Bonn 2020 – scientific programme

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T: Fachverband Teilchenphysik

T 60: Various topics in elementary particle physics

T 60.5: Talk

Wednesday, April 1, 2020, 17:30–17:45, L-2.017

Identification of boosted Higgs bosons decaying into a pair of b-quarks using multivariate analysis techniques with the ATLAS detector at √s=13 TeV — Jochen Dingfelder, Tatjana Lenz, and •Christian Nass — PI Universität Bonn, Bonn, Germany

Studying properties of the Higgs Boson is crucial for testing the Higgs-mechaism. Prerequisite is the identification of Higgs Boson candidates. High transverse momentum Higgs Bosons are of special interest, as those may arise from new heavy resonances. The final state looked at is the decay into a pair of b-quarks (H → bb), since it has the largest Standard Model branching ratio. The main backgrounds are QCD-events and hadronic t-decays. Large-R=1.0 calorimeter-jets are used to reconstruct the collimated Higgs Boson candidate decay products. The ATLAS default Higgs Boson identification algorithm (Higgs-tagger) uses the jet mass and the number of R=0.2 track-jets associated to the large-R jet and identified as b-jets in order to identity Higgs boson candidates.

A new multivariate algorithm is developed based on b-jet identification, jet kinematic and jet substructure informations. An increase in performance by a factor of 1.5 - 2.5 and 2 - 5 for QCD and hadronic t-events, respectively, is achieved over the whole signal efficiency range compared to the default ATLAS analysis. The Higgs-taggers are calibrated in 15.4/fb of 2016 data g → bb. The extrapolation to H → bb is done using Monte Carlo simulations. This talk presents the new Higgs-tagger and its calibration.