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| Format: | Preprint |
| Publié: |
2025
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| Accès en ligne: | https://arxiv.org/abs/2503.02139 |
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| _version_ | 1866918137613516800 |
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| author | CMS Collaboration |
| author_facet | CMS Collaboration |
| contents | Bound states of charm and anticharm quarks, known as charmonia, have a rich spectroscopic structure that can be used to probe the dynamics of hadron production in high-energy hadron collisions. Here, the cross section ratio of excited ($ψ$(2S)) and ground state (J/$ψ$) vector mesons is measured as a function of the charged-particle multiplicity in proton-lead (pPb) collisions at a center-of-mass (CM) energy per nucleon pair of 8.16 TeV. The data corresponding to an integrated luminosity of 175 nb$^{-1}$ were collected using the CMS detector. The ratio is measured separately for prompt and nonprompt charmonia in the transverse momentum range 6.5 $\lt$ $p_\text{T}$ $\lt$ 30 GeV and in four rapidity ranges spanning $-$2.865 $\lt$ $y_\text{CM}$ $\lt$ 1.935. For the first time, a statistically significant multiplicity dependence of the prompt cross section ratio is observed in proton-nucleus collisions. There is no clear rapidity dependence in the ratio. The prompt measurements are compared with a theoretical model which includes interactions with nearby particles during the evolution of the system. These results provide additional constraints on hadronization models of heavy quarks in nuclear collisions. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2503_02139 |
| institution | arXiv |
| publishDate | 2025 |
| record_format | arxiv |
| spellingShingle | Observation of the charged-particle multiplicity dependence of $σ_{ψ(2S)} / σ_{\text{J}/ψ}$ in pPb collisions at 8.16 TeV CMS Collaboration Nuclear Experiment High Energy Physics - Experiment Bound states of charm and anticharm quarks, known as charmonia, have a rich spectroscopic structure that can be used to probe the dynamics of hadron production in high-energy hadron collisions. Here, the cross section ratio of excited ($ψ$(2S)) and ground state (J/$ψ$) vector mesons is measured as a function of the charged-particle multiplicity in proton-lead (pPb) collisions at a center-of-mass (CM) energy per nucleon pair of 8.16 TeV. The data corresponding to an integrated luminosity of 175 nb$^{-1}$ were collected using the CMS detector. The ratio is measured separately for prompt and nonprompt charmonia in the transverse momentum range 6.5 $\lt$ $p_\text{T}$ $\lt$ 30 GeV and in four rapidity ranges spanning $-$2.865 $\lt$ $y_\text{CM}$ $\lt$ 1.935. For the first time, a statistically significant multiplicity dependence of the prompt cross section ratio is observed in proton-nucleus collisions. There is no clear rapidity dependence in the ratio. The prompt measurements are compared with a theoretical model which includes interactions with nearby particles during the evolution of the system. These results provide additional constraints on hadronization models of heavy quarks in nuclear collisions. |
| title | Observation of the charged-particle multiplicity dependence of $σ_{ψ(2S)} / σ_{\text{J}/ψ}$ in pPb collisions at 8.16 TeV |
| topic | Nuclear Experiment High Energy Physics - Experiment |
| url | https://arxiv.org/abs/2503.02139 |