Transcript Folie 1

Neutrino Diffuse Fluxes in KM3NeT
Rezo Shanidze, Thomas Seitz
ECAP, University of Erlangen
(for the KM3NeT consortium)
15 October 2009
Athens, Greece
Layout
•
Introduction
•
Cosmic neutrino fluxes
•
KM3NeT TDR configuration
•
Sensitivity to diffuse neutrino fluxes
•
Summary and outlook
Introduction
•
•
Unobserved neutrino sources will build up
diffuse fluxes of cosmic neutrinos
Propagation of UHECR trough CMBR is producing the
cosmogenic neutrino flux ( GZK neutrinos)
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 g atmospheric neutrino flux
( background for cosmic neutrinos )
cosmic
neutrinos
Energy spectra
Composition
ne:nm:nt
~ E-2
expected
GZK spectra
(En > ~ 107 GeV )
1:1:1
( expected )
Atmospheric
neutrinos
~ E-3.7 ( En < 105-106GeV)
measured
~ E-2.7 (En > 105-106 GeV)
( prompt flux, expected)
mostly nm, low ne, negligble nt
( measured nm )
Neutrinos simulated in the KM3NeT telescope:
- Currently only nmN (CC) events with m-track is considered
- Shower type events nN( NC) not included
( low effective area, but good energy resolution )
Atmospheric neutrino flux: Bartol model + rqpm model for ‘prompt flux’
R. Shanidze, T. Seitz
VLVnT-09, Athens, 15 October, 2009.
KM3NeT Configurations
PMT
KM3NeT
R. Shanidze, T. Seitz
OM
St.
DU
St.
xPMT.
(DU)
8”
3x2
20
127
2540
3”
1x31
20
300
6000
PMTs
Dist(m)
Vol.
(Tot.)
St./DU
(km3)
15240
40/180
2.6
186000
30/130
3.1
VLVnT-09, Athens, 15 October, 2009.
Event rates and diffuse flux sensitivity
N - event rates in the neutrino telescope:
a convolution of :
- neutrino flux F(En)
- neutrino effective are A(En)
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 m-track
Could be used a simple
Energy estimator.
Expected energy resolution
for neutrinos is
~ 0.5 x log En
Mean number of hits in the reconstructed
m-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 g blue curve.
Dotted histogram: c
neutrino events with
Nhit> 200
in the reconstructed
m-track.
R. Shanidze, T. Seitz
VLVnT-09, Athens, 15 October, 2009.
Effective area for string configurations
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
Detector with 310 strings:
130 m, 100 m(scan))
( Seatray simulations)
En [GeV]
Dashed histogram:
neutrino events with
Nhit> 200
in the reconstructed
m-track.
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 10-9 GeV cm2s-1sr-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
Neutrino flux from inner Galaxy g theoretical calculations
based on VHE-g observations
Inner Galaxy:
-40o<l<40o , -2o < b < 2o
W ≈ 0.97 sr, visible from Mediterranean NT.
Calculations for the
KM3NeT CDR configuration
( Based on MILAGRO data)
A .M. taylor et al.,
Astropart. Phys.30(2008),180
(1)
(2)
where E* = 80 GeV,
a=2, a+d=2.7, Ecut=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:
En > 10 TeV:
9 (eqn.1),
10 (eqn. 2, Ecut=1 PeV )
15 (eqn. 2, Ecut=5 PeV )
28 (atm. Neutrinos)
En>20 TeV:
10/10 events for most
optimistic case/ atm-n.
To be (re)calculated for current KM3NeT configuration(s) including:
- reconstruction efficiency.
- energy estimator
atm-n background can be obtained from regions similar extension
R. Shanidze, T. Seitz
VLVnT-09, Athens, 15 October, 2009.
Cosmogenic neutrino flux
Above Ep>1019.6 GeV ( GZK cut-of) for sources with d > 50Mpc
p gCMB g D g np+ / ppo
GZK cut-of in UHECR g cosmogenic neutrino flux .
GZK cut-of confirmed:
HIRES: Phys. Rev. Lett., 100, 2008,
PAO:
Phys. Rev. Lett. 101, 2008,
propagation (Mpc):
10, 20, 50, 100, 200.
Cosmogenic neutrino flux g
guaranteed but unknown.
Calculations with “SOPHIA” MC :
R. Engel, D. Seckel and T. Stanev,
Phys.Rev.D64 (2009) 093010
Event rate expected in KM3NeT very low g
special study is necessary Including shower events.
R. Shanidze, T. Seitz
VLVnT-09, Athens, 15 October, 2009.
Summary and Outlook
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The largest instrumented volume of the detector (above 2 km3 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 10-9 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 En> ~107-108 GeV (cosmogenic neutrinos)
event reconstruction is not optimized.
•
KM3NeT reconstruction could be improved g improved sensitivities
R. Shanidze, T. Seitz
VLVnT-09, Athens, 15 October, 2009.