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1.Aim and Definitions

1.Aim and Definitions. Aim is to formulate an efficient selection procedure for π π o decays of the τ Analysis will optimise:. efficiency. purity. rej. factor. N s =number signal decays in MC sample (2N x BR), n s =number truth-matched candidates selected.

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1.Aim and Definitions

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  1. 1.Aim and Definitions • Aim is to formulate an efficient selection procedure for π πodecays of the τ • Analysis will optimise: efficiency purity rej. factor Ns=number signal decays in MC sample (2NxBR), ns=number truth-matched candidates selected b=total number of background decays selected Nb= number background decays in sample, nb=number background decays selected • To combine MC will scale to a data sample of (so far) 0.134 fb-1 of data Mitchell Naisbit Manchester University Elba 2003

  2. 2.TauUser Preselection Nano Cuts Input 1M generic τ+τ- events Mitchell Naisbit Elba 2003 Mitchell Naisbit Manchester University Elba 2003

  3. 2. TauUser Preselection Nano Cuts Input 1M generic τ+τ- events Level-3 trigger cut Mitchell Naisbit Elba 2003

  4. 2. TauUser Preselection Nano Cuts Input 1M generic τ+τ- events Level-3 trigger cut Stream19 42% pass nanofilter Mitchell Naisbit Elba 2003

  5. 2.TauUser Preselection Micro Cuts Events input from nanofilter Mitchell Naisbit Elba 2003

  6. 2.TauUser Preselection Micro Cuts Events Input from nanofilter # tracks even and <8 Mitchell Naisbit Elba 2003

  7. 2.TauUser Preselection Micro Cuts Events Input from nanofilter # tracks even and <8 Zero net charge Mitchell Naisbit Elba 2003

  8. 2.TauUser Preselection Micro Cuts Events Input from nanofilter # tracks even and <8 Zero net charge Topology classification 36% pass preselection Mitchell Naisbit Elba 2003

  9. 3.Selection Procedure Selection for data and MC samples: For 1-1 events backgrounds reduced by tag Selection requirements πPID (piLHLoose) π not in eMicroLoose Signal side Single AWG πo e or μ PID as tag Tag side or As above for ρ tag Mitchell Naisbit Elba 2003

  10. 4.Monte Carlo truth matching recon. π, πo, γA, γB must match back to particle in truth list of same identity Reconstruction Requirements for signal τ decays π and πomust have same mother which is a true ρ γAandγBmust have same mother which is a true πo Mitchell Naisbit Elba 2003

  11. 5.Results – τ+τ- MC (1) Running on 1M generic τ+τ-events Ns= 508,200 signal decays (1) Truth codes for selected decays (2) (2) Truth codes for truth-matched candidates ns = 48,613 (3) Backgrounds (3) btau = 21,401 Main τbackgrounds are a1 decays and improperly reconstructed signal decays. Mitchell Naisbit Elba 2003

  12. 5.Results – background MC Analysed MC samples of - (hadronic) (leptonic) (photon) Giving scaled results- Ns=61,385 ns=5,872 bτ=2,585 bother=2,208 b = bτ + bother= 4,793 Mitchell Naisbit Elba 2003

  13. 5.Results ε = 9.57 % π = 55.10 % Main backgrounds • Non-signal τ (a1) • Improperly reconstructed • signal decays • Leptonic (bhabha+FSR) • and some hadronic Mitchell Naisbit Elba 2003

  14. 6.Event Parameter Distributions - τ+τ- MC nNeutrals Ranges from 2 to ~15 nChargedTracks Ranges 0 to ~6 thrustMag nNeutrals Ranges from ~0.79 to ~0.99 (but no quantities are of use to eliminate τ) Mitchell Naisbit Elba 2003

  15. 6.Event Parameter Distributions- τ+τ- MC nNeutrals Ranges from 2 to ~15 nChargedTracks Ranges 0 to ~6 thrustMag nNeutrals Ranges from ~0.79 to ~0.99 (but no quantities are of use to eliminate τ) Mitchell Naisbit Elba 2003

  16. 6.Event Parameter Distributions- τ+τ- MC nNeutrals Ranges from 2 to ~15 nChargedTracks Ranges 0 to ~6 thrustMag nNeutrals Ranges from ~0.79 to ~0.99 (but no quantities are of use to eliminate τ) Mitchell Naisbit Elba 2003

  17. 6.Event Parameter Distributions - background MC nNeutrals nChargedTracks cut >~ 12 (hadronics) cut all >~ 6 (hadronics) Mitchell Naisbit Elba 2003

  18. 6.Event Parameter Distributions - background MC cut <~ 0.8(hadronics) cut >~ 0.99(leptonics) thrustMag Mitchell Naisbit Elba 2003

  19. 7.Efficiency and Purity Optimisation nNeutrals nCharged Tracks cut > 6 cut > 12 thrustMag thrustMag cut > 0.988 cut < 0.79 Mitchell Naisbit Elba 2003

  20. 8.Invariant Mass Spectrum ε = 9.57 % ε = 9.51% π = 55.10 % π = 65.52% r~100% Mitchell Naisbit Elba 2003

  21. 9.Future Work • Finalise Selection Procedure • Complete study into τ+ non-τ backgrounds and how • to minimise them • Perform fits to the invariant mass spectrum • Implement detector unfolding techniques Mitchell Naisbit Elba 2003

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