Anomalous muon magnetic moment, supersymmetry, naturalness, LHC search limits and the landscape

TL;DR

This paper investigates supersymmetric explanations for the muon g-2 anomaly, emphasizing naturalness and LHC constraints, and finds that only models with light first/second generation scalars can account for the discrepancy.

Contribution

It identifies a specific natural SUSY model with a normal scalar mass hierarchy that explains the muon g-2 anomaly while satisfying LHC constraints.

Findings

Normal scalar mass hierarchy models can explain the muon g-2 anomaly.

Natural SUSY models with decoupled scalars cannot account for the anomaly.

Recent lattice results could negate the anomaly, aligning theory with experiment.

Abstract

The recent measurement of the muon anomalous magnetic moment a_\mu\equiv (g-2)_\mu/2 by the Fermilab Muon g-2 experiment sharpens an earlier discrepancy between theory and the BNL E821 experiment. We examine the predicted \Delta a_\mu\equiv a_\mu(exp)-a_\mu(th) in the context of supersymmetry with low electroweak naturalness (restricting to models which give a plausible explanation for the magnitude of the weak scale). A global analysis including LHC Higgs mass and sparticle search limits points to interpretation within the normal scalar mass hierarchy (NSMH) SUSY model wherein first/second generation matter scalars are much lighter than third generation scalars. We present a benchmark model for a viable NSMH point which is natural, obeys LHC Higgs and sparticle mass constraints and explains the muon magnetic anomaly. Aside from NSMH models, then we find the (g-2)_\mu anomaly cannot be explained within the context of natural SUSY, where a variety of data point to decoupled first/second generation scalars. The situation is worse within the string landscape where first/second generation matter scalars are pulled to values in the 10-50 TeV range. An alternative interpretation for SUSY models with decoupled scalar masses is that perhaps the recent lattice evaluation of the hadronic vacuum polarization could be confirmed which leads to a Standard Model theory-experiment agreement in which case there is no anomaly.