1. (Tibet AS collaboration)
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

2. Cosmic ray observation with AS array
Neutron monitor
Muon detector
Air shower array
1ry g
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.

3. Tibet ASγ experiment Tibet@China Yangbajing 90゜53E, 30゜11N
4,300 m a.s.l.
Lasa
~300 km
無断転載禁止

4. Resolving the incident direction
trigger rate ~ 680 Hz
angular res. ~ 1
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

5. Sidereal anisotropy on the spinning Earth
d=30.1o
d=90o
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. ● ●
AS flux varies for more than an order of magnitude with the zenith angle due to the different atmospheric depth.
The average flux in each d-band is subtracted.

6. Bi-directional + Uni-directional
2D sky map of CR intensity by Tibet AS
(Amenomori et al., Science, 314, 2006)
Geographical equator
Galactic plane
right ascension (º)
declination (º)
Nose direction
“Normalized” intensity map
(5°x5° pixels)
~120°
90° < ° < °
Bi-directional Uni-directional
Significance map

7. 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

8. 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

9. Best-fitting (preliminary)
(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
: Bi-directional
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

10. “Normalized” intensity (average over dec.-band is subtracted)
Best-fit intensity distribution
“Normalized” intensity
(average over dec.-band is subtracted)
Original intensity
Uni-direct. +
Bi-direct. =
Sum

11. Best-fit performance observation model residual
Mrk421
Crab
Cygnus region
observation
model
residual
(obs.-model)/error
Large-scale feature is well reproduced.　2/d.o.f. = 2.493
(“Trough”, “Peak” and broad enhancement around Cygnus region)
“Skewed” profile of “Peak” needs to be modeled further.

12. Comparison with UG-m in two-hemispheres
UG-m in Japan V (35°N)
Tibet AS
UG-m in Tasmania N (4°N)
UG-m in Tasmania V (36°S)
Tibet AS experiment cannot observe southern hemisphere.
: LIMC model (Tibet AS)
TeV
Hall et al., JGR, 103, 1998 &104, 1999)
: Lallement’s B
Best-fit B direction may be different when unbiased, by properly taking account of the data in southern hemisphere.

13. Summary Original intensity map (in galactic coordinate) + - +
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) + -
l (°)
b (°)
: heliotail (He)
: Lallement’s B +
: B in this model
(bi-directional)
White lines show contour map of the distance to LIC boundary by Redfield & Linsky (2000).

15. Large-scale distribution of proton intensity (not -ray)
Comparison with UG- observations
Two-hemisphere UG- TeV
(Hall et al., JGR, 103, 1998 &104, 1999)
(5°x5° pixels)
(15°x15° pixels)
Large-scale distribution of proton intensity (not -ray)
Deep UG- observations by Super TeV
Guillian et al., PRD, in press (2007)

16. Energy dependence No significant E-dependence up to ~100 TeV 4 TeV 6
“Normalized” intensity
Significance
4 TeV 6
No significant E-dependence up to ~100 TeV 12 50
100

18. Local sidereal time (hour)
銀河異方性と恒星時日周変動
d=90o
d=30.1o
長期安定稼動
大気効果の補正
（等天頂角法、E-W法）
系統誤差  0.01%を実現
Local sidereal time (hour)
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）

19. Energy responses to 1-ry CRs
AS（Tibet III）

20. E-spectra of SDV amplitude
（Before Tibet III）
Nagashima, Fuｊimoto & Jacklyn (1998)
Loss-cone
Tail-In
Both TI &
No significant
TI has a soft E-spectrum
J/J~γE/E with const. E
⇒ accl. in heliotail?
Tail-In
Loss-cone

21. 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)

22. Lallement et al.
(2004)
Tibet AS
28±15°
27°
Gurnett et al. (2006)

23. gal. North
gal. East
gal. East
gal. center

24. Positive (qA>0) Negative (qA<0) 0.5 TV 1 TV 10 TV (meridian)
(equatorial)
(meridian)
(equatorial)
0.5 TV
1 TV
10 TV