Neutrinos are different from charged fermions both by their small mass, and by the large mixing in which they participate. While this can be accommodated in some extended models, no fundamental reason is this far provided. We propose a model of family replication (originating from an extra dimensions approach) in which imposing the Majorana nature of light neutrinos implies a maximal mixing in this sector, and a small one for the charged fermions.
The model also includes Kaluza-Klein recurrences of the gauge bosons (gluon, Z, W), which have interesting flavour violating (but family-number conserving) interactions.
While the compactification scale is not fixed by theory, existing constraints from rare K decays still allow for the detection at LHC of the first Z' recurrences. There are 3 of these, one of which is a simple replication of the current Z, which could be detected with modest luminosity; the other 2 have striking signatures like (antimuon + e ) final states, but would require the full-fledged LHC for detection.
