Observation of Higgs boson production in association with a top quark pair (ttH) at the LHC with the ATLAS detector

by Chen Zhou (University of Wisconsin Madison (US))

Thursday 7 Jun 2018, 12:30 → 14:00 US/Pacific

Other Institutes

Observation of Higgs boson production in association with a top quark
pair (ttH) is presented, based on the analysis of up to 79.8/fb of
proton-proton collision data produced at 13 TeV center-of-mass energy
by the Large Hadron Collider and recorded with the ATLAS detector. The
results for Higgs boson decay channels of bb, γγ, WW, ττ, and ZZ are
combined. The observed significance is 5.8 standard deviations,
compared to an expectation of 4.9 standard deviations. Combined with
the ttH searches using a dataset corresponding to integrated
luminosities of 4.5 and 20.3/fb at 7 and 8 TeV, respectively, the
observed (expected) significance is 6.3 (5.1) standard deviations.
Assuming Standard Model branching fractions, the total ttH production
cross section at 13 TeV is measured to be 670 +/- 90 (stat.) +110/-100
(syst.) fb, while the Standard Model prediction is 507+35−50 fb. CERN
issued a press release for both the ATLAS and CMS ttH results on June
4th 2018.

Moreover, this talk will give detailed description of the new ttH
(H→γγ) analysis. Applying advanced machine learning package XGBoost
BDT, exceptional performance is achieved by using object level
kinematic variables from jets, leptons, and photons to separate the
ttH signal from the background.

chenzhou_20180607 (2).pdf