Search for Higgs Boson Decays into a Z Boson and a Light Hadronically Decaying Resonance Using 13 TeV pp Collision Data from the ATLAS Detector

Abstract

A search for Higgs boson decays into a Z boson and a light resonance in two-lepton plus jet events is performed, using a pp collision dataset with an integrated luminosity of 139 fb−1 collected at ffiffiffi s p ¼ 13 TeV by the ATLAS experiment at the CERN LHC. The resonance considered is a light boson with a mass below 4 GeV from a possible extended scalar sector or a charmonium state. Multivariate discriminants are used for the event selection and for evaluating the mass of the light resonance. No excess of events above the expected background is found. Observed (expected) 95% confidence-level upper limits are set on the Higgs boson production cross section times branching fraction to a Z boson and the signal resonance, with values in the range 17–340 pb (16 þ6 −5–320 þ130 −90 pb) for the different light spin-0 boson mass and branching fraction hypotheses, and with values of 110 and 100 pb (100 þ40 −30 and 100 þ40 −30 pb) for the ηc and J=ψ hypotheses, respectively ; ANPCyT ; YerPhI, Armenia ; Australian Research Council ; BMWFW, Austria ; Austrian Science Fund (FWF) ; Azerbaijan National Academy of Sciences (ANAS) ; SSTC, Belarus ; National Council for Scientific and Technological Development (CNPq) ; Fundacao de Amparo a Pesquisa do Estado de Sao Paulo (FAPESP) ; Natural Sciences and Engineering Research Council of Canada ; NRC, Canada ; Canada Foundation for Innovation ; CERN ; ANID, Chile ; Chinese Academy of Sciences ; Ministry of Science and Technology, China ; National Natural Science Foundation of China (NSFC) ; Departamento Administrativo de Ciencia, Tecnologia e Innovacion Colciencias ; Ministry of Education, Youth & Sports - Czech Republic Czech Republic Government ; Czech Republic Government ; DNRF, Denmark ; Danish Natural Science Research Council ; Centre National de la Recherche Scientifique (CNRS) ; CEA-DRF/IRFU, France ; SRNSFG, Georgia ; Federal Ministry of Education & Research (BMBF) ; HGF, Germany ; Max Planck Society ; Greek Ministry of Development-GSRT ; RGC, China ; Hong Kong SAR, China ; Israel Science Foundation ; Benoziyo Center, Israel ; Istituto Nazionale di Fisica Nucleare (INFN) ; Ministry of Education, Culture, Sports, Science and Technology, Japan (MEXT) ; Ministry of Education, Culture, Sports, Science and Technology, Japan (MEXT) Japan Society for the Promotion of Science ; CNRST, Morocco ; Netherlands Organization for Scientific Research (NWO) Netherlands Government ; RCN, Norway ; Ministry of Science and Higher Education, Poland ; NCN, Poland ; Portuguese Foundation for Science and Technology ; MNE/IFA, Romania ; MES of Russia, Russia Federation ; NRC KI, Russia Federation ; JINR ; MESTD, Serbia ; MSSR, Slovakia ; Slovenian Research Agency - Slovenia ; MIZS, Slovenia ; DST/NRF, South Africa ; Spanish Government ; SRC, Sweden ; Wallenberg Foundation, Sweden ; SERI, Switzerland ; Swiss National Science Foundation (SNSF) ; Canton of Bern, Switzerland ; Canton of Geneva, Switzerland ; Ministry of Science and Technology, Taiwan ; Ministry of Energy & Natural Resources - Turkey ; Science & Technology Facilities Council (STFC) ; United States Department of Energy (DOE) ; National Science Foundation (NSF) ; BCKDF, Canada ; CANARIE, Canada ; Compute Canada, Canada ; CRC, Canada ; European Union (EU) European Research Council (ERC) ; European Union (EU) ; Horizon 2020, European Union ; COST, European Union ; French National Research Agency (ANR) ; German Research Foundation (DFG) ; Alexander von Humboldt Foundation ; Herakleitos programme ; Thales programme ; Aristeia programme ; EU-ESF, Greece ; Greek NSRF, Greece ; BSF-NSF, Israel ; German-Israeli Foundation for Scientific Research and Development ; La Caixa Banking Foundation, Spain ; CERCA Programme Generalitat de Catalunya, Spain ; PROMETEO Programme Generalitat Valenciana, Spain ; GenT Programme Generalitat Valenciana, Spain ; Goran Gustafssons Stiftelse, Sweden ; Royal Society of London ; Leverhulme Trust