1. Sebastian Kuch, Rezo Shanidze Summary of the Detector Simulation Studies in Erlangen KM3NeT Collaboration Meeting Pylos, Greece, 16 - 18 April 2007

2. R.Shanidze, S.KuchKM3NeT, Pylos, Greece2 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.

3. R.Shanidze, S.KuchKM3NeT, Pylos, Greece3 ANTARES software

4. R.Shanidze, S.KuchKM3NeT, Pylos, Greece4 The KM3NeT parameters fixed during simulation: - instrumented volume ~1 km 3 ( 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 km 3 n m /m event samples: 10 GeV <E n < 10 PeV (E -1.4 ), 4p –isotropic 2·10 9 n m MC events (standard sample)

5. R.Shanidze, S.KuchKM3NeT, Pylos, Greece5 Neutrino Effective Area Neutrino Effective Area: (Muon neutrino charged current(CC) interaction effective area) A n eff (E,Q)= V eff (E,Q)·(rN A )·s(E)·P Earth (E,Q) V eff (E,Q) – effective volume: N x (E,Q)/N G (E,Q)x V G N x - events selected (with x criteria) N G - events generated in Volume V G r, N A - density and Avogadro number s(E) - neutrino cross-section P Eaeth (E,Q) - Probability of n transmission through the Earth: Event rates for a neutrino flux F n (E,Q): N = ∫ A n eff (E,Q) F n (E,Q) dE dW

6. R.Shanidze, S.KuchKM3NeT, Pylos, Greece6 Generation Volume Event generation volume (V G ): defined by the m-range at max. energy (E m =E n =10 7 GeV) V G – not homogenous: a) sea water r 1 =1.0404 g/cm 3 b) non transparent part with r 2 =2.65 g/cm 3 sediments (~1km) and oceanic crust r1r1 r2r2 Path length of muons (m), tauons(t) em and had. showers in water a b

7. R.Shanidze, S.KuchKM3NeT, Pylos, Greece7 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 n transmission throug the Earth: P(E n,cosQ n )= exp(-s(E n )·d(cosQ n )· N A ) cos Q n log(d) [ g m -2 ] a b c Log(E ) cos(  )

8. R.Shanidze, S.KuchKM3NeT, Pylos, Greece8 Selection Criteria Reconstructed m track : 5 parameters: - Space point: x, y, z - Direction: Q, f Different criteria (x), for the selection of events: N x Minimal - corresponds to minimal requirement for m 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 m-reconstruction algorithm, with angular error   <5 o. m (x,y,z) Q,f

9. 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

10. R.Shanidze, S.KuchKM3NeT, Pylos, Greece10 Paramters of the PMT List of the PMT parameters used in the simulations: Quantum efficiency QE(l), Angular acceptance, Transit time spread(TTS). QE(l) and angular acceptance of 10” PM (Hamamatsu R7081)

11. 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), L string = 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 13452 [m]

12. R.Shanidze, S.KuchKM3NeT, Pylos, Greece12 Detectors with 10” PMTs Minimal 10” detector with diff, storeys: effective are and their ratio for the minimal and moderate criterion Minimal Moderate

13. R.Shanidze, S.KuchKM3NeT, Pylos, Greece13 Detectors with 10” PMTs Minimal 10” detector with diff, storeys: effective are as a function of cosQ n and their ratio for the minimal and moderate criterion Minimal Moderate

14. R.Shanidze, S.KuchKM3NeT, Pylos, Greece14 Detectors with 10” PMTs Selected 10” detector with diff. storeys: effective area vs E n and cosQ n Selected

15. R.Shanidze, S.KuchKM3NeT, Pylos, Greece15 Detectors with 10” PMTs - 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.

16. R.Shanidze, S.KuchKM3NeT, Pylos, Greece16 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

17. R.Shanidze, S.KuchKM3NeT, Pylos, Greece17 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 ( 4p –max possible) (8 storey/L, 82 m spacing) - 36 PMTs ( 4p ) - 21 PMT ( 2p) (20 storey/L, 31.5 m spacing)

18. R.Shanidze, S.KuchKM3NeT, Pylos, Greece18 Detector with Multi-PMT Storey Selected selected Selected

19. R.Shanidze, S.KuchKM3NeT, Pylos, Greece19 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) Moderate Selected

20. R.Shanidze, S.KuchKM3NeT, Pylos, Greece20 Photodetection Systems: Summary Photocathode area ( x QE) is most important factor defining the Neutrino Detector effective area. Single PMT/storey detectors have poor background ( 40 K) rejection capabilities and have worst performance with used m-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.

