Recent measurement of ΔG/G at COMPASS

We present a preliminary measurement of the gluon polarization ΔG/G in the nucleon, based on the spin asymmetry of quasi-real photoproduction events for which a pair of large transverse momentum hadrons is produced. The data were obtained by the COMPASS experiment at CERN using a 160 GeV polarized muon beam scattered on a large polarized 6LiD target. The preliminary helicity asymmetry for the selected events is AparalleLl /D = 0.002 ± 0.019(stat.) ± 0.003(exp.syst.). From this value, a leading order analysis based on the model of PYTHIA leads to the gluon polarization in the nucleon ΔG/G(xg = 0.095, μ2 = 3 GeV2) = 0.024 ± 0.089(stat.) ± 0.057(syst.). This value is consistent with parameterizations obtained from QCD fits to the g1 data, with a first moment ΔG ≡ ∫01 ΔG(x)dx ≅ 0.5, at the same scale