Search for a new heavy scalar particle decaying into a Higgs boson and a new scalar singlet in final states with one or two light leptons and a pair of τ-leptons with the ATLAS detector
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jats:titleAjats:scbstract</jats:sc> </jats:title>jats:pA search for a new heavy scalar particle jats:italicX</jats:italic> decaying into a Standard Model (SM) Higgs boson and a new singlet scalar particle jats:italicS</jats:italic> is presented. The search uses a proton-proton (jats:italicpp</jats:italic>) collision data sample with an integrated luminosity of 140 fbjats:supjats:italic−</jats:italic>1</jats:sup> recorded at a centre-of-mass energy of jats:inline-formulajats:alternativesjats:tex-math$$ \sqrt{s} $$</jats:tex-math><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> mml:msqrt mml:mis</mml:mi> </mml:msqrt> </mml:math></jats:alternatives></jats:inline-formula> = 13 TeV with the ATLAS detector at the Large Hadron Collider. The most sensitive mass parameter space is explored in jats:italicX</jats:italic> mass ranging from 500 to 1500 GeV, with the corresponding jats:italicS</jats:italic> mass in the range 200–500 GeV. The search selects events with two hadronically decaying jats:italicτ</jats:italic>-lepton candidates from jats:italicH</jats:italic> → jats:italicτ</jats:italic>jats:sup+</jats:sup>jats:italicτ</jats:italic>jats:supjats:italic−</jats:italic></jats:sup> decays and one or two light leptons (jats:italicℓ</jats:italic> = jats:italice</jats:italic>, jats:italicμ</jats:italic>) from jats:italicS</jats:italic> → jats:italicVV</jats:italic> (jats:italicV</jats:italic> = jats:italicW</jats:italic>, jats:italicZ</jats:italic>) decays while the remaining jats:italicV</jats:italic> boson decays hadronically or to neutrinos. A multivariate discriminant based on event kinematics is used to separate the signal from the background. No excess is observed beyond the expected SM background and 95% confidence level upper limits between 72 fb and 542 fb are derived on the cross-section jats:italicσ</jats:italic>(jats:italicpp</jats:italic> → jats:italicX</jats:italic> → jats:italicSH</jats:italic>) assuming the same SM-Higgs boson-like decay branching ratios for the jats:italicS</jats:italic> → jats:italicVV</jats:italic> decay. Upper limits on the visible cross-sections jats:italicσ</jats:italic>(jats:italicpp</jats:italic> → jats:italicX</jats:italic> → jats:italicSH</jats:italic> → jats:italicWWττ</jats:italic>) and jats:italicσ</jats:italic>(jats:italicpp</jats:italic> → jats:italicX</jats:italic> → jats:italicSH</jats:italic> → jats:italicZZττ</jats:italic>) are also set in the ranges 3–26 fb and 6–33 fb, respectively.</jats:p>
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Acknowledgements: We thank CERN for the very successful operation of the LHC, as well as the support staff from our institutions without whom ATLAS could not be operated efficiently. We acknowledge the support of ANPCyT, Argentina; YerPhI, Armenia; ARC, Australia; BMWFW and FWF, Austria; ANAS, Azerbaijan; CNPq and FAPESP, Brazil; NSERC, NRC and CFI, Canada; CERN; ANID, Chile; CAS, MOST and NSFC, China; Minciencias, Colombia; MEYS CR, Czech Republic; DNRF and DNSRC, Denmark; IN2P3-CNRS and CEA-DRF/IRFU, France; SRNSFG, Georgia; BMBF, HGF and MPG, Germany; GSRI, Greece; RGC and Hong Kong SAR, China; ISF and Benoziyo Center, Israel; INFN, Italy; MEXT and JSPS, Japan; CNRST, Morocco; NWO, Netherlands; RCN, Norway; MEiN, Poland; FCT, Portugal; MNE/IFA, Romania; MESTD, Serbia; MSSR, Slovakia; ARRS and MIZŠ, Slovenia; DSI/NRF, South Africa; MICINN, Spain; SRC and Wallenberg Foundation, Sweden; SERI, SNSF and Cantons of Bern and Geneva, Switzerland; MOST, Taiwan; TENMAK, Türkiye; STFC, United Kingdom; DOE and NSF, United States of America. In addition, individual groups and members have received support from BCKDF, CANARIE, Compute Canada and CRC, Canada; PRIMUS 21/SCI/017 and UNCE SCI/013, Czech Republic; COST, ERC, ERDF, Horizon 2020 and Marie Skℓodowska-Curie Actions, European Union; Investissements d’Avenir Labex, Investissements d’Avenir Idex and ANR, France; DFG and AvH Foundation, Germany; Herakleitos, Thales and Aristeia programmes co-financed by EU-ESF and the Greek NSRF, Greece; BSF-NSF and MINERVA, Israel; Norwegian Financial Mechanism 2014-2021, Norway; NCN and NAWA, Poland; La Caixa Banking Foundation, CERCA Programme Generalitat de Catalunya and PROMETEO and GenT Programmes Generalitat Valenciana, Spain; Göran Gustafssons Stiftelse, Sweden; The Royal Society and Leverhulme Trust, United Kingdom. The crucial computing support from all WLCG partners is acknowledged gratefully, in particular from CERN, the ATLAS Tier-1 facilities at TRIUMF (Canada), NDGF (Denmark, Norway, Sweden), CC-IN2P3 (France), KIT/GridKA (Germany), INFN-CNAF (Italy), NL-T1 (Netherlands), PIC (Spain), ASGC (Taiwan), RAL (U.K.) and BNL (U.S.A.), the Tier-2 facilities worldwide and large non-WLCG resource providers. Major contributors of computing resources are listed in ref. [90].
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1029-8479
