Date of Completion


Embargo Period



proton spin semi-inclusive deep inelastic scattering SIDIS TMD FF

Major Advisor

Kyungseon Joo

Associate Advisor

Peter Schweitzer

Associate Advisor

Andrew Puckett

Field of Study



Doctor of Philosophy

Open Access

Open Access


Measurements of the multiplicity, cos\phi_h moment, and cos2\phi_h moment of the semi-inclusive deep inelastic scattering (SIDIS) cross-section have been performed. The data set used was the E1-F run from the CEBAF Large Acceptance Spectrometer (CLAS) at Jefferson National Lab. The run used a 5.498 GeV longitudinally polarized electron beam and an unpolarized liquid hydrogen target. Both charged pion channels were studied over a broad range of kinematics (0.1 < x < 0.6, 1.0 < Q^2 < 4.5 GeV^2, 0.0 < z < 0.9, 0.0 < P_{h\perp}^2 < 1.0 GeV^2, and -180 < \phi_h < 180 degrees). These measurements give access to transverse momentum dependent parton distribution functions (TMDs) which describe the transverse motion of quarks and gluons inside of the proton. Results show evidence of a TMD known as the Boer-Mulders function being non-zero via a flavor dependence on the cos\phi_h and cos2\phi_h modulations of the data. A non-zero Boer-Mulders function requires a non-zero quark orbital angular momentum (L_q) contribution to the proton spin, thus giving insights into the 28 year old puzzle of the missing proton spin.