Sivers Tomography from Charge and Angle Only

TL;DR

This paper introduces a novel, charge-based observable for probing the Sivers effect in deep-inelastic scattering, enabling a clean, angle-only measurement suitable for future Electron-Ion Collider experiments.

Contribution

It proposes the one-point charge-correlator (OPCC) as a new, theoretically robust method to measure the Sivers effect without relying on non-perturbative fragmentation functions.

Findings

The OPCC is IRC finite and factorizes into the Sivers distribution and a perturbative jet function.

Resummed predictions at N extsuperscript{3}LL accuracy for unpolarized distribution.

Validated the factorization against full fixed-order QCD calculations.

Abstract

We propose a one-point charge-correlator (OPCC) probe of the Sivers effect in back-to-back deep-inelastic scattering. This measurement uses only the signs and directions of charged tracks, with no calorimetric or particle-identification information required. The observable weights the final state by its electric charge and measures the azimuthal correlation between the charge flow and the transverse spin of the proton. This probe is shown to be IRC finite and admits a factorization involving the usual Sivers distribution and a perturbatively calculable charge-weighted jet function for small transverse seperation $b\ll \Lambda_{\rm QCD}^{-1}$, with no reliance on non-perturbative fragmentation functions or track functions due to charge conservation. We validate the factorization against the full fixed-order QCD and present resummed predictions at N\(^3\)LL accuracy for the unpolarized distribution and N\(^2\)LL for the Sivers asymmetry. The OPCC provides a theoretically clean and simple experimental measurement, and establishes a charge-and-angle measurement paradigm for spin physics at a future Electron-Ion Collider.