Spin physics by the SMC

Abstract

The Spin Muon Collaboration at CERN has covered a wide range of spin physics. The main aim of the collaboration was the measurement of the g 1 spin structure functions of the proton and the neutron (using deuteron targets) in the range 0.003 < x < 0.7 for Q 2 ≥ 1 GeV 2. This was accompanied by a QCD analysis of all published g 1 data. The spin structure functions g 2 were also measured, which allowed for a reduction on the error in g 1. Semi inclusive data were analyzed in order to produce the first polarized quark distributions. Data obtained with a dedicated low x trigger extend down to x = 6 × 10 −5 for Q 2 ≥ 0.01 GeV 2. Some more specifics channels are still being analyzed, they include asymmetry in diffractive ϱ production, hadron azimuthal asymmetry with a transversely polarized target, measurement of the longitudinal Λ polarization, and the asymmetry in high P t hadron pair production. This last asymmetry is related to the gluon polarization in the nucleon, and this topic will be discussed in some details after a brief review of the main inclusive results.