$Z$ mediated Flavour Changing Neutral Currents with a Fourth Vector-Like Family

Abstract

We discuss $Z$ mediated flavour changing neutral currents within a model where the hierarchical quark and lepton masses are explained via a fourth vector-like family, together with a scalar sector consisting of two Higgs doublets augmented by a gauge singlet scalar field that spontaneously breaks an extra global $U(1{)}^{\prime }$ symmetry. The $Z$ mediated flavor violating interactions arise from the mixings between the SM fermions and the vector-like fermions, where the mixing is discussed in an analytic approximation and also exactly numerically. We first discuss charged lepton flavor violating (CLFV) $\tau \to \mu \gamma ,\tau \to 3\mu$ and $Z\to \mu \tau$ decays and find that they cannot significantly constrain the masses of charged vector-like leptons. However, the $790\text{GeV}$ mass bound arising from collider searches on vector-like lepton doublets can set further constraints on the model parameter space. We also consider rare $t\to cZ$ decays as well as unitarity violation in the CKM mixing in order to constrain the quark sector of the model under consideration.

41 pages. References added, discussions enlarged. Matches published version in PRD

References in corpus (7)

• Observation of a new particle in the search for the Standard Model Higgs boson with the ATLAS detector at the LHC
• Observation of a new boson at a mass of 125 GeV with the CMS experiment at the LHC
• Prospects for vectorlike leptons at future proton-proton colliders
• Are the CKM anomalies induced by vector-like quarks? Limits from flavor changing and Standard Model precision tests
• Addressing the CKM Unitarity Problem with a Vector-like Up Quark
• Fermion mass hierarchies from vector-like families with an extended 2HDM and a possible explanation for the electron and muon anomalous magnetic moments
• New Weinberg operator for neutrino mass and its seesaw origin

Cited by in corpus (4)

• Probing Heavy Neutrino Magnetic Moments at the LHC using Long-Lived Particle Searches
• Global analysis and LHC study of a vector-like extension of the Standard Model with extra scalars
• The Two Scales of New Physics in Higgs Couplings
• Search for single vector-like $B$ quark production in hadronic final states at the LHC