arXiv subjects

Kilian Möhling

Publications and source records attributed to Kilian Möhling.

7 recordsLinked to original sources

arXiv2026

The dipole ellipse from vector-like leptons at next-to-leading order

We consider the SM extended by a 4th generation of vector-like leptons. This model generates strongly correlated contributions to the lepton masses, Higgs couplings and dipole moments. At leading order the Higgs coupling restricts the magnetic and electric dipole moments to an ellipse. Here we compute the one-loop corrections to the Higgs coupling and two-loop corrections to the dipole moments to obtain the correlation at next-to-leading order using the framework of SMEFT. In addition we resum the leading logarithmic corrections from SM couplings through the SMEFT renormalisation group equations. With these results we compute the RG improved correlation at NLO and discuss the implications for the muon, electron and tau correlations. Specifically, for the muon we find that the corrections contract the ellipse such that a larger part of parameter space becomes compatible with the updated SM value of the muon magnetic moment.

hep-ph↗

arXiv2026

From Higgs physics to lepton flavour violation: current bounds and future prospects for vector-like lepton models

We present a comprehensive phenomenological study of a class of six vector-like lepton models with seesaw-like mass contributions and strong modifications to Higgs and lepton phenomenology. We focus on lepton flavour conserving and violating observables across all lepton generations and collider observables like $Z$ and Higgs decays. In light of the recent progress at the LHC and precision measurements such as muon $g-2$, as well as in anticipation of upcoming experiments like MEGII, Mu2e/COMET, Mu3e, Belle II and at the HL-LHC, we systematically survey the viable parameter space and identify patterns and correlations. The considered class of models gives rise to a rich and testable phenomenology with robust and complementary probes that allow to distinguish between models in the coming experimental era.

hep-ph↗

arXiv2026

The Muon Magnetic Moment and Physics Beyond the Standard Model

We review the role of the anomalous magnetic moment of the muon a_μas a powerful probe of physics beyond the Standard Model (BSM), taking advantage of the final result of the Fermilab g-2 experiment and the recently updated Standard Model value. This review provides both a comprehensive summary of the current status, as well as an accessible entry point for phenomenologists with interests in dark matter, Higgs and electroweak or neutrino and flavour physics in the context of a wide range of BSM scenarios. It begins with a qualitative overview of the field and a collection of key properties and typical results. It then focuses on model-independent, generic formulas and classifies types of BSM scenarios with or without chiral enhancements. A strong emphasis of the review are the connections to a large number of other observables -- ranging from the muon mass and the muon--Higgs coupling and related dipole observables to dark matter, neutrino masses and high-energy collider observables. Finally, we survey a number of well-motivated BSM scenarios such as dark photons, axion-like particles, the two-Higgs doublet model, supersymmetric models and models with leptoquarks, vector-like leptons or neutrino mass models. We discuss the impact of the updated Standard Model value for a_μand of complementary constraints, exploring the phenomenology and identifying excluded and viable parameter regions.

hep-ph↗

arXiv2025

Freeze-in at Low Reheating and Direct Detection of Fermion Dark Matter

We investigate a low-reheating-temperature freeze-in scenario within a minimal model of fermionic dark matter interacting through a pseudoscalar mediator. In this setup, dark matter is produced via the decay of the pseudoscalar, which remains in thermal equilibrium with the Standard Model bath. We derive the thermalization and non-thermalization conditions for the new fields and obtain the corresponding direct-detection constraints and projections on the model based on LZ and DARWIN experiments, respectively.

hep-ph↗

arXiv2024

On-shell Renormalization with Vector-like Leptons, One-loop Muon-Higgs Coupling and Muon g-2

Models with vector-like leptons can strongly modify the lepton mass generation mechanism and lead to correlated effects in lepton-Higgs couplings and lepton dipole moments. Here we begin an analysis of higher-order corrections in such models by setting up a renormalization scheme with full on-shell conditions on the lepton self energies, masses and fields. A minimal set of fundamental parameters is renormalized in the $\overline{\text{MS}}$ scheme. We provide a detailed discussion of lepton mixing and redundancies at higher orders, show how the relevant counterterms can be obtained from the renormalization conditions, and determine the $β$-functions corresponding to the scheme. As a first application we calculate the one-loop effective muon--Higgs coupling and analyse its correlation with the muon anomalous magnetic moment $Δa_μ^{\text{VLL}}$. In the interesting case of large masses and opposite-sign coupling, the lowest-order correlation implies a fixed value of $Δa_μ^{\text{VLL}}$ around $22.5\times 10^{-10}$, while the higher-order corrections significantly reduce this value to the interval $(10...18)\times 10^{-10}$.

hep-ph↗

arXiv2024

Coscattering in the Extended Singlet-Scalar Higgs Portal

We study the coscattering mechanism in a simple Higgs portal which add two real singlet scalars to the Standard Model. In this scenario, the lighter scalar is stabilized by a single $\mathcal{Z}_2$ symmetry and acts as the dark matter relic, whose freeze-out is driven by conversion processes. The heavier scalar becomes an unstable state which participate actively in the coscattering. We find viable parameter regions fulfilling the measured relic abundance, while evading direct detection and big-bang nucleosynthesis bounds. In addition, we discuss collider prospects for the heavier scalar as a long-lived particle at present and future detectors.

hep-ph↗

arXiv2021

Two Real Scalar WIMP Model in the Assisted Freeze-Out Scenario

We study a simple dark matter model given by two interacting real singlet scalars, with only one of them coupled to the Higgs. The model therefore presents a minimal assisted-freeze-out framework: both scalars contribute to the dark matter relic density, but only one of them takes part in the elastic scattering with nuclei. This reduces the expected interaction rate in direct detection experiments in such a way that the model in some regions of the parameter space may evade XENON1T constraints. We explore the model under theoretical (perturbativity, stability potential and unitarity) and experimental constraints (Higgs to invisible, relic density, direct detection), with the use of the narrow-width-approximation near the Higgs resonance to calculate the average annihilation cross section. We show that the model is viable in the Higgs resonance region and for scalar singlets masses of hundreds of GeV, although the model becomes highly constrained at high energies.

hep-ph↗