Evidence for light-by-light scattering and searches for axion-like particles in ultraperipheral PbPb collisions at sNN=5.02TeV

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dc.citation.articleNumber134826en_US
dc.citation.journalTitlePhysics Letters Ben_US
dc.citation.volumeNumber797en_US
dc.contributor.authorThe CMS Collaborationen_US
dc.date.accessioned2019-11-05T17:30:05Zen_US
dc.date.available2019-11-05T17:30:05Zen_US
dc.date.issued2019en_US
dc.description.abstractEvidence 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 ETγ>2GeV, pseudorapidity |ηγ|<2.4, diphoton invariant mass mγγ>5GeV, diphoton transverse momentum pTγγ<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 Image 1 process, in the mass range Image 2.en_US
dc.identifier.citationThe CMS Collaboration. "Evidence for light-by-light scattering and searches for axion-like particles in ultraperipheral PbPb collisions at sNN=5.02TeV." <i>Physics Letters B,</i> 797, (2019) Elsevier: https://doi.org/10.1016/j.physletb.2019.134826.en_US
dc.identifier.digitallight-by-light-scatteringen_US
dc.identifier.doihttps://doi.org/10.1016/j.physletb.2019.134826en_US
dc.identifier.urihttps://hdl.handle.net/1911/107598en_US
dc.language.isoengen_US
dc.publisherElsevieren_US
dc.rightsThis is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).en_US
dc.rights.urihttp://creativecommons.org/licenses/by/4.0/).en_US
dc.titleEvidence for light-by-light scattering and searches for axion-like particles in ultraperipheral PbPb collisions at sNN=5.02TeVen_US
dc.typeJournal articleen_US
dc.type.dcmiTexten_US
dc.type.publicationpublisher versionen_US
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