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6 th IGPP meeting in Hawaii: March 21, 2007. Implication of the sidereal anisotropy of ~10 TeV (10 13 eV) cosmic ray intensity observed with the Tibet III air shower array.

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slide1

6th IGPP meeting in Hawaii: March 21, 2007

Implication of the sidereal anisotropy of~10 TeV (1013 eV) cosmic ray intensity observed with the Tibet III air shower array

M. Amenomori, S. Ayabe, X. J. Bi, D. Chen, S. W. Cui, Danzengluobu, L. K. Ding, X. H. Ding, C. F. Feng, Zhaoyang Feng, Z. Y. Feng, X. Y. Gao, Q. X. Geng, H. W. Guo, H. H. He, M. He, K. Hibino, N. Hotta, Haibing Hu, H. B. Hu, J. Huang, Q. Huang, H. Y. Jia, F. Kajino, K. Kasahara, Y. Katayose, C. Kato, K. Kawata, Labaciren,

G. M. Le, A. F. Li, J. Y. Li, Y.-Q. Lou, H. Lu, S. L. Lu, X. R. Meng, K. Mizutani, J. Mu, K. Munakata, A. Nagai,

H. Nanjo, M. Nishizawa, M. Ohnishi, I. Ohta, H. Onuma, T. Ouchi, S. Ozawa, J. R. Ren, T. Saito, T. Y. Saito,

M. Sakata, T. K. Sako, T. Sasaki, M. Shibata, A. Shiomi, T. Shirai, H. Sugimoto, M. Takita, Y. H. Tan,

N. Tateyama, S. Torii, H. Tsuchiya, S. Udo, B. Wang, H. Wang, X. Wang, Y. G. Wang, H. R. Wu, L. Xue,

Y. Yamamoto, C. T. Yan, X. C. Yang, S. Yasue, Z. H. Ye, G. C. Yu, A. F. Yuan, T. Yuda, H. M. Zhang, J. L. Zhang, N. J. Zhang, X. Y. Zhang, Y. Zhang, Yi Zhang, Zhaxisangzhu and X. X. Zhou

(Tibet AS collaboration)

85 people from 25 institutes in Japan and China

slide2

Cosmic ray observation with AS array

1ry g

Air shower array

Muon detector

Neutron monitor

  • Ground-based detectors measure byproducts of the interaction of primary cosmic rays (mostly protons) with Earth’s atmosphere.
  • AS array measures electromagnetic component in the cascade shower.
  • AS array also responds to 1ry g-rays,while the muon detector respond only to 1ry protons.
tibet as experiment

Yangbajing

~300 km

Lasa

Yangbajing

90゜53E, 30゜11N

4,300 m a.s.l.

Tibet ASγ experiment

Tibet@China

slide4

533 counters of 0.5 m2 each placed on a 7.5mx7.5m square grid

  • 22,050 m2 detection area

Achieved…

Highest statistics &

Best angular resolution

in multi-TeV region

  • trigger rate ~ 680 Hz
  • angular res. ~ 1

Resolving the incident direction

slide5

d=90o

d=30.1o

d=30.1o

AS flux varies for more than an order of magnitude with the zenith angle due to the different atmospheric depth.

Sidereal anisotropy on the spinning Earth

The zenith direction at Yanbajing is d=30.1o.

With the spin of Earth, the zenith direction travels along d=30.1o .

Fixed direction in the horizontal coordinate travels along d=const. for 360o of right ascension once every one sidereal day.

The average flux in each d-band is subtracted.

slide6

2D sky map of CR intensity by Tibet AS

“Normalized” intensity map

(5°x5° pixels)

declination (º)

Galactic plane

Geographical equator

Nose direction

90° < 120° < 180°

Bi-directional + Uni-directional

right ascension (º)

~120°

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

Significance map

slide7

LIC (Local Interstellar Cloud)

  • RL~ 0.01pc (for 10TeV p in 1mG)
  • Dist. to LIC boundary ~26km/s3000y =0.08pc
  • Probably within 1 m.f.p. in the weak
  • scattering regime

T~7000K, nH~0.1/cc

Ionization rate~0.52

H

Redfield & Linsky, ApJ, 535, 2000

2 pc

l=90

He

Lallement’s Interstellar B plane

(Lallement et al., Science, 307, 2005)

l=180

GC

lB= 205~240

bB= -38~-60

(or the opposite direction)

l=270

slide8

LIMC (Local Interstellar Magnetic Cloud) model

If cosmic ray density (n) is lower inside LIC than outside….

