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Description
A search for the resonant production of a heavy scalar X decaying into a Higgs boson and a lighter scalar S, through the process X→S ( → b b) H ( → γ γ) , where the two photons are consistent with the Higgs boson decay, is performed. The search is conducted using integrated luminosities of 140 fb^{−1} and 58.6 fb^{−1} of proton--proton collision data at centre-of-mass energies of 13~TeV and 13.6~TeV respectively, recorded with the ATLAS detector at the Large Hadron Collider. The search is performed over the mass ranges of 170 ≤ m X ≤ 1000~GeV and 15 ≤ m S ≤ 500~GeV. No significant excess over the Standard Model background prediction is observed and limits at 95% confidence level are set on the cross-section σ ( X → S ( → b b) H ( → γ γ)) at 13 TeV, ranging from 9 fb to 0.06 fb.
