Search for a new resonance decaying to a Higgs boson and a scalar boson in events with two b jets and two Z bosons in proton-proton collisions at $\sqrt{s}$ = 13.6 TeV

TL;DR

This paper searches for new resonances decaying into Higgs and scalar bosons in proton-proton collisions at 13.6 TeV, using advanced machine learning techniques to analyze bbZZ events and set upper limits on production cross sections.

Contribution

It introduces a comprehensive analysis of bbZZ decay topologies with machine learning discriminants, improving sensitivity to new resonances compared to previous methods.

Findings

No significant deviations from the Standard Model observed.

Upper limits set: 1 pb for HH production, 5 fb for HY production.

Analysis sensitivity comparable to other decay channel studies.

Abstract

A search is performed for a new resonance X decaying into either a pair of Higgs bosons (HH) or into a Higgs boson and a new scalar boson Y (HY), using proton-proton collision data collected at $\sqrt{s}$ = 13 TeV, corresponding to an integrated luminosity of 138 fb$^{-1}$. This study performs a comprehensive exploitation of the bbZZ events, encompassing the following decay topologies. One H candidate is identified through its decay into a bottom quark-antiquark pair, while the other H or the Y candidate is selected through its decay into a pair of Z bosons. One Z boson is required to decay leptonically and the other, to decay into a pair of quarks or neutrinos. Events of interest are categorized based on the Lorentz boosts of the hadronically decaying H and Z bosons. Machine-learning-based discriminants, together with the reconstructed resonance mass, are employed across the different categories to separate signal from backgrounds, and their corresponding distributions are included in a simultaneous fit. No significant deviations from the standard model predictions are observed. Upper limits at the 95% confidence level are set on the HH and HY production cross sections. For resonant HH production, the upper limit on the cross section of pp $\to$ HH production is 1 pb for a high-mass resonance. For HY production, the upper limit on the cross section of the process pp $\to$ X $\to$ bbZZ is approximately 5 fb for a high-mass resonance. This is comparable to the sensitivity achieved in other analyses, which focus on H decays to $\gamma\gamma$ or $\tau\tau$ and Y decays into a pair of bottom quarks or massive vector bosons.