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| Format: | Preprint |
| Published: |
2025
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| Online Access: | https://arxiv.org/abs/2511.21239 |
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| _version_ | 1866912730505543680 |
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| author | Humlova, Vendulka |
| author_facet | Humlova, Vendulka |
| contents | A new phenomenon, gluon saturation, is expected to emerge in quantum chromodynamics (QCD) at high energies, when gluon splitting and recombination processes reach a dynamic equilibrium. In heavy nuclei, this balance is expected to be achieved at lower energies than in protons, making lead-lead collisions at the LHC an ideal environment to probe the onset of saturation. The diffractive photoproduction of the $J/ψ$ vector meson provides an excellent tool to study this regime since it directly probes the gluon distribution in the target. ALICE offers unique kinematic coverage of the photon-nucleon centre-of-mass energy, spanning from 20 to 800 GeV, corresponding to three orders of magnitude in Bjorken-$x$ from about $10^{-2}$ down to $10^{-5}$. This contribution presents the latest ALICE results on the energy dependence of coherent $J/ψ$ production, which is sensitive to the average gluon density, and on the energy and Mandelstam-$t$ dependence of incoherent production, which probes fluctuations of the gluon field at different spatial scales. These measurements provide unprecedented constraints on models of QCD in the high-energy limit and mark a milestone in studying the gluonic structure of nuclei. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2511_21239 |
| institution | arXiv |
| publishDate | 2025 |
| record_format | arxiv |
| spellingShingle | First measurement of the energy and Mandelstam-$t$ dependence of both coherent and incoherent $J/ψ$ photonuclear production Humlova, Vendulka Nuclear Experiment A new phenomenon, gluon saturation, is expected to emerge in quantum chromodynamics (QCD) at high energies, when gluon splitting and recombination processes reach a dynamic equilibrium. In heavy nuclei, this balance is expected to be achieved at lower energies than in protons, making lead-lead collisions at the LHC an ideal environment to probe the onset of saturation. The diffractive photoproduction of the $J/ψ$ vector meson provides an excellent tool to study this regime since it directly probes the gluon distribution in the target. ALICE offers unique kinematic coverage of the photon-nucleon centre-of-mass energy, spanning from 20 to 800 GeV, corresponding to three orders of magnitude in Bjorken-$x$ from about $10^{-2}$ down to $10^{-5}$. This contribution presents the latest ALICE results on the energy dependence of coherent $J/ψ$ production, which is sensitive to the average gluon density, and on the energy and Mandelstam-$t$ dependence of incoherent production, which probes fluctuations of the gluon field at different spatial scales. These measurements provide unprecedented constraints on models of QCD in the high-energy limit and mark a milestone in studying the gluonic structure of nuclei. |
| title | First measurement of the energy and Mandelstam-$t$ dependence of both coherent and incoherent $J/ψ$ photonuclear production |
| topic | Nuclear Experiment |
| url | https://arxiv.org/abs/2511.21239 |