Preliminary MC study on the GRAND prototype scintillator array

Feng ZhaoyangInstitute of High Energy Physics, CAS, China

GRAND Workshop, Paris, Feb. 015

The main challenge of the GRAND project• huge GRAND terrestical background event rate:

TREND50:~30kEvents/day/km²(~1.5 107 valid coincs

in 317 DAQ days)

TREND50 → GRAND:

Antenna density /25Size x40000

GRAND:<15 events/day/km²

(safe estimate)3 108 evts/year over full array

Target rejection factor: 109

Expected n event rate:0-100 events/year

1.5 107 events

7500 events

TREND-50 event multiplicity

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.

Air Shower data sample

• 2000 proton events (full CORSIKA simulation, v7.400)

• Energy:1016.5-1018eV• Zenith angle:40-70 degrees• Azimuth angle:-20-20 degrees• Energy spectrum index:-2.0, reweight to -3.0

2nd particles content

All Events Zenith angle=40-50 degrees

Zenith angle=50-60 degrees Zenith angle=60-70 degrees

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 prototype Grant Array

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

6 configurations of Giant Array Sdet=600m*3600m=2.16km2

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 protoD=300m, 39 detectors,

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

particle numbers and time profile

threshold

saturation

Number of fired detectors

Rec. Core position

i ii

corei

i

xX

i ii

corei

i

yY

ki i

Angular Resolution

Event rate estimation ISolid angle: 40o<θ<70o, -20o<ϕ<20o

Cosmic ray flux: measured by IceTop-73, arXiv:1307.3795Energy range: 1016.5-1018eV

Event rate/day Event rate / year

D=50m 80.8 2.9e4

D=100m 77.4 2.8e4

D=150m 70.1 2.6e4

D=200m 61.5 2.2e4

D=300m 40.4 1.5e4

D=600m 17.4 6.4e3

Very preliminary!

Event rate estimation IISolid angle: 40o<θ<50o, -20o<ϕ<20o

Cosmic ray flux: measured by IceTop-73, arXiv:1307.3795Energy range: 1016.5-1018eV

Event rate/day Event rate / year

D=50m 23.9 8.7e3

D=100m 23.7 8.7e3

D=150m 23.4 8.5e3

D=200m 22.7 8.3e3

D=300m 17.8 6.5e3

D=600m 8.5 3.1e3

Very preliminary!

Event rate estimation IIISolid angle: 50o<θ<60o, -20o<ϕ<20o

Cosmic ray flux: measured by IceTop-73, arXiv:1307.3795Energy range: 1016.5-1018eV

Event rate/day Event rate / year

D=50m 27.5 1.0e4

D=100m 26.8 9.8e3

D=150m 25.3 9.2e3

D=200m 22.5 8.2e3

D=300m 13.6 5.0e3

D=600m 5.4 2.0e3

Very preliminary!

Event rate estimation IVSolid angle: 60o<θ<70o, -20o<ϕ<20o

Cosmic ray flux: measured by IceTop-73, arXiv:1307.3795Energy range: 1016.5-1018eV

Event rate/day Event rate / year

D=50m 28.9 1.1e4

D=100m 25.4 9.3e3

D=150m 17.7 6.5e3

D=200m 10.8 3.9e3

D=300m 3.7 1.4e3

D=600m 1.1 4.0e2

Very preliminary!

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 1016.5eV.

• We still have to cross check the simulation, because of …

One Problem ：A larger detection probability with tilt = 0°, which is not understood

Solid angle: 40o<θ<70o, -20o<ϕ<20o

Thanks for your attention!

Performance of Corsika Events

Different Single Particle Peak (SPP) definition.

5.0MeV

7.11 MeV

Algorithm of detector MC• Geant4 can handle so much 2nd particles at

one time.• One primary event is splitted to many small

piece ( 1piece = 390 * 10 2nd particles ）• Repeat reading 2nd events, need a lot of CPU

time!

header

2nd particles…..

end

Trigger &Rec. efficiency

Performance of Tibet Asgamma simulation package:G4asg

Based on Geant4, surface array +

underground muon detector

Single particle detection efficiency& its spectrum

Threshold of EM particles: 1MeV->5MeV:

arXiv:1307.3795