1. R. Coniglione, VLVnT09, Athens 13.16 october ‘09 Studies of the sensitivity to point-like sources for a flexible-tower geometries for KM3NeT R. Coniglione C. Distefano and P. Sapienza Istituto Nazionale di Fisica Nucleare- Laboratori Nazionali del Sud for the KM3NeT consortium

2. R. Coniglione, VLVnT09, Athens 13.16 october ‘09 Sensitivity to point-like sources  The main physics objective of the KM3NeT consortium is the detection of high energy neutrino fluxes from point-like sources.  Optimization work has been performed since the 2006 in order to find the best detector geometry which is a compromise between performance, technical feasibility and cost. The preferred geometry is based on three- dimensional structures.  Results based on MonteCarlo simulation of the sensitivity to point-like source will be presented. as a function of source declination as a function of the number of structures as a function of the observation years

3. R. Coniglione, VLVnT09, Athens 13.16 october ‘09 Detector lay-out Number of structures -> 127 towers - hexagon Number of storeys/structure -> 20 PMT -> 8” 35%QE Number of PMT/floor -> 6 (2 at bar edges down- horizontally looking) + 2 at the center of the bar down-looking at 45° Distance between floors -> 40m Distance between towers -> 180m Geometry parameters

4. R. Coniglione, VLVnT09, Athens 13.16 october ‘09 ANTARES codes modified for km3 detectors + modifications for large detector Particles generators  generator (all flavours), CC+NC interaction. In simulation:  +  & CC -atmospheric neutrinos: several prescriptions in the code; prompt taken into account. In simulation: Bartol + RQPM-high prescription -Muon generation with MUPAGE: No atmospheric muons in these simulations Detector response -Detector geometry -Light generation and propagation in water ->absorption and scattering taken into account. Simulation input abs =70 m@450nm  and  scat = 50 m@450nm -PMT response (photocade area & quantum efficiency + angular acceptance + total efficiency… ) in the simulation 8-inch PMT with 35%QE -optical background randomly distributed around the event time window. Simulation input 47kHz and ±1  s time window Track reconstruction -Based on PDF maximization -Trigger based on local coincidences to reject hits due to optical background The Monte Carlo codes & inputs

5. R. Coniglione, VLVnT09, Athens 13.16 october ‘09 Sensitivity calculation The binned method is used -> Feldman and Cousins approach with the minimization of the Model Rejection Factor -> cuts on  track reconstruction quality ,nhit (related to the muon energy),R bin (radius of the cone around the source). Sensitivity depends on: Neutrino spectrum & source extension Effective neutrino area -> detector response Source declination -> visibility Oservation years How to identify few events from source amongst large number of background events ? -> statistical approaches Two methods: Binned – analyze the fluctuations on the number of events detected inside a cone. The search of an excess due to events from a source is performed assuming Poisson distribution Unbinned – the expected density distributions of signal and background are described by statistical functions and a likelihood is maximized.  90 is the average maximum limit of background fluctuation at 90% of confidence level observed after hypothetical repetition of an experiment with an expected background and no true signal.

6. R. Coniglione, VLVnT09, Athens 13.16 october ‘09 Il numero di eventi di segnale e di fondo si calcola a partire dall’area efficace: Neutrino cross section nucleons per unit volume Earth Absorption Angle between neutrino and muons  gen Median of the angle distribution between the generated and reconstructed muon Effective neutrino area Effective area    X N QC applied

7. R. Coniglione, VLVnT09, Athens 13.16 october ‘09 Source spectrum for point-like sources source spectrum  E -  normalized at E  dN/dE = 10 -8 cm -2 GeV  -1 s -1 Expected in an angular bin of 1° around a source with  =-60° Energy range of interest 3TeV-100TeV In order to reject atmospheric neutrino background cuts on , N hit, R bin Lambda distribution Nhit distribution

8. R. Coniglione, VLVnT09, Athens 13.16 october ‘09 Sensitivity to point like sources as a function of observation years KM3NeT  = 60° spectrum  E -2 Ratio with respect to 1 year of observation time Improvement in sensitivity decreases with the increasing of the observation time After 3 years is reduced by a factor 2.5 with respect to one year

9. R. Coniglione, VLVnT09, Athens 13.16 october ‘09 Sensitivity to point-like sources as a function of the number of towers E -2 neutrino flux  =-60° 1 year of observation To improve the sensitivity by 20% from 127 towers to 168 towers (32% more towers)

