Quasireal photons exchanged in relativistic heavy ion interactions are powerful probes of the gluonic structure of nuclei. The coherent J/psi photoproduction cross section in ultraperipheral lead-lead collisions is measured as a function of photon-nucleus center-of-mass energies per nucleon (W-gamma N(Pb)) over a wide range of 40 < W-gamma N(Pb) < 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 WPb.N, and plateau above W-gamma N(Pb) approximate to 40 GeV, up to 400 GeV, entering a new regime of small Bjorken-x (approximate to 6 x 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 √sNN = 5.02  TeV

Calligaris, L.;Aimè, C.;Asenov, P.;Bianchini, L.;Bossini, E.;Bruschini, D.;Ciocci, M. A.;Donato, S.;Messineo, A.;Musich, M.;Rizzi, A.;Tonelli, G.;Cipriani, M.;Marini, A. C.;
2023-01-01

Abstract

Quasireal photons exchanged in relativistic heavy ion interactions are powerful probes of the gluonic structure of nuclei. The coherent J/psi photoproduction cross section in ultraperipheral lead-lead collisions is measured as a function of photon-nucleus center-of-mass energies per nucleon (W-gamma N(Pb)) over a wide range of 40 < W-gamma N(Pb) < 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 WPb.N, and plateau above W-gamma N(Pb) approximate to 40 GeV, up to 400 GeV, entering a new regime of small Bjorken-x (approximate to 6 x 10(-5)) gluons being probed in a heavy nucleus. The observed energy dependence is not predicted by current quantum chromodynamic models.
2023
Tumasyan, A.; Adam, W.; Andrejkovic, J.  W.; Bergauer, T.; Chatterjee, S.; Damanakis, K.; Dragicevic, M.; Escalante Del Valle, A.; Hussain, P.  S.; Je...espandi
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11568/1231899
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