Search for a Resonance Decaying Into a Scalar Particle and a Higgs Boson in Final States With Leptons and Two Photons in Proton-Proton Collisions at √s=13 Tev With the Atlas Detector

Abstract

A search for a hypothetical heavy scalar particle, X, decaying into a singlet scalar particle, S, and a Standard Model Higgs boson, H, using 140 fb(-1) of proton-proton collision data at the centre-of-mass energy of 13 TeV recorded with the ATLAS detector at the LHC is presented. The explored mass range is 300 <= m(X) <= 1000 GeV and 170 <= m(S) <= 500 GeV. The signature of this search is one or two leptons (e or mu) from the decay of vector bosons originating from the S particle, S -> (WW -/+)-W-+/-/ZZ, and two photons from the Higgs boson decay, H -> gamma gamma. No significant excess is observed above the expected Standard Model background. The observed (expected) upper limits at the 95% confidence level on the cross- section for gg -> X -> SH, assuming the same S -> WW/ZZ branching ratios as for a SM-like heavy Higgs boson, are between 530 (800) fb and 120 (170) fb.