Fragmentation of transversely polarized quarks probed in transverse momentum distributions

It is shown that the azimuthal dependence of the distribution of hadrons in a quark jet is a probe of the transverse spin of the quark initiating the jet. This results in a new spin-dependent fragmentation function that acts at the twist-2 level. One example of a process where it contributes is semi-inclusive deeply inelastic scattering with a transversely polarized nucleon target but with an unpolarized electron beam. This process is treated in detail. Another process in the cross section for singly polarized hadron-hadron scattering when two high-p _⊥ hadrons are measured in the final state and are close to back-to-back in azimuth. The new fragmentation function is sensitive to the coupling of the fragmentation process to (spontaneous) chiral symmetry breaking.