A search for triple Higgs boson production in the $6b$ final state using $pp$ collisions at $\sqrt{s}=13$ TeV with the ATLAS detector

TL;DR

This paper reports a search for triple Higgs boson production in proton-proton collisions at 13 TeV using the ATLAS detector, setting limits on production cross-sections and Higgs self-couplings.

Contribution

It introduces a comprehensive search for both resonant and non-resonant triple Higgs production in the $6b$ final state with new limits set on cross-sections and Higgs self-couplings.

Findings

No evidence for $HHH$ production was observed.

An upper limit of 59 fb on the SM $HHH$ production cross-section was established.

Constraints on Higgs self-couplings were derived.

Abstract

A search for the production of three Higgs bosons ($HHH$) in the $b\bar{b}b\bar{b}b\bar{b}$ final state is presented. The search uses $126~\text{fb}^{-1}$ of proton-proton collision data at $\sqrt{s}=13$ TeV collected with the ATLAS detector at the Large Hadron Collider. The analysis targets both non-resonant and resonant production of $HHH$. The resonant interpretations primarily consider a cascade decay topology of $X\rightarrow SH\rightarrow HHH$ with masses of the new scalars $X$ and $S$ up to 1.5 TeV and 1 TeV, respectively. In addition to scenarios where $S$ is off-shell, the non-resonant interpretation includes a search for standard model (SM) $HHH$ production, with limits on the tri-linear and quartic Higgs self-coupling set. No evidence for $HHH$ production is observed. An upper limit of 59 fb is set, at 95% confidence level, on the cross-section for Standard-Model $HHH$ production.