Physics Simulations for KM3NeT Giulia Vannoni representing the KM3NeT Consortium

1. Physics Simulations for KM3NeTGiulia Vannonirepresenting the KM3NeT Consortium (CEA Saclay, Irfu) Giulia Vannoni – VLVnT09

2. Optimisation Parameter Space Optical Modules Detection units Requirements, based on 1 km3 detector: Angular res. ≤ 0.1 @ E  30 TeV corresponds to an overall single photon time resolution < 2ns. Site(depth, water properties) Layout Reconstruction Future step in the optimisation Giulia Vannoni – VLVnT09

3. Seabed Layout km3 instrumented volume  100 – 200 DUs Sharp corners worsen the reconstruction capability. 1 km Uneven behaviour in different energy ranges (optimised below 1 TeV and above 100 TeV) for some of the different detector designs under study. Cube Ring Hexagon Chosen as common layout for optimisation and comparison of different detector options. Adopted in the following Giulia Vannoni – VLVnT09

4. Optical Modules 8” PMTs (35% Q.E.) housed in 13” spheres. In order to use time coincidences between hits (for optical background rejection) need to pair OMs. 31x3” PMTs (35% Q.E.) housed in a single 17” sphere. Time coincidences between hits in neighbouring PMTs of the same OM. Giulia Vannoni – VLVnT09

5. Detection Units Strings with grouped OMs (based on Antares design). Towers with bars and 6 OMs per storey (based on NEMO design). Strings with single OMs hosting multiPMTs Giulia Vannoni – VLVnT09

6. Monte Carlo Info • Antares Monte Carlo chain, adapted for a km3-scale detector. • Atmospheric muons: • Mupage (MUon PArametric GEnerator) , fast parametric muon simulation (see Becherini et al., 2005). • Single muons and muon bundles. • Neutrinos (upward going): • 102 GeV < E < 107 GeV. • Atmospheric: Bartol flux (~ E-3.7) (Agrawal et al., 1996). • Source neutrinos: point source mode in generation code or reweighting of direction. • Reweighting for spectral index. • Reconstruction: pre-fit steps and final likelihood minimisation with PDF tuned on Monte Carlo. Giulia Vannoni – VLVnT09

7. Optimisation Criteria • Note:Optimisation for source search between 1 TeV and 1 PeV. • (DM studies ongoing, not presented here) • Angular resolution • Requirement: Da ≤ 0.1 at 30 TeV. (Da : median of the angular error between the reconstructed and MC muon track.) •  Tight quality cuts. • or • Point source sensitivity • 90% confidence limit (Feldman and Cousins method). • Model Rejection Factor minimisation → optimal cuts: - track quality cut • - search cone • - nhits(energy) Giulia Vannoni – VLVnT09

8. DU Density Optimisation Antares-like design: point-like source (E-2) sensitivity as a function of DU distance.  20 × 30m  20 × 45m  30 × 30m 91 lines 154 lines optimum: Dl ≈ 130±20m independent of number and composition of strings. optimum string density: 80-100 per km2 Optimum distance slightly changed by water properties. Giulia Vannoni – VLVnT09

9. DU Density Optimisation Tower design: response as a function of DU distance. Muon angular resolution and neutrino effective area: quality cut applied (~0.1 at 30 TeV) 130_20_30_08 180_20_50_10 bar length storey distance no. storeys per tower (fixed) DU distance Optimum reached around DU distance 150  180 m and storey distance 30  50 m. Ratio 180/130 log10En (GeV) Giulia Vannoni – VLVnT09

10. “Bar Effect” Tower design, 100 GeV < Em <1 TeV Muon hits on 2 towers Muon hits on 1 tower 15 m bar j – jrec q – qrec q – qrec j – jrec 1 m bar q–qrec <3°  40% q–qrec <3°  31% j–jrec <3° 19% j–jrec <3° 4% q–qrec <3° 39% q–qrec <3°  37% j–jrec <3° 25% j–jrec <3° 15% Giulia Vannoni – VLVnT09

11. “Bar Effect” • Concept: 3D structure on single DU. • Two adjacent storeys in tower design. • Larger distances on single storey for Antares-like design. 90 From single OM to pairs on a single arm to preserve time coincidences. Giulia Vannoni – VLVnT09

12. “Bar Effect” Illustration on Antares-like design: storey radius [m] • sensitivity gain for arms due to better angular resolution. • dependence on spectral index: gain 8% for soft spectrum (E-2.2), 5% for E-1.8 for 3m arms. Giulia Vannoni – VLVnT09

13. Design • DU optimum distance: • 130-180 m, depending on details of the design and water properties. • Optimum DU length: • The higher the better (900-1000 m). • - Limited by technical feasibility? (→ preparatory phase) • DU: benefit from extended structure • Tri-dimensional structure with OMs distanced on a barred storey. • OMs: • pairs of OMs or multiPMTs, needed for optical background rejection. Feasibility studies, prototype testing, cost… → Preparatory phase Giulia Vannoni – VLVnT09

14. Point Source Limit For this plot: 127 towers, 6m bars, 180m distance, 20 storeys at 40m, 6x8” OMs. 90% C.L. exclusion limit, spectrum E-2 Antares, 1 yr, unbinned IceCube80, 1 yr, binned (Aharens et al., 2004) 1 yr, binned IceCube80, 1 yr, unbinned (Abbasi et al., 2009) 3 yr, binned sind Galactic centre Giulia Vannoni – VLVnT09

15. Diffuse Flux • E-2 diffuse flux; • neutrinos and antineutrinos; • cut at 10 above horizon, 1 year; • neutrino energy smearing: resolution 0.5 (log10E) 5×10-9GeVcm-2s-1sr-1 Giulia Vannoni – VLVnT09

16. Numbers of Lines Giulia Vannoni – VLVnT09