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. Hu

ang, 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

6th IGPP meeting in Hawaii: March 21, 2007

• 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 -rays, while the muon detector respond only to 1ry protons.

Cosmic ray observation with AS array

Neutron monitor

Muon detector

Air shower array

1ry

Tibet ASγ experiment

Tibet@ChinaTibet@China

Yangbajing 90 ゜ 53E, 30 ゜ 11N 4,300 m a.s.l.

Lasa

Yangbajing~300 km

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 resolutionin multi-TeV region

Sidereal anisotropy on the spinning Earth

● The zenith direction at Yanbajing is =30.1o.

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

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

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

=30.1o =30.1o

=90o

The average flux in each -band is subtracted.

Geographical equator

Galactic plane

right ascension (º)

dec

linat

ion

(º)

Nose direction

“Normalized” intensity map (5°x5° pixels)

Significance map

~120°

90° < 120° < 180°

Bi-directional + Uni-directional

2D sky map of CR intensity by Tibet AS(Amenomori et al., Science, 314, 2006)

•RL~ 0.01pc (for 10TeV p in 1G)

•Dist. to LIC boundary ~26km/s3000y

=0.08pc•Probably within 1 m.f.p. in the weakscattering regime

LIC (Local Interstellar Cloud)T~7000K, nH~0.1/ccIonization rate~0.52

Redfield & Linsky, ApJ, 535, 2000

2 pc

GC

l=90

l=180

l=27

0

Lallement’s Interstellar B plane(Lallement et al., Science, 307, 2005)

lB= 205~240 bB= -38~-60

(or the opposite direction)

H

He

Interstellar B

n

Uni-directional flow(Bxn)

Bi-directional flow

n Low

n HighLIC

G cloud

LIMC (Local Interstellar Magnetic Cloud) model

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

26 km/s

29 km/s

Best-fitting (preliminary)(I/I)cal = a1cos1() : Uni-directional

+ a2+cos2 2() for 0 2/2 + a2-cos2 2(2, 2) for /2 2

1, 2 : angles from reference axes

First choose orientations of reference axes… & (or ): () ()

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

d.o.f. with 6 free parameters is large as…90x360/(5x5)-6=1,290

: Bi-directional

Result: Uni-directional Bi-directional

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

27.547.5, 97.417.

5

Best-fit intensity distribution

Uni-direct.

Bi-direct

.

Sum

+

=

Original intensity“Normalized” intensity

(average over dec.-band is subtracted)

Mrk421

CrabCygnus region

Best-fit performance

• 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.

observation

model

residual(obs.-model)/error

Comparison with UG-in two-hemispheres

Tibet AS experiment cannot observe southern hemisphere.

: Lallement’s B: LIMC model (Tibet AS)

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

UG- @0.5 TeVHall et al., JGR, 103, 1998 &104, 1999)

-0.15

0

0.15

-0.3

0

0.3

0 90 180 270 360

UG

(%

) Tib

et (%

)

R.A. (deg)

-0.15

0

0.15

UG

(%

)

-0.15

0

0.15

-0.3

0

0.3

0 90 180 270 360

UG

(%

) Tib

et (%

)

R.A. (deg)

UG- in Japan V (35°N)

Tibet AS

Tibet AS

UG- in Tasmania N (4°N)

UG- in Tasmania V (36°S)

Summary• 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).

: heliotail (He)

: Lallement’s B

+ : B in this model(bi-directional)

Original intensity map (in galactic coordinate)

+

-

++

-0.0016

+0.0016

+0.0018

+0.0010

l (°)

b (

°)

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

Comparison with UG- observations

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

Two-hemisphere UG- observations @~0.5 TeV(Hall et al., JGR, 103, 1998 &104, 1999)

Deep UG- observations by Super Kamiokande @~10 TeVLarge-scale distribution of proton intensity

(not -ray)

(5°x5° pixels)

(15°x15° pixels)

4 TeV

6

12

50

100

No significant E-dependence up to ~100 TeV

“Normalized” intensity Significance

Energy dependence

銀河異方性と恒星時日周変動

=90o=90o

=30.1o =30.1o

0 6 12 18 24Local 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）

•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

Energy responses to 1-ry CRs

AS（ Tibet III）μ-on

0.01

0.1

1

10

100

1000

0.01 0.1 1 10 100

Nagoya-VMisato-VSakashita-VMatsushiro-V

arb

itra

ry u

nit

primary E (TeV)

-0.2

0

0.2

0 6 12 18 24

Nor.3F(73-87)-0.05Nor.3R(73-87) @10TeVSakV1_corSI(78-94)*4 @300GeV

(%)

hours

Tail-In

Loss-cone

• Both TI & LC @~300GeV• No significant TI @10TeV• TI has a soft E-spectrum

J/J~γE/E with const. E⇒ accl. in heliotail?

E-spectra of SDV amplitude（ Before Tibet III）

Nagashima, Fu ｊ imoto & Jacklyn (1998)

Loss-cone

Tail-In

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

-0.2

0

0.2 TibetIII(99-03)Nor.3R(73-87)Nor.3F(73-87)

0 6 12 18 24

(%)

hours

Tibet III results (AS@10TeV)

Amenomori et al. (ApJL, 626, 2005)

0 6 12 18 24

si_daily15R:-15+00R:+00+05R:+10+15R:+20+25

R:+30+35R:+40+45R:+50+55

hours

Gurnett et al. (2006) Lallement et al.(2004)

Tibet AS

28±15°27°

gal. North

gal. East

gal. East

gal. center

Positive (qA>0)(meridian) (equatorial)

0.5 TV

10 TV

1 TV

Negative (qA<0)(meridian) (equatorial)