Gluon Polarisation Measurements @ COMPASS

TL;DR

This paper reports on measurements of gluon polarisation in the nucleon using DIS data from the COMPASS experiment, employing innovative neural network techniques for analysis.

Contribution

It introduces a new weighted neural network method for analyzing gluon polarisation in DIS, with the first division of high p_T results into three independent measurements at LO.

Findings

Gluon polarisation results from high p_T hadrons are presented at LO with three independent measurements.

Open charm analysis provides gluon polarisation at both LO and NLO.

The neural network approach improves the analysis of gluon polarisation data.

Abstract

One of the missing keys in the present understanding of the spin structure of the nucleon is the contribution from the gluons: the so-called gluon polarisation. This quantity can be determined in DIS through the photon-gluon fusion process, in which two analysis methods may be used: (i) identifying open charm events or (ii) selecting events with high p_T hadrons. The data used in the present work were collected in the COMPASS experiment, where a 160 GeV/c naturally polarised muon beam, impinging on a polarised nucleon fixed target is used. Preliminary results for the gluon polarisation from high p_T and open charm analyses are presented. The gluon polarisation result for high p_T hadrons is divided, for the first time, into three statistically independent measurements at LO. The result from open charm analysis is obtained at LO and NLO. In both analyses a new weighted method based on a neural network approach is used.