Abstract

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 U(1)_F 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 U(1)_F gauge symmetry remains anomaly-free. Second family U(1)_F lepton charges allow a Z^prime 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 Z^prime mediates a beyond the Standard Model contribution to an effective ({bar{b}} s) (bar{mu }mu ) vertex in the combination C_9=-9C_{10} and is able to fit the apparent discrepancy between Standard Model predictions in flavour changing neutral-current B-meson decays and their measurements, whilst simultaneously avoiding current constraints from direct Z^prime searches and other measurements, when 0.8~text {TeV}< M_{Z^prime } < 12.5 ~text {TeV}.

Highlights

  • Various measurements of B meson decays are currently in tension with Standard Model predictions

  • Working to first order in sin αz 1 and substituting for it using Eq 13, we find that the prediction in the DTFHMeg is Comparing this to Eq 33, we find that the DTFHM prediction for the sign is in accordance with the data and may fit the inferred invisible width of the Z boson some 1.7σ better than the Standard Model (SM)

  • We have presented a model which explains the Neutral Current B−Anomalies (NCBAs) whilst avoiding current constraints

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Summary

Introduction

Various measurements of B meson decays are currently in tension with Standard Model predictions. Is predicted to be 1.00 in the Standard Model (SM), for lepton invariant mass squared bin ml2l ∈ [1.1, 6] GeV2. In this bin, LHCb measurements [1,2] imply. – The (3,3) entries of the up quark, down quark, and charged lepton Yukawa matrices were the only ones predicted to be non-zero at the renormalisable level. Small corrections to this picture are expected from nonrenormalisable operators, but the model explains the hierarchical heaviness of the top and bottom quarks and the tau lepton. The most up-to-date experimental bounds on the parameter space of the TFHM are presented in Ref. [58]

Motivation for extending the TFHM
The deformed third family hypercharge model
Anomaly-free deformation
Neutrino masses
Z couplings to fermions
Example case
Phenomenology of the example case
Z width
Neutral meson mixing
TeV MZ
Z boson lepton flavour universality
Invisible width of the Z Boson
Direct Z search constraints on parameter space
Combination of constraints
Summary
A Froggatt-Nielsen structure to obtain a diagonal up Yukawa matrix

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