Single Spin Asymmetries on a transversely polarised proton target at COMPASS

TL;DR

This paper reports preliminary measurements of transverse spin asymmetries in semi-inclusive deep inelastic scattering off transversely polarized proton targets at COMPASS, providing insights into nucleon spin structure.

Contribution

It presents the first results of Collins and Sivers asymmetries for a proton target at COMPASS, comparing them with theoretical models.

Findings

Preliminary Collins asymmetry results for proton targets.

Preliminary Sivers asymmetry results for proton targets.

Comparison with existing model predictions.

Abstract

COMPASS is a running fixed-target experiment at the CERN SPS with a rich physics program focused on nucleon spin structure and on hadron spectroscopy. One of the main goals of the spin program is the measurement of the transverse spin effects in semi-inclusive DIS off transversely polarised nucleons. In the years 2002, 2003 and 2004 data have been taken using a 160 $GeV/c$ naturally polarised $\mu^{+}$ beam and a deuterium target ($^{6}LiD$) transversely polarised respect to the beam direction. In 2007 the run year has been devoted to collect data with a proton ($NH_{3}$) target. The preliminary results for the Collins and Sivers asymmetries, extracted from the 2007 data with transverse target polarisation, are presented here. Results are also compared with existing model predictions.