1. KM3NeT: a project for an underwater cubic kilometre neutrino telescope
R. Coniglione INFN-LNS for KM3NeT collaboration
The KM3NeT consortium aims at developing a deep-sea research infrastructure in the Mediterranean Sea. The construction of a multi-cubic-kilometre Cherenkov telescope for neutrinos with energies above 100 GeV is the principal KM3NeT goal
Introduction
Main objectives
The KM3NeT Technical Design Report
Telescope physics performance
New developments
Summary

2. KM3NeT and the international context
High energy neutrino telescope world map
Antares
Taking data in its final configuration (12 lines) since may 2008.
5 lines data analyzed and ready to be published
ANTARES, NEMO, NESTOR
joined efforts to prepare
a km3-size neutrino telescope in the Mediterranean Sea: KM3NeT
Baikal first operating underwater neutrino telescope: NT200 8 strings of 24 pairs of PMT, NT strings(12 OM each) volume of 5Mton (1 Mton = 10^6 ton= 10^ kg=10^9 kg= 10^9 10^-3 m^3=10^6 10^-9 km^3=10^-3 km^3)
IceCube
IC79 taking data since 2010
IC59 data analysis started

3. The KM3NeT consortium
The KM3NeT consortium includes 40 Institutes from 10 European Countries (Cyprus, France, Germany, Greece, Ireland, Italy, The Netherlands, Rumania, Spain, U.K.)
KM3NeT Design Study (DS) -> define the telescope design and outline the main technological options
Approved under the 6° FP (funded by EC for the period )
Conceptual Design Report (CDR) published in (
Activity of DS culminated with the publication of the Technical Design Report (TDR) that outlines the main technological options for the construction, deployment and maintenance of a deep sea neutrino telescope ( (TDR contents frozen in November 2009)
KM3NeT Preparatory Phase (PP) -> define legal, governance and funding aspects, production planes for the detector elements, infrastructure features and prototype validation will be also defined
Approved under the 7° FP (funded by EC for the period )

4. Motivation for the high energy neutrino detection
Neutrino will provide unique info on High Energy Universe
on the origin of UHE cosmic rays (astrophysics, cosmology and particle physics)
on the high energy gamma production mechanism (hadronic and/or leptonic)
on the source dense inner core
Neutrino observation can be connected with the observed gamma fluxes for sources with low matter density while new high density sources can be observed

5. KM3NeT main objectives Central physics goals:
Investigate neutrino “point sources” in the TeV energy regime
galactic ->Supernova Remnants, Microquasars…
extragalactic -> Active Galactic Nuclei, Gamma Ray Bursts
Complement IceCube field of view
Exceed IceCube sensitivity
Other important physics items:
- High energy diffuse neutrino flux detection
- Indirect search of Dark Matter
- Neutrino particle physics aspects
Exotics (Magnetic Monopoles, Lorentz invariance violation, …)
Interdisciplinary research
geophysics, oceanography, marine biology, …
Implementation requirements:
• Construction time ≤5 years
• Operation over at least 10 years

6. KM3NeT sky view 2p downward coverage assumed
At the Mediterranean sea latitude the source visibility can be less than 24h
>25%
>75%
KM3NeT complements the IceCube field of view
KM3NeT observes a large part of the sky (~3.5p)

7. Neutrino detection principlem
Interaction point 
Upward-going neutrinos interact in rock or water (nm is the golden channel for astronomy)
Emerging charged particles (in particular muons) produce Cherekov light in water at 43° with respect to the neutrino direction
Light detection by array of photomultipliers
From photon arrival times and PMT positions is possible to reconstruct the muon direction gc
43°
Detection volume of the order of 5 km3 to exceed IceCube sensitivity by a substantial factor

8. Technical items
The telescope consists of 3D array of photo-sensors supported by vertical structures (DU) connected to a seabed with a cable network
The construction of a deep sea neutrino telescope is technically highly challenging
Very high pressure
Environment chemically aggressive
Deployment operation safe, robust and precise
Technical items
Optical Modules
Front-end electronics
Readout, data acquisition, data transport
Mechanical structures, backbone cable
General deployment strategy
Sea-bed network: cables, junction boxes
Calibration devices
Shore infrastructure
Assembly, transport, logistics
Risk analysis and quality control
Requirements
Cost-effective
Reliable
Producible
Easy to deploy

9. Other issues addressed in the Design Study
Site characterization:
• Characterization of the site and measure of the water properties
optical background, currents, sedimentation, water properties (absorption and scattering lengths….)
Simulation:
Detector performances (sensitivity and discovery fluxes) optimizing the detector parameters
- Earth and Sea science requirements:
• Define the infrastructure needed to implement multidisciplinary science nodes (marine biology, geology/geophysics, oceanography, environmental studies, alerts, …)

10. Optical modules Two alternative solutions in the TDR for OM
Multi-PMT Optical Module
31 small PMTs (3-inch) inside a 17 inch glass sphere
Single-PMT Optical Module
8-inch PMT with 35% quantum efficiency
inside a 13 inch glass sphere
Evolution from pilot projects
31 PMT bases (total ~140 mW)
Cooling shield and stem
First full prototype ready at the end of 2010

11. Optical modules Two alternative solutions in the TDR for OM
Single-PMT Optical Module
Advantages
Multi-PMT Optical Module
Advantages
photocathode surface greater than 3 8-inch PMTs
insensitive to the Earth’s magnetic field -> no mu-metal shielding
single-photon from multi-photon hits separation
information on the arrival direction of Cherenkov light-> better track reconstruction
large angular acceptance
good timing response
well known technology

