48 research outputs found
The CP-Violating 2HDM in Light of a Strong First Order Electroweak Phase Transition and Implications for Higgs Pair Production
We investigate the strength of the electroweak phase transition (EWPT) within
the CP-violating 2-Higgs-Doublet Model (C2HDM). By applying a renormalisation
scheme which allows efficient scans of the C2HDM parameter space, we analyse
the possibility of a strong first order EWPT required for baryogenesis and
study its phenomenological implications for the LHC. Like in the CP-conserving
(real) 2HDM (R2HDM) we find that a strong EWPT favours mass gaps between the
non-SM-like Higgs bosons. These lead to prominent final states comprised of
gauge+Higgs bosons or pairs of Higgs bosons. In contrast to the R2HDM, the
CP-mixing of the C2HDM also favours approximately mass degenerate spectra with
dominant decays into SM particles. The requirement of a strong EWPT further
allows us to distinguish the C2HDM from the R2HDM using the signal strengths of
the SM-like Higgs boson. We additionally find that a strong EWPT requires an
enhancement of the SM-like trilinear Higgs coupling at next-to-leading order
(NLO) by up to a factor of 2.4 compared to the NLO SM coupling, establishing
another link between cosmology and collider phenomenology. We provide several
C2HDM benchmark scenarios compatible with a strong EWPT and all experimental
and theoretical constraints. We include the dominant branching ratios of the
non-SM-like Higgs bosons as well as the Higgs pair production cross section of
the SM-like Higgs boson for every benchmark point. The pair production cross
sections can be substantially enhanced compared to the SM and could be
observable at the high-luminosity LHC, allowing access to the trilinear Higgs
couplings
and the wrong-sign limit of the Two-Higgs-Doublet Model
We point out the importance of the decay channels and in
the wrong-sign limit of the Two-Higgs-Doublet Model (2HDM) of type II. They can
be the dominant decay modes at moderate values of , even if the
(pseudo)scalar mass is above the threshold where the decay into a pair of top
quarks is kinematically open. Accordingly, large cross sections
and are obtained and currently probed by the LHC experiments,
yielding conclusive statements about the remaining parameter space of the
wrong-sign limit. In addition, mild excesses - as recently found in the ATLAS
analysis - could be explained. The wrong-sign limit makes
other important testable predictions for the light Higgs boson couplings.Comment: 19 pages, 6 figures, v2: journal versio
The forgotten channels: charged Higgs boson decays to a and a non-SM-like Higgs boson
The presence of charged Higgs bosons is a generic prediction of multiplet
extensions of the Standard Model (SM) Higgs sector. Focusing on the
Two-Higgs-Doublet-Model (2HDM), we discuss the charged Higgs boson collider
phenomenology in the theoretically and experimentally viable parameter space.
While almost all existing experimental searches at the LHC target the fermionic
decays of charged Higgs bosons, we point out that the bosonic decay channels --
especially the decay into a non-SM-like Higgs boson and a boson -- often
dominate over the fermionic channels. Moreover, we revisit two genuine BSM
effects on the properties of the discovered Higgs boson -- the charged Higgs
contribution to the diphoton rate and the Higgs decay to two light Higgs bosons
-- and their implication for the charged Higgs boson phenomenology. As main
result of the present paper, we propose five two-dimensional benchmark
scenarios with distinct phenomenological features in order to facilitate the
design of dedicated LHC searches for charged Higgs bosons decaying into a
boson and a light, non-SM-like Higgs boson.Comment: 57 pages, 26 figures, data tables for cross sections and benchmark
scenarios included as ancillary files, updated text to match journal versio
Testing Exotic Scalars with HiggsBounds
The program HiggsBounds is a well-established tool for testing
Beyond-the-Standard Model (BSM) theories with an extended Higgs sector against
experimental limits from collider searches at LEP, Tevatron and LHC. Thus far,
it could be applied to any neutral or charged Higgs bosons originating from the
modified Higgs sector. Implicitly, these particles were assumed to exhibit a
somewhat hierarchical Yukawa structure as present in the Standard Model, where
in particular the couplings to first generation fermions could be neglected. In
this work, we extend the HiggsBounds functionalities to go beyond these
restrictions, thus making the code applicable to any neutral or charged BSM
scalars. Moreover, we develop a new approach to implement experimental searches
whose kinematic acceptance depends significantly on the values of the involved
couplings. We achieve this by recasting the searches to general scalar models.
