A new measurement of the Collins and Sivers asymmetries on a transversely polarised deuteron target

TL;DR

This paper presents high-precision measurements of the Collins and Sivers asymmetries in deep-inelastic scattering on a transversely polarised deuteron target, finding results compatible with zero within improved statistical accuracy.

Contribution

It provides the most precise measurements to date of these asymmetries on a deuteron target, enhancing understanding of nucleon spin structure.

Findings

Both asymmetries are compatible with zero within errors.

Statistical errors are more than twice smaller than previous results.

Results are compared with theoretical models and previous data.

Abstract

New high precision measurements of the Collins and Sivers asymmetries of charged hadrons produced in deep-inelastic scattering of muons on a transversely polarised 6LiD target are presented. The data were taken in 2003 and 2004 with the COMPASS spectrometer using the muon beam of the CERN SPS at 160 GeV/c. Both the Collins and Sivers asymmetries turn out to be compatible with zero, within the present statistical errors, which are more than a factor of 2 smaller than those of the published COMPASS results from the 2002 data. The final results from the 2002, 2003 and 2004 runs are compared with naive expectations and with existing model calculations.