Electromagnetic excitation of nuclei and neutron evaporation in ultrarelativistic ultraperipheral heavy ion collisions

Abstract

We present a new approach for calculating electromagnetic excitation of nuclei as well as probabilities of emission and distributions of neutrons from decays of excited nuclear systems for ultrarelativistic, ultraperipheral heavy ion collisions. Excitation functions for $\gamma$ + Pb $\to$ Pb${}^{\ast }$ are parametrized using physics-motivated components: excitation of giant resonances, quasi-deuteron absorption mechanism, excitation of nucleon resonances as well as high-energy dissociation of protons and neutrons. Neutron emission (up to 10 neutrons) from low-energy excitations of ${}^{208}$Pb is modelled in terms of the Hauser-Feshbach formalism. The probabilities of a given number of neutrons are calculated as a function of excitation energy in a Monte-Carlo code GEMINI. These functions are parametrized by smooth analytical functions. The results are compared to appropriate data for the $\gamma$ Pb $\to$ Pb${}^{\ast }$ $\to$ k n reaction. As an example the approach is used for calculating electromagnetic excitation in UPC processes. Both single photon and double photon excitations are included and discussed. Topological cross sections with a given number of neutrons in forward and backward directions are calculated in the calculation at the LHC energies. Excitation functions are presented. The results of calculation are compared with SPS and more recent ALICE experimental data and good agreement is achieved.

17 pages, 11 figures, 5 tables

References in corpus (6)

• The Physics of Ultraperipheral Collisions at the LHC
• Exclusive muon-pair productions in ultrarelativistic heavy-ion collisions: Realistic nucleus charge form factor and differential distributions
• Exclusive production of rho^0 rho^0 pairs in gamma-gamma collisions at RHIC
• The $\gamma \gamma \to J/\psi J/\psi$ reaction and the $J/\psi J/\psi$ pair production in exclusive ultraperipheral ultrarelativistic heavy ion collisions
• ${\pi }^{+}{\pi }^{-}$ and ${\pi }^0{\pi }^0$ pair production in photon-photon and in ultraperipheral ultrarelativistic heavy ion collisions
• Double -- photon exclusive processes with heavy quark -- heavy antiquark pairs in high-energy Pb-Pb collisions at LHC

Cited by in corpus (10)

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• Exclusive dimuon production in ultraperipheral Pb+Pb collisions at $\sqrt{s_{\mathrm{NN}}}=5.02$ TeV with ATLAS
• Centrality dependence of dilepton production via $\gamma \gamma$ processes from Wigner distributions of photons in nuclei
• Incoherent diffractive photoproduction of $J/\psi$ and ${\rm Y}$ on heavy nuclei in the color dipole approach
• Measurement of photonuclear jet production in ultra-peripheral Pb+Pb collisions at $\sqrt{s_{\text{NN}}}=5.02$ TeV with the ATLAS detector
• Neutron emission in ultraperipheral Pb-Pb collisions at $\sqrt{s_{\mathrm{NN}}}=5.02$ TeV
• Proton emission in ultraperipheral Pb-Pb collisions at $\sqrt{{\text{s}}_{\text{NN}}}=5.02$ TeV
• Photoproduction of light vector mesons in Xe-Xe ultraperipheral collisions at the LHC and the nuclear density of Xe-129
• Electromagnetic interaction of low transverse momentum electrons and positrons with heavy nuclei in ultra-peripheral ultra-relativistic heavy-ion collisions
• Impact of new results from the ultraperipheral collision on modeling the proton and neutron emission in photon-induced nuclear processes