New physics explanations of $a_\mu$ in light of the FNAL muon $g-2$ measurement

TL;DR

The paper assesses how recent Fermilab muon g-2 results impact beyond Standard Model theories, analyzing various models' ability to explain the anomaly while satisfying other experimental constraints.

Contribution

It provides a comprehensive analysis of new physics models explaining the muon g-2 anomaly in light of recent measurements, including detailed MSSM scenarios and other simple models.

Findings

Many models are excluded by the new measurement.

Two-Higgs doublet and leptoquark models are viable only in specific cases.

MSSM can explain g-2 and dark matter simultaneously in certain regions.

Abstract

The Fermilab Muon $g-2$ experiment recently reported its first measurement of the anomalous magnetic moment $a_\mu^{\textrm{FNAL}}$, which is in full agreement with the previous BNL measurement and pushes the world average deviation $\Delta a_\mu^{2021}$ from the Standard Model to a significance of $4.2\sigma$. Here we provide an extensive survey of its impact on beyond the Standard Model physics. We use state-of-the-art calculations and a sophisticated set of tools to make predictions for $a_\mu$, dark matter and LHC searches in a wide range of simple models with up to three new fields, that represent some of the few ways that large $\Delta a_\mu$ can be explained. In addition for the particularly well motivated Minimal Supersymmetric Standard Model, we exhaustively cover the scenarios where large $\Delta a_\mu$ can be explained while simultaneously satisfying all relevant data from other experiments. Generally, the $\Delta a_\mu$ result can only be explained by rather small masses and/or large couplings and enhanced chirality flips, which can lead to conflicts with limits from LHC and dark matter experiments. Our results show that the new measurement excludes a large number of models and provides crucial constraints on others. Two-Higgs doublet and leptoquark models provide viable explanations of $a_\mu$ only in specific versions and in specific parameter ranges. Among all models with up to three fields, only models with chirality enhancements can accommodate $a_\mu$ and dark matter simultaneously. The MSSM can simultaneously explain $a_\mu$ and dark matter for Bino-like LSP in several coannihilation regions. Allowing under abundance of the dark matter relic density, the Higgsino- and particularly Wino-like LSP scenarios become promising explanations of the $a_\mu$ result.