On the spoiling of radiation zeros at the one-loop level and infrared finiteness

We consider the amplitude for the radiative decay $W^{-}\to {\phi }_1{\phi }_2\gamma$ (scalar quarks) including one-loop gluon corrections. We study this process to see if the amplitude (radiation) zeros found in lowest order survive at the one-loop level. The subset of diagrams containing self-mass insertions preserves the zero. Seagull types are shown to have a violation which is similar to $\kappa \ne 1$. Triangle and box diagrams spoil the zeros as they do in the case of a scalar $W$. However, the amplitude is completely free of any mass singularities in the classical null zone. We conjecture that this will remain true for spin-½ quarks.