Rare decays of the top quark in the technicolour model with a massless scalar doublet

The rare decays t→cV (V = Z, γ, g) induced through loop processes are calculated in a minimal technicolour model (MTC) with a massless weak doublet recently presented by Carone and Georgi. We find that these new contributions can enhance the standard model branching fractions by as much as three to four orders of magnitude, i.e. B(t → cZ) ∼ 10-7, B (t → cγ) ∼ 10-9, B( t → cg) ∼ 10-6 for favourable values of the parameters. This might provide a unique window to detect the virtual effects of technipions in MTC theory. (author)