LIC

n High

Uni-directional flow

(Bxn)

n Low

G cloud

n

26 km/s

Bi-directional flow

Interstellar B

29 km/s

best fitting preliminary
Best-fitting (preliminary)

: Bi-directional

(DI/I)cal = a1cos1(a1,d1) : Uni-directional

+ a2+cos2 2(a2,d2) for 0 2/2

+ a2-cos2 2(a2, d2) for /2 2 

1, 2 : angles from reference axes

First choose orientations of reference axes…

a1,a2&d2 (or d1): (a2, d2)  (a1, d1)

then a1, a2+&a2-are given by linear LSM.

d.o.f. with 6 free parameters is large as…

90x360/(5x5)-6=1,290

Result:

Uni-directional Bi-directional

a1=0.0016, a2+=0.0018, a2-=0.0010

a1=27.5,d1=47.5, a2=97.4,d2=-17.5

slide10

Best-fit intensity distribution

“Normalized” intensity

(average over dec.-band is subtracted)

Original intensity

Uni-direct.

+

Bi-direct.

=

Sum

slide11

Best-fit performance

Cygnus region

Crab

Mrk421

observation

model

residual

(obs.-model)/error

  • Large-scale feature is well reproduced.2/d.o.f. = 2.493
  • (“Trough”, “Peak” and broad enhancement aroundCygnus region)
  • “Skewed” profile of “Peak” needs to be modeled further.
slide12

Comparison with UG-m

in two-hemispheres

UG-m in Japan V (35°N)

: LIMC model (Tibet AS)

Tibet AS

: Lallement’s B

UG-m in Tasmania N (4°N)

Tibet AS

UG-m in Tasmania V (36°S)

Best-fit B direction may be different when unbiased, by properly taking account of the data in southern hemisphere.

Tibet AS experiment cannot observe southern hemisphere.

UG-m @0.5 TeV

Hall et al., JGR, 103, 1998 &104, 1999)

slide13

Summary

: Lallement’s B

+

+

: B in this model

(bi-directional)

-0.0016

+0.0010

-

: heliotail (He)

b (°)

+0.0016

+

+

+0.0018

l (°)

  • Large-scale feature of 2D-sky map is well reproduced by the model.
  • (“Trough”, “Peak” and broad enhancement around Cygnus region)
  • “Skewed” profile of the observed “Peak” needs to be modeled further.
  • The model may be biased by the lack of southern hemisphere data.
  • Best-fit B-orientation is in a reasonable agreement with Lallement et al. (2005).

Original intensity map (in galactic coordinate)

White lines show contour map of the distance to LIC boundary by Redfield & Linsky (2000).

slide15

Comparison with UG- observations

Two-hemisphere UG- observations @~0.5 TeV

(5°x5° pixels)

(Hall et al., JGR, 103, 1998 &104, 1999)

(15°x15° pixels)

Large-scale distribution of proton intensity (not -ray)

Deep UG- observations by Super Kamiokande @~10 TeV

Guillian et al., PRD, in press (2007)

slide16

Energy dependence

“Normalized” intensity

Significance

4 TeV

6

No significant E-dependence up to ~100 TeV

12

50

100

slide18

d=90o

d=90o

d=30.1o

d=30.1o

  • 長期安定稼動
  • 大気効果の補正
  • (等天頂角法、E-W法)

恒星時日周変動

系統誤差  0.01%を実現

0 6 12 18 24

Local sidereal time (hour)

銀河異方性と恒星時日周変動

赤緯依存性を観測できない。

(自転軸に平行な流れは検出不可)

slide19

Energy responses to 1-ry CRs

μ-on

AS(Tibet III)

slide20

Nagashima, Fujimoto & Jacklyn (1998)

Loss-cone

Loss-cone

Tail-In

Tail-In

E-spectra of SDV amplitude

(Before Tibet III)

  • Both TI & LC @~300GeV
  • No significant TI @10TeV
  • TI has a soft E-spectrum
    • J/J~γE/E with const. E
    • ⇒ accl. in heliotail?
slide21

Tibet III results (AS@10TeV)

Amenomori et al. (ApJL, 626, 2005)

  • Tibet III all-dec. is consistent with Nor.
  • TI seen in the south
  • TI phase shifts earlier in south (amp. larger)
slide22

27°

28±15°

Lallement et al.

(2004)

Tibet AS

Gurnett et al. (2006)

slide23

gal. East

gal. North

gal. center

gal. East

slide24

Positive (qA>0)

Negative (qA<0)

(meridian)

(equatorial)

(meridian)

(equatorial)

0.5 TV

1 TV

10 TV