Abstract
We describe a class of three Higgs doublet models (3HDMs) with a softly broken U(1) × U(1) family symmetry that enforces a Cabibbo-like quark mixing while forbidding tree-level flavour changing neutral currents. The hierarchy in the observed quark masses is partly explained by a softer hierarchy in the vacuum expectation values of the three Higgs doublets. As a consequence, the physical scalar spectrum contains a Standard Model (SM) like Higgs boson h125 while exotic scalars couple the strongest to the second quark family, leading to rather unconventional discovery channels that could be probed at the Large Hadron Collider. In particular, we describe a search strategy for the lightest charged Higgs boson H±, through the process coverline{s}to {H}^{+}to {W}^{+}{h}_{125} , using a multivariate analysis that leads to an excellent discriminatory power against the SM background. Although the analysis is applied to the proposed class of 3HDMs, we employ a model-independent formulation such that it can be applied to any other model with the same discovery channel.
Highlights
The main background for the signal with one lepton, at least one or two b-tagged jets and missing energy can come from the following Standard Model (SM) processes: T√able 2
We describe a class of three Higgs doublet models (3HDMs) with a softly broken U(1) × U(1) family symmetry that enforces a Cabibbo-like quark mixing while forbidding tree-level flavour changing neutral currents
In this article, introduced a class of 3HDMs with a global U(1)X × U(1)Z family symmetry that is softly broken by bi-linear terms in the scalar potential
Summary
We propose a 3HDM, with features that lead to a simple yet predictive theory. A spontaneously broken U(1)X × U(1)Z global symmetry would lead to massless Goldstone bosons and constrain the model significantly when considering e.g. the precise measurements of the Z-boson width This motivates us to softly break the symmetry by adding additional mass terms in the scalar potential. The reader might note that at higher orders, the Yukawa interactions only allow for a mixing between the first and second quark generations, opening the question of how to reproduce the observed full CKM mixing in the quark sector As this model is thought as an effective theory, one can write the following dimension-6 operators consistent with the imposed symmetries d1R,2 Hi†Q3LbR Hi†Q1L,2. Working in the ξ 1 limit, the mixing matrices S, P and C are identical up to O(ξ) but differ at O(ξ2)
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