  We describe a new way to access the chiral odd transversity parton
distribution in the proton through the photoproduction of lepton pairs on
transversely polarized target. The basic ingredient is the interference of the
Bethe Heitler or Drell-Yan amplitudes with the amplitude of a process, where
the photon couples to quarks through its twist-2 chiral-odd distribution
amplitude. This approach permits to scan experimentally the shape of the
transversity distribution in a nucleon as well as the photon distribution
amplitude.
