Measuring transversity densities in singly polarized hadron-hadron and lepton-hadron collisions

We show how the transverse polarization of a quark initiating a jet can be probed by the azimuthal distribution of two hadrons (of large z) in the jet. This permits a twist-2 asymmetry in hard processes when only one of the initial particles is polarized transversely. Applications to hadron-hadron and lepton-hadron scattering are discussed.