1. 32nd International Cosmic Ray Conference 11-18 August 2011, Beijing China First detection of extensive air showers by the TREND self-triggering radio experiment Olivier Martineau-Huynh (IN2P3, IHEP, NAOC) for Thomas Saugrin (NAOC)

2. THE TREND PROJECT TREND (Tianshan Radio Experiment for Neutrino Detection) is a sino-french collaboration ( ~ 10 researchers) involving: - NAOC, IHEP (China) - IN2P3/CNRS (France): Subatech, LPC Clermont, LPNHE 21CMA / TREND Driving concept : Use the existing infrastructure of the 21CMA radio telescope site (electronics, acquisition,…) to quickly deploy a large antenna array dedicated to EAS autonomous radiodetection. Objectives : - Participate in the development of the autonomous radiodetection technique - In a long-term perspective, use the topology of the Ulastai valley (surrounded by high mountains) to investigate the radiodetection of high-energy neutrinos with earth-skimming trajectory

3. THE 21CMA RADIO TELESCOPE DAQ 4 km 3 km 21CMA is a giant radiotelescope located in the Tianshan Mountains (Xinjiang) Built in 2007 by NAOC (WU X.-P.) to study the epoch of re-ionization North East West South 10160 log-periodic antennas (signal phased by pod of 127) Each pod is linked to the acquistion room by optical fiber Signal acquisition performed by 200 MHz ADC

4. optical fiber64dB 50-100MHz filter TREND acquisition FROM 21CMA TO TREND SETUPpod DAQ room 200MSamples/s ADC+CPU+disk optical fiber 84dB 50-200MHz filter σ N.σ 21CMA acquisition Continuous recording in frequency domain Trigger mode in time domain Antenna signals recorded indepently on dedicated channel: Offline coincidence reconstruction

5. TREND LAYOUT N 250 m 100 m 400 m 800 m 2009 : - Prototype of 6 log-periodic antennas - Test of antenna coincidence identification - Test of EM signal arrival direction reconstruction TREND concept proof-of-feasability 2010 : - Antenna array of 15 log-periodic antennas - 3 particle detectors (scintillators) - Test of EAS radio candidate identification - Offline cross-check between radio candidates and particle events (recorded indepently) - Hybrid antenna/scintillator coincidences found Validation of EAS autonomous radio detection and identification (see Astropart Phys paper: arXiv:1007.4359)

6. TREND LAYOUT ~ 3 km 2011 : - Extension to 50 antennas along the 21CMA East-West arm - New antenna design: «butterfly-shape» passive antenna (based on the CODALEMA design) - Particle detectors still in operation - Redesign of the data preprocessing software In acquistion since March 2011

7. RADIO PERFORMANCES Plane track reconstruction : - 1037 events in 4.5 minutes - Θ > 65° - Max multiplicity: 24 Angular resolution ~ 2° (for high zenithal angle) North

8. RADIO PERFORMANCES Plane track reconstruction : - Distant radio source from the array Radio signal intensity almost constant on all the antennas Cross check for calibration 15% of amplitude variation all along the plane track

9. SHOWER CANDIDATES Background rejection: - Shut-down of antennas with trigger rate > 100 Hz - Rejection of consecutive coincidences for time difference = n.10 ms (signature of power line discharge?) 10 ms - Waveform analysis: rejection of abnormal pulses (saturation, multiple pulses, ToT)

10. SHOWER CANDIDATES Candidate selection: - ~flat wavefront rejection of close background sources - Compact ground pattern (exponential lateral dicrease) rejection of distant background sources Preliminary analysis already shows a few EAS candidates

11. HYBRID RESULTS Look for offline coincidence with ≥4 antennas & ≥2 particle detectors. 10 live days in 2011 + 19 live days in 2010 of hybrid data 13 hybrid events: – 5 with consistent independent source reconstruction – 8 with 2 particle detectors: no direction reconstruction, but consistent trigger time – (3 random coincidences: radio source at ground or/and bad trigger pattern) See Ardouin et al., Astropart Phys 34 (2011) for more details DateN ants θ radio θ scints ϕ radio ϕ scints 03/04/2010461±367±5359±23±4 19/04/2010452±149±3195±2191±4 27/08/2010542±136±355±456±5 01/03/2011445±149±312±110±5 09/03/2011756±253±4323±2331±5

12. CONCLUSIONS In ~ 3 years of operation (Oct. 2008 – August 2011) Validation of the concept of autonomous radio-detection Development of a EAS radio candidate selection procedure Confirmation through detetion of hybrid antenna/scintillator events Deployment of an operational 50-antennas setup (~1.2 km²) Run with present array for one more year (or more) + optimize analysis: large statistics of CR radio showers down to large zenith angles. 21CMA-based DAQ implies reduced performances (time tagging, amplitude)which become a limitation Use of dedicated system (electronics, ADC, DAQ…) Set-up of an array optimized for neutrino search. Requires extensive studies on the layout, antenna design, trigger & noise rejection: ongoing work. What’s next?

13. TREND RADIO ENVIRONNEMENT Local sidereal time Signal noise level TREND @ Ulastai General radio environnement very clear: No major emettor after 20 MHz Galactic plane @ 408 MHz Main noise: Thermal emission from galactic center Minimum possible noise for a radio detector TREND sensitivity is well suited for EAS radiodetection !

17. The 3-scintillators array is a valid EAS detector