Beyond Collins and Sivers: further measurements of the target transverse spin-dependent azimuthal asymmetries in semi-inclusive DIS from COMPASS

TL;DR

This paper reports new measurements of eight azimuthal asymmetries in semi-inclusive deep inelastic scattering, expanding understanding of transverse spin effects and quark distributions using COMPASS data.

Contribution

It presents the first measurements of four additional azimuthal asymmetries related to transverse momentum dependent quark distributions and twist-three contributions at COMPASS.

Findings

Measured four new azimuthal asymmetries for the first time.

Provided preliminary results from 2002-2004 data.

Enhanced understanding of transverse spin phenomena in DIS.

Abstract

In semi-inclusive DIS of polarized leptons on a transversely polarized target eight azimuthal modulations appear in the cross-section. Within QCD parton model four azimuthal asymmetries can be interpreted at leading order, two of them being the already measured Collins and Sivers asymmetries. The other two leading twist asymmetries, related to different transverse momentum dependent quark distribution functions, and also additional four asymmetries which can be interpreted as twist-three contributions have been measured for the first time at COMPASS, using a 160 GeV/c longitudinally polarized ($P_{beam}\simeq -0.8$) muon beam and a transversely polarized $^6LiD$ target. We present here the preliminary results from the 2002-2004 data.