X650 $\to$ ZZ/WW/H125H95/A450Z/$\gamma\gamma$ -- $J=1$, $J=2$, narrow or wide resonance?

TL;DR

This paper investigates the conflicting experimental results on a potential 650 GeV resonance decaying into ZZ, proposing a new interpretation involving spin 2 resonances and a revised theoretical model with multiple scalar and tensor states.

Contribution

It introduces a novel scenario with spin 2 and scalar resonances within the Georgi Machacek model, explaining the experimental discrepancies and predicting new collider signatures.

Findings

A spin 2 T690 resonance can explain WW/ZZ decays and interference effects.

The A450Z resonance may originate from a nearby H650 scalar.

Predictions for future e+e- colliders based on the proposed model.

Abstract

At ICHEP 2024 CMS has published RUN2 results for ZZ->4 leptons and reached the conclusion that there is no evidence for a scalar resonance H650 decaying into ZZ, as was also concluded by ATLAS using an MVA analysis optimised for a scalar particle. Since this resonance is indicated into ZZ by ATLAS in a Cut Based Analysis and into three other modes: WW and h95h125 by CMS, ttZ by ATLAS , the present paper is an attempt to understand these apparent contradictions. Our conclusion is that strict selections for the reaction H650->ZZ cut as much into the signal than into the background, therefore reducing its statistical significance. A plausible interpretation of this behaviour is that these selections are inadequate for a spin 2 particle produced by the VBF process and decaying into ZZ with an angular distribution similar to the Drell Yan background. If true, our description of the various findings in term of the Georgi Machacek model needs to be deeply revised, which is attempted in the present note. A scenario with T690 as a spin 2 narrow resonance is presented which naturally accommodates WW/ZZ and h95h125 decays, while we suggest that A450Z could come from a H650 nearby resonance. We propose a scheme in which scalar resonances are accommodated in three scalar isodoublets, while T690, T450++, T375+ and T350 belong to two tensor isoquintuplets. In this scenario, T690 could be a narrow resonance which interferes with the SM background, as confirmed by its observation in the two photon mode, reinforcing a Kaluza Klein graviton interpretation. If, as indicated by ATLAS and CMS, T690 couples to e+e-, this scenario leads to a dramatic prediction for future $e^+e^-$ colliders.