Download TREND_MCstudy_20141209Fengzhaoyang

MC study of TREND Ground array
Feng Zhaoyang
Institute of High Energy Physics,CAS
2014.12.08
What have been done after the last
meeting？
1, One small bug when estimating particle is
found and corrected.
2, The MC study with 0.5 cm lead on the top
of the scintillator is finished.
All the analysis is repeated at the reconstruction
level again.
Content
• Detector configuration
• Corsika level study
• Detector simulation level study
• Reconstruction level study
 effective area
Core resolution
Angular resolution
• Discussion
Giant Array setup
Giant Array setup: 949 detectors,
distance:50m
The air is vacuum,
To save the CPU time
Giant Array setup
Sdet=600m*3600m=2.16km2
D=50m,949 detectors,
D=200m, 76 detectors,
D=100m, 259 detectors,
D=300m, 39 detectors,
D=150m, 125 detectors,
D=300m or 600m, 21
detectors,
• Detector configuration
• Corsika level study
• Detector simulation level study
• Reconstruction level study
 effective area
Core resolution
Angular resolution
• Discussion
MC data sample
•
•
•
•
•
Energy:1016.5-1018eV
Azimuth:-20-20 degree
Zenith:40-70 degree
Slope:-2.0, reweight to -3.0
~2000 corsika events
Noe: the disk size is 3TB, considering we repeat to
read them 100*2*2 times,
in total the data size to read and do the detector
MC is 1200 TB, huge CPU time.
Performance of Corsika Events
Huge numbers of 2nd particles!
All Events
zen=50-60 degree
zen=40-50 degree
zen=60-70 degree
• Detector configuration
• Corsika level study
• Detector simulation level study
• Reconstruction level study
 effective area
Core resolution
Angular resolution
• Discussion
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
Detector MC & data rec. setup
• Detector: fact to zenith (dθ=0o) or zenith=50
degree (dθ=50o)
• 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
• Tstart: at first hit
MC Core position distribution:
Smc=800m*3800m=3.04km2
Single particle peak
1 GeV VEM
2nd particles(dθ=0o)
particle numbers and time
saturation
threshold
• Detector configuration
• Corsika level study
• Detector simulation level study
• Reconstruction level study
 effective area
Core resolution
Angular resolution
• Discussion
Rec. Core position
Dtheta=0, D=50m
nhit （all data sample）
Trigger &Rec. efficiency
Effective area: all event, zen=40-70 degree
Effective area: zen=40-50 degree
Effective area: zen=50-60 degree
Effective area: zen=60-70 degree
Fluctuation!
Core reconstruction errors
angular resolution
• Detector configuration
• Corsika level study
• Detector simulation level study
• Reconstruction level study
 effective area
Core resolution
Angular resolution
• Discussion
How to understand the abnormal performance？
1)The role of lead ?
2)Geometry?
sec(40o)=1.30
sec(50o)=1.55
sec(60o)=2.0
sec(70o)=2.92
Look back the 2nd particles in Corsika
level： Nem VS Nμ
All Events
zen=50-60 degree
zen=40-50 degree
zen=60-70 degree
Gama
Electron
Muon
Do the MC without Lead！
nhit
Trigger &Rec. efficiency
Effective area: all event, zen=40-70 degree
Effective area: zen=40-50 degree
Effective area: zen=50-60 degree
Effective area: zen=60-70 degree
Core reconstruction errors
angular resolution
How to understand the abnormal performance？
1)The role of lead ? X
2)Geometry? How to considering the geometry
effect?
sec(40o)=1.30
sec(50o)=1.55
sec(60o)=2.0
sec(70o)=2.92
Summary
• MC &rec. software are developed for TREND ground
array based on Tibet array.
• Different detector configurations are compared.
• Effective area, core rec. resolution, angular resolution
are studied with & without 0.5 cm Lead.
• The effect of the 0.5 cm Lead can’t explain the the
abnormal performance of effective area.
• No full understanding of the results now.
• The effect of geometry?
sec(40o)=1.30
sec(50o)=1.55
sec(60o)=2.0
sec(70o)=2.92
Energy spectral index correction of CRss
 The performances of Air Shower(AS) Array is depended on the
energy spectrum index of the sources
 MC data sample is with an index of -2.0
 Other index (β) ：-2.2， -2.4， -2.6，-2.8，-3.0 are be considered
by reweight the events
 In order to keep the size of MC data samples same， the weight
can be calculated ：
Nall
sim =𝛼1
∞
∞
−2 d𝐸 = 𝛼
𝛽
E
E
d𝐸
2
min
min
Esim
Esim
∞
𝛽
min
E−2 d𝐸
Esim
𝛼2 E
−2−𝛽 2+𝛽
2+𝛽
𝜔(𝐸) =
=
E
=
−(1
+
𝛽）E
∞
min E
𝛽
𝛼1 E−2
E d𝐸
Emin
sim
Some number
• Atmospheric depth：1022g/cm2 (sea level)
752g/cm2 (2650m)
sec(40o)=1.30
*752=977g/cm2
sec(50o)=1.55
*752=1165g/cm2
sec(60o)=2.0
*752=1500g/cm2
sec(70o)=2.92
*752=2.196g/cm2
Direction reconstruction
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   i [lxi  myi  nzi  c(ti  to )]
2
2
i
i
i 
 i
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