Particle extrapolation tool JetParticleExtrapolationTool


JetParticleExtrapolationTool is creating jets from truth particles. Basic idea of this tool is to take all interacting particles, make tracks of these particles, extrapolate them to the calorimeter and create from them new jets for all those extrapolated particles matching cluster in RecoJet.


Tool takes MCEventCollection container from GEN_AOD in input file, which contains generated particles in interaction point. By ./atlas/Generators/GenAnalysisTools/TruthHelpler method isGenInteracting tools selects truth particles (truth particles are interacting particles) and these particles are candidates to be constituents of created jets. In next step is tool using truth particle tracking through magnetic field. For every truth particle creates track parameters using algorithm atlas/TrkTools/TrkTruthToTrack/TruthToTrack method makePerigeeParameters. This perigee parameters are needed for extrapolation. Tool is extrapolating particles with eta < |4.9|. For these partices adds mass index (we have 6 mass indexes for particles: gamma, electron, muon, pion, kaon a proton mass index). In next step is tool extrapolating.

For extrapolation is tool using algorithm atlas/Reconstruction/RecoTools/TrackToCalo method extrapolate. This method takes given track, extrapolates it into a calorimeter and returns variables needed to compare with the cluster position. For extrapolating to calorimeter has used method three posibilities: extrapolate to EMB2, EME2 or FCal0. After extrapolation creates collection of particles of type HepLorentzVector (atlas/Event/EventCommonTPCnv/), which has energy and mass of original particle and eta and phi of extrapolated position.

In next step is tool looking for extrapolated particles, which are leading to TopoClusters. Tool makes a look over created jet clusters - jet collection Cone4LCTopoJets constituents CaloClusters. For every cluster looks for extrapolated particle leading to this cluster and add this particle to list by matching criteria. From particles matching cluster create a jet, write it to new jetcollection and record this collection to StoreGate.

-- MartinPecsy - 26 Jan 2009

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Topic revision: r6 - 2009-01-30 - MartinPecsy
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