Analysis and Interpretation of Transverse Spin Dependent Azimuthal Asymmetries in SIDIS at the COMPASS Experiment

In general, eight target transverse spin-dependent azimuthal modulations are allowed in semi-inclusive deep inelastic scattering (SIDIS) of polarized leptons on a transversely polarized target. In the QCD parton model four of these asymmetries can be interpreted within the leading order approach and other four are twist-three level contributions. Two leading twist transverse spin asymmetries, namely Collins and Sivers effects were already published by HERMES and COMPASS collaborations. While the remaining six new asymmetries have been measured for the first time in COMPASS using a high energy longitudinally polarized muon beam and a transversely polarized deuterium target. In the introductory chapter of this thesis we describe the general expression of the cross-section of polarized SIDIS and review the aspects of the QCD parton model with transverse momentum dependent distribution and fragmentation functions. Then we define the target transverse spin asymmetries arising in SIDIS and motivate the importance of their measurement. The two subsequent chapters are dedicated to our study of the double spin asymmetries ALT and ALL; calculations and the prediction plots for x,y,z and PhT dependence of asymmetries for COMPASS, HERMES and JLab experiments are presented. In chapters 5–7 we describe the COMPASS experimental setup, review the general aspects of the data analysis procedure (event selection, analysis methods, systematic st udies and cross-checks) and present the results on target transverse spin dependent azimuthal asymmetries extracted from COMPASS 2002-2004 data. Asymmetries are evaluated as a functions of x,y,z and PhT kinematic variables for positive and negative unidentified hadrons and for positive and negative pions and kaons. At the end of the thesis we summarize the obtained results and draw some conclusions.