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Sebastian Kuch, Rezo Shanidze

Sebastian Kuch, Rezo Shanidze. Preliminary Studies of the KM3NeT Physics Sensitivity. KM3NeT Collaboration Meeting Pylos, Greece, 16 - 18 April 2007. Introduction/Motivation. What is the minimal flux of high energy cosmic neutrinos which can be detected with KM3NeT detector ?

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Sebastian Kuch, Rezo Shanidze

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  1. Sebastian Kuch, Rezo Shanidze Preliminary Studies of the KM3NeT Physics Sensitivity KM3NeT Collaboration Meeting Pylos, Greece, 16 - 18 April 2007

  2. 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 ? KM3NeT, Pylos, Greece

  3. 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 5s) 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- km3), astro-ph/0608513 NEMO-km3: 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 KM3NeT, Pylos, Greece

  4. After WP2 Meeting in Marseille • WP2@Marseille, 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/2007-01. • First very primary estimation of limits on the high energy • cosmic neutrino diffuse flux and neutrino fluxes from • point sources were obtained. KM3NeT, Pylos, Greece

  5. 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”) Cluster 1 Cuboid geometry Ring 1 KM3NeT, Pylos, Greece

  6. Benchmark Neutrino Fluxes • KM3NeT Physics/2007-01 • 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. KM3NeT, Pylos, Greece

  7. 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. KM3NeT, Pylos, Greece

  8. Assessment of Diffuse Flux Limits cyl – cylindrical storey (3” PMT), sph – spherical store (21 x 3” PMT), ANT-ANTARES storey Diffuse flux sensitivity is similar (5% level) for the considered detector models, except clustered model. The limits are obtained for neutrino energies above 105 GeV, where effective areas of different detector models start to converge. KM3NeT, Pylos, Greece

  9. Neutrino Fluxes from Point 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 • Event rates calculated for selected HESS sources, with neutrino flux • calculated from measured gamma flux. The sky-map of the H.E.S.S. catalogue sources (33 sources). VHE g and corresponding n fluxes for HESS J0835-455. (Vela X) . A.Kappes et al., astro-ph/0607286 KM3NeT, Pylos, Greece

  10. 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 < En< 107 GeV. • Event rates calculated in an angular area, • with 2 x angular resolution (DQn(En)), at E=1 TeV • (error dominated by kinematics) • 2D effective area Aeff(En, Qn) used in the calculations • and ANTARES location is assumed for the detector. KM3NeT, Pylos, Greece

  11. Visibility of Point Sources Zenith angle of a source viewed from the detector is defined by detector latitude (LAT), source declination (d) and hour angle (HA). sin(Q)=sin(d)·sin(LAT)+cos(d)·cos(LAT)·cos(HA) HA = Hour angle, 1 day: 0 < HA < 2p Source below horizon cos(QZ) HESS J1713-3935, d=-39o ANTARES site HA (0-2p) 2D Effective area A(E,Q) at moderate selection level. (cube2, with sph.) KM3NeT, Pylos, Greece

  12. Assessment of Point Source Flux Limits b a c • Limits for the point sources with E-2 neutrino flux. Calculations for the selected detectors models and 2 different criteria: • selected/reconstructed events • b) moderate criteria (6 hits /6 storeys) KM3NeT, Pylos, Greece

  13. Flux Limits vs Selection Criteria Note that KM3NeT limits are very preliminary ! Presented plot indicates what can be achieved with 1km3 detector at ANTARES site, with optimistic assumptions. 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. KM3NeT, Pylos, Greece

  14. Comparison of the Flux Limits Note that KM3NeT limit is very preliminary ! Presented plot indicates what can be achieved with 1km3 detector at ANTARES site, with optimistic assumptions. 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). KM3NeT, Pylos, Greece

  15. 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. KM3NeT, Pylos, Greece

  16. 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, 40K background. • Cross-check of the obtained results with different methods / • groups. KM3NeT, Pylos, Greece

  17. Event Rates from HESS J1713-397 Expected number of events from HESS J1713-397 (SNR RX J1713.7-3946) for different detector models and selection steps. (En > 1TeV, T= 1 year) cyl – cylindrical storey (3” PMT), sph – spherical store (21 x 3” PMT), AN-ANTARES storey (10”) KM3NeT, Pylos, Greece

  18. Current Limit ( Point Sources ) Flux model: F(En)= kn E-2 Current AMANDA limit: kn~ 10 -7 ( GeV-1 cm-2 s-1 ) IceCube (1 year): 5s : 7 10-9 E-2 90% c.l.: 2 10-9 E-2 KM3NeT ? T.Montaruli, astro-ph/0608140 Astropart.Phys. 20(2004), 507 astro-ph/0305196 KM3NeT, Pylos, Greece

  19. 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 KM3NeT, Pylos, Greece

  20. 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-2007-01). 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.). Nlimit – is an upper limit of signal events obtained from background event rates in Feldman-Cousins approach. KM3NeT, Pylos, Greece

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