We report on the first measurement of the spin-dependent structure function g1d of the deuteron in the deep inelastic scattering of polarised muons off polarised deuterons, in the kinematical range 0.006

We present the final results of the spin asymmetries A 1 and the spin structure functions g 1 of the proton and the deuteron in the kinematic range 0.0008ϽxϽ0.7 and 0.2ϽQ 2 Ͻ100 GeV 2 . For the determination of A 1 , in addition to the usual method which employs inclusive scattering events and includes a large radiative background at low x, we use a new method which minimizes the radiative background by selecting events with at least one hadron as well as a muon in the final state. We find that this hadron method gives smaller errors for xϽ0.02, so it is combined with the usual method to provide the optimal set of results.

We present a measurement of semi-inclusive spin asymmetries for positively and negatively charged hadrons from deep inelastic scattering of polarised muons on polarised protons and deuterons in the range 0:003 < x < 0 : 7. From these asymmetries and the previously published inclusive spin asymmetries we determine, for the rst time, the x-dependent spin distributions for up and down valence quarks and for non-strange sea quarks. We nd that the rst moments of the valence quark Recent results from the polarised inclusive deep inelastic scattering of leptons by protons and deuterons [1,2,3,4,5] show that the quark spins contribute only about 20% to the nucleon spin with a relatively large negative contribution of about 10% from the strange quarks. These conclusions are based on the analysis of the rst moments of the spin-dependent structure functions g 1 (x) of the proton and deuteron in the framework of the quark parton model (QPM). More detailed information on the spin structure of the nucleon can be obtained from polarised semi-inclusive deep inelastic scattering, where in addition to the scattered lepton also hadrons are detected. An early theoretical pre-

We present a new measurement of the spin-dependent structure function g d 1 of the deuteron in deep inelastic scattering of 190 GeV polarised muons on polarised deuterons, in the kinematic range 0:003 < x < 0 : 7 and 1 GeV 2 < Q 2 < 60 GeV 2 . This structure function is found to be negative at small

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