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Moon shadow analysis --Using ARGO experiment
Wang Bo, Zhang Yi, Zhang Jianli, Guo Yiqing, Hu HongboWang Bo, Zhang Yi, Zhang Jianli, Guo Yiqing, Hu Hongbo
Apri. 27 2008 for NanJing Meeting [email protected]
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OUTLINE1. Why to study Moon shadow?
2. Experiment introduction.3. Data and Reconstruction.4. Moon shadow Analysis5. Observation of the steel beam shadow6. Summary
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Why to study the Moon Why to study the Moon ShadowShadow
Cosmic Rays are blocked by the Moon
Deficit of cosmic rays in the direction of the Moon
Size of the deficit: angular angular resolution of the detectorresolution of the detector
Position of the deficit: pointing pointing errorerror
Geomagnetic field:Geomagnetic field: energy energy calibrationcalibration
Geomagnetic field: Geomagnetic field: proton proton and antiproton ratioand antiproton ratio
monitor the long-term monitor the long-term stability.stability.
The Earth-Moon as a spectrometer
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Longitude 90° 31’ 50” EastLatitude 30° 06’ 38” North
90 Km North from Lhasa (Tibet)
4300 m above the sea level
Astrophysical Radiation withGround-based Observatory
Tibet Asgamma ARGO
YBJ Experiment In TibetYBJ Experiment In Tibet
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
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Experimental Hall
RPC chamber
Cluster
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78 m
99 m
74 m
111 m
Detector Layout
10 Pads = 1 RPC (2.80 1.25 m2)
12 RPC =1 Cluster ( 5.7 7.6 m2 ) 8 Strips = 1 Pad
(56 62 cm2)
Layer of RPC covering 5600 m2
( 92% active surface)+ 0.5 cm lead converter+ sampling guard-ring
time resolution ~ 1 nsspace resolution = 6.5 62 cm2 (1 strip)
Central Carpet:130 Clusters, 1560 RPCs, 124800 Strips
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EAS space-time structureEAS space-time structureHigh space-time granularity+ Full coverage technique
+ High altitude
a unique way to study Extensive Air Showers
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Shower frontShower front
axisaxis
curvaturecurvature
corecore
~20ns~20ns
~2ns~2ns
EAS EAS phenomenologyphenomenology
L
tt
atmosphere
Detector Detector arrayarray
Event reconstructionEvent Rate:~4000HZ
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ReconstruReconstructionction
Angular resolution:
Core Reconstruction: Liklihood Core Reconstruction: Liklihood
Direction reconstruction: Planar fit+Conical correction, Direction reconstruction: Planar fit+Conical correction,
(Robust Method)(Robust Method)
Event Rate:~4000HZ
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Data Data
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)
Data: (Oct. 30, 2006~May. 31 2007)
Event Rate:~4000HZ
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Data Analysis Data Analysis 1.Selection of data time: 1.Selection of data time: Oct. 30, 2006~May. 31 2007 Oct. 30, 2006~May. 31 2007
2.Event Cut: 1.)Zenith angle < 50degrees 2.) Core position < 1500m. 3.) sigma<200. 4.)nHit cut
--Equi-Zenith angle method
Eliminate various detecting effects, such as changes in pressure and temperature.
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MoonMoon shadow for low energy shadow for low energy and high energy's comic ray eventsand high energy's comic ray events
For High energy Cosmic RaysFor Low energy Cosmic Rays
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System error Using Moon shadow of Different energy System error Using Moon shadow of Different energy
1. N-S pointing error:Moon shadow center of N-S direction: 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
Obtain Center of Moon shadowObtain Center of Moon shadow
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N-S direction system pointing error
system pointing error0.22 in N-S direction
N-S direction shift for different nHit
Different nHit ranges:Different nHit ranges: 0~60, 60~100, 100~200, 200~500, 500~2000, 2000~0~60, 60~100, 100~200, 200~500, 500~2000, 2000~
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HIGHT nHits>2000
W-E direction system pointing error :~0.027 with nHit>2000
The system pointing error in E-W 0.03!?
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Using the characteristic: Energy calibrationEnergy calibration Proton/antiproton ratio
If for proton: 1.6deg/E(Tev)
1.6deg/E = 38.6× (nHit) -0.92
E=0.0415×
(nHit)0.92
West-East shift of the center of Moon shadow
W-E direction shift for different nHit
Next work: 1. MC confirm to absolutely calibrate the cosmic ray's energy 2. Increase the data to analyze the Proton/antiproton
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The shadow along W-E direction
20cm
35cm
8mm6mm
Fig1 Fig2
Fig3 Fig1.The map of normalized hit number ratio , using about ten days’ data taken
from tape681 to tape690.
normalizediR ( 1)S
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.
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The shadow along S-N directionThe shadow along S-N direction
Fig1.The map of normalized hit number ratio ,using about ten days’ data taken from tape681 to tape690.
Fig1 Fig2
Fig3
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.
6mm
22cm 2.5mm
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SummarySummary1. 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
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So system pointing error:
Pointing error N-S direction:0.22
Pointing error W-S direction:0.03
Total error:~0.2
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Azimuth angle distribution and N-S direction system error?
So shift a certian degrees(0.2?) of Zenith
direction or characteristic plane(with its
normal direction to zenith)
Considering the geomagnetic field, etc.
uniform??
Rotating 0.2Deg.
Rotating 0.2Deg
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Optimum angular radius(Gaussian function)
1.585/1.177*2.6=3.5
1.585/1.177*2.2=3.1
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