Longitudinal spin physics results from COMPASS

The COMPASS experiment at the CERN SPS has a broad physics program focused on the nucleon spin structure and hadron spectroscopy, using muon and hadron beams, respectively. Results from the COMPASS on the inclusive longitudinal double spin asymmetries $A^{d,p}_{1}$ measured in deep-inelastic polarized muon scattering off the polarized $^{6}LiD$ and $NH_{3}$ targets are presented. The new proton data cover the range $Q^{2}$ > 1( GeV$^{2}/c$), 0.004 < $x$ < 0.7 and improve the statistical precision of $g^{p}_{1} (x)$ by factor of two at $x$ < 0.02 compared to previous measurements. The spin-dependent non-singlet function $g^{NS}_{1} (x, Q^{2})$ extracted from the data allows to evaluate the isovector quark density $Δq_{3}(x, Q^{2})$ and check the Bjorken sum rule prediction. The helicity distributions for the three lightest quark and antiquark flavours extracted from the measured double spin asymmetries for production of charged pions and kaons in semi-inclusive deep-inelastic scattering are also presented and discussed. The gluon polarization in the nucleon was determined using open charm production or high transverse-momentum hadron pairs production in polarized muon scattering off longitudinally polarized target.