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Observation of TeV Gamma Rayswith the Tibet Air Shower Array

and Future Prospects

ICRR, University of Tokyo

Kazumasa Kawata

For the Tibet AS Collaboration

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M.Amenomori(1), X.J.Bi(2), D.Chen(3), S.W.Cui(4), Danzengluobu(5), L.K.Ding(2), X.H.Ding(5), C.Fan(6), C.F.Feng(6), Zhaoyang Feng(2), Z.Y.Feng(7), X.Y.Gao(8), Q.X.Geng(8), H.W.Guo(5), H.H.He(2), M.He(6), K.Hibino(9), N.Hotta(10), Haibing Hu(5), H.B.Hu(2), J.Huang(2,3), Q.Huang(7), H.Y.Jia(7), F.Kajino(11), K.Kasahara(12), Y.Katayose(13), C.Kato(14), K.Kawata(3), Labaciren(5), G.M.Le(15), A.F.Li(6), J.Y.Li(6), Y.-Q.Lou(16), H.Lu(2), S.L.Lu(2), X.R.Meng(5), K.Mizutani(12,17), J.Mu(8), K.Munakata(14), A.Nagai(18), H.Nanjo(1), M.Nishizawa(19), M.Ohnishi(3), I.Ohta(20), T.Ouchi(9), S.Ozawa(12), J.R.Ren(2), T.Saito(21), T.Y.Saito(22), M.Sakata(11), T.K.Sako(3), M.Shibata(13), A.Shiomi(23), T.Shirai(9), H.Sugimoto(24), M.Takita(3), Y.H.Tan(2), N.Tateyama(9), S.Torii(12), H.Tsuchiya(25), S.Udo(12), B.Wang(2), H.Wang(2), X.Wang(3), Y.Wang(2), Y.G.Wang(6), H.R.Wu(2), L.Xue(6), Y.Yamamoto(11), C.T.Yan(3),

X.C.Yang(8), S.Yasue(26), Z.H.Ye(15), G.C.Yu(7), A.F.Yuan(5), T.Yuda(9), H.M.Zhang(2), J.L.Zhang(2), N.J.Zhang(6), X.Y.Zhang(6), Y.Zhang(2), YiZhang(2), Zhaxisangzhu(5) and X.X.Zhou(7)

The Tibet AS Collaboration

(1) Dep. of Phys., Hirosaki Univ., Hirosaki, Japan (2) Key Lab. of Particle Astrophys., IHEP, CAS, Beijing, China (3) ICRR., Univ. of Tokyo, Kashiwa, Japan (4) Dep. of Phys., Hebei Normal Univ., Shijiazhuang, China (5) Dep. of Math. and Phys., Tibet Univ., Lhasa, China (6) Dep. of Phys., Shandong Univ., Jinan, China (7) Inst. of Modern Phys., South West Jiaotong Univ., Chengdu, China (8) Dep. of Phys., Yunnan Univ., Kunming, China (9) Fac. of Eng., Kanagawa Univ, Yokohama, Japan(10) Fac. f of Educ., Utsunomiya Univ., Utsunomiya, Japan(11) Dep of Phys., Konan Univ., Kobe, Japan(12) Advanced Research Inst. for Sci. and Engin., Waseda Univ., Tokyo, Japan(13) Fac. of Eng., Yokohama National Univ., Yokohama , Japan

(14) Dep. of Phys., Shinshu Univ., Matsumoto, Japan(15) Center of Space Sci. and Application Research, CAS, Beijing, China(16) Phys. Dep. and Tsinghua Center for Astrophys., Tsinghua Univ., Beijing, China (17) Dep. of Phys., Saitama Univ., Saitama, Japan(18) Advanced Media Network Center, Utsunomiya University, Utsunomiya, Japan(19) National Inst. of Info., Tokyo, Japan(20) Sakushin Gakuin University, Utsunomiya, Japan(21) Tokyo Metropolitan College of Industrial Tech., Tokyo, Japan(22) Max-Planck-Institut fuer Physik, Muenchen, Germany (23) College of Industrial Technology, Nihon University, Narashino, Japan(24) Shonan Inst. of Tech., Fujisawa, Japan(25) RIKEN, Wako 351-0198, Japan(26) School of General Educ.,Shinshu Univ., Matsumoto, Japan

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Tibet-III Air Shower (AS) Array

Number of Scinti. Det. 0.5 m2 x 789 Effective Area for AS ~37,000 m2

Energy region ~TeV - 100 PeV Angular Resolution ~0.4 @10 TeV (Gamma rays) ~0.2 @100 TeV Energy Resolution ~70% @10 TeV (Gamma rays) ~40% @100TeV F.O.V. ~2 sr

