Leading Neutrons From Polarized Proton-Nucleus Collisions

TL;DR

This paper investigates leading neutron production in polarized proton-nucleus collisions, highlighting nuclear effects, interference mechanisms, and their impact on observed asymmetries, with some results aligning well and others remaining challenging.

Contribution

It extends the  interference mechanism to polarized pA collisions and analyzes nuclear effects on neutron production and asymmetries.

Findings

Nuclear effects significantly enhance absorptive corrections.

The interference mechanism explains the asymmetry in inelastic events.

Diffractive asymmetry remains unexpectedly large.

Abstract

Leading neutron production on protons is known to be subject to strong absorptive corrections, which have been under debate for a long time. On nuclear targets these corrections are significantly enhanced and push the partial cross sections of neutron production to the very periphery of the nucleus. As a result, the A-dependences of inclusive and diffractive neutron production turn out to be similar. The mechanism of \pi-a_1 interference, which successfully explained the observed single-spin asymmetry of neutrons in polarized pp interactions, is extended here to polarized pA collisions. Corrected for nuclear effects it explains well the magnitude and sign of the asymmetry A_N observed in inelastic events, resulting in a violent break up of the nucleus. However the excessive magnitude of A_N observed in the diffractive sample, remains a challenge.