Combined Explanation of LHC Multi-Lepton, Di-Photon and Top-Quark Excesses

TL;DR

This paper proposes a comprehensive model extending the Standard Model with additional scalars to explain multiple LHC anomalies, including multi-lepton events, di-photon excesses, and top-quark production anomalies, achieving consistency with various experimental observations.

Contribution

The paper introduces the $ ext{Δ}2 ext{HDMS}$ model, combining a second scalar doublet, a real scalar singlet, and a Higgs triplet, to simultaneously explain several LHC excesses and anomalies.

Findings

The model reproduces di-photon excesses at 95GeV and 152GeV.

It accounts for the top-quark pair excess at 400GeV.

It explains elevated four-top and ttW cross-sections.

Abstract

The LHC analyses of processes containing two or more leptons and missing energy, possibly in association with b-jets, show strong tensions with the Standard Model predictions and are known as multi-lepton anomalies. In particular, top-quark differential distributions point towards the associated production of new Higgs bosons decaying into bottom quarks and W bosons ($>5\sigma$) with masses consistent with the di-photon excesses at 95GeV and 152GeV ($3.8\sigma$ and $4.9\sigma$, respectively). Furthermore, CMS found indications for resonant top-quark pair production at 400GeV ($3.5\sigma$) and both ATLAS and CMS reported elevated four-top and ttW cross-sections. In this article, we propose a combined explanation of these excesses by supplementing the SM Higgs with a second scalar doublet, a real scalar singlet ($S$) and a Higgs triplet with $Y=0$ ($\Delta$); the $\Delta$2HDMS. We fix the masses of the neutral triplet-like and the singlet-like scalars by the di-photon excesses, i.e. $m_{\Delta^0}=152$GeV and $m_S=95$GeV, respectively. Here, H, the CP-even component of the second doublet, is produced via gluon fusion from a top-loop and decays dominantly to $S+\Delta^0$ whose subsequent decays to WW and bb explain the differential top-quark distributions for $\sigma(pp\to H\to S\Delta^0)\approx6$pb. Fixing the top-Yukawa accordingly, the CP-odd Higgs boson A turns out to have the right production cross-section to account for the resonant top-pair excess at 400GeV, while the top-associated production of H and A results in new physics pollution of Standard Model ttW and four-top cross sections, as preferred by the data. Furthermore, a positive shift in the W mass is naturally induced by the vacuum expectation value of the triplet and we show that the most relevant signal strengths of the 152GeV boson are compatible with the process $pp\to H\to \Delta^0S$ if S is allowed to decay invisibly.