sebastian kuch, rezo shanidze

Sebastian Kuch, Rezo Shanidze

Summary of the Detector Simulation Studies in Erlangen

KM3NeT Collaboration Meeting Pylos, Greece, 16 - 18 April 2007

R.Shanidze, S.Kuch KM3NeT, Pylos, Greece 2

Introduction

• The Summary of the Erlangen detector simulations: Sebastian Kuch, Ph.D-thesis, FAU-PI1-DISS-07-001 Design Studies for the KM3NeT Neutrino Telescope (to be released soon)

• Detector performance was simulated for different: - photo-detector system(s) - geometry configuration of the detector

• Modified ANTARES software, ‘sea model’ and reconstruction algorithms were used in simulations.


ANTARES software


The KM3NeT parameters fixed during simulation:

- instrumented volume ~1 km3 ( 1% precision) - overall photocathode area ( ~ 5% )

Main detector element: storey (cluster of PMTs)

To avoid overlap of parameters: - same geometry for different storey types - same storey for different geometry configurations

Detector performance parameter used for the comparison of the different detector models: Effective area

KM3NeT Detector Models

1 km3

event samples: 10 GeV <E < 10 PeV (E-1.4), 4 –isotropic

2·109 MC events (standard sample)


Neutrino Effective Area Neutrino Effective Area: (Muon neutrino charged current(CC) interaction effective area)

Aeff (E,)=

Veff(E,)·(NA)·(E)·PEarth(E,) Veff(E,) – effective volume: Nx(E,)/NG (E,)x VG

Nx - events selected (with x criteria) NG - events generated in Volume VG

, NA - density and Avogadro number (E) - neutrino cross-section PEaeth(E,) - Probability of transmission through the Earth:

Event rates for a neutrino flux(E,):

N = ∫ Aeff(E,) (E,) dE d


Generation Volume

Event generation volume (VG): defined by the -range at max. energy (E=E=107GeV

VG – not homogenous: a) sea water 1=1.0404 g/cm3 b) non transparent part with 2=2.65 g/cm3

sediments (~1km) and oceanic crust 1

2

Path length of muons (), tauons() em and had. showers in water

a

b


Earth Density Profile

a) Earth density profile in units of the Earth radius b) Column density as a function of neutrino direction. c) Transmission probability vs. neutrino energy and direction

Probability transmission throug the Earth: P(E ,cos)= exp(-(E)·d(cos)· NA )

cos

log(

d) [

g m

-2]

a

b

c

Log(E )

cos(

)


Selection Criteria

Reconstructed track : 5 parameters: - Space point: x, y, z - Direction:

Different criteria (x), for the selection of events: Nx • Minimal - corresponds to minimal requirement for reconstruction: at least 6 signal hits on at least 2 storeys. • Moderate - at least 6 storeys hit ( includes Minimal ) • Selected - corresponds to event which is selected (reconstructed) by the modified ANTARES -reconstruction algorithm, with angular error <5o.

(x,y,z)

Simulated Photodetection Systems

3 PMT types simulated: 1) 10” , Hamamatsu R7081 (used in ANTARES, IceCube) 2) 20” , Hamamatsu R3600 (used in SuperKamiokande) 3) 3” , Photonis XP53X2 Multi-PMT configuration

Multi PMT(3”) story configuration

10” PMT (1) in a glass sphere

3

2

Hamamatsu 20” PMT (RS 3600)

2

1


Paramters of the PMT

List of the PMT parameters used in the simulations: Quantum efficiency QE(), Angular acceptance, Transit time spread(TTS).

QE() and angular acceptance of 10” PM (Hamamatsu R7081)

Detector Model for Different Storeys

KM3NeT geometry for the different storey/PMT configuration: Cuboid geometry

Geometry used for the comparison:

484 strings (22 x 22), Lstring = 567 m, distance between Lines: 63 m

Example of string configurations with large Hamamatsu PMTs.

