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Add algorithm to b-tag with respect to the beamspot

Merged Dan Guest requested to merge dguest/athena:poboybtag into master

Our current b-tagging impact parameter (IP) calculation relies on extrapolating the track to the perigee point with respect to the primary vertex. We might be able to do just about as well with the beamspot perigee point. There are a few advantages to the later:

  • It doesn't depend on atlas extrapolator code, which is a heavy dependency
  • Many of the parameters are still defined without a primary vertex, meaning we could still b-tag without a primary vertex

The second case might be especially useful in the trigger where we might want to b-tag as a preselection step before running full-event tracking and building a primary vertex. We could also use b-tagging algorithms to estimate the primary vertex z-position.

More concretely, this merge request touches code in a few places:

  • Adds another algorithm to calculate the IP with respect to the beamspot,
  • Adds more flexibility in DL2 so that we can run DIPS using this IP definition
  • Removes the default argument for BTagTrackIpAccessor since there might be a few now (and updates some code that uses this class)
  • Moves JetParticleAssociationAlgConfig.py into ParticleJetTools, which is where JetParticleAssociationAlg is defined. This makes it accessible in standalone builds.
  • Removes the configuration to write DL2 outputs to doubles. We migrated to floats a while ago now.

It should not change any variables in any ATLAS data formats.

Edited by Dan Guest