Supersymmetry and the Anomalous Anomalous Magnetic Moment of the Muon

TL;DR

The recently reported measurement of the muon's anomalous magnetic moment differs from the standard model prediction by 2.6 sigma, and model-independent upper bounds on the masses of observable supersymmetric particles are derived.

Abstract

The recently reported measurement of the muon's anomalous magnetic moment differs from the standard model prediction by 2.6 standard deviations. We examine the implications of this discrepancy for supersymmetry. Deviations of the reported magnitude are generic in supersymmetric theories. Based on the new result, we derive model-independent upper bounds on the masses of observable supersymmetric particles. We also examine several model frameworks. The sign of the reported deviation is as predicted in many simple models, but disfavors anomaly-mediated supersymmetry breaking.

Figures (4)

• Figure 1: Allowed values of $M_{\text{LOSP}}$, the mass of the lightest observable supersymmetric particle, and $a_{\mu}^{\text{SUSY}}$ from a scan of parameter space with $M_1=M_2/2$, $A_{\mu} = 0$, and $\tan\beta = 50$. Green crosses (red circles) have smuons (charginos/neutralinos) as the LOSP. The 1$\sigma$ and 2$\sigma$ allowed $a_{\mu}^{\text{SUSY}}$ ranges are indicated. Relaxing the relation $M_1=M_2/2$ leads to the solid envelope curve, and further allowing arbitrary $A_{\mu}$ leads to the dashed curve. The envelope contours scale linearly with $\tan\beta$. A stable LSP is assumed.
• Figure 2: As in Fig. \ref{['fig:mnlsp']}, but assuming a visibly decaying LSP.
• Figure 3: The 2$\sigma$ allowed region for $a_{\mu}^{\text{SUSY}}$ (hatched) in minimal supergravity, for $A_0=0$, $\mu>0$, and two representative values of $\tan\beta$. The dark red regions are excluded by the requirement of a neutral LSP and by the chargino mass limit of 103 GeV, and the medium blue (light yellow) region has LSP relic density $0.1 \le \Omega h^2 \le 0.3$ ($0.025\le \Omega h^2 \le 1$). The area below the solid (dashed) contour is excluded by $B\to X_s \gamma$ (the Higgs boson mass), and the regions probed by the tri-lepton search at Tevatron Run II are below the dotted contours.
• Figure 4: Contours of $a_{\mu}^{\text{SUSY}} \times 10^{10}$ in the minimal anomaly-mediated model, for $\mu>0$ and $\tan\beta = 10$. The dark red region is excluded by $m_{\tilde{\tau}} > 82~\text{GeV}$, the light yellow region is excluded at 2$\sigma$ by $B(B\to X_s \gamma) < 4.10 \times 10^{-4}$, and the LSP is a stau to the left of the dashed line.