1) single OM, 2) double OM, 3) ANTARES 4) twin ANTARES 5) 20” single OM

1 3 4 52

[m]

[m]

[m]


Detectors with 10” PMTs

Minimal

10” detector with diff, storeys: effective are and their ratio for the minimal and moderate criterion

Minimal

ModerateModerate



Minimal

10” detector with diff, storeys: effective are as a function of cos and their ratio for the minimal and moderate criterion

Minimal

ModerateModerate



Selected

Selected

10” detector with diff. storeys: effective area vs E and cos

Selected

Selected



- Effective area for first two steps (minimal, moderate) are very similar for all detectors. For moderate level storeys with single PMT are preferable.

- Effective area at trigger and reconstruction/selection level depends on the background conditions and strongly favors the multi-PMT storey configurations.

-The effective area angular dependence is strongly peaked at large zenith angles (due to the matter density distribution).

- Angular resolution for multi-PMT storeys are slightly better than single and double OM storey detectors.


Detector with Multi-PMT Storey

Multi-PMT ( P.Kooijman, NIM A567(2007), 508 ) pro: high QE, short TTS, good 2-photon separation, stability contra: lack of experience, cost

QE and angular acceptance (‘flat disc”) for 3” PMT (XP53X2) used in the Multi-PMT storey detector simulations


Configurations with Multi-PMT Storey Different Multi-PMT storey layouts: 1) ‘cylindrical’ : 12 PMT/cylinder ( ~ 10’’ photocathode area) ANTARES type story: 3 Multi-PMT cyl: 36 PMT 2) Spherical storey (17” sphere): - 42 PMTs ( 4 –max possible) (8 storey/L, 82 m spacing) - 36 PMTs ( 4 ) - 21 PMT ( 2) (20 storey/L, 31.5 m spacing)


Detector with Multi-PMT Storey

Selected selected

Selected Selected


Detector with 20” PMT Storey large effective photocathode area / low QE, large TTS, low purity of selected hits 2 configurations: a) single PMT/Storey b) ANTARES storey (with ~ 4x ph. cathode area)

ModerateModerate

Selected Selected


Photodetection Systems: Summary

• Photocathode area ( x QE) is most important factor defining the Neutrino Detector effective area.

• Single PMT/storey detectors have poor background (40K) rejection capabilities and have worst performance with used -reconstruction algorithms.

• Multi-PMT storey with (3” PMT) provides promising alternative to ANTRES like configurations ( with 10” PMTs).

• For the same photocathode area Multi-PMT detectors have additional advantages, such as larger number of storeys (for 21 PMT configuration) and better PMT parameters.

• Simulations of the different photo-detector layouts indicate that a multi- PMT storey detector might be the preferable choice.

KM3NeT Detector Geometries5 different types of geometries are considered: 1-3) Cuboid, ring, clustered geometries (13 configurations) 4) IceCube comparable (ICC), ( 4 configurations)

Cuboid geometry Ring geometry Cluster geometry

Same storey is used for these configurations:

ANTARES type Multi-PMT (3 x 12 X 3”PMT) storey (cyl)


KM3NeT Cuboid Geometries Detector Lines (L) Sto./L sto. L(m) Sto.(m)

Hollow 288 17 4896 ~ 60 36

Cube 1 324(18x18) 15 4860 78 44.0

Cube 2 225(15x15) 21 4725 95 28.5

Cube 3 144(12x12) 33 4752 120 17.5


KM3NeT Cuboid Geometries

Selected Selected

Selected Selected


KM3NeT Ring Geometries ( see also talk of P.Vernin, WP2_2006@Marseille)

Detector R L St/L sto. L(m) Sto.(m)

Ring 1 5 312 16 4992 ~60 40

Ring 2 6 312 16 4992 ~ 60 40

Ring 3 8 312 16 4992 ~ 60 40

Ring 4 4 156 32 4992 ~ 60 19

Ring 1

Ring 2 Ring 3 Ring 4


Ring Geometries

Moderate Moderate

Selected Selected


KM3NeT Clustered Geometries

Detector Cl L/Cl St/L sto. L(m) Sto.(m)

Cluster 1 8 12 52 4992 60 12

Cluster 2 8 Ring inside cluster / same n of St./L

Cluster 3 8 Different configuration of Cluster2

Cluster 1 Cluster 2 Cluster 3

Main motivation: increase of efficiency at low neutrino energies.


