Global fits and the 95 GeV diphoton excesses in the Supersymmetric Georgi-Machacek Model

TL;DR

This paper investigates whether the Supersymmetric Georgi-Machacek (SGM) model can explain the 95 GeV diphoton excesses observed at the LHC, performing a comprehensive global fit and analyzing its distinctive predictions.

Contribution

It provides the first detailed global fit of the SGM model including all relevant channels, constraining its parameter space and predicting its unique collider signatures.

Findings

SGM can fit the 95 GeV diphoton excesses with a light custodial singlet Higgs

The model cannot explain the LEP bar{b} excess

Predicted mass spectrum allows targeted collider searches

Abstract

Recently the ATLAS and CMS experiments have reported modest excesses in the diphoton channel at around 95 GeV.~A number of recent studies have examined whether these could be due to an extended electroweak symmetry breaking (EWSB) sector, including the well known Georgi-Machacek (GM) model.~Here we examine whether the excesses can be explained by a light exotic Higgs boson in the \emph{Supersymmetric} GM (SGM) model which has the same scalar spectrum as the conventional GM model, but with a more constrained Higgs potential and the presence of custodial Higgsino fermions.~We perform a global fit of the SGM model including all relevant production and decay channels, some of which have been neglected in previous studies, which severely constrain the parameter space.~We find that the SGM model can fit the data if the LHC diphoton excesses at 95\,GeV are due to the lightest custodial singlet Higgs boson which contributes $(5-7)\%$ to EWSB, but \emph{cannot} accommodate the LEP $b\bar{b}$ excess, in contrast to other recent studies of the GM model.~Since the SGM model has a highly constrained Higgs potential, the rest of the mass spectrum is sharply predicted, allowing for targeted searches at the LHC or future colliders.~We also compare the SGM model with the non-supersymmetric GM model and identify how they can be distinguished at the LHC or future colliders.