xAOD DecayVertexTools

This page is for rough notes and bits of documentation while changing the old V0Tools to work with the xAOD.

Currently working on making the invariant mass functions work with the xAOD TrackPartcle _v1 functions. I have made changes on these but not yet tested them.

Locations of useful files

The current V0Tools is located in /Tracking/TrkVertexFitter/TrkVertexAnalysisUtils/trunk

The header files VxVertex.h, ExtendedVxCandidate.h and VxCandidate.h are located in /Tracking/TrkEvent/VxVertex/trunk/VxVertex

The xAOD files are located in /Event/xAOD

Most of the files that will be used will be located in /Event/xAOD/xAODTracking

Some other xAOD files that are used are /Event/xAOD/xAODBase/trunk/xAODBase/IParticle which links to the TLorentzVector class to allow for the same operations on 4-vectors as used in ROOT

TrackParticle information

The TrackParticle _v1 functions:

• Four momentum -

   TrackParticle::FourMom_t &p4() 

• Energy -

   TrackParticle _v1::e() 

• Mass -

   TrackParticle _v1::m() 

• Transverse momentum -

   TrackParticle _v1::pt() 

• Eta -

   TrackParticle::eta() 

• Rapidity -

   TrackParticle _v1::rapidity() 

 p4.SetPxPyPzE(px, py, pz, e) 

Number of tracks at vertex

The number of tracks at the vertex was previously obtained by:

 unsigned int NTrk = vxCandidate->vxTrackAtVertex()->size(); 

now I think its done by:

 size_t NTrk = Vertex->nTrackParticles();

Current problems

Some of the header files required may be missing, for example those required by the xAOD.
Some header files in the old code are purely for Athena but some may still be required.

Notes

Currently uses the format of the old code, the invariantMass function calls a track4Momentum function which calls a trackMomentum fucntion.

This trackMomentum function uses

 Amg::Vector3D 

not sure what the header for this is at the moment

-- David Lack - 2014-07-29

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