Probing Small Bjorken-x Nuclear Gluonic Structure via Coherent J=? Photoproduction in Ultraperipheral Pb-Pb Collisions at ?sNN = 5.02 TeV
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Dosyalar
Tarih
2023
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Yayıncı
American Physical Society
Erişim Hakkı
info:eu-repo/semantics/openAccess
Özet
Quasireal photons exchanged in relativistic heavy ion interactions are powerful probes of the gluonic structure of nuclei. The coherent J=? photoproduction cross section in ultraperipheral lead-lead collisions is measured as a function of photon-nucleus center-of-mass energies per nucleon (WPb?N) over a wide range of 40 < WPb?N < 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 WPb?N ? 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 CERN, for the CMS Collaboration.
Açıklama
Anahtar Kelimeler
Binary alloys; Germanium alloys; Heavy ions; Ion exchange; Lead alloys; Tellurium compounds; Center-of-mass energies; Centre-of-mass energies; Heaviest nuclei; Heavy ion interactions; Integrated luminosity; Lead collisions; Nucleon-nucleon; Pb-Pb collisions; Photoproductions; Relativistic heavy ions; Photons; article; controlled study; diagnosis
