Flavour decomposition of the polarised quark distributions from semi-inclusive data

Abstract

Spin asymmetries of the semi-inclusive cross section for the production of charged hadrons have been measured in deep-inelastic scattering of polarised leptons from polarised nuclei by the SMC experiment in the kinematic range 0.003 < x < 0.7 and 1 GeV 2 < Q 2 < 56 GeV 2 and by the HERMES experiment in the kinematic range 0.023 < x < 0.6 and 1 GeV 2 < Q 2 < 10GeV 2. Recent results from HERMES on the extraction of polarised quark distributions from the measured spin asymmetries were presented at this conference for the first time. Polarised quark distributions were extracted as a function of x for up ( u + u ) and down ( d + d ) flavours, and for valence and sea quarks. The up quark polarisation is positive and the down quark polarisation is negative in the measured range. The polarisation of the sea is compatible with zero. The moments of the polarised quark distributions are presented. All HERMES results are preliminary.