Transverse spin effects in hadron-pair production from semi-inclusive deep inelastic scattering

TL;DR

This paper reports the first measurements of azimuthal asymmetries in hadron-pair production from deep-inelastic scattering, providing insights into transversity distribution functions and quark spin structure.

Contribution

It presents novel experimental measurements of azimuthal asymmetries in hadron-pair production using polarized targets, offering new data on transversity distributions without Collins effect involvement.

Findings

Significant asymmetries on NH_3 target indicate non-zero u-quark transversity.

Small asymmetries on ^6LiD target suggest cancellation of u- and d-quark transversities.

Results enhance understanding of spin-dependent parton distribution functions.

Abstract

First measurements of azimuthal asymmetries in hadron-pair production in deep-inelastic scattering of muons on transversely polarised ^6LiD (deuteron) and NH_3 (proton) targets are presented. The data were taken in the years 2002-2004 and 2007 with the COMPASS spectrometer using a muon beam of 160 GeV/c at the CERN SPS. The asymmetries provide access to the transversity distribution functions, without involving the Collins effect as in single hadron production. The sizeable asymmetries measured on the NH_ target indicate non-vanishing u-quark transversity and two-hadron interference fragmentation functions. The small asymmetries measured on the ^6LiD target can be interpreted as indication for a cancellation of u- and d-quark transversities.