R. Coniglione, VLVnT09, Athens 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

R. Coniglione, VLVnT09, Athens 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

R. Coniglione, VLVnT09, Athens 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

R. Coniglione, VLVnT09, Athens 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  and  scat = 50 -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

R. Coniglione, VLVnT09, Athens 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.

R. Coniglione, VLVnT09, Athens 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

R. Coniglione, VLVnT09, Athens october ‘09 Source spectrum for point-like sources source spectrum  E -  normalized at E  dN/dE = 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

R. Coniglione, VLVnT09, Athens 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

R. Coniglione, VLVnT09, Athens 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)

R. Coniglione, VLVnT09, Athens 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

nametype  (degree) Spectral index  Gamma Flux  TeV -1 cm -2 s TeV H UID  0.05 stat  0.2 syst 4.3  0.3 stat  1.3 syst RCW86SNR  0.1 stat 2.71  0.35 stat H UID  0.14 stat  0.2 syst 1.3  0.4 stat  0.3 syst H RXJ Vela junior SNR  0.1 stat  0.2 syst 21  2 stat  6 syst H UID  0.12 stat  0.2 syst 4.9  0.9 stat  1 syst H UID  0.08 stat  0.2 syst 9.1  1.1 stat  1.8 syst H UID  0.08 stat  0.2 syst 2.7  0.3 stat  0.5 syst RXJ SNR  0.04 stat  0.2 syst 21.3  0.5 stat  4.2 syst H UID  0.1 stat  0.2 syst 6.1  0.8 stat  1.2 syst H UID  0.08 stat  0.2 syst 12.8  1.3 stat  2.6 syst H UID  0.08 stat  0.2 syst 6.1  0.7 stat  1.2 syst H UID  0.12 stat  0.2 syst 0.6  0.1 stat  0.1 syst Cas ASNR  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)

R. Coniglione, VLVnT09, Athens 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

R. Coniglione, VLVnT09, Athens october ‘09 Mediterranean Sea latitude  36°  = 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

R. Coniglione, VLVnT09, Athens 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°

R. Coniglione, VLVnT09, Athens 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