Determination of Delta G/G from Open Charm events at COMPASS

TL;DR

This paper reports on the first measurement of the gluon polarization in the nucleon using open charm events at COMPASS, providing insights into the spin structure of the proton.

Contribution

It introduces a novel analysis method for extracting Delta G/G from open charm events and presents the first measurement based on 2002-2004 data.

Findings

First measurement of Delta G/G from open charm at COMPASS

Clean selection of photon-gluon fusion events using charm mesons

Results contribute to understanding nucleon spin structure

Abstract

One of the main goals of the COMPASS experiment at CERN is the determination of the gluon polarisation in the nucleon, Delta G/G. It is determined from spin asymmetries in the scattering of 160 GeV/c polarised muons on a polarised LiD target. The gluon polarisation is accessed by the selection of photon-gluon fusion (PGF) events. A very clean selection of PGF events can be obtained with charmed mesons in the final state. Their detection is based on the reconstruction of D* and D0 mesons in the COMPASS spectrometer. The analysis method for the first measurement of Delta G/G from the open charm channel is described and the result from COMPASS for the 2002-2004 data taking period is presented.