Possible indications for new Higgs bosons in the reach of the LHC: N2HDM and NMSSM interpretations

TL;DR

This paper explores whether observed excesses at around 400 GeV in LHC Higgs searches can be explained by the N2HDM or NMSSM models, and examines their compatibility with potential signals at 96 GeV.

Contribution

It analyzes the parameter space of N2HDM and NMSSM to interpret LHC excesses and their compatibility with signals at 96 GeV, providing insights into possible new Higgs bosons.

Findings

Excesses at 400 GeV in $t\bar t$ and $\tau^+\tau^-$ channels suggest different parameter regions.

A combined explanation of 400 GeV excesses and a 96 GeV Higgs is possible in N2HDM.

In NMSSM, a $t\bar t$ signal favors the alignment limit, while $\tau^+\tau^-$ signals are outside this limit.

Abstract

In several searches for additional Higgs bosons at the LHC, in particular in a CMS search exploring decays to pairs of top quarks, $t \bar t$, and in an ATLAS search studying tau leptons, $\tau^+\tau^-$, local excesses of about $3\,\sigma$ standard deviations or above have been observed at a mass scale of approximately $ 400$GeV. We investigate to what extent a possible signal in these channels could be accommodated in the Next-to-Two-Higgs-Doublet Model (N2HDM) or the Next-to Minimal Supersymmetric Standard Model (NMSSM). In a second step we analyze whether such a model could be compatible with both a signal at around $400$GeV and $96$GeV, where the latter possibility is motivated by observed excesses in searches for the $b \bar b$ final state at LEP and the di-photon final state at CMS. The analysis for the N2HDM reveals that the observed excesses at $400GeV$ in the $t \bar t$ and $\tau^+\tau^-$ channels point towards different regions of the parameter space, while one such excess and an additional Higgs boson at around $96$GeV could simultaneously be accommodated. In the context of the NMSSM an experimental confirmation of a signal in the $t \bar t$ final state would favour the alignment-without-decoupling limit of the model, where the Higgs boson at $125$GeV could be essentially indistinguishable from the Higgs boson of the standard model. In contrast, a signal in the $\tau^+\tau^-$ channel can only be accommodated outside of this limit, and parts of the investigated parameter space could be probed with Higgs signal-rate measurements at the (HL-)LHC.