Heavy charged scalars from $$ c\overline{s} $$ fusion: a generic search strategy applied to a 3HDM with U(1) × U(1) family symmetry

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 h 125 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 cs → H + → 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.

Multi-Higgs-doublet models and singular alignment

“…In our case, we may estimate this ratio as (v d M/v 2 τ ) 2 ∼ 10 8 which is still sufficiently small. For example, after substitution in B th r (µ → eγ) = 1.6 × 10 −24 (Λ LN /Λ LFV ) 4 we obtain B th r (µ → eγ) ∼ 10 −16 , where the previous relation was taken from Ref. [27].…”

“…This fact is depicted in Figure 1. We will introduce four Higgs doublets Φ t , Φ b , Φ µ and Φ d , which are responsible for the masses in their respective sets 4 . The corresponding mass-vacuum-like relation in analogy to Eq.…”

“…On the other hand, possible contributions coming from the scalar mediators at the loop level can also be expected to be sufficiently small and consistent with phenomenological tests as suggested by analyses of the minimal lepton-flavour violation hypothesis [27,28] and as discussed in Section 2.5. Notice, however, that this set of flavour-violating processes have a strong dependence in the ratio between the two scales (Λ LN /Λ LFV ) 4 , where the first and second one correspond to the scale where lepton number (LN) is broken and lepton-flavour-violation (LFV) is produced. Therefore, if a large hierarchy exists between these two scales one may obtain observable effects.…”

“…In the following, we assume Yukawa couplings to be order one, y f = O (1), and try to understand the fermion mass patterns through a theory with multiple Higgs doublets. The most extreme approach along this line would be the "private Higgs" scenario, in which among other things, for each fermion a Higgs doublet is introduced [2,3], see also [4][5][6]. The mass hierarchies are explained by hierarchies of vacuum expectation values of the individual Higgs doublets: m f v f , where v f is the vacuum expectation value of the Higgs that is responsible for the fermion f = u, d, c, s, t, b, e, µ, τ .…”

Scalar and gauge sectors in the 3-Higgs Doublet Model under the $$S_3$$ symmetry

“…Discrete symmetries have been extensively studied in this context, both at low and at high energies (for reviews of models with discrete symmetries see [18][19][20][21]). Since these models in general require the addition of more Higgs fields, the phenomenological consequences in all sectors, like allowed extra processes and couplings, have to be analysed, some examples can be found in [22][23][24]. Restrictions are placed on the models by confronting their phenomenology with the experimental results, in this case the ones of ATLAS [25] and CMS [26].…”