Abstract
Motivated by the fermion mass hierarchy we study the phenomenology of two flavorful two-Higgs-doublet model (2HDM) scenarios. By virtue of the flavor or singular alignment ansatz it is possible to link the mass of a subset of fermions to the vacuum-expectation-value (VEV) of a unique Higgs doublet and to simultaneously avoid flavor-changing-neutral-currents at tree-level. We explicitly construct two models called Type-A and B. There, either the top quark alone or all third generation fermions couple to the doublet with the larger VEV. The other fermions acquire their masses through the small VEV of the other doublet. Thus, more natural values for the Yukawa couplings can be obtained. The main differences between these models and conventional ones are studied including a discussion of both their structure and phenomenological consequences. In particular, as distinctive deviations for the Yukawa couplings of the light fermions are predicted we discuss possible tests at the LHC based on searches for $h\to J/\Psi + \gamma$, $h\to\mu\mu$, and heavy scalar resonances decaying to muon pairs. We find that for a wide region of parameter space this specific set of signatures can be used to distinguish among the new proposed types and the conventional ones.
Highlights
Flavor-changing-neutral-current processes (FCNC) have been experimentally observed to be strongly suppressed
Motivated by the mass hierarchy between the top quark and the other fermions, or between the third generation and the first two generation fermions, respectively, we investigated two new, interesting types of 2HDMs with a softly broken Z2 symmetry
Speaking, the new types are closely related to the wellknown types of 2HDMs (I and II)
Summary
Flavor-changing-neutral-current processes (FCNC) have been experimentally observed to be strongly suppressed. Its simplicity requires considering only one Higgs doublet; once two scalar doublets are assumed, potential tree-level flavor transitions are expected. Those FCNCs are mediated by the linear combination of the neutral components of the doublets. The Yukawa sector of these models includes a family or flavor universal Z2-parity assignments, which operates on the Higgs potential This is understandable as natural flavor conserving (NFC) theories demand it [6,7]. The smallness of v1 is natural as setting it to zero, one recovers the initial Z2 symmetry As both VEVs contribute to the W-boson mass they satisfy v2 1⁄4 v21 þ v22 1⁄4 ð174 GeVÞ2: ð12Þ. The requirement that should be met in order to guarantee that the minimum is a global one is [28]
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