Abstract
In the wake of new scalar searches at LHC in various channels, it is interesting to investigate the sacrosanctity of the constraints on the masses and couplings of the heavier scalars in a two-Higgs-doublet model (2HDM). We consider the effects of new physics beyond a 2HDM encoded in terms of bosonic dim-6 operators. Although these constraints are mostly immune to such new physics, we demonstrate for a specific class of bosonic operators, the constraints on the masses of the exotic scalars from cascade decays can get substantially relaxed. We present such effects for both degenerate and hierarchical mass spectra of the heavier scalars in 2HDM. Some decay channels of the new scalars vanish at the alignment limit in the tree-level 2HDM. But the inclusion of dim-6 terms can lead to significant cross-sections for such processes. It is also pointed out that observation of such processes can no longer rule out the alignment limit if such dim-6 operators are present.
Highlights
Even after the discovery of a Higgs boson [1,2] whose characteristics resemble that of the standard model (SM) Higgs, the dynamics of electroweak symmetry breaking and the structure of the scalar sector remains an open question
The noncancellation of quadratic divergence of Higgs mass under the framework of SM has motivated a plethora of beyond-standard model (BSM) theories for decades
In supersymmetric models [3] the motivation behind a second Higgs doublet is twofold: first to cancel chiral anomalies created by the superpartners of such scalars and second from the requirement of the superpotential to be holomorphic. 2HDMs arising in the framework of composite Higgs [4,5], little Higgs [6], and twin Higgs [7] have been studied in the literature
Summary
Even after the discovery of a Higgs boson [1,2] whose characteristics resemble that of the standard model (SM) Higgs, the dynamics of electroweak symmetry breaking and the structure of the scalar sector remains an open question. Along with the signal strengths of the SM-like Higgs, the direct bounds on the masses of exotic scalars play a pivotal role in constraining the parameter space of the 2HDM Such bounds depend on the specifications of the Yukawa sector of the models. In addition to the regular search channels consisting of a pair of SM particles as mentioned earlier, exotic states decaying into one another can provide strong constraints on 2HDM parameter space At this point, we define mA 1⁄4 mH 1⁄4 mHÆ as the “degenerate” case and the case when any of the three exotic scalars is more massive than the other two as the “hierarchical” case. The importance of Higgs cascade decays as the possible probes of an extended scalar sector have been discussed in the literature [55,56,57,58,59,60], and A → ZH decay is dubbed as a “golden channel” in this context [61]
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