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| Format: | Preprint |
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2024
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| Online Access: | https://arxiv.org/abs/2406.12630 |
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| _version_ | 1866910493297344512 |
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| author | Bizé, Nicolas |
| author_facet | Bizé, Nicolas |
| contents | Photon-photon reactions and the production of J/$ψ$ meson through photonuclear reactions have been extensively studied in ultra-peripheral heavy-ion collisions, in which the impact parameter is larger than twice the nuclear radius. In recent years, coherently photoproduced J/$ψ$ and dilepton production via photon-photon interactions have also been observed in nucleus-nucleus (A-A) collisions with nuclear overlap. The former can help to constrain the nuclear gluon distributions at low Bjorken-$x$ and high energy, while the latter could be used to further map the electromagnetic fields produced in heavy-ion collisions. In addition, these measurements can shed light on the theory behind photon-induced reactions in A-A collisions with nuclear overlap, including possible interactions of the measured probes with the formed and fast expanding quark-gluon plasma. Since the produced quarkonium is expected to keep the polarization of the incoming photon due to $s$-channel helicity conservation, the photoproduction origin of the J/$ψ$ yield excess at very low transverse momentum, $p_{\rm T}$, can be confirmed by the measurement of the J/$ψ$ polarization. The ALICE detector can perform quarkonium production measurements at both mid ($|y|<0.9$) and forward ($2.5<y<4$) rapidities down to $p_{\rm T} = 0$. In the following, the new ALICE measurements of the J/$ψ$ $y$-differential cross section and the first polarization results of coherently photoproduced J/$ψ$ via the dimuon decay channel at forward rapidity in Pb-Pb collisions at $\sqrt{s_{NN}}=$ 5.02 TeV are reported. Additionally, the measurement of an excess with respect to expectations from hadronic production in the dielectron yield, at low mass and $p_{\rm T}$, at midrapidity in Pb-Pb collisions at $\sqrt{s_{NN}}=$ 5.02~TeV, is presented. The results are compared with available theoretical models. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2406_12630 |
| institution | arXiv |
| publishDate | 2024 |
| record_format | arxiv |
| spellingShingle | Photoproduction of J/$ψ$ and dileptons in Pb-Pb collisions with nuclear overlap Bizé, Nicolas Nuclear Experiment High Energy Physics - Experiment Photon-photon reactions and the production of J/$ψ$ meson through photonuclear reactions have been extensively studied in ultra-peripheral heavy-ion collisions, in which the impact parameter is larger than twice the nuclear radius. In recent years, coherently photoproduced J/$ψ$ and dilepton production via photon-photon interactions have also been observed in nucleus-nucleus (A-A) collisions with nuclear overlap. The former can help to constrain the nuclear gluon distributions at low Bjorken-$x$ and high energy, while the latter could be used to further map the electromagnetic fields produced in heavy-ion collisions. In addition, these measurements can shed light on the theory behind photon-induced reactions in A-A collisions with nuclear overlap, including possible interactions of the measured probes with the formed and fast expanding quark-gluon plasma. Since the produced quarkonium is expected to keep the polarization of the incoming photon due to $s$-channel helicity conservation, the photoproduction origin of the J/$ψ$ yield excess at very low transverse momentum, $p_{\rm T}$, can be confirmed by the measurement of the J/$ψ$ polarization. The ALICE detector can perform quarkonium production measurements at both mid ($|y|<0.9$) and forward ($2.5<y<4$) rapidities down to $p_{\rm T} = 0$. In the following, the new ALICE measurements of the J/$ψ$ $y$-differential cross section and the first polarization results of coherently photoproduced J/$ψ$ via the dimuon decay channel at forward rapidity in Pb-Pb collisions at $\sqrt{s_{NN}}=$ 5.02 TeV are reported. Additionally, the measurement of an excess with respect to expectations from hadronic production in the dielectron yield, at low mass and $p_{\rm T}$, at midrapidity in Pb-Pb collisions at $\sqrt{s_{NN}}=$ 5.02~TeV, is presented. The results are compared with available theoretical models. |
| title | Photoproduction of J/$ψ$ and dileptons in Pb-Pb collisions with nuclear overlap |
| topic | Nuclear Experiment High Energy Physics - Experiment |
| url | https://arxiv.org/abs/2406.12630 |