Sebastian Kuch, Rezo Shanidze Preliminary Studies of the KM3NeT Physics Sensitivity KM3NeT Collaboration Meeting Pylos, Greece, April 2007

R.Shanidze, S.KuchKM3NeT, Pylos, Greece2 Introduction/Motivation -What is the minimal flux of high energy cosmic neutrinos which can be detected with KM3NeT detector ? -What is the minimal flux which is necessary for discovery of neutrino point sources ? - How does KM3NeT sensitivity depends on detector configuration (geometry, OM) and environmental (site) parameters ? New data for NEMO site: G.Riccobene et al, Astroparticle Physics, 27 (2007), 1 ‘Deep seawater inherent optical properties in the Southern Ionian Sea’. - How does the sensitivity depends on KM3NeT performance parameters, for example energy and angular resolution ?

R.Shanidze, S.KuchKM3NeT, Pylos, Greece3 What to expect ? Sensitivity: - Upper limits of cosmic neutrino fluxes when event rates are comparable with background (no signal detected) - Detection with given significance level ( for example 5  ) ratio of detected events to the standard deviation from expected background events is larger then given significance level Upper limit scales ~linearly with detector effective area/detection time. Detection with given significance scales as ~square root from the effective area/detection time C. Distefano (for NEMO- km 3 ), astro-ph/ NEMO-km 3 : 9 x 9 lines (towers), 5832 x 10’’ PMT, Line=680 m. d(line)=140m, d(storey)=40m 18 storeys/Line, 4 PMT/Storey Absorption length 68 m (440nm), 30 kHz optical noise

R.Shanidze, S.KuchKM3NeT, Pylos, Greece4 October 2006: A few detector models were selected for the sensitivity studies, according to the results of simulations in Erlangen. This selection covers the different geometry concepts as well as different photo-detection systems. A note on benchmark neutrino fluxes for optimization of KM3NeT detector design was released by WP2 group. KM3NeT-Physics/ First very primary estimation of limits on the high energy cosmic neutrino diffuse flux and neutrino fluxes from point sources were obtained. After WP2 Meeting in Marseille

R.Shanidze, S.KuchKM3NeT, Pylos, Greece5 Selected KM3NeT Detector Models Different geometries: Cuboid, ring1, clustered1 (with cyl. Multi-PMT configuration) Different storeys: cuboid with ANTARES story and ANTARES 20” ‘Example’: cube2 configuration with spherical multi-PMT storeys (21x3”) Cuboid geometryRing 1 Cluster 1

R.Shanidze, S.KuchKM3NeT, Pylos, Greece6 Benchmark Neutrino Fluxes KM3NeT Physics/ NOT an exhaustive list of potential sources, rather list of recommended ‘typical’ fluxes: Atmospheric neutrino flux Neutrinos from dark matter annihilation (talk by H.Motz) Neutrino fluxes from Galactic sources Diffuse neutrino flux from extra-Galactic sources (Waxman-Bahcall flux ) GZK Neutrinos KM3NeT detector sensitivity was considered to muon- neutrino charged current events (muon events) for diffuse neutrino flux and fluxe from point sources.

R.Shanidze, S.KuchKM3NeT, Pylos, Greece7 Atmospheric Neutrino Flux 4 different models for the atmospheric neutrino flux are included in the ANTARES software: Volkova, Bartol, Honda and Fluka models. Bartol flux was used in this study, according to WP2 recommendations.

R.Shanidze, S.KuchKM3NeT, Pylos, Greece8 Assessment of Diffuse Flux Limits Detector (Storey) Flux limit ( x E 2 GeV -1 m -2 s -1 sr -1 ) Minimal (ratio)Moderate (ratio) Selected (ratio) Cuboid (cyl) 1.55 (1.00) 1.58 (1.00) 2.27 (1.00) Cluster 1 (cyl) 1.72 (1.11) 1.73 ( 1.10) 2.68 (1.18) Ring 1 (cyl) 1.62 (1.05) 1.64 (1.04) 2.31 (1.02) Cuboid (ANT) 1.57 (1.01) 1.60 (1.01) 2.31 (1.02) Cuboid (20” ANT) 1.54 (0.99) 1.57 (0.99) 2.31 (1.02) Cuboid 3 (sph) 1.54 (0.99) 1.56 (0.99) 2.30 (1.01) Optimal E cut (TeV) ~370 ~500 Diffuse flux sensitivity is similar (5% level) for the considered detector models, except clustered model. The limits are obtained for neutrino energies above 10 5 GeV, where effective areas of different detector models start to converge. cyl – cylindrical storey (3” PMT), sph – spherical store (21 x 3” PMT), ANT-ANTARES storey

R.Shanidze, S.KuchKM3NeT, Pylos, Greece9 Neutrino Fluxes from Point Sources The sky-map of the H.E.S.S. catalogue sources (33 sources). Two methods were applied in the point source studies: 1) An upper limit estimated for the generic point source with E -2 neutrino flux as a function of declination 2)Event rates calculated for selected HESS sources, with neutrino flux calculated from measured gamma flux. VHE  and corresponding fluxes for HESS J (Vela X). A.Kappes et al., astro-ph/

R.Shanidze, S.KuchKM3NeT, Pylos, Greece10 Neutrino Fluxes from Point Sources For the “generic neutrino point sources” : Neutrino flux is of E -2 type. No energy cut, energy range corresponds to simulated energy interval 10 < E n < 10 7 GeV. Event rates calculated in an angular area, with 2 x angular resolution (DQ n (E n )), at E=1 TeV (error dominated by kinematics) 2D effective area A eff (E n, Q n ) used in the calculations and ANTARES location is assumed for the detector.

