Evidence for light-by-light scattering and searches for axion-like particles in ultraperipheral PbPb collisions at sNN=5.02TeV; Physics Letters B; Vol. 797

Evidence for light-by-light scattering and searches for axion-like particles in ultraperipheral PbPb collisions at sNN=5.02TeV; Physics Letters B; Vol. 797

Dettagli Bibliografici
Parent link:Physics Letters B
Vol. 797.— 2019.— [134826, 27 p.]
Ente Autore: Национальный исследовательский Томский политехнический университет Исследовательская школа физики высокоэнергетических процессов
Altri autori: Sirunyan А. М., Tumasyan A. R., Adam W. Wolfgang, Ambrogi F. Federico, Asilar E. Ece, Bergauer T. Thomas, Tyurin N. E. Nikolay Evgenjevich, Babaev A. A. Anton Anatoljevich, Okhotnikov V. V. Vitaly Vladimirovich
Riassunto:Title screen
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 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 process, in the mass range.
Lingua:inglese
Pubblicazione: 2019
Soggetti:
электронный ресурс
труды учёных ТПУ
light-by-light
CMS
UPC
photoproduction
PbPb
Accesso online:https://doi.org/10.1016/j.physletb.2019.134826
Natura: Elettronico Capitolo di libro
KOHA link:https://koha.lib.tpu.ru/cgi-bin/koha/opac-detail.pl?biblionumber=663655

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