arXiv subjects

Thomas Biekötter

Publications and source records attributed to Thomas Biekötter.

23 records · Page 2Linked to original sources

arXiv2022

Vacuum (meta-)stability in the $μν$SSM

We perform an analysis of the vacuum stability of the neutral scalar potential of the $μ$-from-$ν$ Supersymmetric Standard Model ($μν$SSM). As an example scenario, we discuss the alignment-without-decoupling limit of the $μν$SSM, for which the required conditions on the Higgs sector are derived. We demonstrate that in this limit large parts of the parameter space feature unphysical minima that are deeper than the electroweak minimum. In order to estimate the lifetime of the electroweak vacuum, we calculate the rates for the tunneling process into each unphysical minimum. We find that in many cases the resulting lifetime is longer than the age of the universe, such that the considered parameter region is not excluded. On the other hand, we also find parameter regions in which the electroweak vacuum is short-lived. We investigate how the different regions of stability are related to the presence of light right-handed sneutrinos. Accordingly, a vacuum stability analysis that accurately takes into account the possibility of long-lived metastable vacua is crucial for a reliable assessment of the phenomenological viability of the parameter space of the $μν$SSM and its resulting phenomenology at the (HL)-LHC.

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arXiv2021

Reconciling Higgs physics and pseudo-Nambu-Goldstone dark matter in the S2HDM using a genetic algorithm

We investigate a possible realization of pseudo-Nambu-Goldstone (pNG) dark matter in the framework of a singlet-extended 2 Higgs doublet model (S2HDM). pNG dark matter gained attraction due to the fact that direct-detection constraints can be avoided naturally because of the momentum-suppressed scattering cross sections, whereas the relic abundance of dark matter can nevertheless be accounted for via the usual thermal freeze-out mechanism. We confront the S2HDM with a multitude of theoretical and experimental constraints, paying special attention to the theoretical limitations on the scalar potential, such as vacuum stability and perturbativity. In addition, we discuss the complementarity between constraints related to the dark matter sector, on the one hand, and to the Higgs sector, on the other hand. In our numerical discussion we explore the Higgs funnel region with dark matter masses around $60$GeV using a genetic algorithm. We demonstrate that the S2HDM can account for the measured relic abundance while being in agreement with all relevant constraints. We also discuss whether the so-called galactic center excess and the antiproton excess can be accommodated, possibly in combination with a Higgs boson at about $96$GeV that can be the origin of the LEP- and the CMS-excess observed at this mass in the $b \bar b$-quark and the diphoton final state, respectively.

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arXiv2021

Fate of electroweak symmetry in the early Universe: Non-restoration and trapped vacua in the N2HDM

Extensions of the Higgs sector of the Standard Model allow for a rich cosmological history around the electroweak scale. We show that besides the possibility of strong first-order phase transitions, which have been thoroughly studied in the literature, also other important phenomena can occur, like the non-restoration of the electroweak symmetry or the existence of vacua in which the Universe becomes trapped, preventing a transition to the electroweak minimum. Focusing on the next-to-minimal two-Higgs-doublet model (N2HDM) of type II and taking into account the existing theoretical and experimental constraints, we identify the scenarios of electroweak symmetry non-restoration, vacuum trapping and first-order phase transition in the thermal history of the Universe. We analyze these phenomena and in particular their relation to each other, and discuss their connection to the predicted phenomenology of the N2HDM at the LHC. Our analysis demonstrates that the presence of a global electroweak minimum of the scalar potential at zero temperature does not guarantee that the corresponding N2HDM parameter space will be physically viable: the existence of a critical temperature at which the electroweak phase becomes the deepest minimum is not sufficient for a transition to take place, necessitating an analysis of the tunnelling probability to the electroweak minimum for a reliable prediction of the thermal history of the Universe.

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arXiv2021

munuSSM: A python package for the $μ$-from-$ν$ Supersymmetric Standard Model

We present the public python package munuSSM that can be used for phenomenological studies in the context of the $μ$-from-$ν$ Supersymmetric Standard Model ($μν$SSM). The code incorporates the radiative corrections to the neutral scalar potential at the full one-loop level. Sizable higher-order corrections, required for an accurate prediction of the SM-like Higgs-boson mass, can be consistently included via an automated link to the public code FeynHiggs. In addition, a calculation of effective couplings and branching ratios of the neutral and charged Higgs bosons is implemented. This provides the required ingredients to check a benchmark point against collider constraints from searches for additional Higgs bosons via an interface to the public code HiggsBounds. At the same time, the signal rates of the SM-like Higgs boson can be tested applying the experimental results implemented in the public code HiggsSignals. The python package is constructed in a flexible and modular way, such that it provides a simple framework that can be extended by the user with further calculations of observables and constraints on the model parameters.

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arXiv2019

Precise prediction for the Higgs-Boson Masses in the $μν$SSM with three right-handed neutrino superfields

The $μν$SSM is a simple supersymmetric extension of the Standard Model (SM) capable of describing neutrino physics in agreement with experiments. We perform the complete one-loop renormalization of the neutral scalar sector of the $μν$SSM with three generation of right-handed neutrinos in a mixed on-shell/$\overline{\mathrm{DR}}$ scheme. We calculate the full one-loop corrections to the neutral scalar masses of the $μν$SSM. The one-loop contributions are supplemented by available MSSM higher-order corrections. We obtain numerical results for a SM-like Higgs-boson mass consistent with experimental bounds, while simultaneously agreeing with neutrino oscillation data. We illustrate the distinct phenomenology of the $μν$SSM in scenarios in which one or more right-handed sneutrinos are lighter than the SM-like Higgs boson, which might be substantially mixed with them. These scenarios are experimentally accessible, on the one hand, through direct searches of the right-handed sneutrinos decaying into SM particles, and on the other hand, via the measurements of the SM-like Higgs-boson mass and its couplings. In this way the parameter space of the $μν$SSM can be probed without the need to propose model dependent searches at colliders. Finally, we demonstrate how the $μν$SSM can simultaneously accommodate two excesses measured at LEP and LHC at $\sim 96$ GeV at the $1σ$ level, while at the same time reproducing neutrino masses and mixings in agreement with neutrino oscillation measurements.

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