Triple Regge exchange and transverse single-spin asymmetries of the very forward neutral pion production in polarized $p+p$ collisions

TL;DR

This paper analyzes large transverse single-spin asymmetries in very forward neutral pion production in polarized proton-proton collisions at 510 GeV, using triple Regge exchange models to interpret the data as diffractive processes.

Contribution

It introduces a novel application of baryonic triple Regge exchanges to describe RHICf data on forward neutral pion asymmetries at low transverse momentum.

Findings

Large asymmetries observed at high pseudorapidity and low p_T.

Triple Regge exchange model successfully describes the data.

Neutral pion production at low p_T interpreted as diffractive.

Abstract

Recently, the RHICf Collaboration measured the transverse single-spin asymmetries of the very forward neutral pion in polarized $p+p$ collisions at $\sqrt{s}=510$ GeV, produced at large pseudorapidity ($\eta\gtrsim 6$). The data show large asymmetries both in longitudinal momentum fraction $x_F$ and transverse momentum $p_T$ at $p_T<1\,\mathrm{GeV}/c$. Employing baryonic triple Regge exchanges, we describe the complete RHICf data for the first time and show that the neutral pion production at low $p_T$ can be interpreted as a diffractive one.