Searching for gluon saturation effects in the momentum transfer dependence of coherent charmonium electroproduction off nuclei
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arXiv
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| Format: | Preprint |
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2025
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| author | Nemchik, J. Óbertová, J. |
| author_facet | Nemchik, J. Óbertová, J. |
| contents | We study for the first time the transverse momentum transfer distributions $dσ/dt$ in coherent production of charmonia in nuclear ultra-peripheral and electron-ion collisions within the QCD color dipole approach based on a rigorous Green function formalism. This allows us to treat properly the color transparency effects, as well as the higher and leading-twist shadowing corrections associated with the $|Q\bar Q\rangle$ and $|Q\bar QnG\rangle$ Fock components of the photon. While the multi-gluon photon fluctuations represent the dominant source of nuclear shadowing at kinematic regions related to the recent LHC and its future upgrade to LHeC, the upcoming electron-ion collider at RHIC will additionally require the proper incorporation of reduced quark shadowing. The latter effect leads to a significant decrease in the differential cross sections $dσ/dt$ compared to standard calculations based on the eikonal form for the dipole-nucleus amplitude. The leading-twist shadowing corrections, corresponding to a non-linear QCD evolution of a partial dipole-nucleus amplitude, reduce substantially charmonium $t$-distributions in the LHeC energy range. We predict a non-monotonic energy dependence of $dσ/dt$ suggesting so possible gluon saturation effects with increased onset at larger $t$-values. In addition to shadowing corrections, we study how the color transparency effects affect the shape of $t$-dependent nuclear modification factor. We also briefly discuss several aspects that can modify the charmonium production rate and thus may have a large impact on the search for gluon saturation effects. |
| format | Preprint |
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arxiv_https___arxiv_org_abs_2507_01531 |
| institution | arXiv |
| publishDate | 2025 |
| record_format | arxiv |
| spellingShingle | Searching for gluon saturation effects in the momentum transfer dependence of coherent charmonium electroproduction off nuclei Nemchik, J. Óbertová, J. High Energy Physics - Phenomenology High Energy Physics - Theory We study for the first time the transverse momentum transfer distributions $dσ/dt$ in coherent production of charmonia in nuclear ultra-peripheral and electron-ion collisions within the QCD color dipole approach based on a rigorous Green function formalism. This allows us to treat properly the color transparency effects, as well as the higher and leading-twist shadowing corrections associated with the $|Q\bar Q\rangle$ and $|Q\bar QnG\rangle$ Fock components of the photon. While the multi-gluon photon fluctuations represent the dominant source of nuclear shadowing at kinematic regions related to the recent LHC and its future upgrade to LHeC, the upcoming electron-ion collider at RHIC will additionally require the proper incorporation of reduced quark shadowing. The latter effect leads to a significant decrease in the differential cross sections $dσ/dt$ compared to standard calculations based on the eikonal form for the dipole-nucleus amplitude. The leading-twist shadowing corrections, corresponding to a non-linear QCD evolution of a partial dipole-nucleus amplitude, reduce substantially charmonium $t$-distributions in the LHeC energy range. We predict a non-monotonic energy dependence of $dσ/dt$ suggesting so possible gluon saturation effects with increased onset at larger $t$-values. In addition to shadowing corrections, we study how the color transparency effects affect the shape of $t$-dependent nuclear modification factor. We also briefly discuss several aspects that can modify the charmonium production rate and thus may have a large impact on the search for gluon saturation effects. |
| title | Searching for gluon saturation effects in the momentum transfer dependence of coherent charmonium electroproduction off nuclei |
| topic | High Energy Physics - Phenomenology High Energy Physics - Theory |
| url | https://arxiv.org/abs/2507.01531 |