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 0.0031 GeV2. Compared to our previous publication on this subject, with the new data the statistical errors have been reduced by nearly a factor of two. From these asymmetries and our inclusive spin asymmetries we determine the polarised quark distributions of valence quarks and non-strange sea quarks at Q2=10 GeV2. The polarised u valence quark distribution, Δuv(x), is positive and the polarisation increases with x. The polarised d valence quark distribution, Δdv(x), is negative and the non-strange sea distribution, is consistent with zero over the measured range of x

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 virtual photon proton asymmetry A p 1 from deep inelastic scattering of polarized muons on polarized protons in the kinematic range 0:0008 < x < 0:7 and 0:2 < Q 2 < 100 GeV 2 . With this, the statistical uncertainty of our measurement has improved by a factor of 2 compared to our previous measurements. The spin-dependent structure function g p 1 is determined for the data with Q 2 > 1 GeV 2 . A perturbative QCD evolution in next-to-leading order is used to determine g p 1 (x) at a constant Q 2 . A t Q 2 = 10 GeV 2 we nd, in the measured range, R 0:7 0:003 g p 1 (x)dx = 0 : 139 0:006 (stat) 0:008 (syst) 0:006 (evol).The value of the rst moment p 1 = R 1 0 g p 1 ( x )dx of g p 1 depends on the approach used to describe the behaviour of g p 1 at low x. We nd that the Ellis-Jae sum rule is violated. With our published result for d 1 we conrm the Bjorken sum rule with an accuracy of 15% at the one standard deviation level.