Studies of Spin-Orbit Correlations with Longitudinally Polarized Target

We are proposing a comprehensive program to study transverse momentum dependence of valence quark transverse and longitudinal spin distributions through measurements of single-spin and double-spin azimuthal asymmetries in semi-inclusive electroproduction of pions using the upgraded JLab 11 GeV polarized electron beam and the CLAS12 detector with a longitudinally polarized proton and deuteron targets. Main objectives include studies of correlations of the transverse spin of quarks with their transverse momentum, leading to observable single spin asymmetries (SSA), and flavor decomposition of distributions of quarks aligned, q+, and anti-aligned, q−, with proton spin as a function of both longitudinal, x, and transverse momentum of the quark, kT . The measurement of the sin 2φ azimuthal moment of the target spin-dependent part of the cross section, in particular will provide direct information on spin-orbit correlations by measuring the leading twist transverse momentum dependent (TMD) parton distribution related to the interference between states with different orbital momenta. The PT dependence of the double spin asymmetry will provide additional information on the flavor and polarization dependence of transverse momentum dependence of helicity distributions of quarks, providing complimentary to SSA measurements access to spin-orbit correlations. The x, z, PT and Q 2 dependences of the sinφ to sin 2φ moments will be studied to probe the underlying T-odd distribution and fragmentation functions as well as verify the hypothesis that the former is twist-3, and the later twist-2. The experiment will use the upgraded CLAS12 detector, 11 GeV highly polarized electron beam, and longitudinally polarized solid ammonia targets (NH3 and ND3). Large acceptance of CLAS12, would allow simultaneous detection of the scattered electrons and leading hadrons from the hadronization of the struck quark, providing information on its flavor and transverse momentum. We request 30 days of running on NH3 and 50 days of running on ND3 (or possibly 6LiD or HD), including about 20% overhead for target anneals, polarization reversal, and auxiliary measurements.