Transverse force distributions in the proton from lattice QCD

TL;DR

This paper uses lattice QCD to calculate the spatial distribution of color-Lorentz forces inside the proton, providing insights into the mechanisms behind single-spin asymmetries in deep-inelastic scattering.

Contribution

It presents the first lattice QCD calculation of the spatial distribution of color-Lorentz forces in the proton, including spin-dependent and independent forces relevant to the Sivers asymmetry.

Findings

Identified a spin-independent confining force of about 3 GeV/fm.

Mapped spin-dependent force distributions related to the Sivers effect.

Provided a complementary picture of the mechanisms behind single-spin asymmetries.

Abstract

Single-spin asymmetries observed in polarised deep-inelastic scattering are important probes of hadron structure. The Sivers asymmetry has been the focus of much attention in QCD phenomenology and is yet to be understood at the quark level. In this Letter, we present a lattice QCD calculation of the spatial distribution of a colour-Lorentz force acting on the struck quark in a proton. We determine a spin-independent confining force, as well as spin-dependent force distributions with local forces on the order of 3 GeV/fm. These distributions offer a complementary picture of the Sivers asymmetry in transversely polarised deep-inelastic scattering.