21. KM3NeT Detector Geometries 5 different types of geometries are considered: 1-3) Cuboid, ring, clustered geometries (13 configurations) 4) IceCube comparable (ICC), ( 4 configurations) Cuboid geometry Ring geometryCluster geometry Same storey is used for these configurations: ANTARES type Multi-PMT (3 x 12 X 3”PMT) storey (cyl)

22. R.Shanidze, S.KuchKM3NeT, Pylos, Greece22 KM3NeT Cuboid Geometries Detector Lines (L)Sto./L sto. L(m)Sto.(m) Hollow28817 4896 ~ 6036 Cube 1324(18x18)15 4860 7844.0 Cube 2225(15x15) 21 4725 9528.5 Cube 3144(12x12)33 4752 12017.5

23. R.Shanidze, S.KuchKM3NeT, Pylos, Greece23 KM3NeT Cuboid Geometries Selected

24. R.Shanidze, S.KuchKM3NeT, Pylos, Greece24 KM3NeT Ring Geometries ( see also talk of P.Vernin, WP2_2006@Marseille ) Detector R LSt/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 2Ring 3Ring 4

25. R.Shanidze, S.KuchKM3NeT, Pylos, Greece25 Ring Geometries Moderate Selected

26. R.Shanidze, S.KuchKM3NeT, Pylos, Greece26 Ring Geometries Moderate Selected

27. R.Shanidze, S.KuchKM3NeT, Pylos, Greece27 KM3NeT Clustered Geometries DetectorClL/ClSt/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 1Cluster 2 Cluster 3 Main motivation: increase of efficiency at low neutrino energies.

28. R.Shanidze, S.KuchKM3NeT, Pylos, Greece28 Clustered Geometries Selected

29. R.Shanidze, S.KuchKM3NeT, Pylos, Greece29 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 cm 2, “flat disk” acceptance) IceCube: Astropart.Phys.20(2004),507 IceCube KM3NeT density r 0.9 (ice) 1.04 (sea water) Absorption length (m) 50- 150 60 Background rate < 1 kHz 40 kHz

30. R.Shanidze, S.KuchKM3NeT, Pylos, Greece30 IceCube Comparable Geometry Detectors with different geometries but same IceCube type lines (IceCube comparable ICC) and storey : ICCcube, ICCring, ICCcluster, with L string =1000 m Detector L St/L Sto. L(m)d (m) IceCube 80 60 4800 125.017.0 ICCcube 81 60 4860 125.0 17.0 ICCring 80 60 4800 125.0 17.0 ICCcluster70(7x10) 68 4760 60.0 15.0 IceCube ICCcubeICCring ICCcluster

31. R.Shanidze, S.KuchKM3NeT, Pylos, Greece31 IceCube Comparable Geometry Moderate Selected Moderate

32. R.Shanidze, S.KuchKM3NeT, Pylos, Greece32 Detectors Geometries: Summary Different detector configurations for 1km 3 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 n < 10 7 GeV) For low energies (E n < ~10 3 GeV) clustered and ring geometries have larger effective area. For high energy (E n > 10 3 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.

33. R.Shanidze, S.KuchKM3NeT, Pylos, Greece33 Example of KM3NeT detector ++ 225 strings (15 x 15) 36 storeys per string 21 3” PMTs per storey

34. R.Shanidze, S.KuchKM3NeT, Pylos, Greece34 The neutrino Effective area (A eff (E n )) of the “Example detector” at different selection steps. The true A eff (E n ) will be between minimal and selected (reconstructed) criteria. KM3NeT Effective Area

35. R.Shanidze, S.KuchKM3NeT, Pylos, Greece35 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 m-reconstruction and selection criteria is necessary step in the selection of the final configuration.

36. R.Shanidze, S.KuchKM3NeT, Pylos, Greece36 The neutrino Effective area (A eff (E n )) of the “Example detector” at different selection steps for the up-going neutrinos. The true A eff (E n ) will be between minimal and selected (reconstructed) criteria. KM3NeT Effective Area

37. R.Shanidze, S.KuchKM3NeT, Pylos, Greece37 Ratio of neutrino effective area (A eff (E n )) of the “Example detector” for up-going neutrinos (2p) to effective area for all neutrino directions (4p). Line corresponds to the 4p case, dashed line to 2p/4p effective area ratios for a) minimal, b) moderate and c) selected (reconstructed) levels. For Low Energies due to the fact that detector is looking down 2p areas are better. At high energies, were absorption In the earth is dominant effect, 4p areas are superior. 2p / 4p Effective Areas a b c

38. Selection of the Photo-detectors(PMT) 8 inch10 inch 13 inch 20 inch AMANDA ANTARES ICeCube SuperKamiokande NESTOR PMT (Hamamatsu) used in the Neutrino Cherenkov Detectors