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Phenomenological comparison of models with extended Higgs sectors
Publication . Muehlleitner, Margarete; Sampaio, Marco O. P.; Santos, Rui; Wittbrodt, Jonas
Beyond the Standard Model (SM) extensions usually include extended Higgs sectors. Models with singlet or doublet fields are the simplest ones that are compatible with the rho parameter constraint. The discovery of new non-SM Higgs bosons and the identification of the underlying model requires dedicated Higgs properties analyses. In this paper, we compare several Higgs sectors featuring 3 CP-even neutral Higgs bosons that are also motivated by their simplicity and their ability to solve some of the flaws of the SM. They are: the SM extended by a complex singlet field (CxSM), the singlet extension of the 2-Higgs-Doublet Model (N2HDM), and the Next-to-Minimal Supersymmetric SM extension (NMSSM). In addition, we analyse the CP-violating 2-Higgs-Doublet Model (C2HDM), which provides 3 neutral Higgs bosons with a pseudoscalar admixture. This allows us to compare the effects of singlet and pseudoscalar admixtures. Through dedicated scans of the allowed parameter space of the models, we analyse the phenomenologically viable scenarios from the view point of the SM-like Higgs boson and of the signal rates of the non-SM-like Higgs bosons to be found. In particular, we analyse the effect of singlet/pseudoscalar admixture, and the potential to differentiate these models in the near future. This is supported by a study of couplings sums of the Higgs bosons to massive gauge bosons and to fermions, where we identify features that allow us to distinguish the models, in particular when only part of the Higgs spectrum is discovered. Our results can be taken as guidelines for future LHC data analyses, by the ATLAS and CMS experiments, to identify specific benchmark points aimed at revealing the underlying model.
Two-loop stability of a complex singlet extended standard model
Publication . Costa, Raul; Morais, Antonio P.; Sampaio, Marco O. P.; Santos, Rui
Motivated by the dark matter and the baryon asymmetry problems, we analyze a complex singlet extension of the Standard Model with a Z(2) symmetry (which provides a dark matter candidate). After a detailed two-loop calculation of the renormalization group equations for the new scalar sector, we study the radiative stability of the model up to a high energy scale (with the constraint that the 126 GeV Higgs boson found at the LHC is in the spectrum) and find it requires the existence of a new scalar state mixing with the Higgs with a mass larger than 140 GeV. This bound is not very sensitive to the cutoff scale as long as the latter is larger than 10(10) GeV. We then include all experimental and observational constraints/measurements from collider data, from dark matter direct detection experiments, and from the Planck satellite and in addition force stability at least up to the grand unified theory scale, to find that the lower bound is raised to about 170 GeV, while the dark matter particle must be heavier than about 50 GeV.
On the dynamical complexity of a seasonally forced discrete SIR epidemic model with a constant vaccination strategy
Publication . Rashidinia, Jalil; Sajjadian, Mehri; Duarte, Jorge; Januário, Cristina; Martins, Nuno
In this article, we consider the discretized classical Susceptible-Infected-Recovered (SIR) forced epidemic model to investigate the consequences of the introduction of different transmission rates and the effect of a constant vaccination strategy, providing new numerical and topological insights into the complex dynamics of recurrent diseases. Starting with a constant contact (or transmission) rate, the computation of the spectrum of Lyapunov exponents allows us to identify different chaotic regimes. Studying the evolution of the dynamical variables, a family of unimodal-type iterated maps with a striking biological meaning is detected among those dynamical regimes of the densities of the susceptibles. Using the theory of symbolic dynamics, these iteratedmaps are characterized based on the computation of an important numerical invariant, the topological entropy.The introduction of a degree (or amplitude) of seasonality, 𝜀, is responsible for inducing complexity into the population dynamics. The resulting dynamical behaviors are studied using some of the previous tools for particular values of the strength of the seasonality forcing, 𝜀. Finally, we carry out a study of the discrete SIR epidemic model under a planned constant vaccination strategy.We examine what effect this vaccination regime will have on the periodic and chaotic dynamics originated by seasonally forced epidemics.
Chaos analysis and explicit series solutions to the seasonally forced SIR epidemic model
Publication . Duarte, Jorge; Januário, Cristina; Martins, Nuno; Rogovchenko, Svitlana; Rogovchenko, Yuriy
Despite numerous studies of epidemiological systems, the role of seasonality in the
recurrent epidemics is not entirely understood. During certain periods of the year
incidence rates of a number of endemic infectious diseases may fluctuate dramatically.
This influences the dynamics of mathematical models describing the spread
of infection and often leads to chaotic oscillations. In this paper, we are concerned
with a generalization of a classical Susceptible–Infected–Recovered epidemic model
which accounts for seasonal effects. Combining numerical and analytic techniques,
we gain new insights into the complex dynamics of a recurrent disease influenced by
the seasonality. Computation of the Lyapunov spectrum allows us to identify different
chaotic regimes, determine the fractal dimension and estimate the predictability of the
appearance of attractors in the system. Applying the homotopy analysis method, we
obtain series solutions to the original nonautonomous SIR model with a high level of
accuracy and use these approximations to analyze the dynamics of the system. The
efficiency of the method is guaranteed by the optimal choice of an auxiliary control
parameter which ensures the rapid convergence of the series to the exact solution of
the forced SIR epidemic model.
Phenomenological comparison of models with extended Higgs sectors
Publication . Muehlleitner, Margarete; Sampaio, Marco O. P.; Santos, Rui; Wittbrodt, Jonas
Beyond the Standard Model (SM) extensions usually include extended Higgs sectors. Models with singlet or doublet fields are the simplest ones that are compatible with the rho parameter constraint. The discovery of new non-SM Higgs bosons and the identification of the underlying model requires dedicated Higgs properties analyses. In this paper, we compare several Higgs sectors featuring 3 CP-even neutral Higgs bosons that are also motivated by their simplicity and their ability to solve some of the flaws of the SM. They are: the SM extended by a complex singlet field (CxSM), the singlet extension of the 2-Higgs-Doublet Model (N2HDM), and the Next-to-Minimal Supersymmetric SM extension (NMSSM). In addition, we analyse the CP-violating 2-Higgs-Doublet Model (C2HDM), which provides 3 neutral Higgs bosons with a pseudoscalar admixture. This allows us to compare the effects of singlet and pseudoscalar admixtures. Through dedicated scans of the allowed parameter space of the models, we analyse the phenomenologically viable scenarios from the view point of the SM-like Higgs boson and of the signal rates of the non-SM-like Higgs bosons to be found. In particular, we analyse the effect of singlet/pseudoscalar admixture, and the potential to differentiate these models in the near future. This is supported by a study of couplings sums of the Higgs bosons to massive gauge bosons and to fermions, where we identify features that allow us to distinguish the models, in particular when only part of the Higgs spectrum is discovered. Our results can be taken as guidelines for future LHC data analyses, by the ATLAS and CMS experiments, to identify specific benchmark points aimed at revealing the underlying model.
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Funding agency
Fundação para a Ciência e a Tecnologia
Funding programme
5876
Funding Award Number
UID/MAT/04106/2013