Neutron emission in ultraperipheral Pb-Pb collisions at $\sqrt{s_{\mathrm{NN}}}=5.02$ TeV

Abstract

In ultraperipheral collisions (UPCs) of relativistic nuclei without overlap of nuclear densities, the two nuclei are excited by the Lorentz-contracted Coulomb fields of their collision partners. In these UPCs, the typical nuclear excitation energy is below a few tens of MeV, and a small number of nucleons are emitted in electromagnetic dissociation (EMD) of primary nuclei, in contrast to complete nuclear fragmentation in hadronic interactions. The cross sections of emission of given numbers of neutrons in UPCs of ${}^{208}$Pb nuclei at $\sqrt{s_{\mathrm{NN}}}=5.02$ TeV were measured with the neutron zero degree calorimeters (ZDCs) of the ALICE detector at the LHC, exploiting a similar technique to that used in previous studies performed at $\sqrt{s_{\mathrm{NN}}}=2.76$ TeV. In addition, the cross sections for the exclusive emission of one, two, three, four, and five forward neutrons in the EMD, not accompanied by the emission of forward protons, and thus mostly corresponding to the production of ${}^{207,206,205,204,203}$Pb, respectively, were measured for the first time. The predictions from the available models describe the measured cross sections well. These cross sections can be used for evaluating the impact of secondary nuclei on the LHC components, in particular, on superconducting magnets, and also provide useful input for the design of the Future Circular Collider (FCC-hh).

26 pages, 5 captioned figures, 7 tables, authors from page 21, published version, figures at http://alice-publications.web.cern.ch/node/8400

References in corpus (3)

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• A Centrality Detector Concept
• Two-Photon Interactions with Nuclear Breakup in Relativistic Heavy Ion Collisions

Cited by in corpus (6)

• The ALICE experiment: a journey through QCD
• Proton emission in ultraperipheral Pb-Pb collisions at $\sqrt{{\text{s}}_{\text{NN}}}=5.02$ TeV
• Design of a SiPM-on-Tile ZDC for the future EIC and its Performance with Graph Neural Networks
• Measurement of the impact-parameter dependent azimuthal anisotropy in coherent ${\rho }^0$ photoproduction in Pb$-$Pb collisions at $\sqrt{s_{\mathrm{NN}}}$ = 5.02 TeV
• Physics with high-luminosity proton-nucleus collisions at the LHC
• Impact of new results from the ultraperipheral collision on modeling the proton and neutron emission in photon-induced nuclear processes