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T: Fachverband Teilchenphysik

T 24: Higgs: Higgs mit tops I

T 24.2: Vortrag

Montag, 9. März 2015, 17:00–17:15, M.10.12 (HS 14)

Search for the decay H→ bb in association with a pair of hadronically decaying top quarks at 8 TeV in ATLAS — •Nello Bruscino, Markus Cristinziani, Mazuza Ghneimat, Sebastian Heer, Vadim Kostyukhin, Evan Machefer, Liza Mijović, and Kaven Yau Wong — Physikalisches Institut, Universität Bonn

The observation of the Higgs boson in association with a top-quark pair will open a window to the direct study of the Yukawa couplings of the top quark, which is the fermion expected to couple most strongly to the Higgs boson. ttH events are produced with a very small cross section (0.13 pb at m_H=125 GeV). Therefore the H→ bb decay channel, which is the dominant decay mode for the Higgs boson, and tt decays with no leptons, which occur in >50% of cases, are considered as the final state.
The signal signature is characterized by eight jets, out of which four are b-tagged, no leptons and no missing transverse momentum. The background is dominated by multijet events followed by tt events with at least two extra jets.
The analysis is split in different categories, according to jet and b-jet multiplicities. The multijet background is estimated through a data-driven method. After the preselection a multivariate approach (BDT) is used to distinguish the ttH signal against background. Finally a fit is performed in order to set a limit on the cross section of the process and establish the strength of the Higgs-boson signal.