Aachen 2019 – scientific programme

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T: Fachverband Teilchenphysik

T 82: Flavor-Tagging, Jet-Kalibration

T 82.5: Talk

Thursday, March 28, 2019, 17:00–17:15, S09

Double-b-tagging calibration in g→ bb events with the ATLAS experiment — •Ruth Jacobs, Tatjana Lenz, and Norbert Wermes — Physikalisches Institut, Universität Bonn

In 2018, the ATLAS and CMS collaborations announced the discovery of the Higgs boson decay into two b-quarks with the main contribution from the vector boson associated production mode. To access other production modes, such as gluon gluon fusion, in connection with the H→ bb decay, it is useful to consider Higgs bosons with a large transverse momentum, as the relative background contribution is reduced in this kinematic regime. In boosted H→ bb decays, the b-quark fragmentation products are reconstructed using a single large-R jet. A Higgs boson identification algorithm ("Higgs tagging") can be used to decide whether a jet originated from a Higgs boson decay, based on the large-R jet properties. One of the main ingredients for Higgs tagging is the determination of the flavour content of the candidate large-R jet. This is achieved by the so-called double-b-tagging method where a b-jet identification ("b-tagging") algorithm is used on two small-R sub-jets associated to the large-R jet. Since b-tagging algorithms are optimized on simulated events only, they must be calibrated in data. In order to calibrate double-b-tagging directly, a data sample of close-by b-jet events is needed. One possibility is to use data events of gluons splitting into b-quark pairs, which are produced abundantly at the LHC. In my talk I will present the strategy and results of the first direct double-b-tagging calibration in g→ bb events with the ATLAS experiment using data collected at the LHC in 2015 and 2016.