We present the latest COMPASS results on the proton spin structure function g[Formula: see text](x) at 200[Formula: see text]GeV. The data improve the statistical precision by a factor of [Formula: see text]2 at low x. A reevaluation of the Bjorken sum rule based on COMPASS proton and deuteron data confirms its validation to a 9% accuracy. Finally, results from a global NLO QCD fit of g1 world data are shown. The extracted spin singlet distribution leads to an integrated value of [Formula: see text] at Q[Formula: see text] (GeV/c)2. The large uncertainty is mainly driven by the unknown shape of the distribution.
Measurement of the proton spin structure at long distances