Single Spin Asymmetries at COMPASS with transverse target polarization

TL;DR

This paper reports on measurements of single-spin asymmetries in semi-inclusive deep-inelastic scattering at CERN's COMPASS experiment, providing insights into the nucleon's transverse spin structure and quark transverse momentum effects.

Contribution

It presents new experimental results on Collins and Sivers asymmetries for identified pions and kaons, advancing understanding of nucleon spin phenomena.

Findings

Observation of non-zero Collins asymmetries for pions and kaons.

Measurement of Sivers asymmetries indicating quark transverse momentum effects.

First results on two-hadron interference asymmetries in this context.

Abstract

COMPASS is a fixed target experiment at CERN investigating the spin structure of the nucleon and performing hadron spectroscopy. The transverse spin structure of the nucleon is studied in semi-inclusive deep-inelastic scattering of 160 GeV/c muons off a transversely polarized proton or deuteron target. In 2002-2005, a transversely polarized 6LiD, and in 2007 a transversely polarized NH3 target were used. To get access to the transversity distribution, different single-spin asymmetries have been measured: the Collins asymmetry, the hadron-pair asymmetry and the transverse lambda polarization. In addition, transverse momentum effects of quarks have been studied by the Sivers effect. New results for the Collins and the Sivers asymmetries on the proton for identified pions and kaons and for the two hadron interference asymmetry will be presented.