Mainz 2014 – scientific programme

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T: Fachverband Teilchenphysik

T 106: Higgs: Zerfall in Fermionen 3

T 106.5: Talk

Thursday, March 27, 2014, 17:45–18:00, P10

Search for the Standard Model Higgs boson produced in association with top quarks and decaying to bb in pp collisions at √s = 8 TeV with the ATLAS detector at the LHC — Kevin Kröninger, Maria Moreno Llacer, Olaf Nackenhorst, Arnulf Quadt, •Leonid Serkin, and Elizaveta Shabalina — II. Physikalisches Institut, Georg-August-Universität Göttingen

The recently discovered Higgs-like particle has shown properties so far consistent with the Standard Model (SM), however the excess in fermionic decay channels is still not firmly established. In this talk, we present a search for the Standard Model Higgs boson production in association with a pair of top quarks (ttH), providing a direct measurement of the top-quark Yukawa coupling. The presented overview of the search in ATLAS at the LHC is focused on the semileptonic decay of the tt system with the Higgs decaying to a pair of b-quarks (H→ bb), and combines different topologies given by the jet and b-tagged jet multiplicities of the event. A selection of events with characteristics resembling those of the desired signal, while rejecting as many non-signal events as possible, 95% dominated by top pair plus jets production, is performed. For events with at least five jets and three or more b-tagged jets, the final separation is performed by training an Artificial Neural Network based on a Bayesian approach. A simultaneous fit to the background-dominated topologies with lower jet and/or b-tagged jet multiplicities and those with signal is performed to obtain an improved background prediction with reduced uncertainties, resulting in a better search sensitivity compared to fitting the signal region alone.