1. Preliminary MC study on the GRAND prototype scintillator array Feng Zhaoyang Institute of High Energy Physics, CAS, China GRAND Workshop, Paris, Feb. 015

2. The main challenge of the GRAND project huge GRAND terrestical background event rate: TREND50: ~30kEvents/day/km² (~1.5 10 7 valid coincs in 317 DAQ days) TREND50 → GRAND: Antenna density /25 Size x40000 GRAND: <15 events/day/km² (safe estimate) 3 10 8 evts/year over full array Target rejection factor: 10 9 Expected event rate: 0-100 events/year 1.5 10 7 events 7500 events TREND-50 event multiplicity Olivier’s talk at Monday 10:00

3. GRAND prototype: a hybrid array Prototype array of 35 tripole antennas ( ) + 21 scintillators ( ) – Principle of EAS selection: For all events detected: Measure polarization on all triggering antennas Select events with polarization pattern compatible with EAS. Offline cross-check with scintillator data. – Allows a quantitative evaluation of the EAS selection procedure.

4. Grand prototype scintillator detector Plastic scintillator – Type: EJ-200 – Size:707mm*707mm*20mm – Surface: four clear edges, one polished face and one sanded face. Reflective material: – Tyvek 1082D PMT - Hamamatsu R7725. 4

5. Air Shower data sample 2000 proton events (full CORSIKA simulation, v7.400) Energy:10 16.5 -10 18 eV Zenith angle:40-70 degrees Azimuth angle:-20-20 degrees Energy spectrum index:-2.0, reweight to -3.0

6. 2 nd particles content All Events Zenith angle=40-50 degrees Zenith angle=50-60 degrees Zenith angle=60-70 degrees

7. Grand proto (21 detectors) ->Giant Array: 949 detectors, distance 50m G4trend (Geant4.9.5,upaded from G4asg) + Rec. code ( updated from Tibet array) The air is vacuum, To save the CPU time GRAND prototypeGrant Array

8. G4trend/G4asg: in good agreement with data Core position Angular resolution Zenith angle Particle number Muon detector prototype ： Muon number in the 100 TeV energy range Single muon peak

9. 6 configurations of Giant Array S det =600m*3600m=2.16km 2 D=50m,949 detectors,D=100m, 259 detectors,D=150m, 125 detectors, D=200m, 76 detectors, D=600m (Y axis) or 300m (X axis, 21 detectors, GRAND proto D=300m, 39 detectors,

10. Detector simulation & rec. setup Detector: tilt=50 degrees The core position is uniformly random distribution in 800m *3800 m Each event is repeated 100 times The coincident background muon is considered. One PMT, with 0-50 MIPs dynamic range TDC dynamic range ： 0-60us TDC resolution: 2ns Trigger condition: any 3 fired detectors (>0.6 MPs) in 20 us

11. particle numbers and time profile threshold saturation

12. Number of fired detectors

13. Rec. Core position

14. Angular Resolution

15. Event rate estimation I Solid angle: 40 o <θ<70 o, -20 o <ϕ<20 o Cosmic ray flux: measured by IceTop-73, arXiv:1307.3795 Energy range: 10 16.5 -10 18 eV Event rate/dayEvent rate / year D=50m80.82.9e4 D=100m77.42.8e4 D=150m70.12.6e4 D=200m61.52.2e4 D=300m40.41.5e4 D=600m17.46.4e3

16. Event rate estimation II Solid angle: 40 o <θ<50 o, -20 o <ϕ<20 o Cosmic ray flux: measured by IceTop-73, arXiv:1307.3795 Energy range: 10 16.5 -10 18 eV Event rate/dayEvent rate / year D=50m23.98.7e3 D=100m23.78.7e3 D=150m23.48.5e3 D=200m22.78.3e3 D=300m17.86.5e3 D=600m8.53.1e3

17. Event rate estimation III Solid angle: 50 o <θ<60 o, -20 o <ϕ<20 o Cosmic ray flux: measured by IceTop-73, arXiv:1307.3795 Energy range: 10 16.5 -10 18 eV Event rate/dayEvent rate / year D=50m27.51.0e4 D=100m26.89.8e3 D=150m25.39.2e3 D=200m22.58.2e3 D=300m13.65.0e3 D=600m5.42.0e3

18. Event rate estimation IV Solid angle: 60 o <θ<70 o, -20 o <ϕ<20 o Cosmic ray flux: measured by IceTop-73, arXiv:1307.3795 Energy range: 10 16.5 -10 18 eV Event rate/dayEvent rate / year D=50m28.91.1e4 D=100m25.49.3e3 D=150m17.76.5e3 D=200m10.83.9e3 D=300m3.71.4e3 D=600m1.14.0e2

19. Summary Detector simulation &rec. software are developed for GRAND prototype scintillator array based on Tibet AS array. Preliminary performance of GRAND prototype is obtained: core rec. resolution, angular resolution, effective area, event rate…. We have to consider other layouts, or larger set of scintillators to reach a much better detection efficiency above 10 16.5 eV. We still have to cross check the simulation, because of …

20. One Problem ： A larger detection probability with tilt = 0°, which is not understood Solid angle: 40 o <θ<70 o, -20 o <ϕ<20 o

21. Thanks for your attention!

22. Performance of Corsika Events

23. Different Single Particle Peak (SPP) definition. 5.0MeV 7.11 MeV

24. Algorithm of detector MC Geant4 can handle so much 2 nd particles at one time. One primary event is splitted to many small piece ( 1piece = 390 * 10 2 nd particles ） Repeat reading 2 nd events, need a lot of CPU time! header 2 nd particles ….. end

25. Trigger &Rec. efficiency

26. Performance of Tibet Asgamma simulation package:G4asg Based on Geant4, surface array + underground muon detector

27. Single particle detection efficiency & its spectrum Threshold of EM particles: 1MeV->5MeV:

28. arXiv:1307.3795