Measurement of 'pretzelosity' asymmetry of charged pion production in semi-inclusive deep inelastic scattering on a polarizedHe3target

An experiment to measure single-spin asymmetries of semi-inclusive production of charged pions in deep-inelastic scattering on a transversely polarized $^{3}\mathrm{He}$ target was performed at Jefferson Laboratory in the kinematic region of $0.16lxl0.35$ and $1.4l{Q}^{2}l2.7$ ${\mathrm{GeV}}^{2}$. Pretzelosity asymmetries on $^{3}\mathrm{He}$, which are expressed as the convolution of the ${h}_{1T}^{\ensuremath{\perp}}$ transverse-momentum-dependent distribution functions and the Collins fragmentation functions in the leading order, were measured for the first time. Under the effective polarization approximation, we extracted the corresponding neutron asymmetries from the measured $^{3}\mathrm{He}$ asymmetries and cross-section ratios between the proton and $^{3}\mathrm{He}$. Our results show that both ${\ensuremath{\pi}}^{\ifmmode\pm\else\textpm\fi{}}$ on $^{3}\mathrm{He}$ and on neutron pretzelosity asymmetries are consistent with zero within experimental uncertainties.