Higgs sector extensions beyond the Standard Model (BSM) provide additional sources of CP violation and further scalar states that help to trigger a strong first order electroweak phase transition (SFOEWPT) required to generate the observed baryon asymmetry of the Universe through electroweak baryogenesis. We investigate the CP-violating 2-Higgs-Doublet Model (C2HDM) and the Next-to-Minimal 2-Higgs-Doublet Model (N2HDM) with respect to their potential to generate an SFOEWPT while being compatible with all relevant and recent theoretical and experimental constraints. The implications of an SFOEWPT on the collider phenomenology of the two models are analysed in detail in particular with respect to Higgs pair production. We provide benchmark points for parameter points that are compatible with an SFOEWPT and provide distinct di-Higgs signatures.
We provide the C++ tool BSMPT for calculating the strength of the electroweak phase transition in extended Higgs sectors. This relies on the loop-corrected effective potential at finite temperature including daisy resummation of the bosonic masses. The program allows to compute the vacuum expectation value (VEV) $v$ of the potential as a function of the temperature, and in particular the critical VEV $v_c$ at the temperature $T_c$ where the phase transition takes place. In addition, the loop-corrected trilinear Higgs self-couplings are provided. We apply an on-shell renormalization scheme in the sense that the loop-corrected masses and mixing angles are required to be equal to their tree-level input values. This allows for efficient scans in the parameter space of the models. The models implemented so far are the CP-conserving and the CP-violating 2-Higgs-Doublet Models (2HDM) and the Next-to-Minimal 2HDM (N2HDM). The program structure is such that the user can easily implement further models. Our tool can be used for the investigation of electroweak baryogenesis in models with extended Higgs sectors and the related Higgs self-couplings. The combination with parameter scans in the respective models allows to study the impact on collider phenomenology and to make a link between collider phenomenology and cosmology. The program package can be downloaded at: https://github.com/phbasler/BSMPT.
Light new physics weakly coupled to the Higgs can induce a strong first-order electroweak phase transition (EWPT). Here, we argue that scenarios in which the EWPT is driven first-order by a light scalar with mass between $sim 10$ GeV - $m_h/2$ and small mixing with the Higgs will be conclusively probed by the high-luminosity LHC and future Higgs factories. Our arguments are based on analytic and numerical studies of the finite-temperature effective potential and provide a well-motivated target for exotic Higgs decay searches at the LHC and future lepton colliders.
We describe a numerical calculation tool H-COUP written in Fortran, which provides one-loop electroweak corrected vertices for the discovered Higgs boson $h(125)$ in various Higgs sectors. The renormalization is based on the improved on-shell scheme without gauge dependence. In the first version H-COUP_1.0, the following models are included, namely, the Higgs singlet model, four types (Type-I, Type-II, Type-X, Type-Y) of two Higgs doublet models with a softly-broken $Z_2$ symmetry and the inert doublet model. We first briefly introduce these models and then explain how to install and run this tool in an individual machine. A sample of numerical outputs is provided for user information.
Precision predictions play an important role in the search for indirect New Physics effects in the Higgs sector itself. For the electroweak (EW) corrections of the Higgs bosons in extended Higgs sectors several renormalization schemes have been worked out that provide gauge-parameter-independent relations between the input parameters and the computed observables. Our recently published program codes 2HDECAY and ewN2HDECAY allow for the computation of the EW corrections to the Higgs decay widths and branching ratios of the Two-Higgs-Doublet Model (2HDM) and the Next-to-Minimal-2HDM (N2HDM) for different renormalization schemes of the scalar mixing angles. In this paper, we present a comprehensive and complete overview over the relative size of the EW corrections to the branching ratios of the 2HDM and N2HDM neutral Higgs bosons for different applied renormalization schemes. We quantify the size of the EW corrections of Standard Model(SM)- and non-SM-like Higgs bosons and moreover also identify renormalization schemes that are well-behaved and do not induce unnaturally large corrections. We furthermore pin down decays and parameter regions that feature large EW corrections and need further treatment in order to improve the predictions. Our study sets the scene for future work in the computation of higher-order corrections to the decays of non-minimal Higgs sectors.
We present the concept of H-COUP_ver 2, which evaluates the decay rates (including higher order corrections) for the Higgs boson with a mass of 125 GeV in various extended Higgs models. In the previous version (H-COUP_1.0), only a full set of the Higgs boson vertices are evaluated at one-loop level in a gauge invariant manner in these models. H-COUP_ver 2 contains all the functions of H-COUP_1.0. After shortly introducing these extended Higgs models and discussing their theoretical and experimental constraints, we summarize formulae for the renormalized vertices and the decay rates. We then explain how to install and run H-COUP_ver 2 with some numerical examples.