BTagging Common Interface

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B-Tagging CommonInterface
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• Y.D. Mutaf, S. Towers
• 20 March 2003

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Motivation

• The taggers are currently provided by some macros
  specific to different data formats (TMB, TMBTree
  etc.)
• Due to different developers, the interfaces to
  these macros are quite different
• Increases the messiness index of the user
  analysis code
• A clear sign of inefficient coding (from the
  users perspective)
• Time spent to learn different implementations is
  a waste
• We need a common interface, common ground
• B-id group recently started an effort for
  combining all the tagger algorithms in one
  package with the same interface

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btags_cert package

• Initially designed for doing smearing of MC track
  information related to jets, in order to make MC
  look more like our data (will talk about this
  later)
• It now includes a common interface to Impact
  Parameter and Secondary Vertex B-tagging
  macros/code
• Not heavily advertising its use, since this
  method will become obsolete when the B-id groups
  package comes along
• However this is a utility we will use for the
  near future

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B-tagging Methods

• Secondary Vertex Tagging
• A jet is tagged if there is an associated
  secondary vertex
• Soft Lepton Tagging
• Relies on the identification and properties of
  the lepton from the leptonic decay of the
  B-meson.

• Impact Parameter Tagging
• Assigns a combined probability to the jet using
  the associated tracks for belonging to the
  Primary Vertex
• Counting Signed IP tagging is a variation

PV
SV
N/A
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Implementation

• Btagger object is the driving source of the
  taggers.
• Switches and cases are eased with the use of
  enumerations.

• Contains a pointer to an abstract base class
  through which we will access the individual
  tagger classes.

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Tag Classes

• Everything is defined in btags_cert namespace

Pure virtual methods that are implemented by the
daughter classes
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Implementation

• The package has an example directory which
  contains an example package accessing TMB chunks
• Most of the tagging related parameters are driven
  by package owned RCPs.
• Can give more info if anyone needs to use for
  immediate purposes

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Example Package

• The btags_cert package contains an example
  directory which contains a full example package
  to do the implementation of this package in TMBs
• Need to copy the example package into the working
  release are (SRT_PRIVATE)
• There is more to do before hand (due to
  requirements from the individual taggers), well
  talk about these

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More on the Example

• Instantiation of the individual taggers
• Through the enumerations

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More on the Example
Need to feed the PV information before using the
taggers
Reading the tracks from the event One can
directly feed the tracks as well.
Need to reset all the information in the taggers
before the next event.
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More on the Example

• Doing the tagging which, for now returns a
  three-fold quality ie. LOOSE, MEDIUM and TIGHT.
• Will soon add methods to return a continuous
  variable eg. Probability
• The method uses a jetidJet but it can also
  accept two values of jet direction ie. eta, phi.

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Things need to be done beforehand

• Follow the instructions for the packages to be
  compiled needed for the SVTX tagging (even if you
  dont use it)
• I am not sure if all the packages are needed!
  Try and let me know