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A Northern Sky Survey for Both TeV CR anisotropy and -ray Sources with Tibet Air Shower Array Hongbo Hu (huhb@ihep.ac.cn) For Tibet AS collaboration The Tibet AS-gamma Experiment ; Two Analyses Methods; Preliminary Results; Discussion and Conclusions. 2004.8 Institute of High Energy Physics
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YangBaJing Observatory and its Experiments –Located at an elevation of 4300 m (Yangbajing, China) –Atmospheric depth 606g/cm 2 –Wide field of view –High duty cycle (>90%) ARGO Experimental Hall ASγ air shower array
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3,600m 2 (in area) Tibet-HD Tibet array: ~250 x 250 m 2 HD: 60 x 60m 2 Tibet-III: ~150x150 m 2 Tibet-III Tibet-HD Operation Time Live Time Selected Events Mode Energy Resolution (@3TeV ) Area Tibet- HD 1997.2~1999.9555.9 days1.5×10 9 ~3TeV0.9 o 3600m 2 Tibet-III 1999.11~2001.5456.8 days5.5×10 9 ~3TeV0.9 o 22050m 2 Tibet Air Shower Array
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Method I -----Equal-zenith method Zenith North Pole On-source Off-source 6.8°< zenith <40.0° Making use of the fact that events are uniformly distributed within equal-zenith belt; 10 off-source windows (side band) are chosen to estimate BKG.
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Equal ! Method II----Global CR. Intensity fitting method Zenith Equal ? All sky survey based on an anisotropy correction of relative CR intensity, which is obtained by LSQ fitting for the data in each of equal zenith ring
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DEC RA. Duldig, PASA,Vol18,No.1 ~ ±0.1% Large scale anisotropy (by method II) I - 1
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Large scale anisotropy of diff. Data sample Anisotropy measurements agree with each other from using HD detector or TibetIII detector, means small systematic effects.
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Large scale anisotropy correction σ=1.258 Before subtraction After subtraction σ=1.018
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Sky Map NO.R.A.(˚)DEC(˚)Signifi(σ)NO.R.A.(˚) Signifi(σ) 138.913.94.213221.632.84.4 239.231.94.014253.258.84.1 366.812.34.115278.338.44.3 4*70.111.94.616*286.75.64.6 570.418.04.317301.78.74.1 671.947.54.018*304.336.74.2 778.918.94.219309.549.14.4 8*83.321.85.020309.939.64.5 9*88.830.25.621318.040.64.7 10*115.317.54.122330.350.34.0 11*165.538.45.323333.034.74.0 12199.929.74.024336.912.74.0 Crab Mrk421 List of sky cells with clustered directions (24)having statistic significance larger than 4.0σ. (88.8,30.2)
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Discussion Hot point I ---evt. No.9 (88.8°, 30.2 °) SNR counterpart G179.0+2.6, RA : 88.42 DEC :31.08 Size (/arc min): 70 Type: Shell 3.7σ 4.5 σ 5.6 σ b=+5˚ b=0˚ b=-5˚ b=+5˚ b=0˚ b=-5˚
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Hot Point II - - No.18(304.3 °, 36.7 °), No19(309.9 °, 39.6 °) Amenomori,in Proc.27 th ICRC,2315. Observed 4.15 σ; S.W. Cui and C.T. Yan, in Proc. 28 th ICRC, 2315. Observed 4 σ; EGRET counterpart 3EG J2016+3657 RA :304.008 DEC : 37.2 Milagro (306.6,38.9) 4.2 σ (Atkins,R., et al 2004, ApJ, 608,680) ~0 σ 4.2 σ b=+5˚ b=0˚ b=-5˚ b=+5˚ b=0˚ b=-5˚ b=+5˚ b=0˚ b=-5˚ 3.9 σ 4.4 σ 4.5 σ 2.9 σ
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Up flux limit (by method I) (30 degree of declination related to YBJ zenith direction)
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Conclusions Large scale anisotropy of CR. intensity with a magnitude about 0.1% are observed in two dimensions in TeV energy range. Crab and Mrk421 are detected with 5 σ level. No other significant point source is found, and an upper-flux limit curve is given
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