Probing the Sivers function with an unpolarized target: GTMD distributions and the Odderons

TL;DR

This paper reveals that the gluon Sivers function can be directly probed through exclusive pion production in unpolarized electron-proton scattering, linking it to the QCD Odderon, challenging previous beliefs about its association with polarized targets.

Contribution

It introduces a novel method to probe the gluon Sivers function using unpolarized targets via the QCD Odderon, expanding the understanding of spin-momentum correlations.

Findings

Exclusive pion production in unpolarized scattering probes the gluon Sivers function.

The connection between the Sivers function and the QCD Odderon is established.

The approach offers a new way to study spin-dependent gluon distributions.

Abstract

It is commonly believed that the Sivers function has uniquely to do with processes involving a transversely polarized nucleon. In this paper we show that it is not necessarily the case. We demonstrate that exclusive pion production in $un$polarized electron-proton scattering in the forward region is a direct probe of the gluon Sivers function due to its connection to the QCD Odderon.