Transcript Slides - Agenda INFN

Development of the 21CMA radio-detection array
(Xinjiang/China) for the observation of UHE neutrinos
showers
Didier Charrier1, Pascal Lautridou1, Olivier Martineau-Huynh2 ,
Olivier Ravel1 , Xiang-Ping Wu3, Meng Zhao3, D.A.1
1 ) Subatech-Nantes (France) ; 2) LPNHE-Paris (France) ;3) NAOC - Bejing (China)
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Objectives
• Neutrinos: possible direct messengers
for sources above 10^15 eV beyond
several Mpc
• Very low event rates imply km3
sensitive volumes (IceCube,
ANTARES,NEMO,AUGER,…)
•
only upper limits set (~1.10-7to10-6 GeV.cm-2.s-1.sr-1 )
Use of high density target medium (Earth,
rocks) to generate n-N interactions (=>
leptons).
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• 2 constraints above PeV energies : limited medium
thickness and large detection area to follow-up
lepton-decay
=> Earth skimming or through-mountains neutrino trajectories
( cf D Fargion- F Vannucci)
detection volume
t decay
X0
n
XS
Xint
XD
n converter target
+ shielding
Conditions met at 21CMA
combined with radio-technique
characterisation of air -showers
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A few advantages of radiodetection
• Radio technique allows large effective detection
volumes
• coherence effect in the RF domain ,
• very good electric signal sensitivity (up to several kms )
• => large detection acceptance
• => sampling of a longer development phase of the EAS
• ~100% duty cycle.
• Signal recognition firmly demonstrated
•
self- triggering mode with an array of antennas under
control
(see presentations by P.Lautridou/CODALEMA and B.Revenu/RAuger)
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The 21CM Array layout (Xinjiang/China)
ARRAY
LNA
FILTERS
FILTER
60dB
Optical
transmitter
[50-100 Mhz]
Fiber
Optical
receiver
ADC
200 MS/s
81 pods of 127
antennas.
81quad-core PC
10287 (50-200 MHz)
Log periodic
antennas
2 arms (4km NS
+3km EW)
Solar cells powered
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(On- line
filtering process)
data room
First unique advantage of the 21CMA site
Target & shield volume :
20 000 km3
year - exposure :
~2.10 20 cm2. s
(for a point-like source)
21CMA
Second unique advantage of the 21CMA site
50MHz
200MHz
Absence of RF or anthropic signals above 15 Mhz
=> [20-200 Mhz] quiet band
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Operating procedure and first tests of UHCR radiodetection at the 21CMA
•
•
•
Stand-alone antenna mode
81 Quad-processor PCs & on-line software trigger (duty cycle 100%)
Search on each stored buffer for a sample of events satisfying :
v > vav+ n. s
waveform
-Event-by-event transient
radio signal analysis
-Arrival direction
and wave form reconstruction (FFT)
Example of coinc. transient
events on 3 antennas with
[50-100 Mhz ] band-filter
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Time
10 ms
some criteria for discrimination
of n-t showers
•
Event-by-event air-shower profiles and trajectories obtained in a
customary way (see P.Lautridou/CODALEMA)
•
Low elevation and 80° azimutal antenna acceptance diagram
•
Large antenna multiplicity along (or close to ) the arm directions
( shielding effect for other CR trajectories)
•
Correlation between the spatial profile of decay-shower and the
spreading of the electric signal
•Trajectory elevation filter (accuracy Dq
< 0.1° ) against downwards usual CR
showers using the time sequence ( Dt~
5 ns ) over successive fired antennas
and known environment relief profile .
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Perspectives
• Atmosphere length available: 5.7-10.5 km
• average detection efficiency of 1.2 to 6.10-3
between 10 18 and 10 20 eV
• Preliminary estimation ~0.3 event. yr-1
(based on energy flux E2.F= 4.10-8 [GeV.s-1.cm-2.sr-1]
• Data acquisition presently running
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Conclusion
Demonstration of the whole 21CMA set-up ability for CR transient signal
characterisation
This neutrino conversion method associated with a radio-detection of resulting
t - decay showers is capable of achieving a sensitivity similar that of existing big
detectors.
The multiplicity, longitudinal spread and elevation dependence of the radio signals
are expected to pin-down the n-t origin (and energy dependence) of the inclined
t-showers.
Possible study of isotropy distribution of UHECR arrival directions with an
azimuthal exploration of events
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