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Physics Laboratory

Physics Laboratory. School of Science and Technology. Hellenic Open University. HOU Reconstruction & Simulation (HOURS): A complete simulation and reconstruction package for Very Large Volume underwater neutrino Telescopes. A.Leisos, A. G. Tsirigotis , S.E.Tzamarias.

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Physics Laboratory

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  1. Physics Laboratory School of Science and Technology Hellenic Open University HOU Reconstruction & Simulation (HOURS): A complete simulation and reconstruction package for Very Large Volume underwater neutrino Telescopes. A.Leisos, A. G. Tsirigotis, S.E.Tzamarias VLVnT 2009 - Athens, 15October 2009 In the framework of the KM3NeT Design Study

  2. The HOURS software chain • Underwater Neutrino Detector • Generation of atmospheric muons and neutrino events (F77–CORSIKA,Pythia) • Detailed detector simulation (GEANT4-GDML) (C++) • Optical noise and PMT response simulation (F77) • Filtering Algorithms (F77 –C++) • Muon reconstruction (C++) • Effective areas, angular resolution and sensitivities calculation (scripts) • Extensive Air Shower Calibration Detector (Sea Top) • Atmospheric Shower Simulation (CORSIKA) – Unthinning Algorithm (F77) • Detailed EAS detector response Simulation (GEANT4) (C++) • Reconstruction of the shower direction (F77) • Muon Transportation to the Underwater Detector (C++) • Estimation of: resolution, offset (F77)

  3. The HOURS software chain Flow Chart CORSIKA (Extensive Air Shower Simulation) All Flavor Neutrino Interaction Events (Secondary Particles Generation) Atmospheric Muon Generation from CORSIKA GEANT4 (Muon Propagation to KM3NeT) GEANT4 (KM3NeT Detector Description and Simulation) Optical Noise, PMT response and Electronics Simulation EAS detector Simulation Prefit & Filtering Algorithms Shower direction reconstruction Muon Reconstruction Neutrino Telescope Performance SeaTop Calibration

  4. Event Generation – Flux Parameterization μ ν ν • Atmospheric Muon Generation • (CORSIKA) • Neutrino Interaction Events • (PYTHIA) • Atmospheric Neutrinos • (Bartol Flux) Earth • Cosmic Neutrinos • (AGN – GRB – GZK and more)

  5. Event Generation – Shadowing of neutrinos by Earth Earth Density Profile Column Depth Probability of a νμ to cross Earth Nadir Angle Survival probability

  6. GEANT4 Simulation– Detector Description • Any detector geometry can be described in a very effective way Use of Geomery Description Markup Language (GDML-XML) software package • All the relevant physics processes are included in the simulation • (OPTICAL PHOTON SCATTERING ALSO) Fast Simulation EM Shower Parameterization • Number of Cherenkov Photons Emitted (~shower energy) • Angular and Longitudal profile of emitted photons Visualization Angular Distribution of Cherenkov Photons Particle Tracks and Hits Detector components

  7. Arrival Pulse Time resolution Single Photoelectron Spectrum Quantum Efficiency Πρότυπος παλμός mV Simulation of the PMT response to optical photons Standard electrical pulse for a response to a single p.e.

  8. Prefit, filtering and muon reconstruction algorithms d L-dm (x,y,z) θc dγ Track Parameters θ : zenith angle φ: azimuth angle (Vx,Vy,Vz): pseudo-vertex coordinates dm (Vx,Vy,Vz) pseudo-vertex • Local (storey) Coincidence (Applicable only when there are more than one PMT looking towards the same hemisphere) • Global clustering (causality) filter • Local clustering (causality) filter • Prefit and Filtering based on clustering of candidate track segments (Direct Walk technique) • Combination of Χ2fit and Kalman Filter (novel application in this area) using the arrival time information of the hits • Charge – Direction Likelihood using the charge (number of photons) of the hits

  9. Kalman Filter – Muon Track Reconstruction - Algorithm Filtering Prediction Update the state vector Extrapolate the state vector Update the covariance matrix Extrapolate the covariance matrix Calculate the residual of predictions Decide to include or not the measurement (rough criterion) Calculate the contribution of the filtered point Decide to include or not the measurement (precise criterion) Initial estimates for the state vector and covariance matrix

  10. Kalman Filter – Muon Track Reconstruction - Algorithm State vector Initial estimation Update Equations timing uncertainty Kalman Gain Matrix Updated residual and chi-square contribution (rejection criterion for hit) Many (40-200) candidate tracks are estimated starting from different initial conditions The best candidate is chosen using the chi-square value and the number of hits each track has accumulated.

  11. Muon Track Reconstruction Chi-square probability Angular resolution Neutrino Muon Energy (log(E/GeV))

  12. Charge Likelihood – Used in muon energy estimation Hit charge in PEs Probability depends on muon energy, distance from track and PMT orientation Not a poisson distribution, due to discrete radiation processes E=1TeV D=37m θ=0deg Ln(F(n)) Ln(n) Log(E/GeV)

  13. Muon energy reconstruction Results 1 Simulation data from E-2 neutrino flux and SeaWiet detector (300 Strings, 130m between strings, 20 MultiOMs/string, 40m MultiOM distance) True muon energy at the closest approach to the detector center (impact point) True and reconstructedmuon energy distribution Log(Ereco/GeV) Log(E/GeV) Δ(Log(E/GeV)) Log(Etrue/GeV)

  14. Muon energy reconstruction Results 2 RMS(Δ(Log(E/GeV))) Mean(Δ(Log(E/GeV))) Log(Etrue/GeV) Log(Etrue/GeV)

  15. Neutrino Detector Performance Point Source Sensitivity Atmospheric Muon background + Atmospheric Neutrino Background Neutrino Effective area m2 Neutrino Energy (log(E/GeV)) signal Angular resolution (median) degrees Neutrino Energy (log(E/GeV))

  16. Sea top Detector Simulation Tools CORSIKA (Extensive Air Shower Simulation) GEANT4 (Scintillation, WLS & PMT response) Unthinning Algorithm Fast Simulation also available

  17. At the Detector Center • Data - Monte Carlo Prediction Charge (in units of mean p.e. charge) Sea top Detector Simulation Tools DAQSIM (DAQ Simulation) HOUANA (Analysis & Track Reconstruction) Zentih (degrees)

  18. d L-dm (x,y,z) θc dγ Track Parameters θ : zenith angle φ: azimuth angle (Vx,Vy,Vz): pseudo-vertex coordinates dm (Vx,Vy,Vz) pseudo-vertex Sea top Detector Simulation Tools GEANT4 Muon Propagation to KM3 HOU-KM3 Muon track (s) reconstruction

  19. Conclusions • The study of the response of a km3-scale underwater neutrino telescope isacrucial point both for the design of the detector and for the experimentalanalysis. • The HOU Reconstruction & Simulation (HOURS) software package is acomplete simulation package of the detector response from the expectedneutrino fluxes tothe event reconstruction and sensitivity estimation fordifferent neutrino sources.

  20. GEANT4 Simulation– Detector Description • Any detector geometry can be described in a very effective way Use of Geomery Description Markup Language (GDML, version 2.5.0) software package • All the relevant physics processes are included in the simulation

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