Abstract
We discuss a possibility that the parameter space of the two Higgs doublet model is significantly narrowed down by considering the synergy between direct searches for additional Higgs bosons at the LHC and its luminosity upgraded operation and precision measurements of the Higgs boson properties at future electron-positron colliders such as the International Linear Collider. We show that, in the case where the coupling constants of the discovered Higgs boson are slightly different from the predicted values in the standard model, most of the parameter space is explored by the direct searches of extra Higgs bosons, in particular for the decays of the extra Higgs bosons into the discovered Higgs boson, and also by the theoretical arguments such as perturbative unitarity and vacuum stability. This can be done because there appears an upper limit on the mass of the extra Higgs bosons as long as the deviation exists in the Higgs boson coupling. We also show that in the alignment limit where all the Higgs boson couplings take the standard model like values most of the parameter space cannot be excluded because most of the Higgs to Higgs decays are suppressed and also there is no upper limit on the masses from the theoretical arguments.
Highlights
The current observations at the LHC experiments indicate that properties of the discovered Higgs boson with the mass of 125 GeV coincide with those predicted in the standard model (SM) [1, 2]
We show that in the alignment limit; i.e., all the Higgs boson couplings are exactly same as the SM values, plenty of the parameter space still remains even if the mass of the additional Higgs bosons are around the EW scale
Let us turn to investigate how the current parameter space in the two Higgs doublet models (THDMs) discussed in the previous section can be explored further in future experiments, especially by direct searches for heavy Higgs bosons at the high-luminosity LHC (HL-LHC) as well as by precision measurements of the Higgs boson couplings at the International Linear Collider (ILC)
Summary
The current observations at the LHC experiments indicate that properties of the discovered Higgs boson with the mass of 125 GeV coincide with those predicted in the standard model (SM) [1, 2]. The important thing is that if κhV = 1 and/or κhf = 1 are found at future collider experiments, we cannot take the decoupling limit This provides us a new no-loose theorem [28, 87, 95], where we can extract the upper bound on the mass scale of the second Higgs boson. This provides us a new no-loose theorem [28, 87, 95], where we can extract the upper bound on the mass scale of the second Higgs boson2 Such a bound is given by imposing the constraints from perturbative unitarity and vacuum stability as we will discuss them below. In the small tan β region, the neutral meson mixing processes B0 − B0 give a stronger bounds for mH± compared to the bound from B → Xsγ, and these exclude the wide region in all the types of THDMs
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
