  We describe a new way to access the chiral odd transversity parton
distribution in the proton through the photoproduction of lepton pairs. The
basic ingredient is the interference of the usual Bethe Heitler or Drell-Yan
amplitudes with the amplitude of a process, where the photon couples to quarks
through its chiral-odd distribution amplitude, which is normalized to the
magnetic susceptibility of the QCD vacuum. A promising phenomenology of single
and double spin observables emerges from the unusual features of this
amplitude.
