Observation of forward neutron multiplicity dependence of dimuon acoplanarity in ultraperipheral Pb-Pb collisions at √sNN = 5.02 TeV

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=5.02TeV, with an integrated luminosity of approximately 1.5 nb−1, are co...

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Detalles Bibliográficos
Autores: CMS Collaboration, Cabrillo, I. J., Calderon, Alicia, Chazin Quero, B., Duarte Campderros, J., Fernández-García, Marcos, Fernández Manteca, P. J., Gómez, Gervasio, Martínez-Rivero, Celso, Martínez Ruiz del Arbol, P., Matorras, Francisco, Piedra, Jonatan, Prieels, C., Ricci-Tam, F., Rodrigo Anoro, Teresa, Ruiz Jimeno, Alberto, Scodellaro, Luca, Vila, Iván, Vizán, J.
Tipo de recurso: artículo
Estado:Versión publicada
Fecha de publicación:2021
País:España
Institución:Consejo Superior de Investigaciones Científicas (CSIC)
Repositorio:DIGITAL.CSIC. Repositorio Institucional del CSIC
OAI Identifier:oai:digital.csic.es:10261/260395
Acceso en línea:http://hdl.handle.net/10261/260395
Access Level:acceso abierto
Palabra clave:ddc:530
Descripción
Sumario: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=5.02TeV, 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<60GeV 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.