Polarised Quark Distributions in the Nucleon from Semi-Inclusive Spin Asymmetries

Spin Muon Collaboration

Paper

Polarised Quark Distributions in the Nucleon from Semi-Inclusive Spin Asymmetries

Abstract

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

and

1 GeV

. 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

=10 GeV

. The polarised

valence quark distribution,

, is positive and the polarisation increases with

. The polarised

valence quark distribution,

, is negative and the non-strange sea distribution,

, is consistent with zero over the measured range of

. We find for the first moments

and

, where we assumed

. We also determine for the first time the second moments of the valence distributions