4,300 m a.s.l. (606 g/cm2)

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Constant fitting-0.0034o 0.011o+

Systematic pointing error < 0.01o

Absolute EnergyScale error –4.4% +- 7.9%stat +- 8%sys

Energy dependence ofDisplacementsCaused by Geomagnetic field

Verification Absolute energy scale Angular resolution Pointing error

Cosmic Ray Energy Calib. by the Moon’ Shadow

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Energy Spectrum of the Crab Nebula

90%CL

Centered atCrab position

ICRC2007, MexicoSubmitted to ApJ

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0 360R.A. (deg)

Amenomori et al, Science, 314, 439 (2006)

Cygnus region

Tail-In Loss-Cone

MGRO J2019+37 (800 mCrabs @ 20TeV)

MGRO J2031+41 (900 mCrabs @ 20TeV)Cygnus region

Cosmic-ray/Gamma-ray anisotropy

Anisotropy map

0.9 deg. radius

A.A.Abdo et al., ApJ, 664 L91 (2007)

Window size: 5 deg. radius

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Future Plan

Tibet muon detector (MD) project

& Prototype MD in Tibet

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MAGICVERITAS

HESS

Present Status of the TeV Ray Astronomy

90%CL

Antoni et al, ApJ, 608, 865 (2004)Atkins et al, ApJ, 608, 680 (2004)Amenomori et al, ApJ, 633, 1005 (2005)

McKay et al, ApJ, 417, 742 (1993)

Improve sensitivity to gamma raysin 100 TeV region (10 – 1000 TeV)

Number of muons in air showers（ <100m from shower core, 4300m a.s.l. ）

100TeV proton~50

100TeV gamma~1

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Tibet Muon Detector (MD) Array

7.2m x 7.2m x 1.5m depth 　 Water cell20”PMT x 2 　 (HAMAMATSU R3600)Underground 2.5m ( ~515g/cm2~19X0)

Material: Concrete pool White paint　　　　 192 detctors　　　　　　　　 Total 　 ~10,000 m2

We will count the number of muons by an air shower triggerFull Monte Carlo Simulation

extends AS to~83,000m2

MD ~10,000m2

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Muon Number vs. Shower Size (Simulation) : Sum of particle density by all scintillation det. >> Shower SizeNPE:Sum of photoelectrons by all muon det. >> Muon number　　　 (Threshold of ＭＤ　 NPE >10 p.e.)

( Shower Size)

NP

E(

Muo

n N

um

ber)

10TeV 100TeV 1000TeV

20%50%80%

(gamma)

0

(~10TeV)

0

(~100TeV)

Gamma

Gamma

CR

CR

99.8%Rejection

~99.99%Rejection

CR

Gamma

0

NPE( Muon Number)

NPE( Muon Number)

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Future Sensitivity （ 5 or 10 events）

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52m2x 2

Prototype Muon Detector in Tibet

Construction starts from Sep. 2007Data taking starts from Dec. 2007

• Construction feasibility in Tibet• Development of MC simulation• observation above several 100 TeV

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September, 2007 – Start construction

Cement Concrete mixer

On Sep. 1st, start construction Sep. 4th - finish almost digging

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Sep. 13th - finish substructure Oct. 5th – Steel bars, forms

Oct. 15th – concrete works Oct 20th – remove forms

September ~ October　

1516 November, 2007 　 Prototype Muon Detector

16Prototype Muon Detector after covering

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White paint

Pouring very clear well-water Filled up water 1.5 m in depth

Inside of the MD 　

Clear underground water from a nearby well

20”PMT x 3:(Normal gain x 2, 1/100 gain x 1 for test)

Water depth : 1.5 m

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Summary Tibet MD Project ~83,000 m2 Air Shower array + ~10,000 m2 Water Cerenkov Muon Detector array (~7M US$) Gamma-ray astrophysics in the 100 TeV region (10 – 1000 TeV) – Diffuse and point-like sources – Study on the maximum energy of gamma rays – Origin and acceleration limit of cosmic rays (p0 decay /IC)

Sensitivity (based on detailed simulation) – BG rejection power 99.8% rejected (50% gamma-ray events retained) @ 10 TeV 99.99% rejected (83% gamma-ray events retained) @ 100 TeV – Improve by an order of magnitude compared with the present Tibet AS array >~10 TeV Surpass existing IACTs >~40 TeV Surpass future plans of IACTs

Prototype MD (52 m2 x 2 cells) – successfully completed – data taking started in Dec. 2007 – in good agreement with MC simulation