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Tuning the GEANT4 simulator to K2K through-going muon data

Tuning the GEANT4 simulator to K2K through-going muon data. Maximilien Fechner , Saclay. Work in collaboration with S. Dazeley and C. Walter. Theory. Using reconstructed real thrumus at the 1KT, prepare an input file for G4 ( momentum, direction, entry point)

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Tuning the GEANT4 simulator to K2K through-going muon data

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  1. Tuning the GEANT4 simulatorto K2K through-going muon data Maximilien Fechner , Saclay Work in collaboration with S. Dazeley and C. Walter

  2. Theory • Using reconstructed real thrumus at the 1KT, prepare an input file for G4 ( momentum, direction, entry point) • Simulate 2500 thru µ using the new 1KT G4 setting • Reconstruct them using « mfmufit », adapted to the G4 geometry (only change) • Tuning : adjust the water and surface parameters in ConstructMaterials.cc + the efficiency/cutoff parameters in WCDigitizer.cc

  3. Re-tuning • Many changes have been made since last August for the • ‘1kt’ setting : • New geometry (in better agreement with K2K) • especially regarding the black sheet and endcap pmts (they • used to be truncated) • 2. New surface models for BS/water and PMT/water • 3. Changed the absorption lengths (used to be too short) Changes still underway (PMT surface parameters), so that the simulator is not tuned at the moment very preliminary !!!

  4. Thrumu reconstruction Z (cm) Y (cm) Rec-True entry point Much better : efficiency > 50 % (was 25 %) Black = tight entry and exit cuts Green = no cuts X (cm)

  5. degrees Rec-True exit point, X & Y Angle between true and reconst tracks Significant improvement ! (see last talk)

  6. Why ? • Better simulation of charge on top/ bottom • Better agreement for indirect light

  7. G4 : black K2K thrumu data : Red Charge Charge ratios Not enough total charge , Slightly too much indirect light Total charge

  8. G4 : black K2K thrumu data : Red Charge profile Corrected charge degrees

  9. Timing ns Too much reflectivity (PMT & BS surface)

  10. Conclusion • Changes to the G4 simulator are a big improvement • Tuning the direct light is much easier than the indirect light • Need to reduce reflections (PMT surface), maybe slightly increase scattering • K2K neutrino beam simulation in G4 has started (test phase), I will start mass production as soon as thrumu tuning is done comparison with K2K neutrino data (e.g. pi0mass peak, etc.)

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