New results on gluon polarisation from COMPASS

The gluon polarisation in the nucleon has been determined by tagging photon-gluon fusion events via Open-Charm production. The data were taken by the COMPASS Collaboration at CERN between 2002 and 2006, colliding a polarised muon beam on a polarised deuteron target. A new method based on Neural Networks was used to efficiently separate the signal from the uncorrelated background, allowing a new contribution of two low purity channels. At leading order QCD, an average gluon polarisation of $\langle\Delta g/g\rangle x$ $= -$0:39 $\pm$ 0:24($stat$) $\pm$ 0:11($syst$) at a scale $\mu^{2}\approx$ 13 $(GeV/c)^{2}$, and at an average gluon momentum fraction $\langle x\rangle\approx$ 0:11, was estimated