Observation of coherent $ϕ$(1020) meson photoproduction in ultraperipheral PbPb collisions at $\sqrt{s_\text{NN}}$ = 5.36 TeV
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arXiv
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| Format: | Preprint |
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2025
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| _version_ | 1866917197326057472 |
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| author | CMS Collaboration |
| author_facet | CMS Collaboration |
| contents | The first observation of coherent $ϕ$(1020) meson photoproduction off heavy nuclei is presented using ultraperipheral lead-lead collisions at a center-of-mass energy per nucleon pair of 5.36 TeV. The data were collected by the CMS experiment and correspond to an integrated luminosity of 1.62 $μ$b$^{-1}$. The $ϕ$(1020) meson signals are reconstructed via the K$^+$K$^-$ decay channel. The production cross section is presented as a function of the $ϕ$(1020) meson rapidity in the range 0.3 $\lt$ $\lvert y\rvert$ $\lt$ 1.0, probing gluons that carry a fraction of the nucleon momentum ($x$) around $10^{-4}$. The observed cross section exhibits little dependence on rapidity and is significantly suppressed, by a factor of ${\sim}$5, compared to a baseline model that treats a nucleus as a collection of free nucleons. Theoretical models that incorporate the nuclear shadowing effect generally provide a better description of the $ϕ$(1020) data than those incorporating gluon saturation. This study establishes a powerful new tool for exploring nuclear effects and nuclear gluonic structure in the small-$x$ regime at a unique energy scale bridging the perturbative and nonperturbative quantum chromodynamics domains. |
| format | Preprint |
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arxiv_https___arxiv_org_abs_2504_05193 |
| institution | arXiv |
| publishDate | 2025 |
| record_format | arxiv |
| spellingShingle | Observation of coherent $ϕ$(1020) meson photoproduction in ultraperipheral PbPb collisions at $\sqrt{s_\text{NN}}$ = 5.36 TeV CMS Collaboration Nuclear Experiment High Energy Physics - Experiment The first observation of coherent $ϕ$(1020) meson photoproduction off heavy nuclei is presented using ultraperipheral lead-lead collisions at a center-of-mass energy per nucleon pair of 5.36 TeV. The data were collected by the CMS experiment and correspond to an integrated luminosity of 1.62 $μ$b$^{-1}$. The $ϕ$(1020) meson signals are reconstructed via the K$^+$K$^-$ decay channel. The production cross section is presented as a function of the $ϕ$(1020) meson rapidity in the range 0.3 $\lt$ $\lvert y\rvert$ $\lt$ 1.0, probing gluons that carry a fraction of the nucleon momentum ($x$) around $10^{-4}$. The observed cross section exhibits little dependence on rapidity and is significantly suppressed, by a factor of ${\sim}$5, compared to a baseline model that treats a nucleus as a collection of free nucleons. Theoretical models that incorporate the nuclear shadowing effect generally provide a better description of the $ϕ$(1020) data than those incorporating gluon saturation. This study establishes a powerful new tool for exploring nuclear effects and nuclear gluonic structure in the small-$x$ regime at a unique energy scale bridging the perturbative and nonperturbative quantum chromodynamics domains. |
| title | Observation of coherent $ϕ$(1020) meson photoproduction in ultraperipheral PbPb collisions at $\sqrt{s_\text{NN}}$ = 5.36 TeV |
| topic | Nuclear Experiment High Energy Physics - Experiment |
| url | https://arxiv.org/abs/2504.05193 |