Spin physics by the SMC Original Research Article

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 g1 spin structure functions of the proton and the neutron (using deuteron targets) in the range 0.003 < x < 0.7 for Q2 ≥ 1 GeV2. This was accompanied by a QCD analysis of all published g1 data. The spin structure functions g2 were also measured, which allowed for a reduction on the error in g1. 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 Q2 ≥ 0.01 GeV2. 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 Pt 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.