Searching for family-number conserving neutral gauge bosons from extra   dimensions
  Previous studies have shown how the three generations of the Standard Model fermions can arise from a single generation in more than four dimensions, and how off-diagonal neutral couplings arise for gauge-boson Kaluza-Klein recurrences. These couplings conserve family number in the leading approximation. While an existing example, built on a spherical geometry, suggests a high compactification scale, we conjecture that the overall structure is generic, and work out possible signatures at colliders, compatible with rare decays data. 
J.M. Frere, M.V. Libanov, E.Ya. Nugaev, S.V. Troitsky