Search for a resonance decaying into a scalar particle and a Higgs boson in the final state with two bottom quarks and two photons in proton-proton collisions at a center of mass energy of 13 TeV with the ATLAS detector

TL;DR

This paper reports a search for a heavy scalar decaying into a Higgs boson and a lighter scalar using proton-proton collision data, setting upper limits on production cross sections and observing a local excess at specific masses.

Contribution

It introduces a novel search method using parameterized neural networks to improve sensitivity in the ($m_{X}$, $m_{S}$) parameter space.

Findings

No significant excess found overall.

Upper limits on cross section times branching ratio range from 39 fb to 0.09 fb.

A local excess with 3.5 sigma significance at (575, 200) GeV.

Abstract

A search for the resonant production of a heavy scalar $X$ decaying into a Higgs boson and a new lighter scalar $S$, through the process $X \to S(\to bb) H(\to \gamma\gamma)$, where the two photons are consistent with the Higgs boson decay, is performed. The search is conducted using an integrated luminosity of 140 fb$^{-1}$ of proton-proton collision data at a centre-of-mass energy of 13 TeV recorded with the ATLAS detector at the Large Hadron Collider. The search is performed over the mass range 170 $\leq$ $m_{X}$ $\leq$ 1000 GeV and 15 $\leq$ $m_{S}$ $\leq$ 500 GeV. Parameterised neural networks are used to enhance the signal purity and to achieve continuous sensitivity in a domain of the ($m_{X}$, $m_{S}$) plane. No significant excess above the expected background is found and 95% CL upper limits are set on the cross section times branching ratio, ranging from 39 fb to 0.09 fb. The largest deviation from the background-only expectation occurs for ($m_{X}$, $m_{S}$) = (575, 200) GeV with a local (global) significance of 3.5 (2.0) standard deviations.