b+Jet+MET topology-based physics signatures

Top quark cross section measurement in the missing ET + b-jet channel

Inclusive missing ET + multi-b search

missing ET + 4b analysis

ttH

Jet reconstruction, calibration, and resolution

Jet algorithms

Inputs to jet reconstruction: Calorimeter towers with noise suppression (TopoTowers)

Jet energy resolution improvements using tracks

Jet energy resolution improvements using longitudinal calorimeter segmentation

Jet-Vertex association algorithm

Baseline correction for pile-up and noise

Semi-leptonic b-jet energy scale

Measurement of the jet energy resolution

b-tagging

Track-jet based b-tagging

High pT b-tagging

Event Tagging

Hadronic flavor tagging

gluon bb tagging

highly boosted (bb)-jets

Quark/gluon separation

High Level Trigger b-tagging

Tagging b-jets at the trigger level can expand the physics reach of ATLAS in many ways: it allows to lower the jet ET threshold to increase the acceptance of interesting physics events containing
multiple b-jets (like bbH and ttH ), and can be used to reduce non-b backgrounds and improve the purity of Super-symmetry searches involving b-jets in the ?nal state.

The SLAC group has implemented one of the two ATLAS b-tagging algorithms at level 2 trigger: the Impact Parameter ?2 Probability tagger (IPChi2)

Current and future work involves the optimization of the operational parameters of the algorithm, determination of performance in real data events, and the investigation of new trigger menus involving b-quarks and missing transverse energy for Super-symmetry searches.

LVL2 impact parameter Chi2 algorithm

The IPChi2 tagger is based on the impact parameter distribution of mis-tags, which can be derived directly from data and does not require the use of Monte Carlo templates as in the likelihood ratio b-tagger.

b+MET combined trigger

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