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.

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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

The cross section for exclusive zr + electroproduction on the proton has been measured near threshold for the first time at two different values of the virtual photon polarization (e-0.2 and e~0.7). Using the low energy theorem for this reaction we deduce the axial and pseudoscalar weak form factors GA and G P at |f | =0.073, 0.139, and 0.179 (GeV/c) 2 . The slope of G A agrees with the value obtained in neutrino experiments. Gp satisfies the pion pole dominance hypothesis, which is thus verified for the first time in this range of transfer.PACS numbers: 13.60. Le, 11.40.Ha, 14.20.Dh The electroweak form factors provide a significant test of our understanding of the nucleon structure. Continuous efforts are devoted to their experimental determination but, as compared to the electromagnetic form factors of the nucleon (Ff'^Ff'"), the axial {GA) and pseudoscalar (Gp) weak form factors are still poorly known. In particular, very little is known about Gp which is very sensitive to the pion cloud of the nucleon. This Letter reports the first determination of both GA and Gp at / =-0.073, -0.139, and -0.179 (GeV/c) 2 , using near threshold n + electroproduction on the proton with detection of the pion and electron in coincidence.To fix our conventions we write the matrix element of the axial current between nucleon states of momenta p\ and/?2 U == (pi -pi)(1) From p decay and muon capture one can determine the weak form factors in the range |/1 -0-0.01 (GeV/c) 2 , but at larger / the only direct information comes from neutrino scattering on nuclei. From these experiments, only the mass parameter MA of the dipole parametrization of GA can be obtained, assuming that the vector and magnetic weak form factors can be taken from electron scattering using the isotriplet hypothesis and that Gp is given by pion pole dominance [1], which we write in the form Gp(t) = -2MG A (t)/U-mZ). The well established approximate chiral symmetry of strong interactions allows us to write a low energy theorem [1,2] which relates the low energy pion electroproduction amplitude to GA, Gp, F p,n , and Ff ,n , up to corrections which vanish in the chiral limit (pion mass going to zero). For our purpose, F p>n and Ff'" are known with sufficient accuracy. Therefore, a measurement at the same t for two values of the virtual photon polarization e allows a simultaneous determination of GA and Gp. Previous experiments (see Ref.[3] for a list of references) performed the measurement only at a single value of e except in Ref. [4] where the neutral pions were not separated from the charged ones. Therefore the determination of GA relied either on the pion pole dominance hypothesis for Gp or on a model for the estimation of the neutral pion contribution. Our experiment is the first exclusive experiment which uses two values of e (e~0.2 and £~~0.7) different enough to allow an independent determination of GA and Gp. Up to now, the latter is known only at the muon point [5]: G P =0.082 ±0.018 MeV _1 c 2 at t 0.0112 (GeV/c) 2 . In the following, p\, pi, q, and...