Explaining excesses in four-leptons at the LHC with a double peak from a CP violating Two Higgs Doublet Model

TL;DR

This paper proposes that the excess in four-lepton events observed at the LHC can be explained by a CP violating Two Higgs Doublet Model featuring two heavy neutral scalars, predicting additional signals and near-current electric dipole moment bounds.

Contribution

It introduces a specific Two Higgs Doublet Model explanation for the four-lepton excess, including a detailed fit and predictions for related processes and EDM constraints.

Findings

Two heavy scalars with masses 540 GeV and 631 GeV explain the excess.

Predicted additional signals in $t\bar t$, $W^+W^-$, $4b$, and $\gamma\gamma$ channels.

Electron EDM close to current experimental bounds.

Abstract

Extended scalar sectors with additional degrees of freedom appear in many scenarios beyond the Standard Model. Heavy scalar resonances that interact with the neutral current could be discovered via broad resonances in the tails of the four-lepton invariant mass spectrum, where the Standard Model background is small and well understood. In this article we consider a recent ATLAS measurement of four-lepton final states, where the data is in excess over the background for invariant masses above 500 GeV. We discuss the possibility that this excess could be interpreted as a "double peak" from the two extra heavy neutral scalars of a CP violating Two Higgs Doublet Model, both coupling to the $Z$ boson. We apply an iterative fitting procedure to find viable model parameters that can match the excess, resulting in a benchmark point where the observed four-lepton invariant mass spectrum can be explained by two scalar particles $H_2$ and $H_3$, with masses of 540 GeV and 631 GeV, respectively, being admixtures of the CP eigenstates. Our explanation predicts additional production processes for $t\bar t$, $W^+W^-$, $4b$ and $\gamma\gamma$, some of which have cross sections close to the current experimental limits. Our results further imply that the electric dipole moment of the electron should be close to the present bounds.