Spatial resolution of dijet photoproduction in near-encounter ultraperipheral nuclear collisions
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| Main Authors: | , , , , |
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| Format: | Preprint |
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2024
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| _version_ | 1866910630005440512 |
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| author | Eskola, Kari J. Guzey, Vadim Helenius, Ilkka Paakkinen, Petja Paukkunen, Hannu |
| author_facet | Eskola, Kari J. Guzey, Vadim Helenius, Ilkka Paakkinen, Petja Paukkunen, Hannu |
| contents | We present next-to-leading order perturbative QCD predictions for inclusive dijet photoproduction in ultra-peripheral nucleus-nucleus collisions (UPCs) within the impact-parameter dependent equivalent photon approximation. Taking into account the finite size of both the photon-emitting and the target nucleus, we show that this process is sensitive to the transverse-plane geometry of the UPC events. We show that this leads to a sizeable, 20-40% effect for large values of the $z_γ$ variable in the dijet photoproduction cross section in lead-lead UPCs at 5.02 TeV compared to the widely-used pointlike approximation where the nuclear radius is accounted for only as a sharp cut-off in the photon flux calculation. This resolution of the spatial degrees of freedom is a result of having high-transverse-momentum jets in the final state, which at the large-$z_γ$ kinematics requires a highly energetic photon in the initial state, thus biasing the collisions to small impact-parameter ''near-encounter'' configurations. We further discuss the role of the forward-neutron event-class selection in isolating the photonuclear cross section in the nucleus-nucleus collisions, and employ the needed electromagnetic breakup survival factor in our predictions. |
| format | Preprint |
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arxiv_https___arxiv_org_abs_2404_09731 |
| institution | arXiv |
| publishDate | 2024 |
| record_format | arxiv |
| spellingShingle | Spatial resolution of dijet photoproduction in near-encounter ultraperipheral nuclear collisions Eskola, Kari J. Guzey, Vadim Helenius, Ilkka Paakkinen, Petja Paukkunen, Hannu High Energy Physics - Phenomenology We present next-to-leading order perturbative QCD predictions for inclusive dijet photoproduction in ultra-peripheral nucleus-nucleus collisions (UPCs) within the impact-parameter dependent equivalent photon approximation. Taking into account the finite size of both the photon-emitting and the target nucleus, we show that this process is sensitive to the transverse-plane geometry of the UPC events. We show that this leads to a sizeable, 20-40% effect for large values of the $z_γ$ variable in the dijet photoproduction cross section in lead-lead UPCs at 5.02 TeV compared to the widely-used pointlike approximation where the nuclear radius is accounted for only as a sharp cut-off in the photon flux calculation. This resolution of the spatial degrees of freedom is a result of having high-transverse-momentum jets in the final state, which at the large-$z_γ$ kinematics requires a highly energetic photon in the initial state, thus biasing the collisions to small impact-parameter ''near-encounter'' configurations. We further discuss the role of the forward-neutron event-class selection in isolating the photonuclear cross section in the nucleus-nucleus collisions, and employ the needed electromagnetic breakup survival factor in our predictions. |
| title | Spatial resolution of dijet photoproduction in near-encounter ultraperipheral nuclear collisions |
| topic | High Energy Physics - Phenomenology |
| url | https://arxiv.org/abs/2404.09731 |