Sivers asymmetry extracted in SIDIS at the hard scale of the Drell-Yan process at COMPASS

TL;DR

This paper reports on the extraction of Sivers asymmetries from COMPASS semi-inclusive deep inelastic scattering data across different Q^2 regions, enabling future comparison with Drell-Yan measurements to test QCD predictions.

Contribution

It provides the first simultaneous extraction of Sivers asymmetries in SIDIS at various Q^2 regions aligned with Drell-Yan kinematics, facilitating direct comparison of transverse-momentum-dependent PDFs.

Findings

Sivers asymmetries are positive across measured regions.

Results are precise enough to test the predicted sign change of the Sivers function.

Kinematic dependences of asymmetries are presented in detail.

Abstract

Proton transverse-spin azimuthal asymmetries are extracted from the COMPASS 2010 semi-inclusive hadron measurements in deep inelastic muon-nucleon scattering in those four regions of the photon virtuality $Q^2$, which correspond to the four regions of the di-muon mass $\sqrt{Q^2}$ used in the ongoing analysis of the COMPASS Drell-Yan measurements. This allows for a future direct comparison of the nucleon transverse-momentum-dependent parton distribution functions extracted from these two alternative measurements. Various two-dimensional kinematic dependences are presented for the azimuthal asymmetries induced by the Sivers transverse-momentum-dependent parton distribution function. The integrated Sivers asymmetries are found to be positive with an accuracy that appears to be sufficient to test the sign change of the Sivers function predicted by Quantum Chromodynamics.