Quasireal photons exchanged in relativistic heavy ion interactions are powerful probes of the gluonic structure of nuclei. The coherent J=ψ photoproduction cross section in ultraperipheral lead-lead collisions is measured as a function of photon-nucleus center-of-mass energies per nucleon (WPbγN) over a wide range of 40 < WPbγN < 400 GeV. Results are obtained using data at the nucleon-nucleon center-of-mass energy of 5.02 TeV collected by the CMS experiment at the CERN LHC, corresponding to an integrated luminosity of 1.52 nb−1. The cross section is observed to rise rapidly at low WPbγN, and plateau above WPbγN ≈ 40 GeV, up to 400 GeV, entering a new regime of small Bjorken-x (≈6 × 10−5) gluons being probed in a heavy nucleus. The observed energy dependence is not predicted by current quantum chromodynamic models.

Probing Small Bjorken-x Nuclear Gluonic Structure via Coherent J/ψ Photoproduction in Ultraperipheral Pb-Pb Collisions at sqrt[s_{NN}]=5.02 TeV

Bruschini, D.;
2023

Abstract

Quasireal photons exchanged in relativistic heavy ion interactions are powerful probes of the gluonic structure of nuclei. The coherent J=ψ photoproduction cross section in ultraperipheral lead-lead collisions is measured as a function of photon-nucleus center-of-mass energies per nucleon (WPbγN) over a wide range of 40 < WPbγN < 400 GeV. Results are obtained using data at the nucleon-nucleon center-of-mass energy of 5.02 TeV collected by the CMS experiment at the CERN LHC, corresponding to an integrated luminosity of 1.52 nb−1. The cross section is observed to rise rapidly at low WPbγN, and plateau above WPbγN ≈ 40 GeV, up to 400 GeV, entering a new regime of small Bjorken-x (≈6 × 10−5) gluons being probed in a heavy nucleus. The observed energy dependence is not predicted by current quantum chromodynamic models.
2023
Settore PHYS-01/A - Fisica sperimentale delle interazioni fondamentali e applicazioni
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11384/154757
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