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| Format: | Preprint |
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2026
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| Online Access: | https://arxiv.org/abs/2604.05814 |
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| _version_ | 1866917388309495808 |
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| author | CMS Collaboration |
| author_facet | CMS Collaboration |
| contents | The first measurement of coherent $Υ$(1S) meson photoproduction off heavy nuclei is performed using ultraperipheral lead-lead collisions collected by the CMS experiment at a nucleon-nucleon center-of-mass energy of 5.02 TeV. The nuclear gluonic structure is probed at a nucleon momentum fraction of order $x$ $\sim$ 10$^{-3}$, determined by the kinematics of the process. Owing to the large $Υ$(1S) mass, the measurement reaches the highest scale accessible so far through coherent vector-meson photoproduction, $μ^2$ = 22.4 GeV$^2$, where nonlinear quantum chromodynamics effects are expected to be minimal. In the $Υ$(1S) rapidity range $\lvert y\rvert$ $\lt$ 1, the ratio of the measured photoproduction cross section to a baseline model prediction that neglects nuclear effects is $S_{Υ\text{(1S)}}$ = 0.25 $\pm$ 0.06 (stat) $\pm$ 0.02 (syst), thereby demonstrating nuclear suppression in this process. Expressed in terms of a nuclear gluon suppression factor, the result yields $R_\text{g}^\text{Pb}$($x$ $\approx$ 10$^{-3}$, $μ^2$ = 22.4 GeV$^2$) = 0.55 $\pm$ 0.12 (stat) $\pm$ 0.02 (syst). The measured $R_\text{g}^\text{Pb}$ is only slightly larger than the values previously reported for coherent $ϕ$ photoproduction, despite the probed $μ^2$ differing by approximately two orders of magnitude. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2604_05814 |
| institution | arXiv |
| publishDate | 2026 |
| record_format | arxiv |
| spellingShingle | Observation of nuclear suppression in coherent $Υ$(1S) photoproduction off heavy nuclei at the LHC CMS Collaboration Nuclear Experiment High Energy Physics - Experiment Nuclear Theory The first measurement of coherent $Υ$(1S) meson photoproduction off heavy nuclei is performed using ultraperipheral lead-lead collisions collected by the CMS experiment at a nucleon-nucleon center-of-mass energy of 5.02 TeV. The nuclear gluonic structure is probed at a nucleon momentum fraction of order $x$ $\sim$ 10$^{-3}$, determined by the kinematics of the process. Owing to the large $Υ$(1S) mass, the measurement reaches the highest scale accessible so far through coherent vector-meson photoproduction, $μ^2$ = 22.4 GeV$^2$, where nonlinear quantum chromodynamics effects are expected to be minimal. In the $Υ$(1S) rapidity range $\lvert y\rvert$ $\lt$ 1, the ratio of the measured photoproduction cross section to a baseline model prediction that neglects nuclear effects is $S_{Υ\text{(1S)}}$ = 0.25 $\pm$ 0.06 (stat) $\pm$ 0.02 (syst), thereby demonstrating nuclear suppression in this process. Expressed in terms of a nuclear gluon suppression factor, the result yields $R_\text{g}^\text{Pb}$($x$ $\approx$ 10$^{-3}$, $μ^2$ = 22.4 GeV$^2$) = 0.55 $\pm$ 0.12 (stat) $\pm$ 0.02 (syst). The measured $R_\text{g}^\text{Pb}$ is only slightly larger than the values previously reported for coherent $ϕ$ photoproduction, despite the probed $μ^2$ differing by approximately two orders of magnitude. |
| title | Observation of nuclear suppression in coherent $Υ$(1S) photoproduction off heavy nuclei at the LHC |
| topic | Nuclear Experiment High Energy Physics - Experiment Nuclear Theory |
| url | https://arxiv.org/abs/2604.05814 |