Neutron emission associated with $\gamma\gamma\to\gamma\gamma$ scattering in UPC of heavy ions at the LHC

TL;DR

This paper calculates neutron emission cross sections associated with photon-photon scattering in ultra-peripheral heavy ion collisions at the LHC, providing detailed predictions for various neutron emission classes and distributions.

Contribution

It introduces a detailed calculation of neutron emission cross sections linked to photon-photon scattering in UPCs, validated against existing data, and offers predictions for experimental testing.

Findings

Good agreement with existing $ ho^0$ production data.

Predictions for neutron class cross sections and distributions.

Distinct impact parameter and photon distribution shapes for different neutron classes.

Abstract

We calculate cross sections for the production of different neutron classes $0n 0n$, $0nXn+Xn0n$ and $Xn Xn$, possible to measure in Zero Degree Calorimeters (ZDCs), associated with photon-photon scattering in UPC of lead on lead. The calculations are performed for the ATLAS kinematics. Our calculations for neutron classes are tested against existing data for $\rho^0$ production in UPC. We get a good agreement for absolute cross section as well as very good results for fractional cross section which gives confidence to the analogous calculation for diphoton production, corresponding to $\gamma \gamma \to \gamma \gamma$ scattering. We present both absolute as well as fractional cross sections for the different neutron classes. We also show different distributions in impact parameter, photon rapidity, transverse momentum, diphoton invariant mass and photon rapidity difference. The shapes of the photon distributions depend on the neutron classes which we quantify in this paper. It would be valuable to test our predictions using the ATLAS main detector and the ATLAS ZDCs.