@article{10902/18222,
year = {2019},
month = {10},
url = {http://hdl.handle.net/10902/18222},
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 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.},
publisher = {Elsevier},
publisher = {Physics Letters B, 797 134826 (2019)},
title = {Evidence for light-by-light scattering and searches for axion-like particles in ultraperipheral PbPb collisions at √sNN=5.02TeV},
author = {Sirunyan, A. M. and Cabrillo Bartolomé, José Iban and Calderón Tazón, Alicia and Chazin Quero, Bárbara and Duarte Campderros, Jorge and Fernández García, Marcos and Fernández Manteca, Pedro José and García Alonso, Andrea and García Ferrero, Juan and Gómez Gramuglio, Gervasio and López Virto, María Amparo and Marco de Lucas, Jesús and Martínez Rivero, Celso and Martínez Ruiz del Árbol, Pablo and Matorras Weinig, Francisco and Piedra Gómez, Jonatan and Prieëls, Cédric and Rodrigo Anoro, Teresa and Ruiz Jimeno, Alberto and Scodellaro, Luca and Trevisani, Nicolo and Vila Álvarez, Iván  and Vilar Cortabitarte, Rocío},
}