The Deuteron Spin-dependent Structure Function g1(d) and its First Moment

The article presents the measurement of the deuteron spin-dependent structure function g1 based on the data collected by the COMPASS experiment at CERN during the years 2002–2004. The data provide an accurate evaluation for Γ1 , the first moment of g1 (x), and for the matrix element of the singlet axial current, a0. The results of QCD fits in the next to leading order (NLO) on all g1 deep inelastic scattering data are also presented. They provide two solutions with the gluon spin distribution function Delta G positive or negative, which describe the data equally well. In both cases, at Q2 = 3 (GeV/c)2 the first moment of Delta G(x) is found to be of the order of 0.2–0.3 in absolute value. Comparison with previous results are also given.