R. Coniglione, VLVnT08, Toulon 22.24 April ‘08 KM3NeT: optimization studies for a cubic kilometer...

R. Coniglione, VLVnT08, Toulon 22.24 April ‘08

KM3NeT: optimization studies for a cubic kilometer neutrino detector

R. Coniglione P. SapienzaIstituto Nazionale di Fisica Nucleare- Laboratori Nazionali del Sud

K. Fratini Istituto Nazionale di Fisica Nucleare- Genova

for the KM3NeT collaboration


Optimization studies

In order to give a “reference” for the sensitivity, the effective neutrino areas and the detector resolution in the Conceptual Design Report of the KM3Net collaboration a “reference detector” is reported even if it is not the final detector configuration

An optimization work is going on in order to find the best detector geometry which is a compromise between performance, technical feasibility and cost


The MonteCarlo simulations

Simulation codes used ANTARES codes modified for km3 detectors + LNS improvements

and generation- water absorption and scattering- optical background isotropic distributed around the event time window- event trigger based on local coincidences

In order to get the angular resolution of 0.1° at 30 TeV (design goal of the detector) quality cuts on the reconstruction are applied.

Optimization of the basic elements of the detector geometry:

the detection unit (tower vs string) the photo-sensor unit (PMT quantum efficiency and

directionality)


Detection units optimizationthree dimensional vs monodimensional

Some examples of operative “Detection Units”

The mono-dimensional

H = 360 m

Antares Icecube

Storey 1

Storey 2

Storey 3

Storey 60

17 m

H = 1000 m H = 70 m

Baikal NT 200


Detection units optimizationthree dimensional vs monodimensional

Some examples of operative “Detection Units”

The three-dimensional

40m

20m

NestorNEMO

H = 600 m H = 330 m

Storey 12

Storey 1

Storey 2

Storey 3

30m


Detection units optimizationthree-dimensional vs mono-dimensional

20m 1 mfrom to …..

Simulated detection unit characteristics:- instrumented 680 m- number of bars 18- number of PMTs per bar 4 (down-horizontal looking)- bar vertical distance 40 m- PMT 10’’ with QE max 23%81 towers 140m distant

SIMULATIONS AS A FUNCTION OF THE BAR LENGTHBar length 20, 15, 10, 7.5, 1 m -> same detector volume

same number of PMT photocatode area

From a three-dimensional to a mono-dimensional detection unit


Bar length effect

Muon effective areamedian rec

bar length 20m bar length 15mbar length 10mbar length 7.5mbar length 1m

No quality cut applied

Worsening of the angular resolution with shorter bar length


Bar length effect

quality cut applied

Effective area ratio with respect to 20m

Muon effective area

bar length 15mbar length 10mbar length 7.5mbar length 1m

bar length 20m bar length 15mbar length 10mbar length 7.5mbar length 1m


Bar length effect

1m bar length

15m bar length

E 102 104 GeV

RMS ~55°

RMS ~65°

rec

rec rec

rec

Vertical muons ->cos >0.8 (~36°)

RMS ~24°

RMS ~27°

cou

nts

cou

nts

cou

nts

cou

nts


Bar length effect

E 102 104 GeVVertical muons -> cos >0.8 (~36°)

Muon hits in only one tower

15m bar length 1m bar length

recrec

cou

nts

cou

nts

In mono-dimensional detection units the phi angle for vertical muons is not well determined


The simulated geometries

Reference detector

169 towers

Number of detection units 225 169

Detection units distance (m) 95 140

PMT type & QE3”

max 33%

10” max 23%

Number of OM 8325 12168

Number of PMT 174825 12168Storey distance (m) 16.5 40

PMT total catode

area (m2)682 535

Volume (km3) 1.05 1.92

Reference detector OM -> 21 PMTs 3”

PMT Quantum efficiency

169 towers OM ->1 PMT 10”


Quantum efficiency effect

From Hamamatsu catalog PMT < 3”

45%

35%


Quantum efficiency effectpreliminary results

169 towers QE max 23% 169 towers QE max 45% 169 towers QE max 35% ▬ ref det with QE 33%

max 45% /max 23% max 35% /max 23%

Ratio for 169 towers detector

Neutrino effective areas

Quality cuts applied (~0.1°@30TeV)


Direction sensitive OM

R

x

R

x

Standard PMT


mirror

Photocatode

In order to get information on the

Cherenkov light direction -> Light guide

and multi-anodic PMT

Prototype already realized

No information on the arrival direction of

Cherenkov light



81 towers 140 m distant detector PMT with standard QE (max 23%)

RatioNeutrino effective areas

< 2°


Direction sensitive OMpreliminary results

169 towers 140 m distant detectorNo quality cuts applied

RatioNeutrino effective areas

Direction sensitive OMPMT standard

log10E(GeV)

Aeff (m

2)

log10E(GeV)

Rati

o A

eff


Summary

Three-dimensional detection units shows a better reconstruction in particular at low energy E<10÷100 TeV

PMT quantum efficiency and direction sensitive OM improve the effective area at low energy E<10÷100 TeV

R. Coniglione, VLVnT08, Toulon 22.24 April ‘08 KM3NeT: optimization studies for a cubic kilometer...

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