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Moon shadow analysis -- Using ARGO experiment

Wang Bo, Zhang Yi, Zhang Jianli, Guo Yiqing, Hu Hongbo. Apri. 27 2008 for NanJing Meeting. wangb@ihep.ac.cn. Moon shadow analysis -- Using ARGO experiment. OUTLINE. 1. Why to study Moon shadow? 2. Experiment introduction . 3. Data and Reconstruction. 4. Moon shadow Analysis

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Moon shadow analysis -- Using ARGO experiment

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  1. Wang Bo, Zhang Yi, Zhang Jianli, Guo Yiqing, Hu Hongbo Apri. 27 2008 for NanJing Meeting wangb@ihep.ac.cn Moon shadow analysis--Using ARGO experiment

  2. OUTLINE 1. Why to study Moon shadow? 2. Experiment introduction. 3. Data and Reconstruction. 4. Moon shadow Analysis 5. Observation of the steel beam shadow 6. Summary

  3. Why to study the Moon Shadow The Earth-Moon as a spectrometer Cosmic Rays are blocked by the Moon Deficit of cosmic rays in the direction of the Moon • Size of the deficit:angular resolution of the detector • Position of the deficit: pointing error • Geomagnetic field:energy calibration • Geomagnetic field: proton and antiproton ratio • monitor the long-term stability.

  4. YBJ Experiment In Tibet Tibet Asgamma ARGO Astrophysical Radiation with Ground-based Observatory Longitude 90° 31’ 50” East Latitude 30° 06’ 38” North 90 Km North from Lhasa (Tibet) 4300 m above the sea level large field of view (> 2 sr) • high duty cycle • full coverage of RPC • high altitude (4300m a.s.l) • energy threshold: ~100GeV • high granularity imaging of the shower front by a uniform carpet of RPC

  5. Experimental Hall Cluster RPC chamber

  6. Detector Layout 12 RPC =1 Cluster ( 5.7  7.6 m2 ) 8 Strips = 1 Pad (56  62 cm2) 99 m 74 m 10 Pads = 1 RPC (2.80  1.25 m2) 78 m 111 m Layer of RPC covering 5600 m2 (  92% active surface) + 0.5 cm lead converter + sampling guard-ring time resolution ~ 1 ns space resolution = 6.5  62 cm2 (1 strip) Central Carpet: 130 Clusters, 1560 RPCs, 124800 Strips

  7. EAS space-time structure High space-time granularity + Full coverage technique + High altitude a unique way to study Extensive Air Showers

  8. Event reconstruction Shower front ~20ns axis  curvature ~2ns t  core L EAS phenomenology Event Rate:~4000HZ atmosphere Detector array

  9. Reconstruction Event Rate:~4000HZ Core Reconstruction: Liklihood Direction reconstruction: Planar fit+Conical correction, (Robust Method) Angular resolution:

  10. Data Data: (Oct. 30, 2006~May. 31 2007) Moon time in each month: 2007_05: 84.3(hours) 2007_04: 95.6 (hours) 2007_03: 99.8(hours) 2007_02: 77.6(hours) 2007_01: 110.5(hours) 2006_12: 95.9(hours) 2006_11: 112.8(hours) Event Rate:~4000HZ

  11. Data Analysis --Equi-Zenith angle method 1.Selection of data time: Oct. 30, 2006~May. 31 2007 2.Event Cut: 1.)Zenith angle < 50degrees 2.) Core position < 1500m. 3.) sigma<200. 4.)nHit cut Eliminate various detecting effects, such as changes in pressure and temperature.

  12. Moonshadow for low energy and high energy's comic ray events For Low energy Cosmic Rays For High energy Cosmic Rays

  13. Obtain Center of Moon shadow System error Using Moon shadow of Different energy 1. N-S pointing error:Moon shadow center of N-S direction: N-S displacement of the Moon shadow center are unaffected due to the ~0 of the geomagnetic field in E-W . 2.E-W pointing error: .It is difficult to determine the right position of moon shadow in low nhit due to geomagnetic field influence.. but we can using Moon shadow center of high nHit,For example, nHit>2000 Explanation of Projection Analysis to obtain Moon Shadow position ～Corresponding to MC Optimized distance

  14. N-S direction system pointing error Different nHit ranges: 0~60, 60~100, 100~200, 200~500, 500~2000, 2000~ N-S direction shift for different nHit system pointing error 0.22 in N-S direction

  15. W-E direction system pointing error :~0.027 with nHit>2000 HIGHT nHits>2000 The system pointing error in E-W0.03!?

  16. West-East shift of the center of Moon shadow Using the characteristic: Energy calibration Proton/antiproton ratio Next work: 1. MC confirm to absolutely calibrate the cosmic ray's energy 2. Increase the data to analyze the Proton/antiproton W-E direction shift for different nHit If for proton: 1.6deg/E(Tev) 1.6deg/E = 38.6×(nHit) -0.92 E=0.0415×(nHit)0.92

  17. Fig1 Fig2 20cm 8mm 6mm 35cm Fig3 The shadow along W-E direction Fig1.The map of normalized hit number ratio , using about ten days’ data taken from tape681 to tape690. Fig2 The radio map selecting the normalized radio 3 times the deviation less than the mean value. Fig3 The radio map selecting the normalized radio 3 times the deviation less than the mean value. So the W-E direction steel beam Shadows are observed cleary.

  18. Fig2 Fig1 6mm 22cm 2.5mm Fig3 The shadow along S-N direction Fig1.The map of normalized hit number ratio ,using about ten days’ data taken from tape681 to tape690. Fig2 The radio map selecting the normalized radio 3 times the deviation less than the mean value. Fig3 The radio map selecting the normalized radio 3 times the deviation less than the mean value. So the S-N direction steel beam Shadows are also observed. Because the steel beam size, it is not as clear as W-E direction.

  19. Summary 1. ARGO-YBJ is almost completed, and runing steadily. Data shows good performance in shower reconstruction 2. Very clear Moon shadow is obtained using ARGO-YBJ data 3. By moon shadow analysis, the system error is about 0.22degrees in S-N direction and 0.03degrees in W-E direction. 4. The Steel beam Shadow is clearly observed Using ARGO data. 5. Interesting physics results are coming. For example: Mrk421, Crab and so on

  20. Total error:~0.2 So system pointing error: Pointing error N-S direction:0.22 Pointing error W-S direction:0.03

  21. Azimuth angle distribution and N-S direction system error? Rotating 0.2Deg. Considering the geomagnetic field, etc. So shift a certian degrees(0.2?) of Zenith direction or characteristic plane(with its normal direction to zenith) Rotating 0.2Deg uniform??

  22. 1.585/1.177*2.6=3.5 Optimum angular radius(Gaussian function) 1.585/1.177*2.2=3.1

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