Search for the Higgs boson decays $H \to ee$ and $H \to e\mu$ in $pp$ collisions at $\sqrt{s} = 13$ TeV with the ATLAS detector

TL;DR

This paper reports on searches for rare Higgs boson decays into electron pairs and electron-muon pairs using ATLAS data, setting new upper limits that improve previous constraints and finding no evidence of these decays.

Contribution

First search to set stringent upper limits on $H o ee$ and $H o e $ decays at 13 TeV with ATLAS, significantly improving previous bounds.

Findings

No significant signals observed for $H o ee$ and $H o e $.

Upper limits on branching fractions are $3.6 imes 10^{-4}$ and $6.1 imes 10^{-5}$ respectively.

Results improve previous limits by factors of about five and six.

Abstract

Searches for the Higgs boson decays $H \to ee$ and $H \to e \mu$ are performed using data corresponding to an integrated luminosity of 139 fb$^{-1}$ collected with the ATLAS detector in $pp$ collisions at $\sqrt{s} = 13$ TeV at the LHC. No significant signals are observed, in agreement with the Standard Model expectation. For a Higgs boson mass of 125 GeV, the observed (expected) upper limit at the 95% confidence level on the branching fraction $\mathcal{B}(H \to ee)$ is $3.6 \times 10^{-4}$ ($3.5 \times 10^{-4} $) and on $\mathcal{B}(H \to e \mu)$ is $6.1\times 10^{-5} $ ($5.8\times 10^{-5}$). These results represent improvements by factors of about five and six on the previous best limits on $\mathcal{B}(H \to ee)$ and $\mathcal{B}(H \to e \mu)$ respectively.