Damping of forward neutrons in pp collisions

TL;DR

This paper calculates absorptive corrections to leading neutron production in pp collisions, revealing stronger damping effects than previously estimated and highlighting discrepancies with older ISR data.

Contribution

It introduces a novel approach applying corrections directly to spin amplitudes and identifies a specific proton Fock state responsible for absorption effects.

Findings

Non-flip amplitude is more suppressed by absorption than spin-flip.

Calculated cross sections are significantly smaller than ISR measurements.

Recent data from ZEUS and NA49 support the need to re-evaluate older experimental normalization.

Abstract

We calculate absorptive corrections to single pion exchange in the production of leading neutrons in pp collisions. Contrary to the usual procedure of convolving the survival probability with the cross section, we apply corrections to the spin amplitudes. The non-flip amplitude turns out to be much more suppressed by absorption than the spin-flip one. We identify the projectile proton Fock state responsible for the absorptive corrections as a color octet-octet 5-quarks configuration. Calculations within two very different models, color-dipole light-cone description, and in hadronic representation, lead to rather similar absorptive corrections. We found a much stronger damping of leading neutrons than in some of previous estimates. Correspondingly, the cross section is considerably smaller than was measured at ISR. However, comparison with recent measurements by the ZEUS collaboration of neutron production in deep-inelastic scattering provides a strong motivation for challenging the normalization of the ISR data. This conjecture is also supported by preliminary data from the NA49 experiment for neutron production in pp collisions at SPS.