New measurement of transverse spin effects in (di-)hadron production from muon-deuteron semi-inclusive DIS at COMPASS

TL;DR

This paper reports new measurements of transverse spin asymmetries in (di-)hadron production from muon-deuteron deep inelastic scattering at COMPASS, providing more precise data to understand nucleon spin structure.

Contribution

It presents the first results from 2022 data with reduced uncertainties, enhancing constraints on d-quark transversity and Sivers functions in nucleon spin studies.

Findings

Uncertainties reduced by up to a factor of three compared to previous measurements.

Results help balance existing proton target data for nucleon spin structure.

New data improve understanding of transverse spin effects in nucleon.

Abstract

The COMPASS experiment is a fixed-target high-energy physics experiment that has been collecting data for 20 years (2002 to 2022) at the M2 beamline (SPS, North Area) at CERN. One of the goals of the experiment's broad physics program was to perform semi-inclusive measurements of target-spin dependent asymmetries in (di-)hadron production in deep inelastic scattering (DIS) with high-energy muons scattering off polarized nucleons. The latest COMPASS semi-inclusive DIS measurements were performed in 2022 using a transversely polarized $^6$LiD target and a 160 GeV/$c$ muon beam. The first results from approximately two-thirds of the new data exhibit total uncertainties that are up to a factor of three smaller than those observed in previous deuteron measurements. These results serve to balance the existing data collected with transversely polarized proton targets, which is of particular importance in constraining the $d$-quark transversity and Sivers functions.