Carla Distefano for the NEMO Collaboration

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Carla Distefanofor the NEMO Collaboration
Status of NEMO Results from the NEMO Phase 1
detector
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Outline of the talk

• NEMO-RD activities
• sites exploration the Capo Passero site
• preliminary design of a km3 detector
• NEMO-Phase1
• aim and objectives of the project
• experimental set-up
• data analysis
• Environmental parameters
• Atmospheric muon tracks reconstruction
• NEMO-Phase2
• the Capo Passero infrastructure
• the NEMO-Phase2 16 floor tower
• status of the project

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The Capo Passero deep sea site
After several years (1998-2004) of activity in
seeking and monitoring abyssal sites in the
Mediterranean Sea the NEMO Collaboration has
selected a site close to Capo Passero, Sicily
(36 16 N, 16 06 E) .

• The average depth is 3500 m, the distance from
  shore is 100 km.
• It is located in a wide abyssal plateau far from
  shelf breaks and geologically stable.
• The light absorption length is close to the
  optically pure water La 70 m _at_ 440 nm
  (astro-ph\0603701).
• Optical background is low (30 kHz on 10 PMT
  at 0.5 s.p.e. threshold) and mainly due to 40K
  decay since the bioluminescence activity is
  extremely low.
• Underwater currents are very low (2.5 cm/s) and
  stable.

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NEMO km3 architecture the Tower
Conceptual detector layout
9 x 9 81 Towers with 3 dimensional and
non homogeneous distribution of sensors
Reference Geometry - Square array of 81
towers - 140 m between each tower - 16 floors for
each tower - Vertical distance 40 m - Floor
length 815 m - 4 PMTs for each floor - 5832 PMTs
Floor
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Detector architecture has been studied in order
to reduce the number of structures to reduce the
number of underwater connections and allow
operation with a ROV ? Detector modularity
Optical modules
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Expected detector performances
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NEMO Phase 1
A technological demonstrator for a km3 underwater
neutrino telescope as been constructed in order
to validate the key technologies proposed for the
km3 detector and the possibility to detect and
trace muons ? NEMO Phase-1
Mini-Tower unfurled
Shore laboratory, Port of Catania
25 km E offshore Catania Test-Site 2000 m depth
NEMO mini-tower (4 floors, 16 OM)
Buoy
e.o. connection
e.o. cable from shore
e.o. cable 10 optical fibre, 6 conductors
TSS Frame
Junction Box
300 m
Junction Box
Mini-Tower compacted
15 m
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The NEMO Mini-Tower
FLOOR
Optical modules
Floor 4
Floor 3
Floor control module
Floor 2
4 conductors 4 fibers
Floor 1
Break-out
Tensioning ropes
Tensioning ropes
Backbone e.o. cable
Tower Base Module
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NEMO Phase 1 Deployment
Deployment of the Mini-Tower
Deployment of the JB
Deployment and operation 18 December
2006 Detector turning off 18 May 2007
Connection in the frame
Connection of the Mini-Tower
Connection of the JB
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NEMO mini-tower, big success but also some
problem
The mini-tower deployment, connection to the main
EOC and unfolding operations went smoothly. All
active elements (PMTs, electronics, acoustic
positioning, data transmission and acquisition,
worked correctly.

• Junction Box
• After 4 months, we observed an attenuation in
  optical fibers transmission inside the JB
• In May 2007 a short-circuit in the power
  distribution system
• The JB was recovered in June 2007, it was
  repaired and re-installed in April 2008. Its
  working since then.
• Mini-Tower
• A loss of buoyancy in the main buoy, due to a
  production error, caused a slow sinking of the
  whole tower
• In April 2008 the mini-tower was laying on the
  sea-bed
• At this moment the mini-tower does not take data.