R.Shanidze, S.KuchKM3NeT, Pylos, Greece11 Visibility of Point Sources sin(  )=sin(  )·sin(LAT)+cos(  )·cos(LAT)·cos(HA) HA = Hour angle, 1 day: 0 < HA < 2p Zenith angle of a source viewed from the detector is defined by detector latitude (LAT), source declination (d) and hour angle (HA). HESS J ,  =-39 o ANTARES site HA (0-2  ) cos(  Z ) Source below horizon 2D Effective area A(E,Q) at moderate selection level. (cube2, with sph.)

R.Shanidze, S.KuchKM3NeT, Pylos, Greece12 Assessment of Point Source Flux Limits c a b Limits for the point sources with E -2 neutrino flux. Calculations for the selected detectors models and 2 different criteria: a)selected/reconstructed events b) moderate criteria (6 hits /6 storeys)

R.Shanidze, S.KuchKM3NeT, Pylos, Greece13 Flux Limits vs Selection Criteria Neutrino flux limits (very preliminary!) for point sources evaluated as a function of source declination, for the cuboid detector with cyl. storeys, at different selection steps. ANTARES limit is plotted for the comparison. Note that KM3NeT limits are very preliminary ! Presented plot indicates what can be achieved with 1km 3 detector at ANTARES site, with optimistic assumptions.

R.Shanidze, S.KuchKM3NeT, Pylos, Greece14 Comparison of the Flux Limits Comparison of the neutrino flux limits vs. source declination obtained for example detector, to the limits from experimental data (MACRO, AMANDA) and the other neutrino telescope projects (ANTARES, IceCube). Note that KM3NeT limit is very preliminary ! Presented plot indicates what can be achieved with 1km 3 detector at ANTARES site, with optimistic assumptions.

R.Shanidze, S.KuchKM3NeT, Pylos, Greece15 Summary KM3NeT sensitivity has been considered for the detector models selected from the simulation studies in Erlangen, corresponding to different geometrical layouts and photo-sensors. Upper limit of cosmic neutrino diffuse flux (E -2 ) was estimated for selected detectors using Bartol model for atmospheric neutrino flux. The upper limit is similar (within 5%) for all detectors, except clustered one (0.9 CL). Upper limits for the point sources were estimated for E -2 neutrino flux model as function of source declination.

R.Shanidze, S.KuchKM3NeT, Pylos, Greece16 Outlook What is still missing: Energy estimation of the selected/reconstructed muon neutrino events. Important for diffuse flux limit calculation. Can be used in the optimization of the point source analysis. Dedicated event selection and reconstruction. Dependence on site parameters, like optical properties of the selected site, 40 K background. Cross-check of the obtained results with different methods / groups.

R.Shanidze, S.KuchKM3NeT, Pylos, Greece17 Event Rates from HESS J Detector mean number of events / number of atmospheric events MinimalModerate Selected Cuboid 1 (cyl) 2.7 / / /2.9 Cluster 1 (cyl) 1.7 / / /2.9 Ring 1 (cyl) 2.5 / / /3.4 Cuboid (AN) 2.6/ / /3.1 Cuboid (20” AN) 3.2/ / /3.1 Cuboid3 (sph) 2.8/ / /3.2 cyl – cylindrical storey (3” PMT), sph – spherical store (21 x 3” PMT), AN-ANTARES storey (10”) Expected number of events from HESS J (SNR RX J ) for different detector models and selection steps. (E > 1TeV, T= 1 year)

R.Shanidze, S.KuchKM3NeT, Pylos, Greece18 Current Limit ( Point Sources ) Flux model:  (E )= k E -2 Current AMANDA limit: k  ~ ( GeV -1 cm -2 s -1 ) IceCube (1 year): 5  : E -2 90% c.l.: E -2 T.Montaruli, astro-ph/ Astropart.Phys. 20(2004), 507 astro-ph/ KM3NeT ?

R.Shanidze, S.KuchKM3NeT, Pylos, Greece19 Preliminary Diffuse Flux Limits Comparison of the calculated KM3NeT diffuse flux limits to the current experimental data and upper limits of ANTARES and the Waxman-Bahcall flux expectation

R.Shanidze, S.KuchKM3NeT, Pylos, Greece20 Assessment of Flux Limits Cosmic neutrino flux limits (for diffuse and point like sources) for considered detector models were calculated in Feldman-Cousins approach, assuming Poisson statistics for the signal and background neutrino events. The event rates (for T=1 year) were calculated from the corresponding effective areas. (more in: S.Kuch, Ph.D thesis, FAU-PI1-DISS ). Example for the diffuse flux calculations: integrated events rates for the diffuse (signal) and atmospheric (background) neutrino fluxes as a function of threshold energy for the Cuboid detector (cyl.). N limit – is an upper limit of signal events obtained from background event rates in Feldman-Cousins approach.