1. The GRAND proto A prototype array to evaluate the potential of EAS identification of the radio technique.

2. GRAND neutrino sensitivity GRAND could reach 5-10x better sensitivity than Antartica projects. Angular resolution better than 0.1°. To be confirmed/optimized with full MC. PRELIMINARY GRAND : 90% CL limit assuming 0 candidates in 3 years threshold = 3 10 16 eV  =  0 E -2 spectrum Tens of GZK /year expected!

3. Non-cosmic background GRAND bckgd event rate estimation: TREND50: ~6 10 5 events/day/km² (~2.8 10 8 valid coincs in 317 DAQ days) GRAND: <300 events/day/km² (safe estimate) 2 10 7 evts/year over full array Target rejection factor: 10 8 - 10 9 Expected event rate: 0-100 events/year Factor 5 10 -4 L=30 TREND-50 event multiplicity L=5 TREND50 → GRAND: Size x40000 Antenna density /25 (Trig density /2000): Large step size helps you kill background!

4. GRAND background rejection Trigger pattern E sh =10 18 eV  =90° 472 antennas triggered … probably not enough (shortest tracks) E sh =10 18 eV  =87° 27 antennas triggered

5. EAS polarization EAS radio emission associated to 2 major sources: – Geosynchrotron effect F L = q v.B geo E field linearly polarized:  B geo  direction of propagation – Charge excess: radial polarization Polarization info can be predicted, provided other shower parameters (E, , x core ) are known. Very unlikely that bckgrd event would exhibit similar polarization signature. Polarization as a reliable signature for EAS (?) AERA, arXiv:1402.3677v2

6.  = atan(|V y |/|V x |)  =atan(|V plane |/|V z |) Test setup: «GRAND-proto»: a hybrid setup to evaluate quantitativly bckgrd rejection potential of polarization information 32 3-polar antennas + 21 scintilator array Deployed at the noisiest location of TREND array, aiming at showers coming from North. Principle: – Wave triggers 5+ antennas – Reconstruct direction of origin & polarization @ trig’d antennas location: GRAND-proto  = 65°,  = 8° x (EW) y (NS) z P   TREND antenna Reconstructed source position GRAND proto site

7. Principle of EAS polarization measurment in GRAND-proto – For all trig’d antennas, simulate expected polarization assuming signal due to air shower. EWNS Vert Expected  for E field Expected  for voltage Simulated shower 10 17 eV, (65°,8°) Noise at antenna output → V≠0 in any case → Error for extreme values (  = 0° or 90°) Expected  for voltage + noise

8. Polarization computation precision

9. Principle of EAS polarization measurment in GRAND If experimental polar matches one from simulated shower: EAS tag Off-line validation of EAS candidates with scintillator array Quantitative evaluation of EAS identification based on wave polarization. How good do we have to be (a rough estimate): If we perform 15° precision on reconstructed  : – Random polar may be tagged as valid for one antenna with p = 0.03 – p=0.03 5 = 1.6 10 -8 for 5 antennas (4.6 10 -10 for 6 antennas) How GRANDproto can be instrumental for GRAND: – ~100Hz coincidence rate expected on GRANDproto – 10 9 events reached within 3 months live R=10 9 may be tested within one year.

10. GRAND-proto status Fully funded, deployment May 2015-early 2016 Radio antenna status – Radio array: 3D active antennas (CODALEMA/AERA type, D. Charier @ SUBATECH) – All LNAs delivered, 6 prototype antennas in test during January-March 2014. 1 event triggering all 3 channels

11. GRAND-proto status Radio DAQ -> Jacques David + Patrick Nayman Scintillator array -> Feng Zhaoyang