Apostolos Apostolos TsirigotisTsirigotis

KM3NeT Design Study: Detector Architecture, KM3NeT Design Study: Detector Architecture, Event Filtering and Reconstruction Event Filtering and Reconstruction

AlgorithmsAlgorithms

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)

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

Event Generation – Flux Parameterization

•Neutrino Interaction Events

•Atmospheric Muon Generation (2 Parameterization Models)

μ

•Atmospheric Neutrinos 1 Conventional (no prompt) Model

ν

ν

•Cosmic Neutrinos 5 diffuse flux modelsIt is going to be updated

Earth

Event Generation

Shadowing of neutrinos by Earth Survival probability

Nadir Angle P

rob

abil

ity

of

a ν μ

to

cro

ss E

arth

Neutrino Interaction Probability in the active volume of the detector

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

•All the interactions and transportations of the secondary particles are simulated (Multiple track simulation)

•For the simulation of the neutrino interaction events PYTHIA is used

•Fast simulation techniques and EM shower parameterization

•Optical Noise and PMT response simulation

•Visualization of detector components, particle tracks and hits

Filtering, Prefit and Reconstruction Algorithms

Local (storey) CoincidenceApplicable only when there are more than one PMT looking towards the same hemisphere

Global 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 segments

•Χ2 fit without taking into account the charge (number of photons)•Kalman Filter (novel application in this area)

MultiPMT Optical Module (NIKHEF Design)

Outside view Inside View

20 x 3” PMTs (Photonis XP53X2) in each 17” Optical Module

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)

Optical Module ReadoutOptical Module Readout

•Use a time-over-threshold (TOT) system (multiple thresholds)•Estimation of charge from the time-over-thresholds

+

multiplicity

Time (ns)

Trigger

Input

125 meters

IceCube 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) >4

Number of Active OMs

Events passing the clustering criteria

Noise

Signal

Noise

Signal

Number of Active OMs

Signal

Noise

Number of Active OMs

Events passing the clustering criteria after background filtering

Prefit Resolution

Space angle difference (degrees) Zenith angle difference (degrees)

σ = 0.47 degrees

(1 TeV Muons, uniform flux, IceCube Geometry)

Fit Resolution (1 TeV Muons, uniform flux, IceCube Geometry)

Space angle difference (degrees) Zenith angle difference (degrees)

σ = 0.1 degrees

Fit Resolution (1 TeV Muons, uniform flux, IceCube Geometry)

pool (θsim – θrec)/σrec

σ = 1.05

Azimuth angle difference (degrees)

σ = 0.14 degrees

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

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)

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

σ=0.11 degrees

σ=0.11 degrees

σ=0.12 degrees

Zenith angle difference (degrees)

Zenith angle difference (degrees)

Zenith angle difference (degrees)

Atmospheric (CC) neutrino events (1-10TeV)Comparison of three different Geometries

Space angle difference (degrees) Muon Energy (GeV)

Rec

on

stru

ctio

n E

ffic

ien

cyIceCube Geometry (Down looking OMs)

IceCube Geometry (Up-Down looking OMs)

Nestor Geometry (Up Down looking OMs)