Impact of new results from ultraperipheral collisions on modeling the proton and neutron emission in photon-induced nuclear processes

Ultrarelativistic collisions of heavy ions provide a rich spectrum of possibilities to discuss the response of the nucleus to photons. Newly published neutron and proton multiplicities measured in the ALICE experiment in ultraperipheral collisions allow us to investigate the influence of the electromagnetic fields on colliding nuclei for the <a:math xmlns:a="http://www.w3.org/1998/Math/MathML"> <a:mrow> <a:mmultiscripts> <a:mi>Pb</a:mi> <a:mprescripts/> <a:none/> <a:mn>208</a:mn> </a:mmultiscripts> <a:mo>+</a:mo> <a:mmultiscripts> <a:mi>Pb</a:mi> <a:mprescripts/> <a:none/> <a:mn>208</a:mn> </a:mmultiscripts> </a:mrow> </a:math> at <b:math xmlns:b="http://www.w3.org/1998/Math/MathML"> <b:mrow> <b:msqrt> <b:msub> <b:mi>s</b:mi> <b:mrow> <b:mi>N</b:mi> <b:mi>N</b:mi> </b:mrow> </b:msub> </b:msqrt> <b:mo>=</b:mo> <b:mn>5.02</b:mn> </b:mrow> </b:math> TeV. The theoretical predictions are done within a hybrid model including equivalent photon approximations, GiBUU modeling of preequilibrium processes, and generation of the excited nuclear remnants, where decay is modeled by a statistical approach: GEM2 or <c:math xmlns:c="http://www.w3.org/1998/Math/MathML"> <c:mrow> <c:mtext>GEMINI</c:mtext> <c:mo>+</c:mo> <c:mo>+</c:mo> </c:mrow> </c:math> . The cross sections of the mass-charge distributions of nuclear remnants as well as the neutron, proton, and other charged particle multiplicities are estimated. We concentrate on production of protons and isotopes coming from the electromagnetic dissociation. Special attention is devoted to emission of a single proton. It is explained in the paper that cross section for <d:math xmlns:d="http://www.w3.org/1998/Math/MathML"> <d:mrow> <d:mn>1</d:mn> <d:mi>p</d:mi> </d:mrow> </d:math> emission is very close to maximal available one based on reactions of photon with individual nucleons (protons or neutrons) inside the nucleus.

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