Azimuthal single- and double-spin asymmetries in semi-inclusive deep-inelastic lepton scattering by transversely polarized protons

TL;DR

This paper reports comprehensive measurements of azimuthal asymmetries in semi-inclusive deep-inelastic scattering with transversely polarized protons, revealing significant effects related to the worm-gear (II) distribution and other asymmetries.

Contribution

It extends previous analyses to include protons and antiprotons, employs three-dimensional kinematic binning, and provides new insights into spin-dependent distributions in nucleons.

Findings

Significant $ ext{cos}( ext{ extphi}- ext{ extphi}_S)$ modulation indicates a sizable $g_{1T}$ distribution.

Most asymmetries are consistent with zero, except for large $ ext{ extsin}( ext{ extphi}_S)$ modulations for charged pions and positive kaons.

Extended analysis includes additional particle types and kinematic binning, enhancing understanding of spin asymmetries.

Abstract

A comprehensive set of azimuthal single-spin and double-spin asymmetries in semi-inclusive leptoproduction of pions, charged kaons, protons, and antiprotons from transversely polarized protons is presented. These asymmetries include the previously published HERMES results on Collins and Sivers asymmetries, the analysis of which has been extended to include protons and antiprotons and also to an extraction in a three-dimensional kinematic binning and enlarged phase space. They are complemented by corresponding results for the remaining four single-spin and four double-spin asymmetries allowed in the one-photon-exchange approximation of the semi-inclusive deep-inelastic scattering process for target-polarization orientation perpendicular to the direction of the incoming lepton beam. Among those results, significant non-vanishing $\cos{\phi-\phi_S}$ modulations provide evidence for a sizable worm-gear (II) distribution, $g_{1T}$. Most of the other modulations are found to be consistent with zero with the notable exception of large $\sin{\phi_S}$ modulations for charged pions and positive kaons.