Search for heavy scalar resonances decaying to Lorentz-boosted Higgs and Higgs-like bosons in the $\mathrm{b\bar{b}}$4q final state at $\sqrt{s}$ = 13 TeV

TL;DR

This paper reports a search for heavy scalar particles decaying into a Higgs boson and a Higgs-like boson in all-hadronic final states using CMS data at 13 TeV, employing machine learning for jet identification, and sets new upper limits on production cross sections.

Contribution

First LHC search for scalar resonances decaying to bar{b} and VV in all-hadronic final states using advanced machine learning techniques.

Findings

No significant excess observed above background.

Upper limits on cross section times branching fraction as low as 0.2 fb.

First search of its kind at the LHC.

Abstract

A search is performed for a heavy scalar resonance X decaying to a Higgs boson (H) and a Higgs-like scalar boson (Y) in the two bottom quark (H $\to$ $\mathrm{b\bar{b}}$) and four quark (Y $\to$ VV $\to$ 4q) final state, where V denotes a W or Z boson. Masses of the X between 900 and 4000 GeV and the Y between 60 and 2800 GeV are considered. The search is performed in data collected by the CMS experiment at the CERN LHC from proton-proton collisions at 13 TeV center-of-mass energy, with a data set corresponding to a total integrated luminosity of 138 fb$^{-1}$. It targets the Lorentz-boosted regime, in which the products of the H $\to$ $\mathrm{b\bar{b}}$ decay can be reconstructed as a single large-area jet, and those from the Y $\to$ VV $\to$ 4q decay as either one Y $\to$ 4q or two V to $\mathrm{q\bar{q}}$ jets. Jet identification and mass reconstruction exploit machine-learning tools, including a novel attention-based "particle transformer" for Y $\to$ 4q identification. No significant excess is observed in the data above the standard model background expectation. Upper limits on the product of production cross section and branching fraction as low as 0.2 fb are derived at 95% confidence level for various mass hypotheses. This is the first search at the LHC for scalar resonances in the all-hadronic $\mathrm{b\bar{b}}$VV decay channel.