MC study of TREND Ground array Feng Zhaoyang Institute of High Energy Physics,CAS

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 S det =600m*3600m=2.16km 2 D=50m,949 detectors, D=100m, 259 detectors, D=150m, 125 detectors, D=200m, 76 detectors, D=300m or 600m, 21 detectors, D=300m, 39 detectors,

Detector configuration Corsika level study Detector simulation level study Reconstruction level study  effective area  Core resolution  Angular resolution Discussion

MC data sample Energy: eV Azimuth: 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 2 nd particles! All Events zen=40-50 degree zen=50-60 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 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

Detector MC & data rec. setup Detector: fact to zenith (dθ=0 o ) or zenith=50 degree (dθ=50 o ) 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: S mc =800m*3800m=3.04km 2

Single particle peak 1 GeV VEM 2 nd particles(dθ=0 o )

particle numbers and time threshold saturation

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(40 o )=1.30 sec(50 o )=1.55 sec(60 o )=2.0 sec(70 o )=2.92

Look back the 2 nd particles in Corsika level ： Nem VS Nμ All Events zen=40-50 degree zen=50-60 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(40 o )=1.30 sec(50 o )=1.55 sec(60 o )=2.0 sec(70 o )=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(40 o )=1.30 sec(50 o )=1.55 sec(60 o )=2.0 sec(70 o )=2.92

Energy spectral index correction of CRss

Some number Atmospheric depth ： 1022g/cm 2 (sea level) 752g/cm 2 (2650m) sec(40 o )=1.30 *752=977g/cm 2 sec(50 o )=1.55 *752=1165g/cm 2 sec(60 o )=2.0 *752=1500g/cm 2 sec(70 o )=2.92 *752=2.196g/cm 2

Direction reconstruction