Neutrino Diffuse Fluxes in KM3NeT Rezo Shanidze, Thomas Seitz ECAP, University of Erlangen (for the KM3NeT consortium) 15 October 2009 Athens, Greece

Introduction Cosmic neutrino fluxes KM3NeT TDR configuration Sensitivity to diffuse neutrino fluxes Summary and outlook  Layout

Unobserved neutrino sources will build up diffuse fluxes of cosmic neutrinos Propagation of UHECR trough CMBR is producing the cosmogenic neutrino flux ( GZK neutrinos)  Introduction Diffuse neutrino fluxes considered in in KM3NeT:  Extragalactic flux from unresolved sources  Cosmogenic (GZK) flux  Galactic flux R. Shanidze, T. Seitz VLVnT-09, Athens, 15 October, 2009.

Cosmic neutrinos vs. atmospheric neutrinos Largest neutrino diffuse flux at Earth  atmospheric neutrino flux ( background for cosmic neutrinos ) Neutrinos simulated in the KM3NeT telescope: - Currently only  N (CC) events with  -track is considered - Shower type events N( NC) not included ( low effective area, but good energy resolution ) Atmospheric neutrino flux: Bartol model + rqpm model for ‘prompt flux’ cosmic neutrinos Atmospheric neutrinos Energy spectra ~ E -2 expected ~ E -3.7 ( E  < GeV) measured GZK spectra (E > ~ 10 7 GeV ) ~ E -2.7 (E  > GeV) ( prompt flux, expected) Composition e :  :  1:1:1 ( expected ) mostly , low e, negligble  ( measured  ) R. Shanidze, T. Seitz VLVnT-09, Athens, 15 October, 2009.

KM3NeT Configurations PMT OM xPMT. St. (DU) DU St. PMTs (Tot.) Dist(m) St./DU Vol. (km3) KM3NeT 8”3 x / ”1x / R. Shanidze, T. Seitz VLVnT-09, Athens, 15 October, 2009.

 Event rates and diffuse flux sensitivity N - event rates in the neutrino telescope: a convolution of : - neutrino flux  (E ) - neutrino effective are A(E ) Full simulations include – event reconstruction, “ quality cuts”, energy estimator, cuts for the background reduction. ( different for different analysis) Sensitivity to the diffuse cosmic neutrino flux: obtained for the case when the detected events are close to expectations form the atmospheric neutrino flux. Same method is used as in a point source sensitivity study: Feldman-Cousins statistics and MRF (model rejection factor) R. Shanidze, T. Seitz VLVnT-09, Athens, 15 October, 2009.

Neutrino Energy Estimator Neutrino energy is estimated From the detected Cherenkov photons. Number of hits in the reconstructed  track Could be used a simple Energy estimator. Expected energy resolution for neutrinos is ~ 0.5 x log E Mean number of hits in the reconstructed  -track as function of neutrino energy for the tower and string configurations. R. Shanidze, T. Seitz VLVnT-09, Athens, 15 October, 2009.

Effective are for KM3NeT tower configuration KM3NeT TDR detector (Catania, optimazed for point sources ) CDR detector (KM3Net CDR, p. 238 ) Neutrino effective area obtained for KM3NeT tower configuration for different simulations ( Catania, Erlangen) Parameterization obtained for KM3NeT CDR configuration  blue curve. Dotted histogram: c neutrino events with N hit > 200 in the reconstructed  -track. R. Shanidze, T. Seitz VLVnT-09, Athens, 15 October, 2009.

Effective area for string configurations Detector with 310 strings: 130 m, 100 m(scan)) ( Seatray simulations) Neutrino effective area obtained for KM3NeT string configurations from different simulations in Erlangen: simulations with SeaTray: (310 DU detector) and 300 DU detector with the modifies ANTARES software Dashed histogram: neutrino events with N hit > 200 in the reconstructed  -track. E  [GeV]

Diffuse flux limit Diffuse flux limit obtained for the KM3NeT detector ( configuration with 127 DU of “flexible towers”) KM3NeT limit: ( 1 year of explosure ) 5 x GeV cm 2 s -1 sr -1 together with results from AMANDA an expectations form ANTARES and IceCube R. Shanidze, T. Seitz VLVnT-09, Athens, 15 October, 2009.

