Probing small Bjorken-x nuclear gluonic structure via coherent J/ψ photoproduction in ultraperipheral PbPb collisions at sNN = 5.02 TeV

The CMS collaboration
Phys.Rev.Lett. 131 (2023) 262301, 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 (WγNPb), over a wide range of 40 < WγNPb< 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 nb1. The cross section is observed to rise rapidly at low WγNPb, and plateau above WγNPb 40 GeV, up to 400 GeV, a new regime of small Bjorken-x ( 6 × 105) gluons being probed in a heavy nucleus. The observed energy dependence is not predicted by current quantum chromodynamic models.

  • Table 1

    Data from Figure 2

    10.17182/hepdata.138867.v2/t1

    The differential coherent J/ψ photoproduction cross section as a function of rapidity, in different neutron multiplicity classes: 0n0n, 0nXn, XnXn...

  • Table 2

    Data from Figure 3

    10.17182/hepdata.138867.v2/t2

    The total coherent J/ψ photoproduction cross section as a function of photon-nuclear center-of-mass energy per nucleon WγNPb, measured in...

  • Table 3

    Data from Figure 4

    10.17182/hepdata.138867.v2/t3

    The nuclear gluon suppression factor RgPb as a function of Bjorken x extracted from the CMS measurement of the coherent...

  • Table 4

    Photon flux values used in Equation 2

    10.17182/hepdata.138867.v2/t4

    The photon flux values from STARLight as a function of rapidity, in different neutron multiplicity classes: 0n0n, 0nXn, and XnXn.

  • Flux Covariance Matrix 0n0n

    Covariance matrix for 0n0n

    10.17182/hepdata.138867.v2/t5

    The covariance matrix for the flux in the 0n0n neutron multiplicity class.

  • Flux Covariance Matrix 0nXn

    Covariance matrix for 0nXn

    10.17182/hepdata.138867.v2/t6

    The covariance matrix for the flux in the 0nXn neutron multiplicity class.

  • Flux Covariance Matrix XnXn

    Covariance matrix for XnXn

    10.17182/hepdata.138867.v2/t7

    The covariance matrix for the flux in the XnXn neutron multiplicity class.

  • Total covariance matrix

    Total covariance matrix for data from Figure 3

    10.17182/hepdata.138867.v2/t8

    The total covariance matrix of the total coherent photoproduction cross section as a function of photon-nuclear center-of-mass energy per nucleon...

  • Experimental covariance matrix

    Experimental covariance matrix for data from Figure 3

    10.17182/hepdata.138867.v2/t9

    The experimental covariance matrix of the total coherent photoproduction cross section as a function of photon-nuclear center-of-mass energy per nucleon...

  • Theoretical covariance matrix

    Theoretical covariance matrix for data from Figure 3

    10.17182/hepdata.138867.v2/t10

    The theoretical (photon flux) covariance matrix of the total coherent photoproduction cross section as a function of photon-nuclear center-of-mass energy...

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