Searches for ttH (Multilepton+Diphoton) Production in ATLAS

Abstract: After the discovery of a Higgs boson, the measurements of its properties are at the forefront of research. The determination of the associated production of a Higgs boson and a pair of top quarks is of particular importance as the ttH Yukawa coupling is large and thus an excellent probe for physics beyond the Standard Model (SM). For the complete LHC Run-1 dataset, the combined ATLAS and CMS signal strength (defined as the ratio of measured cross-section to the SM prediction) was $\mu=2.3^{+0.7}_{-0.6}$, which indicated a mild excess with respect to the SM expectation. The results of the ttH search with multilepton and diphoton signatures are presented for the first LHC Run-2 data (13 fb$^{-1}$ at 13 TeV) recorded by the ATLAS experiment: $\mu=2.5^{+1.3}_{-1.1}$ for the multilepton analyses and $\mu=-0.3^{+1.2}_{-1.0}$ for the diphoton analyses. Both measurements are in agreement with the SM expectation.