C P Properties of Higgs Boson Interactions with Top Quarks in the t tH and tH Processes Using H to gamma gamma with the ATLAS Detector

M.T.DOVA ET AL; ATLAS COLL., M.AABOUD

PHYSICAL REVIEW LETTERS

AMER PHYSICAL SOC

Lugar: New York; Año: 2020

0031-9007

A study of the CP properties of the interaction between the Higgs boson and top quarks ispresented. Higgs bosons are identified via the diphoton decay channel (H → γγ) and theirproduction in association with a top quark pair (ttH¯ ) or single top quark (tH) is studied. Theanalysis uses 139 fb−1 of proton?proton collision data recorded at a center-of-mass energy of 13 TeV with the ATLAS detector at the Large Hadron Collider. Assuming a CP-evencoupling, the ttH¯ process is observed with a significance of 5.2 standard deviations. Themeasured 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 ttH¯ 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 theStandard Model expectation is set. A CP-mixing angle greater (less) than 43 (-43)◦is excluded at 95% confidence level.