Transverse target spin asymmetries on a proton target at COMPASS

Transversity and transverse momentum-dependent parton distribution functions (TMDs) are been measured in semi-inclusive deep inelastic scattering (SIDIS) by using a transversely polarized target at the COMPASS experiment. COMPASS is a fixed target experiment at the CERN M2 beamline, which provides a 160GeV/c polarized m+ beam. In the years 2002-2004 COMPASS has collected data with a transversely polarized deuteron 6LiD target. In 2007, COMPASS has used for the first time a proton NH3 target. To access transversity COMPASS has used three different quark polarimeters: the Collins effect, responsible for an azimuthal asymmetry in the single hadron distribution, azimuthal target spin asymmetries of charged hadron pairs and the transverse polarisation of L hyperons. Beside this also the Sivers asymmetry arising from the correlation between the transverse nucleon spin and the quark intrinsic transverse momentum was measured. European