Observation of Forward Neutron Multiplicity Dependence of Dimuon Acoplanarity in Ultraperipheral Pb-Pb Collisions at √sNN = 5.02  TeV
Physical Review Letters 2021
Viesturs Veckalns

The first measurement of the dependence of γγ→μ+μ- production on the multiplicity of neutrons emitted very close to the beam direction in ultraperipheral heavy ion collisions is reported. Data for lead-lead interactions at sNN=5.02 TeV, with an integrated luminosity of approximately 1.5 nb-1, are collected using the CMS detector at the LHC. The azimuthal correlations between the two muons in the invariant mass region 8<mμμ<60 GeV are extracted for events including 0, 1, or at least 2 neutrons detected in the forward pseudorapidity range |η|>8.3. The back-to-back correlation structure from leading-order photon-photon scattering is found to be significantly broader for events with a larger number of emitted neutrons from each nucleus, corresponding to interactions with a smaller impact parameter. This observation provides a data-driven demonstration that the average transverse momentum of photons emitted from relativistic heavy ions has an impact parameter dependence. These results provide new constraints on models of photon-induced interactions in ultraperipheral collisions. They also provide a baseline to search for possible final-state effects on lepton pairs caused by traversing a quark-gluon plasma produced in hadronic heavy ion collisions.


DOI
10.1103/PhysRevLett.127.122001
Hipersaite
https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.127.122001

CMS Collaboration, A.M.Sirunyan, A.Tumasyan, V.Veckalns ... [et al.] Observation of Forward Neutron Multiplicity Dependence of Dimuon Acoplanarity in Ultraperipheral Pb-Pb Collisions at √sNN = 5.02  TeV. Physical Review Letters, 2021, Vol. 127, No. 12, Article number 122001. ISSN 0031-9007. e-ISSN 1079-7114. Available from: doi:10.1103/PhysRevLett.127.122001

Publikācijas valoda
English (en)
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