CP violation and BSM Higgs bosons

6th International Workshop Charged 2016.We study extensions of the Standard Model (SM) in which copies of the SM scalar SU(2) doublet are added to the Higgs sector. These scalar doublets either acquire a Vacuum Expectation Value (VEV) and hence are active or do not develop a VEV and are inert. We consider CP-violation (CPV) in both the active and inert sector. As an example of a model with CPV in the active sector, we present a Type-I 2-Higgs-Doublet Model (2HDM) with two active doublets and show Large Hadron Collider (LHC) signals of such a scenario. The amount of CPV in this case is very limited due to constraints coming from Electric Dipole Moment experiments. Moreover, 2HDMs with only active doublets do not provide a Dark Matter (DM) candidate. As a result, we turn to 3-Higgs-Doublet Models (3HDMs) where unbounded CPV and viable DM candidates could be introduced simultaneously in the inert sector. We investigate DM phenomenology of such models.Peer reviewe

Symmetries of the Scalar Sector of Multi-Higgs-Doublet Models

Classifying the symmetries of the scalar sector in multi-Higgs-doublet models is the main focus of this thesis. We have found certain symmetries that are always broken in models with more than two doublets, which we name "frustrated symmetries". In the attempt towards the classification of possible symmetries in the scalar sector of the NHDM, we find that these symmetry groups are either subgroups of the maximal torus, or certain finite Abelian groups which are not subgroups of maximal tori. For the subgroups of the maximal torus, we present an algorithmic strategy that gives the full list of possible realizable Abelian symmetries for any given $N$. We extend this strategy to include Abelian antiunitary symmetries (with generalized CP transformations) in NHDM. We also show that multi-Higgs-doublet models can naturally accommodate scalar dark matter candidates protected by the group $\Z_p$, since these groups are realizable in NHDM. These models do not require any significant fine-tuning and can lead to a variety of forms of microscopic dynamics among the dark matter candidates.Comment: PhD thesi

Baryogenesis from a CP-Violating Inflation

Funding Information: The author acknowledges financial support from Academy of Finland projects “Particle cosmology and gravitational waves” No. 320123 and “Particle cosmology beyond the Standard Model” No. 310130, and would like to thank the organisers of the BSM-2021 conference for creating the opportunity for lively scientific discussions. Publisher Copyright: © 2021 CERN. All rights reserved.We introduce the novel phenomena of CP-violating inflation in the frameworks of a 3-Higgs doublet model where the inflaton doublets have a non-minimal coupling to gravity. We allow for this coupling to be complex, thereby introducing CP-violation - a necessary source of the baryon asymmetry - in the inflaton couplings. We investigate the inflationary dynamics of such a framework and the inflaton decay in the reheating phase. We discuss how the CP-violation of the model is imprinted on the particle asymmetries.Peer reviewe

Stabilizing the Higgs potential with a Z '

Current data point toward metastability of the electroweak vacuum within the Standard Model. We study the possibility of stabilizing the Higgs potential in U(1) extensions thereof. A generic Z' boson improves stability of the scalar potential in two ways: it increases the Higgs self-coupling, due to a positive contribution to the beta-function of the latter, and it decreases the top quark Yukawa coupling, which again has a stabilizing effect. We determine the range of U(1) charges which leads to a stable electroweak vacuum. In certain classes of models, such stabilization is possible even if the Z' does not couple to the Higgs and is due entirely to the reduction of the top Yukawa coupling. We also study the effect of the kinetic mixing between the extra U(1) and hypercharge gauge fields. (C) 2015 The Authors. Published by Elsevier B.V.Peer reviewe

P -even, C P-violating signals in scalar-mediated processes

Most studies of Higgs sector CP violation focus on the detection of CP-violating neutral Higgs-fermion Yukawa couplings, which yield P-odd, CP-violating phenomena. There is some literature on purely bosonic signatures of Higgs sector CP violation, where the simultaneous observation of three processes (suitably chosen) constitutes a signal of P-even CP violation. However, in the examples previously analyzed, some of the processes are strongly suppressed in the approximate Higgs alignment limit (corresponding to the existence of a Standard Model-like Higgs boson as suggested by LHC data), in which case the proposed CP-violating signals are difficult to observe in practice. In this paper, we extend the existing literature by examining processes that do not vanish in the Higgs alignment limit and whose simultaneous observation would provide unambiguous evidence for scalar-mediated P-even CP violation. We assess the discovery potential of such signals at various future multi-TeV lepton (and γγ) colliders. The potential for detecting loop-induced P-even, CP-violating phenomena is also considered.info:eu-repo/semantics/publishedVersio

CP violating Two-Higgs-Doublet Model : constraints and LHC predictions

Two-Higgs-Doublet Models (2HDMs) are amongst the simplest extensions of the Standard Model. Such models allow for tree-level CP Violation (CPV) in the Higgs sector. We analyse a class of CPV 2HDM (of Type-I) in which only one of the two Higgs doublets couples to quarks and leptons, avoiding dangerous Flavour Changing Neutral Currents. We provide an up to date and comprehensive analysis of the constraints and Large Hadron Collider (LHC) predictions of such a model. Of immediate interest to the LHC Run 2 is the golden channel where all three neutral Higgs bosons are observed to decay into gauge boson pairs, W W and Z Z, providing a smoking gun signature of the CPV 2HDM.Peer reviewe

Higgs-flavon mixing and h -> mu tau

ATLAS and CMS have reported an excess in the flavor violating decay of the Higgs boson, h -> mu tau. We show that this result can be accommodated through a mixing of the Higgs with a flavon, the field responsible for generating the Yukawa matrices in the lepton sector. We employ a version of the Froggatt-Nielsen mechanism at the electroweak scale, with only the leptons and the flavon transforming non-trivially under the corresponding symmetry group. Non-observation of charged lepton flavor violation (LFV) in other processes imposes important constraints on the model, which we find to be satisfied in substantial regions of parameter space.Peer reviewe

Direct and indirect probes of Goldstone dark matter

There exists a general model framework where dark matter can be a vanilla weakly-interacting-massive-particle-like thermal relic with a mass of O(100 GeV), but it still escapes direct detection. This happens if the dark matter particle is a Goldstone boson whose scattering with ordinary matter is suppressed at low energy due to momentum-dependent interactions. We outline general features of this type of models and analyze a simple realization of these dynamics as a concrete example. In particular, we show that although direct detection of this type of dark matter candidate is very challenging, the indirect detection can already provide relevant constraints. Future projections of the indirect-detection experiments allow for even more stringent exclusion limits and can rule out models of this type.Peer reviewe