  Twisted photons (i.e. photons carrying non-zero orbital angular momentum) are
well-known in optics. Recently, it was suggested to use Compton backscattering
off an ultra-relativistic electron beam to boost optical twisted photons into
the high energy range. However, only the case of strictly forward/backward
scattering has been studied so far. Here, we consider generic kinematic
features of processes in which a twisted particle scatters with non-zero
transverse momentum transfer.
