Observation of the Naive-T-odd Sivers Effect in Deep-Inelastic Scattering

TL;DR

This paper reports the first observation of a naive-T-odd Sivers effect in deep-inelastic scattering, indicating a transverse-momentum-dependent parton distribution function, through measured azimuthal asymmetries in pion and kaon production.

Contribution

It provides experimental evidence for the naive-T-odd Sivers function in deep-inelastic scattering, advancing understanding of spin-momentum correlations in nucleons.

Findings

Non-zero Sivers asymmetries for pi+, pi0, K+, and K-

Evidence of a naive-T-odd transverse-momentum-dependent distribution

Differences observed between pi+ and pi- cross sections

Abstract

Azimuthal single-spin asymmetries of lepto-produced pions and charged kaons were measured on a transversely polarized hydrogen target. Evidence for a naive-T-odd, transverse-momentum-dependent parton distribution function is deduced from non-vanishing Sivers effects for pi+, pi0, and K+, K-, as well as in the difference of the pi+ and pi- cross sections.