Apostolos TsirigotisKM3NeT Design Study: Detector Architecture, Event Filtering and Reconstruction AlgorithmsXXV Workshop on recent developments in High Energy Physics & Cosmology, 28-31/3/2007,NTUA, GreeceThe project is co-funded by the European Social Fund & National Resources EPEAEK-II (PYTHAGORAS)

The Underwater Neutrino Telescope software chainGeneration of atmospheric muons and neutrino eventsDetailed detector simulation (GEANT4)Optical noise and PMT response simulationPrefit & Filtering AlgorithmsMuon reconstruction

Event Generation Flux ParameterizationNeutrino Interaction EventsEarth

Event GenerationShadowing of neutrinos by Earth Survival probabilityNeutrino Interaction Probability in the active volume of the detector

Detector Simulation Any detector geometry can be described in a very effective wayUse of Geomery Description Markup Language (GDML, version 2.5.0) software packageAll the relevant physics processes are included in the simulationAll the interactions and transportations of the secondary particles are simulated (Multiple track simulation)For the simulation of the neutrino interaction events PYTHIA is usedFast simulation techniques and EM shower parameterizationOptical Noise and PMT response simulationVisualization of detector components, particle tracks and hits

Filtering, Prefit and Reconstruction AlgorithmsLocal (storey) CoincidenceApplicable only when there are more than one PMT looking towards the same hemisphereGlobal clustering (causality) filter50% Background rejection while all signal hits survive (1km3 Grid & 1 TeV muon)Local clustering (causality) filter75% Background rejection while 90% of signal hits survive (1km3 Grid & 1 TeV muon)Prefit and Filtering based on clustering of candidate track segments2 fit without taking into account the charge (number of photons)Kalman Filter (novel application in this area)

MultiPMT Optical Module (NIKHEF Design)Outside viewInside View20 x 3 PMTs (Photonis XP53X2) in each 17 Optical ModuleSingle PMT Rate (dark current + K40) ~ 4kHz120 Hz Double coincidence rate per OM (20 ns window)3.5 Noise Hits per 6sec window (4800 MultiPMT OMs in a KM3 Grid)

Optical Module ReadoutUse a time-over-threshold (TOT) system (multiple thresholds)Estimation of charge from the time-over-thresholds+multiplicity

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

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

Prefit ResolutionZenith angle difference (degrees) = 0.47 degrees(1 TeV Muons, uniform flux, IceCube Geometry)

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

Fit Resolution(1 TeV Muons, uniform flux, IceCube Geometry)Azimuth angle difference (degrees) = 0.14 degrees

Comparison of three different GeometriesIceCube Geometry (4800 down looking MultiPMT OMs)IceCube Geometry with 2 MultiPMT OMs per Storey, one looking down the other upNestor 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)y(m)

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

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

20 3 buizen -> 40 PMTspolystyrene