Diffuse neutrino flux from inner Galaxy Calculations for the KM3NeT CDR configuration ( Based on MILAGRO data) A.M. taylor et al., Astropart. Phys.30(2008),180 Neutrino flux from inner Galaxy  theoretical calculations based on VHE-  observations Inner Galaxy: -40 o <l<40 o, -2 o < b < 2 o  ≈ 0.97 sr, visible from Mediterranean NT. (1) (2) where E * = 80 GeV,  =2,  +  =2.7, E cut =1(5) PeV R. Shanidze, T. Seitz VLVnT-09, Athens, 15 October, 2009.

Galactic neutrino rates Event rates in the KM3NeT neutrino telescope from “inner galactic” neutrinos and atmospheric neutrinos for 1 year: E > 10 TeV: 9 (eqn.1), 10 (eqn. 2, E cut =1 PeV ) 15 (eqn. 2, E cut =5 PeV ) 28 (atm. Neutrinos) E >20 TeV: 10/10 events for most optimistic case/ atm-. To be (re)calculated for current KM3NeT configuration(s) including: - reconstruction efficiency. - energy estimator atm- background can be obtained from regions similar extension R. Shanidze, T. Seitz VLVnT-09, Athens, 15 October, 2009.

Cosmogenic neutrino flux Above E p > GeV ( GZK cut-of) for sources with d > 50Mpc p  CMB    n  + / p  o GZK cut-of in UHECR  cosmogenic neutrino flux. GZK cut-of confirmed: HIRES: Phys. Rev. Lett., 100, 2008, PAO: Phys. Rev. Lett. 101, 2008, Cosmogenic neutrino flux  guaranteed but unknown. Calculations with “SOPHIA” MC : R. Engel, D. Seckel and T. Stanev, Phys.Rev.D64 (2009) propagation (Mpc): 10, 20, 50, 100, 200. Event rate expected in KM3NeT very low   special study is necessary Including shower events. R. Shanidze, T. Seitz VLVnT-09, Athens, 15 October, 2009.

Summary and Outlook The largest instrumented volume of the detector (above 2 km 3 in the current configuration) makes KM3NeT telescope the most sensitive tool for a search for diffuse fluxes of cosmic neutrinos. KM3NeT is sensitive to different fluxes of cosmic neutrinos: - For extragalactic E -2 flux, for 1 year of data taking, sensitivity limit (90% C.L.) : < 5.2 x GeV cm -2 s -1 sr -1 - In the favorable scenario same rate of 10 events/year expected for Galactic and atmospheric neutrinos above 20 TeV. ( To be confirmed with full simulations ) - For the neutrinos with E > ~ GeV (cosmogenic neutrinos) event reconstruction is not optimized. KM3NeT reconstruction could be improved  improved sensitivities R. Shanidze, T. Seitz VLVnT-09, Athens, 15 October, 2009.

Preliminary results and comparison The results with MEDUSA and NuOne configurations: ( from J.P. Ernenwein) MEDUSA, with 127 DU: Energy range: – GeV ( 90% of events) Full simulations (  –included), N-hits/fitted track as an E-estimator Diffuse flux limit for E -2 flux ( 1 year of data-taking): < 8.1 x10 -9 GeV cm -2 s -1 sr -1 NuOne Energy estimator: neutrino energy with resolution of 0.5 x logE < 5.2 x GeV cm -2 s -1 sr -1 IceCube E -2 diffuse flux limit ( Astropart. Phys. 20(2004), 507 ) 1 year, for N ch > 227 ( E > 10 5 GeV) < 8.1 x GeV cm -2 s -1 sr -1 The analysis of diffuse flux sensitivity in this study is now cross-checked with other simulations at the effective area levels. Few others items still to be tested, numbers will be ready for VLVnT-09. expected diffuse flux sensitivity (E> 100 TeV): [ 3(KM3NeT CDR) - 8 (IceCube) ] x GeV cm -2 s -1 sr -1