Evidence for light-by-light scattering in ultraperipheral PbPb collisions at sNN=5.02TeV

CMS Collaboration

Risultato della ricerca: Contributo su rivistaArticolo in rivistapeer review

Abstract

Evidence for light-by-light (LbL) scattering, γγ→γγ in ultraperipheral PbPb collisions at a nucleon-nucleon center-of-mass energy of 5.02 TeV is reported. LbL scattering processes are selected in events with just two photons produced, with transverse energy ET γ>2GeV, pseudorapidity |ηγ|<2.4; and diphoton invariant mass mγγ>5GeV, transverse momentum pT γγ<1GeV, 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.

Lingua originaleInglese
pagine (da-a)791-794
Numero di pagine4
RivistaNuclear Physics A
Volume982
DOI
Stato di pubblicazionePubblicato - feb 2019
Pubblicato esternamente

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