Measurements of transverse-momentum dependent effects in semi-inclusive DIS at COMPASS

TL;DR

This paper discusses measurements of transverse-momentum-dependent effects in semi-inclusive deep inelastic scattering at COMPASS, providing insights into quark distributions and hadronisation processes within nucleons.

Contribution

It presents new experimental data from COMPASS that enhances understanding of TMD PDFs and fragmentation functions, including potential first-time extraction of the Boer-Mulders function.

Findings

Improved knowledge of d-quark transversity, reducing uncertainties by a factor of 2.5 at large Bjorken x.

Data collected may enable the first extraction of the Boer-Mulders function.

Upcoming data will provide new insights into transverse momentum and polarization effects.

Abstract

Its cornerstone were studies of hadron production in deep inelastic scattering (DIS), which can be interpreted in the transverse-momentum-dependent (TMD) factorisation framework, allowing to access the distributions of polarisation and transverse momentum of quarks within the nucleon in the language of TMD PDFs, and the hadronisation in terms of TMD fragmentation functions. The data collected with a liquid hydrogen target in 2016-2017 will soon bring new information on the transverse momentum and may allow for the first time to extract the transverse polarisation of quarks within an unpolarised nucleon described by the Boer-Mulders function. The unique data collected with a transversely polarised deuteron target have already improved the knowledge of the d-quark transversity (transverse counterpart of the helicity PDF), reducing the uncertainties by a factor of 2.5 at large Bjorken x, and are yet to yield a number of interesting results.