An exact calculation of the flavour-changing quark-photon vertex

An exact calculation of the sdγ vertex in the unitary gauge is presented, and its applications are considered. It is found that flavour-changing radiative decays of strange hyperons appear to be explainable in terms of flavour-changing quark vertices involving either a photon or a gluon emission. But the CP-violating effects in such decays are estimated to be too small to be measurable. The exact expression for the sdγ vertex improves the old estimate for the neutron electric dipole moment to 10-33 e cm. The possibility of bare top flavour production from e+e-->tanti c or e-u->e-t is shown to be very unlikely. (orig.)