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Results from NEMO Phase 1 Environmental
parameters
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Mini-Tower Slow Control Instrumentation
Compass Tilt meter

• Acoustic Doppler Current Profile
• Sea Currents

4th Floor
FCM
ADCP

• Light Transmissivity in Water

3rd Floor
FCM

• Conductivity Temperature Pressure (Depth)

2nd Floor
FCM
C-Star
1st Floor
FCM

• Acoustic Positioning

CTD
Hydrophone
Base tower
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Instrumentation Data Sea currents
An Acoustic Doppler Current Profiler (ADCP) was
mounted on 4th floor, downward oriented, in order
to continuous monitoring the underwater currents
below that depth, in a range of about 150 m.
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Optical background PMT rates
The instantaneous rate value is calculated by the
Front-End board of the PMT averaging, in a time
window of 1 ms, all the hits whose amplitude
exceeds a given threshold equivalent to 0.3 spe.
Floor 4
The measured baseline is between 70 and 80 kHz
for PMTs on floors 2, 3 and 4 as expected from
40K decay plus a contribution of diffuse
bioluminescence
PMT
Rates measured from 1020 Jan 07
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Acoustic Positioning System
The position of the PMTs (required for muon
tracking) is achieved by measuring time delays of
acoustic signals between acoustic beacons placed
on the sea floor and hydrophones installed on
each tower floor.
Hydrophones
CTD sound velocity measurement csf(C,T,D)
COMPASS PMTs orientation
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APS Data analysis
The acoustic positioning system provides the
positions of hydrophones every second. The
results provided by the real-time monitoring
system are affected by errors quantified by the
Quality Factor (QF) of the measurement
1st Feb h.17-23 (6 hr)
Construction 14.250.01 m
Measured distance 14.240.06 m
Distance H0-H1 measured on floor 2 Each point is
averaged over 300 s
Accuracy ?10 cm
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Results from NEMO Phase 1 Atmospheric muons
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OMs Data Data Acquisition

• On-Line TRIGGER
• Simple Coincidence (SC) Coincidence between 2
  hits in 2 adjacent PMTs of the same floor (?TCS
  20 ns)
• An event is recorded if a SC occurs hits in a
  given time window centered around the SC are
  saved (Trigger Window 4-10 µs)

• TRIGGER rates
• R 1.5-2 kHz
• Its consistent with hit coincidences induced by
  the measured Optical Background (75-80 kHz)
• Expected muon trigger rate (from simulations) R
  1 Hz
• The signal is dominated by the noise an
  Off-Line trigger is mandatory

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OMs Data Hit Decompression and Calibration
Before the application of the off-line trigger,
the hits are calibrated.
PMT DATA Features Signal Digitization Sampling
200 MHz Time resolution 5 ns Charge Threshold
0.3 s.p.e. Trigger Window 4-10 µs

• Hit Decompression and Calibration
• Time resolution 1 nsec
• Total Charge determination with
• s0.3 pC
• Hit charge converted in p.e.
• (1 p.e. 8 pC )

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OMs Data Off-Line Trigger
Trigger Seeds 1- Simple Coincidence (SC)
Coincidence between 2 close hits in the same
storey ?TCS 20 ns 2- Floor Coincidence
(FC) Coincidence between 2 hits recorded at the
opposite ends of a same storey ?TFC 200
ns 3- Charge Shooting (CS) A hit exceeding a
charge threshold of 2.5 p.e.

• Monte Carlo Simulations
• Atm. ? generated with MuPage
• Light absorp. length ( 50 m _at_440 nm)
• Optical Bkg from data ( 80 kHz avg.)
• Mini-Tower front-end electronics
• On-Line Trigger efficiency

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OMs Data Off-Line Trigger

• We require at least 7 trigger seeds inside the
  event
• bkg excess will be rejected during the next
  steps
• a stronger request affects the muon
  reconstruction rate

More efficient trigger strategy under study
multiple seeds, neural network approach .
Data 23-24 Jan 2007 Data Set MuPage atm. muons
simulated with MuPage OnlyBkg simulated events
containing only bkg hits they are
normalized to reproduce the data rate for
Nseedmin1
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Reconstructed events

• A Causality Filter is applied to reject
  background hits in the muon events
• (dtltdr/v20 ns)
• Muon events are reconstructed the ANTARES
  reconstruction code based on the maximization
  likelihood method (taking into account the
  Cherenkov features and the possible presence of
  background hits).

