Target Spin Asymmetries from CLAS/JLab

The CLAS detector at Jefferson lab was used to measure semi-inclusive deep-inelastic scattering of 5.7 GeV electrons from longitudinally polarized protons in an NH$_3$ target. The target single spin asymmetry is observed to have a significant azimuthal angle dependence for $\pi^+$, $\pi^0$, and $\pi^-$, which have been fit with a combination of $\sin(\phi)$ and $\sin(2\phi)$ terms, sensitive to the product of the spin-dependent Collins fragmentation function and twist-3 and twist-2 transverse momentum dependent quark distribution functions, respectively. The data suggest non-zero quark transverse polarization in a longitudinally polarized target, in agreement with a prediction in the quark chiral soliton model. Studies of the double spin asymmetries $A_{LL}$ in the same data set support the applicability of factorization in the kinematic region studied ($W>2$ GeV, $Q^2>1.1$ GeV$^2$, and $0.4