R. Coniglione, VLVnT08, Toulon April ‘08 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 April ‘08 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 April ‘08 The MonteCarlo simulations Simulation codes used ANTARES codes modified for km 3 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)

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

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

R. Coniglione, VLVnT08, Toulon April ‘08 Detection units optimization three-dimensional vs mono-dimensional 20m 1 m from 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 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

R. Coniglione, VLVnT08, Toulon April ‘08 Bar length effect Muon effective area median   rec  bar length 20m bar length 15m  bar length 10m  bar length 7.5m  bar length 1m No quality cut applied  Worsening of the angular resolution with shorter bar length

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

R. Coniglione, VLVnT08, Toulon April ‘08 Bar length effect 1m bar length 15m bar length E  10 2  10 4 GeV RMS ~55° RMS ~65°  rec  rec Vertical muons -> cos  >0.8 (~36°) RMS ~24° RMS ~27° counts

R. Coniglione, VLVnT08, Toulon April ‘08 Bar length effect E  10 2  10 4 GeV Vertical muons -> cos  >0.8 (~36°) Muon hits in only one tower 15m bar length 1m bar length  rec  rec counts  In mono-dimensional detection units the phi angle for vertical muons is not well determined

R. Coniglione, VLVnT08, Toulon April ‘08 The simulated geometries Reference detector 169 towers Number of detection units Detection units distance (m) PMT type & QE 3” max 33% 10” max 23% Number of OM Number of PMT Storey distance (m) PMT total catode area (m 2 ) Volume (km 3 ) Reference detector OM -> 21 PMTs 3” PMT Quantum efficiency 169 towers OM ->1 PMT 10”

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

R. Coniglione, VLVnT08, Toulon April ‘08 Quantum efficiency effect preliminary 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

R. Coniglione, VLVnT08, Toulon April ‘08 Direction sensitive OM R x R x Standard PMT Direction sensitive OM 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

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

R. Coniglione, VLVnT08, Toulon April ‘08 Direction sensitive OM preliminary results 169 towers 140 m distant detector No quality cuts applied Ratio Neutrino effective areas Direction sensitive OM PMT standard log 10 E (GeV) A eff (m 2 ) log 10 E (GeV) Ratio A eff

R. Coniglione, VLVnT08, Toulon April ‘08 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