Clustered Geometries

Selected Selected

SelectedSelected


Comparison with IceCube

Use of IceCube configuration was suggested at WP2 meeting (Marseille, Oct. /2006) Inter-storey/Line separation 17 / 125 m Number of lines /storey line 80 /60 Orientation of OMs Downwards Height of first storey 100 m Site Characteristics: Depth of sea bed 2450 m IOP: absorption length: 60 m, no scattering, refraction index 1.35(450 nm) PMT : 10” Hamamtsu ( with photocathode area= 500 cm2, “flat disk” acceptance)

IceCube: Astropart.Phys.20(2004),507 IceCube KM3NeT density 0.9 (ice) 1.04 (sea water) Absorption length (m) 50- 150 60 Background rate < 1 kHz 40 kHz


IceCube Comparable GeometryDetectors with different geometries but same IceCube type lines (IceCube comparable ICC) and storey : ICCcube, ICCring, ICCcluster, with Lstring=1000 m

Detector L St/L Sto. L(m) d (m)

IceCube 80 60 4800 125.0 17.0

ICCcube 81 60 4860 125.0 17.0

ICCring 80 60 4800 125.0 17.0

ICCcluster 70(7x10) 68 4760 60.0 15.0

IceCube

ICCcube ICCring ICCcluster


IceCube Comparable Geometry

ModerateSelected

SelectedModerate


Detectors Geometries: Summary

• Different detector configurations for 1km3 instrumented volume (cube, ring, clustered, IceCube comparable). • Within considered detector configurations there is no single one which is preferable at all considered energies (10 < E < 107 GeV)

• For low energies (E < ~103 GeV) clustered and ring geometries have larger effective area.

• For high energy (E > 103 GeV) effective area for cube and ring type configurations are very similar, effective area for the clustered configurations are significantly worse.

• Detector with cuboid configuration (Cube 2) was selected as an example detector for the further studies.


Example of KM3NeT detector

+ +

225 strings (15 x 15) 36 storeys per string

21 3” PMTs per storey


The neutrino Effective area (Aeff(E)) of the “Example detector” at different selection steps. The true Aeff(E) will be between minimal and selected (reconstructed) criteria.

KM3NeT Effective Area


Summary and Outlook • Different models for the KM3NeT detector were simulated, corresponding to several photo-detection systems and geometrical configurations.

• For considered KM3NeT models neutrino effective area were

calculated and compared for the selection of ‘KM3NeT candidate configurations’.

• For the Mediterranean Neutrino Telescope the ANTARES-type or Multi-PMT storey detector has a significant advantage in background reduction, event triggering and reconstruction. • Photocathode area of the detector is the most important parameter in the effective area calculations.

• Optimization of -reconstruction and selection criteria is necessary step in the selection of the final configuration.


The neutrino Effective area (Aeff(E)) of the “Example detector” at different selection steps for the up-going neutrinos. The true Aeff(E) will be between minimal and selected (reconstructed) criteria.

KM3NeT Effective Area


Ratio of neutrino effective area (Aeff(E)) of the “Example detector” for up-going neutrinos (2) to effective area for all neutrino directions (4). Line corresponds to the 4 case,dashed line to 2/4 effective area ratios for a) minimal, b) moderate andc) selected (reconstructed) levels.

For Low Energies due to the fact that detector is looking down 2 areas arebetter. At high energies, were absorption In the earth is dominant effect, 4 areas are superior.

2 / 4 Effective Areas

a

b

c

sebastian kuch, rezo shanidze

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