Compass Results on Gluon Polarisation from High pT hadron pairs

TL;DR

The COMPASS experiment measured gluon polarisation elta G/G using high p_T hadron pairs from deep inelastic scattering, employing a neural network method to analyze data collected between 2002-2004, providing new preliminary results.

Contribution

This work introduces a novel neural network weighted method to extract elta G/G from high p_T hadron pairs in DIS data.

Findings

Preliminary elta G/G result for Q^2>1 (GeV/c)^2 events.

Additional elta G/G estimate for quasi-real photoproduction events.

Use of a neural network approach to improve gluon polarisation measurement.

Abstract

One of the goals of the COMPASS experiment is the determination of the gluon polarisation \Delta G/G, for a deep understanding of the spin structure of the nucleon. In DIS the gluon polarisation can be measured via the Photon-Gluon-Fusion (PGF) process, identified by open charm production or by selecting high p_T hadron pairs in the final state. The data used for this work were collected by the COMPASS experiment during the years 2002-2004, using a 160 GeV naturally polarised positive muon beam scattering on a polarised nucleon target. A new preliminary result of the gluon polarisation \Delta G/G from high p_T hadron pairs in events with Q^2>1 (GeV/c)^2 is presented. In order to extract \Delta G/G, this analysis takes into account the leading process \gamma q contribution together with the PGF and QCD Compton processes. A new weighted method based on a neural network approach is used. A preliminary \Delta G/G result for events from quasi-real photoproduction (Q^2<1 (GeV/c)^2) is also presented.