Leading-order determination of the gluon polarisation from semi-inclusive deep inelastic scattering data
Abstract
Using a novel analysis technique, the gluon polarisation in the nucleon is re-evaluated using the longitudinal double-spin asymmetry measured in the cross section of semi-inclusive single-hadron muoproduction with photon virtuality Q(2) > 1 ( GeV/c)(2). The data were obtained by the COMPASS experiment at CERN using a 160 GeV/c polarised muon beam impinging on a polarised (LiD)-Li-6 target.
By analysing the full range in hadron transverse momentum p(T), the different pT-dependences of the underlying processes are separated using a neural-network approach. In the absence of pQCD calculations at next-to-leading order in the selected kinematic domain, the gluon polarisation Delta g/g is evaluated at leading order in pQCD at a hard scale of mu(2) = = 3( GeV/c)(2).
It is determined in three intervals of the nucleon momentum fraction carried by gluons, x(g), covering the range 0.04 = 0.113 +/- 0.038(stat) +/- 0.036( syst) at approximate to 0.10, suggests that the gluon polarisation is positive in the measured x(g) range.