12. Front-end electronics: Time-over-Threshold
Common solutions in the TDR for the front-end electronics

13. Detection Units
Three alternative solutions in the TDR for DUs
Triangular arrangements of OMs with single-PMTs or multi-PMT
Evolution of the ANTARES storey
Slender string
Vertical sequence of multi-PMTs OMs
Flexible tower with horizontal bars equipped with single-PMTs or multi-PMT OMs
Simulations indicate that local 3D OM arrangement resolve ambiguities in the reconstruction of the muon azimuthal angle

14. Successful deployment test in February 2010
Deployment strategy
Common deployment strategy in the TDR
Main deployment concepts
Compact package
Self unfurling
Connection to seabed network by Remotely Operated Vehicle
The packed flexible tower
(20 storey)
Spherical deployment structure for string with single OM with multi-PMT
Successful deployment test in February 2010
Successful deployment test in December 2009

15. KM3NeT: an artistic view
Detection Units
Primary Junction box
Secondary Junction boxes
Electro-optical cable

16. Simulations: optimization studies
Examples for the flexible tower
Optimization of Detection Unit separation
Bar length optimization
ratio of the effective area relative to 3m
ratio of the effective area relative to 100m
Low energy region
100GeV<En<500 GeV
Quality cuts applied
DWm-mrec~ 2° (close to the DWn-m)
Point like sources
3TeV<En<100 TeV
Quality cuts applied
DWm-mrec~ 0.4°
(close to the search cone radius)
Diffuse flux studies & GRB
En>100 TeV
No quality cuts applied
DWm-mrec  0.9°

17. Simulations: optimization studies
Sensitivity ratio for point like source - 1 year – d =-60°
Flexible tower
Bar length
Detection unit separation
Final bar length choice is a compromise between physical performance and technical constraints
180 m preferred DU distance

18. Similar sensitivity per euro for the three configurations
Simulation results
A detector with a total cost of about 220M€ is required to surpass the performance of IceCube by a substantial factor
Full KM3NeT detectors made of the three DU configurations at the same cost were considered in the simulations
concept
Number of DU for 220M€
Flexible tower with 6 8” PMT per bar
20 bars
310
(2x154)
Slender strings
20 floors with 1 multi-PMT per floor
620 (2X310)
Triangles 6 8” PMT per floor
20 floors
254
(2x127)
Sensitivity to point source (flux E-2) vs declination for one year of observation time
Black Slender string
Red Flexible tower
Green Triangles
20*2*310*31= PMT il seawiet full detector OM
6*20*310=37200 tower full detector
In the cost are not included: human resources for assembly, contingency and spare, on shore installation (except read-out)
Deployment is included
Similar sensitivity per euro for the three configurations

19. KM3NeT: effective area & resolution
Detector resolution
Median of DW n-mrec
Neutrino effective area
median of the q n-m distribution
Kinematics
☐Quality Cuts applied
Quality Cuts optimized for sensitivity m
q n-m n

20. KM3NeT: sensitivity & discovery
Sensitivity and discovery fluxes for point like sources with a E-2 spectrum for 1 year of observation time
KM3NeT sensitivity 90%CL
KM3NeT discovery 5s 50%
IceCube sensitivity 90%CL
IceCube discovery 5s 50% 2.5÷3.5 above sensitivity flux. (extrapolation from IceCube 40 string configuration)
unbinned method
binned method
| Observed Galactic TeV-g sources (SNR, unidentified, microquazars)
F. Aharonian et al. Rep. Prog. Phys. (2008)
Abdo et al., MILAGRO, Astrophys. J. 658 L33-L36 (2007)
 Galactic Centre

21. Developments after the TDR
In the recent months developments towards a technology convergence on a unique design
“bar” option with horizontal extent and 6 8-inch PMTs
Optimised design and plan for extensive deployment tests defined
Study of the advantages offered by a “hibrid” solution
DU with horizontal extent
Multi-PMT Optical Module
Multi-PMT option
Needs validation of technology and integration procedures
Common development of the multi-PMT Optical Module and its implementation on the tower
Optimization of simulation of the detector performance ongoing

22. Flexible tower DU with 6 13” spheres: stacking concept
Height = 1.43 m

23. Flexible tower DU with 2 17” OM: preliminary storey design

24. Summary
A design for the KM3NeT neutrino telescope complementing the IceCube field of view and surpassing it in sensitivity by a substantial factor is presented
The required sensitivity can be achieved within an overall budget of ≈ 250 M€
Staged implementation, with increasing discovery potential, is technically possible
Convergence process toward a unique technical design under way
Development plan for qualification of a pre-production model of the detection unit defined
Remaining technical decisions have to be taken within the next spring
Readiness for construction expected at the end of the Preparatory Phase (march 2012)
Installation could start in 2013 and data taking soon after

25. The end

26. Simulations: optimization studies
Sensitivity ratio for point like source - 1 year – d =-60°
Flexible tower
Bar length
Detection unit separation
a=-2
a=-2.2
Final bar length choice is a compromise between physical performance and technical constraints
180 m preferred DU distance

27. Theta versus declination
Below the horizon
Above the horizon
Mediterranean sea latitude 36°
Near the horizon the effect of Earth absorption is reduced for high energy neutrinos
+50
+40
+20
-10
-20
-30
d=-40
-50
-60
-70
-80