Search for a resonance decaying into a scalar particle and a Higgs boson in the final state with two bottom quarks and two photons with 199 fb${}^{-1}$ of data collected at $\sqrt{s}$=13 and 13.6 TeV with the ATLAS detector

Abstract

A search for the resonant production of a heavy scalar $X$ decaying into a lighter scalar $S$ and a Higgs boson, through the process $X\to S(\to b\bar{b})H(\to {\hat{I}}^3{\hat{I}}^3)$, where the two photons are consistent with the Higgs boson decay, is performed. The search is conducted using integrated luminosities of 140 and 59 fb${}^{-1}$ of proton-proton collision data at centre-of-mass energies of 13 and 13.6 TeV, respectively, recorded with the ATLAS detector at the LHC. The search is performed over the mass ranges of 170 $\le$ $m_X$ $\le$ 1000 GeV and 15 $\le$ $m_S$ $\le$ 500 GeV. No significant excess over the Standard Model background prediction is observed and limits at 95% confidence level are set on the product of cross section and branching fraction for the process $X\to S(\to b\bar{b})H(\to {\hat{I}}^3{\hat{I}}^3)$ at 13 TeV, ranging from 9 fb to 0.06 fb.

39 pages in total, author list starting page 22, 3 figures, 2 tables, published in PLB 877 (2026) 140425. All figures including auxiliary figures are available at https://atlas.web.cern.ch/Atlas/GROUPS/PHYSICS/PAPERS/HIGP-2024-34/