# Slow neutron production as a probe of hadron formation in high-energy $\gamma^*A$ reactions

## TL;DR

This paper investigates low-energy neutron production in high-energy photon and muon-induced nuclear reactions, using hybrid models to understand hadron formation and final state interactions, with implications for future collider experiments.

## Contribution

It provides new hybrid dynamical+statistical calculations of neutron production in $
u$- and photon-nucleus collisions, linking experimental data to hadron formation models and small-$x$ dynamics.

## Key findings

- E665 data shows strong suppression of final state interactions for hadrons above 1 GeV/c.
- Neutron multiplicity and $p_t$ spectra predictions for LHC and RHIC energies.
- Ultraperipheral heavy-ion collisions can probe small-$x$ dynamics and photon wave function components.

## Abstract

Deep Inelastic Scattering (DIS) experiments at the planned Electron-Ion Collider will be affected by details of the hadron formation inside the nuclear volume. Besides semi-inclusive particle production experiments decays of the target nucleus via emission of neutrons provide an additional opportunity to probe this domain. This paper reports on the hybrid dynamical+statistical calculations of low-energy neutron production in muon- and virtual photon-induced collisions with nuclei. We confirm the conclusion that the E665 data on neutron production in $\mu^-$ + Pb DIS at 470 GeV indicate a strong suppression of the final state interaction for hadrons with momenta above $\sim 1$ GeV/c. Ultraperipheral heavy-ion collisions at the Large Hadron Collider (LHC) and the Relativistic Heavy Ion Collider (RHIC) can be used to test this suppression. The calculations of the neutron multiplicity distributions and $p_t$-spectra in photon - nucleus collisions at the energies accessible at the LHC and RHIC are presented for several models of hadron formation. We argue that studies of neutron production in ultraperipheral heavy ion collisions open a new window on the small-$x$ dynamics and hadron component of the photon wave function.