CP Properties of Higgs Boson Interactions with Top Quarks in the (tt)over-barH and tH Processes Using H -> gamma gamma with the ATLAS Detector

• Published in: Physical review letters 2020-08, Vol.125 (6)
• Main Authors: Onofre, A., Castro, Nuno Filipe, ATLAS Collaboration
• Format: Article
• Language: English
• Subjects: Ciências Físicas; Ciências Naturais; Science & Technology
• ISSN: 1079-7114
• DOI: 10.1103/PhysRevLett.125.061802

A study of the charge conjugation and parity (CP) properties of the interaction between the Higgs boson and top quarks is presented. Higgs bosons are identified via the diphoton decay channel (H→γγ), and their production in association with a top quark pair (t¯tH) or single top quark (tH) is studied. The analysis uses 139  fb−1 of proton–proton collision data recorded at a center-of-mass energy of √s=13  TeV with the ATLAS detector at the Large Hadron Collider. Assuming a CP-even coupling, the t¯tH process is observed with a significance of 5.2 standard deviations. The measured cross section times H→γγ branching ratio is 1.64+0.38−0.36(stat)+0.17−0.14(sys)  fb, and the measured rate for t¯tH is 1.43+0.33−0.31(stat)+0.21−0.15(sys) times the Standard Model expectation. The tH production process is not observed and an upper limit on its rate of 12 times the Standard Model expectation is set. A CP-mixing angle greater (less) than 43 (−43)° is excluded at 95% confidence level. 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; SSTC, Belarus; CNPq and FAPESP, Brazil; NSERC, NRC, and CFI, Canada; CERN; CONICYT, Chile; CAS, MOST, and NSFC, China; COLCIENCIAS, Colombia; MSMT CR, MPO CR, and VSC CR, Czech Republic; DNRF and DNSRC, Denmark; IN2P3-CNRS and CEA-DRF/IRFU, France; SRNSFG, Georgia; BMBF, HGF, and MPG, Germany; GSRT, Greece; RGC and Hong Kong SAR, China; ISF and Benoziyo Center, Israel; INFN, Italy; MEXT and JSPS, Japan; CNRST, Morocco; NWO, Netherlands; RCN, Norway; MNiSW and NCN, Poland; FCT, Portugal; MNE/IFA, Romania; MES of Russia and NRC KI, Russia Federation; JINR; MESTD, Serbia; MSSR, Slovakia; ARRS and MIZS, Slovenia; DST/NRF, South Africa; MINECO, Spain; SRC andWallenberg Foundation, Sweden; SERI, SNSF, and Cantons of Bern and Geneva, Switzerland; MOST, Taiwan; TAEK, Turkey; STFC, United Kingdom; and DOE and NSF, USA. In addition, individual groups and members have received support from BCKDF, CANARIE, Compute Canada, and CRC, Canada; ERC, ERDF, Horizon 2020, Marie Sklodowska-Curie Actions, and COST, European Union; Investissements d'Avenir Labex, Investissements d'Avenir Idex, and ANR, France; DFG and AvH Foundation, Germany; Herakleitos, Thales, and Aristeia programs cofinanced by EU-ESF and the Greek NSRF, Gre