Transverse target spin asymmetries on a proton target at COMPASS

COMPASS is a fixed target experiment at the CERN M2 external beamline using a 160 GeV/c polarised μ+ beam. After the data taking in 2002-04 with a transversely polarised deuterium target, in 2007 COMPASS has taken data with a transversely polarised proton (NH3) target. For getting a full description of the spin structure of the nucleon at leading twist at quark level it is necessary to know three quark distribution functions, namely the unpolarised distribution function q(x), the helicity distribution function Δq(x) and the transverse spin distribution function ΔTq(x). One possible way to extract the transverse spin distribution function is the measurement of the Collins effect in semi-inclusive DIS on a transversely polarised target, describing the fragmentation of transversely polarised quarks in to spinless hadrons. Simultaneously the Sivers effect was studied, measuring the correlation of the transverse polarisation of a nucleon and the transverse momentum of an unpolarised quark. Results on the Collins and Sivers asymmetries are presented and are compared to COMPASS deuteron data.