arXiv : Combined Explanation of the $Z\to b\bar b$ Forward-Backward Asymmetry, the Cabibbo Angle Anomaly, $\tau\to\mu\nu\nu$ and $b\to s\ell^+\ell^-$ Data

Crivellin, Andreas; Alguero, Marcel; Matias, Joaquim; Manzari, Claudio Andrea

doi:10.1103/PhysRevLett.127.011801

Article
Report number	arXiv:2010.14504 ; CERN-TH-2020-177 ; PSI-PR-20-18 ; UZ-TH 40/20
Title	Combined Explanation of the $Z\to b\bar b$ Forward-Backward Asymmetry, the Cabibbo Angle Anomaly, $\tau\to\mu\nu\nu$ and $b\to s\ell^+\ell^-$ Data
Related title	Combined Explanation of the Z→bb¯ Forward-Backward Asymmetry, the Cabibbo Angle Anomaly, and τ→μνν and b→sℓ+ℓ- Data
Author(s)	Crivellin, Andreas (CERN ; PSI, Villigen ; Zurich U.) ; Manzari, Claudio Andrea (PSI, Villigen ; Zurich U.) ; Alguero, Marcel (Barcelona, Autonoma U. ; Barcelona, IFAE) ; Matias, Joaquim (Barcelona, Autonoma U. ; Barcelona, IFAE)
Publication	2021-07-02
Imprint	2020-10-27
Number of pages	8
Note	8 pages, 2 figures, version accepted for publication in PRL
In:	Phys. Rev. Lett. 127 (2021) 011801
DOI	10.1103/PhysRevLett.127.011801 (publication)
Subject category	nucl-th ; Nuclear Physics - Theory ; nucl-ex ; Nuclear Physics - Experiment ; hep-ex ; Particle Physics - Experiment ; hep-ph ; Particle Physics - Phenomenology
Abstract	In this article we propose a simple model which can provide a combined explanation of the $Z\to b\bar b$ forward-backward asymmetry, the Cabibbo Angle Anomaly (CAA), $\tau\to\mu\nu\nu$ and $b\to s\ell^+\ell^-$ data. This model is obtained by extending the Standard Model (SM) by two heavy vector-like quarks (an $SU(2)_L$ doublet (singlet) with hypercharge $-5/6$ (-1/3)), two new scalars (a neutral and a singly charged one) and a gauged $L_\mu-L_\tau$ symmetry. The mixing of the new quarks with the SM ones, after electroweak symmetry breaking, does not only explain $Z\to b\bar b$ data but also generates a lepton flavour universal contribution to $b\to s\ell^+\ell^-$ transitions. Together with the lepton flavour universality violating effect, generated by loop-induced $Z^\prime$ penguins involving the charged scalar and the heavy quarks, it gives an excellent fit to data ($6.1\,\sigma$ better than the SM). Furthermore, the charged scalar (neutral vector) gives a necessarily constructive tree-level (loop) effect in $\mu\to e\nu\nu$ ($\tau\to \mu\nu\nu$), which can naturally account for the CAA (${\rm Br}[\tau\to\mu\nu\nu]/{\rm Br}[\tau\to e\nu\nu]$ and ${\rm Br}[\tau\to\mu\nu\nu]/{\rm Br}[\mu\to e\nu\nu]$).
Copyright/License	preprint: (License: arXiv nonexclusive-distrib 1.0) publication: Published by the American Physical Society (License: CC BY 4.0), sponsored by SCOAP³

$Diagramatic representation of how the Feynman diagrams (A)-(D) within our model contribute to $Z\to \bar{b}b(\bar{s}s)$, muon decay, $\tau\to\mu\nu\nu$ and $b\to s\ell\ell$ and explain the associated anomalies.$