MEASUREMENT OF THE SPIN-DEPENDENT STRUCTURE-FUNCTION G1(X) OF THE DEUTERON

We report on the first measurement of the spin-dependent structure function gd of the deuteron in the deep inelastic scattering of polarised muons off polarised deuterons, in the kinematical range 0.006 < x < 0.6, 1 GeV2 < Q2 < 30 GeV2. The first moment, GAMMA1d = integral-1/0 g1d dx = 0.023 +/- 0.020 (stat.) +/- 0.015 (syst.), is smaller than the prediction of the Ellis-Jaffe sum rules. Using earlier measurements of g1p, we infer the first moment of the spin-dependent neutron structure function g1n. The difference GAMMA1p - GAMMA1n = 0.20 +/- 0.05 (stat.) +/- 0.04 (syst.) agrees with the prediction of the Bjorken sum rule, GAMMA1p - GAMMA1n = 0. 191 +/- 0.002