KM3NeT: optimization studies for a cubic kilometer neutrino detector

1. KM3NeT: optimization studies for a cubic kilometer neutrino detector R. Coniglione P. Sapienza Istituto Nazionale di Fisica Nucleare- Laboratori Nazionali del Sud K. Fratini Istituto Nazionale di Fisica Nucleare- Genova for the KM3NeT collaboration R. Coniglione, VLVnT08, Toulon 22.24 April ‘08

2. 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 R. Coniglione, VLVnT08, Toulon 22.24 April ‘08

3. The MonteCarlo simulations • Optimization of the basic elements of the detector geometry: • the detection unit (tower vs string) • the photo-sensor unit (PMT quantum efficiency and directionality) • Simulation codes used • ANTARES codes modified for km3 detectors + LNS improvements • m and n 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. R. Coniglione, VLVnT08, Toulon 22.24 April ‘08

4. Detection units optimizationthree dimensional vs monodimensional Storey 60 Storey 3 Storey 2 17 m Storey 1 Some examples of operative “Detection Units” The mono-dimensional Icecube Baikal NT 200 Antares H = 360 m H = 1000 m H = 70 m R. Coniglione, VLVnT08, Toulon 22.24 April ‘08

5. Detection units optimizationthree dimensional vs monodimensional 40m 20m Some examples of operative “Detection Units” The three-dimensional NEMO Nestor Storey 12 30m Storey 3 Storey 2 Storey 1 H = 600 m H = 330 m R. Coniglione, VLVnT08, Toulon 22.24 April ‘08

6. Detection units optimizationthree-dimensional vs mono-dimensional • 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 LENGTH • Bar 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 from to ….. 1 m 20m R. Coniglione, VLVnT08, Toulon 22.24 April ‘08

7. Bar length effect median DW m-mrec Muon effective area No quality cut applied bar length 20m  bar length 15m bar length 10m bar length 7.5m bar length 1m Worsening of the angular resolution with shorter bar length R. Coniglione, VLVnT08, Toulon 22.24 April ‘08

8. Bar length effect Muon effective area Effective area ratio with respect to 20m quality cut applied bar length 20m  bar length 15m bar length 10m bar length 7.5m bar length 1m  bar length 15m bar length 10m bar length 7.5m bar length 1m R. Coniglione, VLVnT08, Toulon 22.24 April ‘08

9. Bar length effect 15m bar length RMS ~24° RMS ~55° counts counts Em 102104 GeV Vertical muons -> cos qm >0.8 (~36°) j- jrec q-qrec 1m bar length RMS ~27° RMS ~65° counts counts q-qrec j- jrec R. Coniglione, VLVnT08, Toulon 22.24 April ‘08

10. Bar length effect Em 102104 GeV Vertical muons -> cos qm >0.8 (~36°) Muon hits in only one tower counts 15m bar length 1m bar length counts j- jrec q-qrec  In mono-dimensional detection units the phi angle for vertical muons is not well determined R. Coniglione, VLVnT08, Toulon 22.24 April ‘08

11. The simulatedgeometries PMT Quantum efficiency Reference detector OM -> 21 PMTs 3” 169 towers OM ->1 PMT 10” R. Coniglione, VLVnT08, Toulon 22.24 April ‘08

12. Quantum efficiency effect From Hamamatsu catalog PMT < 3” 45% 35% R. Coniglione, VLVnT08, Toulon 22.24 April ‘08

13. Quantum efficiency effectpreliminary results Ratio for 169 towers detector Neutrino effective areas Quality cuts applied(~0.1°@30TeV)  max 45% /max 23%  max 35% /max 23% 169 towersQE max 23%  169 towersQE max 45% 169 towersQE max 35% ▬ ref det with QE 33% R. Coniglione, VLVnT08, Toulon 22.24 April ‘08

14. Direction sensitive OM x x R R Standard PMT No information on the arrival direction of Cherenkov light Direction sensitive OM In order to get information on the Cherenkov light direction -> Light guide and multi-anodic PMT Prototype already realized mirror Photocatode R. Coniglione, VLVnT08, Toulon 22.24 April ‘08

15. Direction sensitive OM 81 towers 140 m distant detector PMT with standard QE (max 23%) Ratio Neutrino effective areas DW < 2° R. Coniglione, VLVnT08, Toulon 22.24 April ‘08

16. Direction sensitive OMpreliminary results Ratio Aeffn 169 towers 140 m distant detector No quality cuts applied Ratio Neutrino effective areas Aeffn (m2) Direction sensitive OM • PMT standard log10En(GeV) log10En(GeV) R. Coniglione, VLVnT08, Toulon 22.24 April ‘08

17. Summary Three-dimensional detection units shows a better reconstruction in particular at low energy Em<10÷100 TeV PMT quantum efficiency and direction sensitive OM improve the effective area at low energyEn<10÷100 TeV R. Coniglione, VLVnT08, Toulon 22.24 April ‘08