Transverse Spin Physics at COMPASS

TL;DR

This paper reports on the COMPASS collaboration's measurements of transverse spin and momentum effects in deep inelastic scattering, providing insights into nucleon structure and quark transverse momentum distributions.

Contribution

It presents new experimental results on azimuthal asymmetries related to transversity and Boer-Mulders functions using COMPASS data.

Findings

Measured azimuthal asymmetries in semi-inclusive DIS

Accessed transversity distribution via Collins and dihadron channels

Estimated quark transverse momentum and Boer-Mulders function

Abstract

The investigation of transverse spin and transverse momentum effects in deep inelastic scattering is one of the key physics programs of the COMPASS collaboration. Three channels have been analyzed at COMPASS to access the transversity distribution function: The azimuthal distribution of single hadrons, involving the Collins fragmentation function, the azimuthal dependence of the plane containing hadron pairs, involving the two-hadron interference fragmentation function, and the measurement of the transverse polarization of Lambda hyperons in the final state. Azimuthal asymmetries in unpolarized semi-inclusive deep-inelastic scattering give important information on the inner structure of the nucleon as well, and can be used to estimate both the quark transverse momentum k_T in an unpolarized nucleon and to access the so-far unmeasured Boer-Mulders function. COMPASS has measured these asymmetries using spin-averaged 6LiD data.