Observation of strong nuclear suppression in exclusive $J/\psi$ photoproduction in Au$+$Au ultra-peripheral collisions at RHIC

Abstract

We report a measurement of exclusive $J/\psi$ photoproduction in Au$+$Au ultra-peripheral collisions at $\sqrt{s_{{}_{\mathrm{NN}}}}=200$ GeV using the STAR detector. For the first time, i) the rapidity correlation between $J/\psi$ photoproduction and neutron emission from nuclear breakups has been experimentally measured; ii) nuclear suppression factors are measured for both the coherent and incoherent $J/\psi$ production. At photon-nucleon center-of-mass energy of 25.0 GeV, the coherent and incoherent $J/\psi$ cross sections of Au nuclei are found to be $71\pm 10\%$ and $36\pm 7\%$, respectively, of that of free protons. The stronger suppression observed in the incoherent production provides a new experimental handle to study the initial-state parton density in heavy nuclei. Data are compared with theoretical models quantitatively.

Final published version

References in corpus (5)

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• Exclusive diffractive processes in electron-ion collisions
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Cited by in corpus (6)

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• Measurement of exclusive $J/\psi$ and $\psi (2S)$ production at $\sqrt{s}=13$ TeV
• Probing gluon fluctuations in nuclei with the first energy-dependent measurement of incoherent J/$\psi$ photoproduction in ultraperipheral PbPb collisions
• Probing Quantum Phenomena through Photoproduction in Relativistic Heavy-Ion Collisions
• Coherent photo- and electroproduction of charmonia on nuclear targets revisited: Green function formalism
• Observation of coherent $\varphi$(1020) meson photoproduction in ultraperipheral PbPb collisions at $\sqrt{s_{\text{NN}}}$ = 5.36 TeV