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Physics Laboratory

Physics Laboratory. School of Science and Technology. Hellenic Open University. Apostolos Tsirigotis. KM3NeT Design Study: Detector Architecture, Event Filtering and Reconstruction Algorithms. XXV Workshop on recent developments in High Energy Physics & Cosmology, 28-31/3/2007,NTUA, Greece.

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Physics Laboratory

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  1. Physics Laboratory School of Science and Technology Hellenic Open University Apostolos Tsirigotis KM3NeT Design Study: Detector Architecture, Event Filtering and Reconstruction Algorithms XXV Workshop on recent developments in High Energy Physics & Cosmology, 28-31/3/2007,NTUA, Greece The project is co-funded by the European Social Fund & National Resources EPEAEK-II (PYTHAGORAS)

  2. The Underwater Neutrino Telescope software chain • Generation of atmospheric muons and neutrino events • Detailed detector simulation (GEANT4) • Optical noise and PMT response simulation • Prefit & Filtering Algorithms • Muon reconstruction

  3. Event Generation – Flux Parameterization • Atmospheric Muon Generation • (2 Parameterization Models) μ ν ν • Atmospheric Neutrinos • 1 Conventional (no prompt) Model • Cosmic Neutrinos • 5 diffuse flux models • It is going to be updated • Neutrino Interaction Events Earth

  4. Event Generation Probability of a νμ to cross Earth Nadir Angle Shadowing of neutrinos by Earth Survival probability Neutrino Interaction Probability in the active volume of the detector

  5. Detector Simulation • 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 • For the simulation of the neutrino interaction events PYTHIA is used • All the interactions and transportations of the secondary particles are simulated (Multiple track simulation) • Fast simulation techniques and EM shower parameterization • Optical Noise and PMT response simulation • Visualization of detector components, particle tracks and hits

  6. Filtering, Prefit and Reconstruction Algorithms Local (storey) Coincidence Applicable only when there are more than one PMT looking towards the same hemisphere Global clustering (causality) filter 50% Background rejection while all signal hits survive (1km3 Grid & 1 TeV muon) Local clustering (causality) filter 75% Background rejection while 90% of signal hits survive (1km3 Grid & 1 TeV muon) Prefit and Filtering based on clustering of candidate track segments • Χ2fit without taking into account the charge (number of photons) • Kalman Filter • (novel application in this area)

  7. MultiPMT Optical Module (NIKHEF Design) 20 x 3” PMTs (Photonis XP53X2) in each 17” Optical Module Outside view Inside View Single PMT Rate (dark current + K40) ~ 4kHz 120 Hz Double coincidence rate per OM (20 ns window) 3.5 Noise Hits per 6μsec window (4800 MultiPMT OMs in a KM3 Grid)

  8. Optical Module Readout • Use a time-over-threshold (TOT) system (multiple thresholds) • Estimation of charge from the time-over-thresholds + multiplicity

  9. Input Trigger Time (ns)

  10. IceCube Geometry: 4800 OMs looking down in a hexagonal grid. 80 Strings, 60 OMs each. 17m between OMs 125 meters

  11. Prefit and Filtering Efficiency (1 TeV Muons, uniform flux, IceCube Geometry) Events with number of hits (noise+signal) >4 Events passing the clustering criteria Noise Noise Signal Signal Number of Active OMs Number of Active OMs Noise Events passing the clustering criteria after background filtering Signal Number of Active OMs

  12. Prefit Resolution (1 TeV Muons, uniform flux, IceCube Geometry) Space angle difference (degrees) σ = 0.47 degrees Zenith angle difference (degrees)

  13. Fit Resolution (1 TeV Muons, uniform flux, IceCube Geometry) Space angle difference (degrees) σ = 0.1 degrees Zenith angle difference (degrees)

  14. Fit Resolution (1 TeV Muons, uniform flux, IceCube Geometry) σ = 1.05 pool (θsim – θrec)/σrec σ = 0.14 degrees Azimuth angle difference (degrees)

  15. Comparison of three different Geometries IceCube Geometry (4800 down looking MultiPMT OMs) IceCube Geometry with 2 MultiPMT OMs per Storey, one looking down the other up y(m) Nestor Geometry with 37 Towers in a hexagonal formation. Each tower has 21 floors, with 50 meters between floors. 2 MultiPMT OMs per Storey, one looking down the other up x(m)

  16. Comparison of three different Geometries Atmospheric (CC) neutrino events (1-10TeV) IceCube Geometry (Down looking OMs) σ=0.11 degrees σ=0.11 degrees IceCube Geometry (Up-Down looking OMs) Zenith angle difference (degrees) σ=0.12degrees Zenith angle difference (degrees) Nestor Geometry (Up Down looking OMs) Zenith angle difference (degrees) Muon Energy (GeV)

  17. Comparison of three different Geometries Atmospheric (CC) neutrino events (1-10TeV) IceCube Geometry (Down looking OMs) IceCube Geometry (Up-Down looking OMs) Reconstruction Efficiency Nestor Geometry (Up Down looking OMs) Space angle difference (degrees) Muon Energy (GeV)

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