TY - JOUR
T1 - Evidence for light-by-light scattering in ultraperipheral PbPb collisions at sNN=5.02TeV
AU - CMS Collaboration
AU - d'Enterria, David
N1 - Publisher Copyright:
© 2018
PY - 2019/2
Y1 - 2019/2
N2 - 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.
AB - 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.
KW - CMS
KW - Heavy ions
KW - LHC
KW - Light-by-light scattering
KW - Ultraperipheral collisions
UR - http://www.scopus.com/inward/record.url?scp=85060158155&partnerID=8YFLogxK
U2 - 10.1016/j.nuclphysa.2018.10.018
DO - 10.1016/j.nuclphysa.2018.10.018
M3 - Article
SN - 0375-9474
VL - 982
SP - 791
EP - 794
JO - Nuclear Physics A
JF - Nuclear Physics A
ER -