Search for heavy Higgs bosons with flavour-violating couplings in multi-lepton plus $b$-jets final states in $pp$ collisions at 13 TeV with the ATLAS detector

TL;DR

This paper reports a search for heavy Higgs bosons with flavour-violating decays in multi-lepton plus $b$-jets final states using 13 TeV proton-proton collision data from the ATLAS detector, setting limits on scalar masses and couplings.

Contribution

It introduces a novel search strategy for heavy scalars with flavour-violating couplings in multi-lepton final states, using deep neural network categorization and interpreting results in two-Higgs-doublet and R-parity violating SUSY models.

Findings

Excluded scalar masses between 200-630 GeV at 95% CL.

Set limits on couplings $ ho_{tt}$, $ ho_{tc}$, $ ho_{tu}$.

Provided interpretations in supersymmetry models.

Abstract

A search for new heavy scalars with flavour-violating decays in final states with multiple leptons and $b$-tagged jets is presented. The results are interpreted in terms of a general two-Higgs-doublet model involving an additional scalar with couplings to the top-quark and the three up-type quarks ($\rho_{tt}$, $\rho_{tc}$, and $\rho_{tu}$). The targeted signals lead to final states with either a same-sign top-quark pair, three top-quarks, or four top-quarks. The search is based on a data sample of proton-proton collisions at $\sqrt{s}=13$ TeV recorded with the ATLAS detector during Run 2 of the Large Hadron Collider, corresponding to an integrated luminosity of 139f b$^{-1}$. Events are categorised depending on the multiplicity of light charged leptons (electrons or muons), total lepton charge, and a deep-neural-network-based categorisation to enhance the purity of each of the signals. Masses of an additional scalar boson $m_{H}$ between $200-630$ GeV with couplings $\rho_{tt}=0.4$, $\rho_{tc}=0.2$, and $\rho_{tu}=0.2$ are excluded at 95% confidence level. Additional interpretations are provided in models of $R$-parity violating supersymmetry, motivated by the recent flavour and $(g-2)_\mu$ anomalies.