Differences between data and simulations decrease
at the reconstruction level.
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Reconstructed Atmospheric Muon Tracks
?2260 Tracks Reconstructed for the analyzed data
set (23-24 Jan 2007)
Run 15 Event 11 Date 23 Jan 2007 H. 2021 Hits
17 Selected Hits 14 Hits in Reconstruction
12 ? 168 Trigger Seed 17 SC 4 FC 5 CS
8 LikelihoodRED - 8,3
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Reconstructed Atmospheric Muon Tracks
?2260 Tracks Reconstructed for the analyzed data
set (23-24 Jan 2007)
Run 17 Event 38 Date 24 Jan 2007 H. 0220 Hits
24 Selected Hits 17 Hits in Reconstruction
16 ? 132 Trigger Seeds 23 SC 3 FC
14 CS 6 LikelihoodRED - 6,9
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Angular distribution comparisons with
simulations
23-24 January, 2007 LiveTime 11.3 hours OnLine
Trigger 6?107 OffLine Trigger
184709 Reconstructed tracks 2260 Selected
tracks 965
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5-26 March, 2007 analysis results
5-26 March, 2007 LiveTime 123.8
hours Reconstructed tracks 14144 Rec. Rate
0.032 Hz
23-24 January, 2007 LiveTime 11.3
hours Reconstructed tracks 2260 Rec. Rate 0.056
Hz
More statistics but a lower rate of reconstructed
tracks due to the smaller number of PMTs
participating to the muon detection (because of
the mini-tower sinking, the bottom floors reached
the sea-bottom).
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The NEMO Phase-2 project

• OBJECTIVES
• Realization of an underwater infrastructure at
  3500 m on the CP site
• Test of the detector structure installation
  procedures at 3500 m
• Installation of a 16 storey tower
• Long term monitoring of the site
• INFRASTRUCTURE UNDER CONSTRUCTION
• Shore station in Portopalo di Capo Passero
• 100 km electro optical cable
• Underwater infrastructures
• STATUS
• Electro-optical cable (gt50 kW, 20 fibres)
  deployed in July 2007
• Renovation of a building (1000 m2) located inside
  the harbour area of Portopalo completed.
• Installation of Alcatel DC power supply system
  with DC/DC converter in October 2008
• Construction of the 16 storey tower under way
• Project completion planned in beginning 2009

A deep sea station on the Capo Passero site
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The NEMO Phase-2 project
July 2007 Deployment of the 100 km long
electro-optical cable at Capo Passero
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Conclusions and Outlook

• NEMO Phase-1 detector it has been constructed
  and successfully operated, demonstrating the
  validity of the proposed key technologies for the
  km3 telescope
• Environmental parameters data analysis
• Optical module positions recovered for all the
  data set accuracy lt10 cm
• Magnitude of the underwater currents lt10 cm/sec
  and average direction 180 (South)
• The baseline for each PMT was measured to be
  70-80 kHz (Optical Noise)
• Atmospheric muon tracks reconstruction
• - Analyzed LiveTime ?140 hr
• Atmospheric muon track reconstruction more than
  16000 rec. tracks
• Angular distributions of atmospheric muons
  measured
• Good agreement with simulations
• Data analysis of the whole data set acquired by
  the Phase-1 detector is in progress.
• NEMO Phase-2 detector installation of a full
  NEMO tower at the Capo Passero Site, expected at
  the beginning of 2009
• Since 2006, partecipation to the KM3Net
  Consortium