Transverse single spin asymmetries at small x and the anomalous magnetic moment

TL;DR

This work identifies a spin-dependent odderon generated by axial distortions in the transverse color-source distribution of a transversely polarized proton within the MV model as the leading source of transverse single spin asymmetries at small $x$. The polarized odderon induces SSA in backward-region jet production in $pp$ collisions and in open-charm SIDIS, with a strength controlled by the proton’s anomalous magnetic moment contributions through the GPD ${ m E}$. A key result is the relation between the $k_ot$-moment of the polarized odderon and the C-odd tri-gluon correlation, providing a bridge between CGC/saturation physics and collinear twist-3 formalisms and offering a concrete experimental test of the BLV odderon solution via the $x$-dependence of SSAs. The paper outlines extensions to other processes and outlines a program to compare CGC-based and twist-3 predictions for SSAs at small $x$.

Abstract

We show that in the Mclerran-Venugopalan model, an axial asymmetrical valence quark distributions in the transverse plane of a transversely polarized proton can give rise to a spin dependent odderon. Such polarized odderon is responsible for the transverse single spin asymmetries(SSAs) for jet production in the backward region of pp collisions and open charm production in semi-inclusive DIS process.