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Some additional Studies in Particle Flow Tau identification

Some additional Studies in Particle Flow Tau identification. Mike Bachtis UW. Introduction. Optimize the signal cone reconstruction Look at possible cuts for three cases One prong/No Pi0s One Prong/Pi0s Three Prongs Look at the Isolation Technicalities

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Some additional Studies in Particle Flow Tau identification

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  1. Some additional Studies in Particle Flow Tau identification Mike Bachtis UW

  2. Introduction • Optimize the signal cone reconstruction • Look at possible cuts for three cases • One prong/No Pi0s • One Prong/Pi0s • Three Prongs • Look at the Isolation • Technicalities • My demo code runs on the PFTauTagInfo • MC Visible Tau Pt>15 GeV unless noted otherwise

  3. Signal Cone Reconstructionby Cluster expansion • Signal Cone Cluster expansion • Starts from the leading candidate (Charged/Gamma) • Associates all candidates with DR<radius • Reweighs the Cluster • Repeats until the Cluster axis is stable • Clustering is also applied to all candidates in the jet (clusters in isolation cone) • To be used for isolation cuts

  4. Nearest Isolation Candidate to the signal Cluster (radius=0.15) • There are some candidates that flow outside the lead Cluster • Most of them are three prongs (verified) • However 0.15 is a good cone in most cases • I am going to try a larger cone now and apply cuts on the cluster dimensions suitable for each type I look at. (So I pick 0.25) • In three prongs I think it is important to reconstruct the charge properly (at least at my analysis) There is more tau here..

  5. One prong / No Pi0s(Lead Track) • Reco Preselection: • Require 1 or 2 prongs reconstructed • No more restrictions • PFGammas can be there and have any Pt • All of the tau Pt goes to the track so a tight Lead Track cut here helps a lot • Apply 15 GeV! Z Z QCD-20-170 QCD-20-170

  6. One prong/ No Pi0sCluster Dimensions • Lead Track Pt >15 GeV applied • Lets require 0.05 eta, 0.1 phi Dimensions Z Z QCD-20-170 QCD-20-170

  7. One prong/ No Pi0s Lead Track Fraction • Previous Cuts applied • Lets apply an 85% Cut on the lead Track Fraction • In case of two prongs If all the above criteria are applied we are certain that the second track is insignificant so we can calculate the charge from the lead Track • Actually maybe we can even remove it (but I am not doing it now) Z QCD-20-170

  8. One Prong /No Pi0sEfficiency • No Isolation Applied Yet (that can drop the curve on the right) • Isolation can be looser that 0 candidates (Will show that later) • Generally good performance (0.5% QCD efficiency) • Most background comes from single pions • MVA on those variables could do better Z->tautau QCD

  9. One Prong +Pi0s • Reco preselection • 1 or 2 Prongs • Here Photon seeding is important • Highest Branching Ratio is on this mode too • I will select leadTrackPt + leadGammaPt >15 GeV Z Z Z QCD-20-170 QCD-20-170 QCD-20-170

  10. One Prong+Pi0s Cluster Dimensions • Previous Cuts Applied • Apply eta Dimension < 0.1 Z Z QCD-20-170 QCD-20-170

  11. One Prong+Pi0sEfficiency Z to tau tau QCD • No isolation applied • Here we need more work • We can gain more by looking at the cluster shapes and merging near cluster to create the individual pi0s .Then Look at the Pi zeros

  12. Three ProngsCharge Compatibility+Lead Track • Preselection: 3 prongs • Require proper reconstruction of charge • Kills ½ of background • Usefull for offline analysis • Apply Lead Track Cut of 8 GeV Z QCD-20-170 Z QCD-20-170

  13. Three prongsCluster Dimensions • Lead Track Cut applied • Require etaDim<0.1 • Require phiDim<0.1 • Invariant mass cannot provide significant separation Z Z QCD-20-170 QCD-20-170

  14. Three prongs :Efficiency • No Isolation Applied • We can relax the cluster dimension cuts to get higher efficiency Z to tau tau QCD

  15. Isolation Discriminators • DeltaR RMS of the clusters /(or candidates) in the whole jet Contributes to the isolation • Maybe it could be used in combination of requiring not 0 but maximum 1 candidate in annulus (Happens often)

  16. Conclusion • Clustering on PF Tau Candidates provides significant improvement since it provides also cuts in the signal cone • Those variables and cuts are proposed for MVAs • Maybe we can gain a lot from proper Pi0 reconstruction – merging of clusters/ cluster profiles

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