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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 lxi myi nzi c(ti to ) i [lxi myi nzi c(ti to )] 2 2 i i i i i