A. Adam, W. Ambrogi, F. Asilar, E. Bergauer, T. Troshin, S. |
Keywords: | Cms Light-By-Light Pbpb Photoproduction Upc |
Publisher: | Elsevier B.V. |
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 5.02TeV is reported. The analysis is conducted using a data sample corresponding to an integrated luminosity of 390μb−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 ET γ>2GeV, pseudorapidity |ηγ|<2.4, diphoton invariant mass mγγ>5GeV, diphoton transverse momentum pT γγ<1GeV, 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 (Figure presented.) process, in the mass range (Figure presented.). © 2019 The Author(s) |
URI: | https://doi.org/10.1016/j.physletb.2019.134826 |
ISSN: | 0370-2693 |
Appears in Collections: | Rectorate / Rektörlük Scopus İndeksli Yayınlar Koleksiyonu / Scopus Indexed Publications Collection WoS İndeksli Yayınlar Koleksiyonu / WoS Indexed Publications Collection |
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