Polarization of valence and non-strange sea quarks in the nucleon from semi-inclusive spin asymmetries.

Adeva B, Arik E, Arvidson A, et al. Polarisation of valence and non-strange sea quarks in the nucleon from semi-inclusive spin asymmetries. Phys.Lett. B. 1996;369(1):93-100.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 first time, the x-dependent spin distributions for up and down valence quarks and for non-strange sea quarks. We find that the first moments of the valence quark spin distributions are Delta u(v) = 1.01 +/- 0.19 +/- 0.14 and Delta d(v) = -0.57 +/- 0.22 +/- 0.11. The spin distribution function of non-strange sea quarks is consistent with zero over the measured range of x and the first moment is Delta (u) over bar = Delta (d) over bar = -0.02 +/- 0.09 +/- 0.03

A NEW MEASUREMENT OF THE SPIN-DEPENDENT STRUCTURE-FUNCTION G(1)(X) OF THE DEUTERON

We present a new measurement of the spin-dependent structure function g(1)(d) 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 IGeV2,Q(2)<60GeV(2). This structure function is found to be negative at small x. The first moment Gamma(1)(d)=integral(0)(1)g(1)(d)dx evaluated at Q(0)(2)=10GeV(2) is 0.034+/-0.009(stat.)+/-0.006(syst). This value is below the Ellis-Jaffe sum rule prediction by three standard deviations. Using our earlier determination of Gamma(1)(p), we obtain Gamma(1)(p)-Gamma(1)(n)=0.199+/-0.038 which agrees with the Bjorken sum rule