32nd International Cosmic Ray Conference 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)

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

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 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

optical fiber64dB MHz filter TREND acquisition FROM 21CMA TO TREND SETUPpod DAQ room 200MSamples/s ADC+CPU+disk optical fiber 84dB MHz 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

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: )

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

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

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

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)

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

HYBRID RESULTS Look for offline coincidence with ≥4 antennas & ≥2 particle detectors. 10 live days in 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/ ±367±5359±23±4 19/04/ ±149±3195±2191±4 27/08/ ±136±355±456±5 01/03/ ±149±312±110±5 09/03/ ±253±4323±2331±5

CONCLUSIONS In ~ 3 years of operation (Oct – 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?

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

The 3-scintillators array is a valid EAS detector