Smuon contribution to muon g-2 in Grand Unified supersymmetric theories

TL;DR

This paper investigates the potential for light smuons in GUT-constrained NMSSM models to significantly contribute to the muon g-2 anomaly, challenging previous assumptions about mass hierarchies and annihilation mechanisms.

Contribution

It demonstrates that in GUTc-NMSSM, the smuon can be lighter than stau, allowing larger smuon-neutralino contributions to muon g-2, which was previously considered unlikely.

Findings

Light smuon can be lighter than stau in GUTc-NMSSM.

Smuon-neutralino loop can dominate muon g-2 contribution.

Dark matter annihilation involves slepton or chargino co-annihilation.

Abstract

In GUT-scale constrained (GUTc) supersymmetric (SUSY) models, the mass of smuon $\tilde{\mu}_1$ is typically heavier than that of stau $\tilde{\tau}_1$, and stau co-annihilation is a typical annihilation mechanism of dark matter. However, light smuon is more favored by the muon $g-2$ anomaly, thus smuon-neutralino loop contribution to muon $g-2$ is usually smaller than that of sneutrino-chargino. Inspired by the latest muon $g-2$ results, we take the GUTc- Next-to-Minimal Supersymmetric Model (NMSSM) as an example, where the gaugino (Higgs) masses are not unified to the usual parameter $M_{1/2}$ ($M_0$), exploring its possibility of light smuon and its contribution to muon $g-2$. After complicated calculations and discussions, we conclude that in GUTc-NMSSM the smuon can be lighter than stau. In this light-smuon scenario, the contribution of smuon-neutralino loop to the muon $g-2$ can be larger than that of the sneutrino-chargino loop. The annihilation mechanisms of dark matter are dominated by multiple slepton or chargino co-annihilation. In our calculations, we consider also other latest related constraints like Higgs data, SUSY searches, dark matter relic density and direct detections, etc.