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
wangb@ihep.ac.cn
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
Why to study the Moon ShadowWhy to study the Moon Shadow
Cosmic Rays are blocked bythe Moon
Deficit of cosmic rays in thedirection of the Moon
angularresolution of the detectorSize of the deficit: angularresolution of the detector
pointingerrorPosition of the deficit: pointingerror
Geomagnetic field: energycalibrationGeomagnetic field: energycalibration
Geomagnetic field: proton andantiproton ratioGeomagnetic field: proton andantiproton ratio
monitor the long-term stability.monitor the long-term stability.
The Earth-Moon as a spectrometer
Longitude 90° 31’ 50” East
Latitude 30° 06’ 38” North
90 Km North from Lhasa(Tibet)
4300 m above the sea level
Astrophysical Radiation with
Ground-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 auniform carpet of RPC
Experimental Hall
RPC chamber
Cluster
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 ns
space resolution = 6.5 62 cm2 (1 strip)
Central Carpet:
130 Clusters, 1560 RPCs, 124800 Strips
EAS space-time structureEAS space-time structure
High space-time granularity
+ Full coverage technique
+ High altitude
a unique way to study Extensive Air Showers
Shower frontShower front
axisaxis
curvaturecurvature
corecore
~20ns~20ns
~2ns~2ns
EAS phenomenologyEAS phenomenology
L
tt
atmosphere
DetectorarrayDetectorarray
Event reconstruction
Event Rate:~4000HZ
ReconstructionReconstruction
Angular resolution:
Core Reconstruction: LiklihoodCore Reconstruction: Liklihood
Direction reconstruction: Planar fit+Conical correction,Direction reconstruction: Planar fit+Conical correction,
(Robust Method)(Robust Method)
Event Rate:~4000HZ
DataData
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
Data AnalysisData 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.
Moonshadow for low energy Moon shadow for low energy
and high energy's comic ray eventsand high energy's comic ray events
For High energy Cosmic Rays
For Low energy Cosmic Rays
System error Using Moon shadow of Different energySystem 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 fieldin E-W .
2.E-W pointing error:
.It is difficult to determine the right position of moon shadow in low nhit due to geomagnetic fieldinfluence.. but we can using Moon shadow center of high nHit,For example, nHit>2000
Explanation of Projection Analysis toobtain Moon Shadow position
～Corresponding to
MC Optimized distance
Obtain Center of Moon shadowObtain Center of Moon shadow
N-S direction system pointing error
system pointing error
0.22 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~
HIGHT nHits>2000
W-E direction system pointing error
:~0.027 with nHit>2000
The system pointing error in E-W 0.03!?
Using the characteristic:
Energy calibration Energy 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
The shadow along W-E direction
20cm
35cm
8mm
6mm
Fig1
Fig2
Fig3
Fig1.The map of normalized hit number ratio , using about ten days’ data takenfrom tape681 to tape690.
Fig2 The radio map selecting the normalized radio 3 times the deviation lessthan the mean value.
Fig3 The radio map selecting the normalized radio 3 times the deviation lessthan the mean value.
So the W-E direction steel beam
Shadows are observed cleary.
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 lessthan the mean value.
Fig3 The radio map selecting the normalized radio 3 times the deviation lessthan the mean value.
So the S-N direction steel beam
Shadows are also observed. Because thesteel beam size, it is not as clear as W-Edirection.
6mm
22cm
2.5mm
SummarySummary
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
So system pointing error:
Pointing error N-S direction:0.22
Pointing error W-S direction:0.03
Total error:~0.2
Azimuth angle distribution and N-S direction system error?
So shift a certian degrees(0.2?) of Zenithdirection or characteristic plane(with itsnormal direction to zenith)
Considering the geomagnetic field, etc.
uniform??
Rotating 0.2Deg.
Rotating 0.2Deg
Optimum angular radius(Gaussianfunction)
1.585/1.177*2.6=3.5
1.585/1.177*2.2=3.1