Using this approach we incorporate relevant current experimental limits from
LHC searches for exotic scalars, and present the implications of these limits
for a dark matter scalar mediator model, a flipped Two-Higgs-Doublet Model and
a supersymmetric model with R-parity violation.Comment: 28 pages, 7 figures, the FeynRules implementation of the generic
scalar model is included as an ancillary file; v2: matches version published
in EPJ
Models with extended Higgs sectors at future e⁺e⁻ colliders
We discuss the phenomenology of several beyond the Standard Model (SM) extensions that include extended Higgs sectors. The models discussed are the SM extended by a complex singlet field, the 2-Higgs-doublet model with a CP-conserving and a CP-violating scalar sector, the singlet extension of the 2-Higgs-doublet model, and the next-to-minimal supersymmetric SM extension. All the above models have at least three neutral scalars, with one being the 125 GeV Higgs boson. This common feature allows us to compare the production and decay rates of the other two scalars and therefore to compare their behavior at future electron-positron colliders. Using predictions on the expected precision of the 125 GeV Higgs boson couplings at these colliders we are able to obtain the allowed admixtures of either a singlet or a pseudoscalar to the observed 125 GeV scalar. Therefore, even if no new scalar is found, the expected precision at future electron-positron colliders, such as CLIC, will certainly contribute to a clearer picture of the nature of the discovered Higgs boson
The dark phases of the N2HDM
We discuss the dark phases of the Next-to-2-Higgs Doublet model. The model is an extension of the Standard Model with an extra doublet and an extra singlet that has four distinct CP-conserving phases, three of which provide dark matter candidates. We discuss in detail the vacuum structure of the different phases and the issue of stability at tree-level of each phase. Taking into account the most relevant experimental and theoretical constraints, we found that there are combinations of measurements at the Large Hadron Collider that could single out a specific phase. The measurement of h125 → γγ together with the discovery of a new scalar with specific rates to τ+τ− or γγ could exclude some phases and point to a specific phase
Vacuum instabilities in the N₂HDM
The Higgs sector of the Next-to-Minimal Two-Higgs-Doublet Model (N2HDM) is obtained from the Two-Higgs-Doublet Model (2HDM) containing two complex Higgs doublets, by adding a real singlet field. In this paper, we analyse the vacuum structure of the N2HDM with respect to the possibility of vacuum instabilities. We show that while one type of charge-and CP-preserving vacuum cannot coexist with deeper charge or CP-breaking minima, there is another type of vacuum whose stability is endangered by the possible occurrence of deeper charge-and CP-breaking minima. Analytical expressions relating the depth of different vacua are deduced. Parameter scans of the model are carried out that illustrate the regions of parameter space where the vacuum is either stable or metastable as well as the regions where tunnelling to deeper vacua gives rise to a too short lifetime of the vacuum. Taking other experimental and theoretical constraints into account, we find that the vacuum stability constraints have an important impact on the phenomenology of the N2HDM
CP in the dark
We build a model containing two scalar doublets and a scalar singlet with a
specific discrete symmetry. After spontaneous symmetry breaking, the model has
Standard Model-like phenomenology, as well as a hidden scalar sector which
provides a viable dark matter candidate. We show that CP violation in the
scalar sector occurs exclusively in the hidden sector, and consider possible
experimental signatures of this CP violation.We acknowledge the contribution of the research training group GRK1694 'Elementary particle physics at highest energy and highest precision'. PF and RS are supported in part by the National Science Centre, Poland, the HARMONIA project under contract UMO-2015/18/M/ST2/00518 and by a CERN fund grant CERN/FIS-PAR/0002/2017. JW gratefully acknowledges funding from the PIER Helmholtz Graduate School.info:eu-repo/semantics/publishedVersio
HiggsBounds-5: Testing Higgs Sectors in the LHC 13 TeV Era
We describe recent developments of the public computer code HiggsBounds. In
particular, these include the incorporation of LHC Higgs search results from
Run 2 at a center-of-mass energy of 13 TeV, and an updated and extended
framework for the theoretical input that accounts for improved Higgs cross
section and branching ratio predictions and new search channels. We furthermore
discuss an improved method used in HiggsBounds to approximately reconstruct the
exclusion likelihood for LHC searches for non-standard Higgs bosons decaying to
final states. We describe in detail the new and updated
functionalities of the new version HiggsBounds-5.Comment: 42 pages, 4 figures, HiggsBounds is available at
https://gitlab.com/higgsbounds/higgsbound