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
INTRODUCTION
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, on-line and off-line validation, 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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Test