  The transversity was recently extracted from data on the production of hadron
pairs in semi-inclusive deep-inelastic scattering. This analysis can be
conveniently performed in the framework of collinear factorization where the
elementary mechanism is represented by the simple product of transversity and
of a suitable chiral-odd function describing the fragmentation of a
transversely polarized parton into a pair of hadrons inside the same current
jet. The same elementary mechanism was predicted long ago to generate an
asymmetry in the azimuthal distribution of the hadron pairs when they are
produced in proton-proton collisions with one transversely polarized proton.
Recently, the STAR Collaboration has observed this asymmetry. We analyze the
impact of these data on our knowledge of transversity and we present its first
preliminary extraction from a global fit of all data in hard processes with
inclusive di-hadron production.
