Measurement of Transverse Momentum Dependent Asymmetries with COMPASS Experiment at CERN

Abstract

The COMPASS experiment, which started running at the European Council for Nuclear Research, CERN, in Geneva in 2001, is currently investigating in a wide ranging programme the spin structure of the nucleon through deep-inelastic scatter- ing (DIS). The experiment uses a polarized muon beam and a polarized deuterium target, which together allow access to all terms of the polarized DIS cross-section. Two of the most important functions which COMPASS is designed to ful¯l are a precision measurement of the gluon polarization ¢G and the investigation of the transverse spin e®ects, specially extracting the transverse polarized quark distribu- tion functions ¢T q. In Semi-Inclusive DIS of polarized leptons on a transversely polarized target, eight azimuthal modulations appear in the cross-section. Within the QCD parton model, four azimuthal asymmetries can be interpreted at leading order, two of them being the Collins and Sivers asymmetries. The other two leading twist asymmetries are related to di®erent transverse momentum dependent quark distribution functions. There are four additional asymmetries which can be inter- preted as twist-three contributions. This thesis describes the analysis with the data taken with transverse spin con¯guration during the COMPASS beam-time 2002 - 2004, resulting in the extraction of the eight Transverse Momentum Dependent (TMD) asymmetries.