Gluon polarization in the nucleon from quasi-real photoproduction of high-PT hadron pair

We present a determination of the gluon polarization Delta G/G in the nucleon, based on the helicity asymmetry of quasi-real photoproduction events, Q(2) < 1 (GeV/c)(2), with a pair of large transverse-momentum hadrons in the final state. The data were obtained by the COMPASS experiment at CERN using a 160 GeV polarized muon beam scattered on a polarized (LiD)-Li-6 target. The helicity asymmetry for the selected events is (A(parallel to)/D) = 0.002 +/- 0.019(stat) +/- 0.003(syst). From this value, we obtain in a leading-order QCD analysis Delta G/G = 0.024 +/- 0.089(stat) +/- 0.057(syst) at x(g) = 0.095 and mu(2) similar or equal to 3 (GeV/c)(2). (c) 2005 Elsevier B.V. All rights reserved.