https://doi.org/10.1140/epjc/s10052-019-7414-z
Regular Article - Theoretical Physics
Naturalising the third family hypercharge model for neutral current 
DAMTP, University of Cambridge, Wilberforce Road, Cambridge, CB3 0WA, UK
* e-mail: joedavighi@gmail.com
Received:
19
July
2019
Accepted:
19
October
2019
Published online:
11
November
2019
We consider a deformation of the Third Family Hypercharge Model, which arguably makes the model more natural. Additional non-zero charges of the spontaneously broken, family-dependent 
gauge symmetry are assigned to the second family leptons, and the third family leptons’ charges are deformed away from their hypercharges in such a way that the gauge symmetry remains anomaly-free. Second family lepton charges allow a 
coupling to muons without having to assume large charged lepton mixing, which risks violating tight lepton flavour violation bounds. In this deformed version, only the bottom and top Yukawa couplings are generated at the renormalisable level, whereas the tauon Yukawa coupling is absent. The mediates a beyond the Standard Model contribution to an effective 
vertex in the combination 
and is able to fit the apparent discrepancy between Standard Model predictions in flavour changing neutral-current 
meson decays and their measurements, whilst simultaneously avoiding current constraints from direct searches and other measurements, when 
.
© The Author(s), 2019
