Generalised leptonic colour

It is conceivable that there is an SU(N)ℓ 'colour' gauge group for leptons, analogous to the gauged SU(3)q colour group of the quarks. The standard model emerges as the low energy effective theory when the leptonic colour is spontaneously broken. The simplest such generalised leptonic colour models are constructed. We show that the see-saw mechanism for small neutrino masses, along with the theoretical constraint of electric charge quantisation, suggests that the models with N=3, 5, 7 are the theoretically most promising cases. A striking feature of generalised leptonic colour is the physics associated with the extra leptonic degrees of freedom-the liptons. These particles can potentially be discovered at future colliders, such as the LHC, making the idea testable in the near future.