10. R. Coniglione, VLVnT09, Athens 13.16 october ‘09 From Aharens et al. Astr. Phys. (2004) – binned method Average value of sensitivity from R. Abbasi et al. Astro-ph (2009) Sensitivity to point like source as a function of the source declination for three years of observation time Black lines IceCube sensitivity Red lines KM3NeT sensitivity From R. Abbasi et al. Astro-ph (2009) scaled – unbinned method  Observed Galactic source (SNR, unidentified, microquasar) declination - From F. Aharonian et al. Rep. Prog. Phys. (2008) and MILAGRO sources from Abdo et al. Astrophys. Jour. 658 L33-L36 (2007)  Galactic center declination Neutrino spectrum  E -2

11. nametype  (degree) Spectral index  Gamma Flux  TeV -1 cm -2 s -1 @1 TeV H1303-631UID- 63.11 2.44  0.05 stat  0.2 syst 4.3  0.3 stat  1.3 syst RCW86SNR-62.29 2.51  0.1 stat 2.71  0.35 stat H1427-608UID- 60.51 2.16  0.14 stat  0.2 syst 1.3  0.4 stat  0.3 syst H0852-463 RXJ0852-4622 Vela junior SNR- 46.20 2.1  0.1 stat  0.2 syst 21  2 stat  6 syst H1626-490UID- 49.05 2.18  0.12 stat  0.2 syst 4.9  0.9 stat  1 syst H1702-420UID- 42.04 2.07  0.08 stat  0.2 syst 9.1  1.1 stat  1.8 syst H1708-410UID- 41.04 2.46  0.08 stat  0.2 syst 2.7  0.3 stat  0.5 syst RXJ1713.7-3946 SNR-39.46 2.04  0.04 stat  0.2 syst 21.3  0.5 stat  4.2 syst H1731-347UID- 34.43 2.26  0.1 stat  0.2 syst 6.1  0.8 stat  1.2 syst H1841-055UID- 5.3 2.41  0.08 stat  0.2 syst 12.8  1.3 stat  2.6 syst H1857+026UID+2.6 2.39  0.08 stat  0.2 syst 6.1  0.7 stat  1.2 syst H1858+020UID+2.6 2.17  0.12 stat  0.2 syst 0.6  0.1 stat  0.1 syst Cas ASNR+58 2.5  0.4 stat  0.1 syst 0.60  0.12 stat  0.12 syst Source list from F. Aharonian et al. Rep. Prog. Phys. (2008)

12. R. Coniglione, VLVnT09, Athens 13.16 october ‘09 Sensitivity for 3 years of observation time Neutrino spectrum  E -2 Flat behaviour of sensitivity vs declination for a large region of sin . Not to ascribe only to the visibility effect Visibility correction Sens(  =0°,T=3year) = sens(  =-60°,  T)  T is the fraction of time below the horizon Sensitivity vs declination behaviour analysis KM3NeT  =60° corrected for the visibility KM3NeT sensitivity

13. R. Coniglione, VLVnT09, Athens 13.16 october ‘09 Mediterranean Sea latitude  36° -80 -70 -60 -50  =-40 -30 -20 -10 0+20 +40 +50 Above the horizon Below the horizon Near the horizon the effect of Earth absorption is reduced for high energy neutrinos Sensitivity vs declination Phi versus theta as a function of declination

14. R. Coniglione, VLVnT09, Athens 13.16 october ‘09 Effective neutrino area for point-like sources (theta <96°) No quality cuts applied    = 0°  = -20°  = -60° Values scaled for the visibility Balance between Earth absorption and visibility effects Sensitivity vs declination Effective neutrino areas as a function of declination For E>30 TeV effect of Earth absorbtion visible log 10 E (GeV) Aeff (m 2 )    = 0°  = -20°  = -60°

15. R. Coniglione, VLVnT09, Athens 13.16 october ‘09 General behaviour of sensitivity to point like sources has been studied for KM3NeT detector Sub-linear increase of sensitivity with the number of detector towersSub-linear increase of sensitivity with the number of detector towers Saturation effect with the number of observation yearsSaturation effect with the number of observation years Shows a flat behavior with a very large acceptance (>3  ) in source declination -> balance between visibility and Earth absorption -> dependence on the site latitudeShows a flat behavior with a very large acceptance (>3  ) in source declination -> balance between visibility and Earth absorption -> dependence on the site latitude KM3NeT sensitivity estimated with the binned method Improvement on sensitivity for point-like sources expected with unbinned method and exploitation of energy info