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Development of 21CMA Radio Detection Array for UHE Neutrino Showers in Xinjiang, China

This paper discusses the development of the 21CMA radio detection array in Xinjiang, China for the observation of ultra-high energy neutrino showers. The array utilizes a high density target medium to generate n-n interactions and detects the resulting radio signals. The advantages of radio-detection include large effective detection volumes, high signal sensitivity, and the ability to sample a longer development phase of the EAS.

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Development of 21CMA Radio Detection Array for UHE Neutrino Showers in Xinjiang, China

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  1. 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) D.ARDOUIN ARENA 2008

  2. Objectives • Neutrinos: possible direct messengers for sources above 10^15eV 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). D.ARDOUIN ARENA 2008

  3. detection volume t decay X0 n XS Xint XD nconverter target + shielding • 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) Conditions met at 21CMA combined with radio-technique characterisation of air -showers D.ARDOUIN ARENA 2008

  4. A few advantages of radio-detection • 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) D.ARDOUIN ARENA 2008

  5. Optical receiver Optical transmitter FILTERS ADC ARRAY LNA FILTER Fiber 200 MS/s 60dB [50-100 Mhz] 81 pods of 127antennas. 10287 (50-200 MHz) Log periodic antennas 2 arms (4km NS +3km EW) Solar cells powered 81quad-core PC(On- line filtering process) data room The 21CM Array layout (Xinjiang/China) D.ARDOUIN ARENA 2008

  6. Google Earth 21CMA 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)

  7. Second unique advantage of the 21CMA site Absence of RF or anthropic signals above 15 Mhz => [20-200 Mhz] quiet band D.ARDOUIN ARENA 2008

  8. Example of coinc. transient events on 3 antennas with [50-100 Mhz ] band-filter Operating procedure and first tests of UHCR radio-detection atthe21CMA • 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) D.ARDOUIN ARENA 2008 Time10 ms

  9. 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 . D.ARDOUIN ARENA 2008

  10. 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 D.ARDOUIN ARENA 2008

  11. Conclusion Demonstration of the whole 21CMA set-up ability for CR transient signal characterisation This neutrino conversion method associated with a radio-detection of resultingt - 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 D.ARDOUIN ARENA 2008

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