Two-dimensional observation on TeV Cosmic-ray anisotropy

using the Tibet Air Shower Array

2008.9 TeVP

Zhang Yi

For the Tibet AS collaboration

OUTLINE

• The Tibet Air shower Array;• Analysis method;• Sidereal time cosmic rays anisotropy;• Solar time cosmic rays anisotropy; • Periodicity search;• Conclusion ；

ARGO HallTibet AS array

1. The Tibet Air shower Array

中尼公路

Geothermal power plant

The Tibet Air shower Array

– Located at an elevation of 4300 m (Yangbajing , China)– Atmospheric depth 606g/cm2

– Wide field of view – High duty cycle (>90%)– Angular resolution (~0.9 。 )– Data (1997~2005, 37*109)

Advantage in measurement of Cosmic rayLarge scale anisotropy

Zenith

On-source

Off-sourceOff-source

,on onI N N

Ion

on

N

Ioff

off

——Global fitting method

2on on

2

2

2

1on on off,i off,in

N I -<N/I> i2on 2 21

on on off,i off,ini

N I - N I

χ =N I + N I

2 2,

,t on

t on

Equal

,off offI N

Two dimension analysis method

Zenith belt

One-dimensional observation

Amplitude ～ 0.1%

2. Sidereal time anisotropy

——NFJ model

zoh_N

zoh_V

zoh_S

-0.1

0

0.1

lia_2N

zoh_2S

lia_N

lia_V

0 6 12 18 24 30 36 42 48

lia_S

57.0N

34.5N

11.2N

8.2S

4.4N

36.2S

14.7S

57.6S

zoh_N

zoh_V

zoh_S

-0.1

0

0.1

lia_2N

zoh_2S

lia_N

lia_V

0 6 12 18 24 30 36 42 48

lia_S

57.0N

34.5N

11.2N

8.2S

4.4N

36.2S

14.7S

57.6S

Sidereal time anisotropy components

Tibet analysis in one dimension

Tibet analysis

Declination ranges.

The CR anisotropy is fairly stable and insensitiveto solar activities.

Three Componets ：I--------Tail-in;II-------Loss-coneIII------Cygnus 区；

Tibet measurement in two dimensions

4 TeV

6.2 TeV

12 TeV

50 TeV

300 TeV

Celestial Cosmic Ray intensity map in five energy range

<12TeV Energy independent >12TeV Fade away

“Tail-in” effect exists in 50TeVrule out the solar causation

Δ I< I >

= ( + 2 ) v c　 cos

Due to terrestrial orbital motion around the Sun

j

8

E-

V=30km/s,

D.J. Cutler, D.E. Groom, Nature 322, L434 (1986)

3. Solar time anisotropy —— Compton-Getting effect

Differential E spectrum :

The amplitude is ~0.04%

——Compton-Getting effect （ 12TeV ）

The solar time anisotropy is table in two intervals with different solar activity

The 1D modulation (solid line) is consitent with the expected one (dash line) 。

Tibet measurement in solar time I

–Kota et al. (icrc0229) Matsushiro

With the compton-getting effect subtracted.The amplitude ～ 0.04% ， Preliminary result

——Additional effect (4TeV)

Tibet measurement in solar time II

Preliminary

3. Periodicity search in 3 energy ranges

Solar diurnal.Compton-Getting effect Sidereal-diurnal

Sidereal semi-diurnal

3. Periodicity search

With the solar and sidereal time modulation subtracted.

Conclusion•In　the　sidereal　time　frame,　revealing　finer　details　of　the　anisotropies　components　“tail-in”　and　“loss-cone”　and　“Cygnus”　region　direction.　

•In　the　solar　time　frame,　Compton-Getting　effect　is　observed　in　12.5TeV,　An　additional　modulation　appears　to　exist　in　case　of　low　energy.

•Besides　solar,　sidereal,　semi-sidereal　diurnal　Variation,　no　other　periodic　modulation observed.

中意 ARGO 实验大厅

中日 AS 探测阵列

365.2422364.2422T Solar day

365.2422367.2422T= Solar day

——Observation in other periods

Anti sidereal time ；

Ext-sidereal time ；

No signal is expected, the amplitude observed is within statistic error.

Two-dimension Analysis check II

原初宇宙线各向异性的实验观测二

Nagashima, Fujimoto, Jacklyn (JGR, 103, 1998) Hall et al. (JGR, 103, 1998)

地方恒星时的宇宙线强度变化

Tail-In

Loss-Cone

Tail-In max. shifts earlier in the south

1) 一些地下 μ实验一维观测

Galactic Magnetic field 3uG

Galactic cosmic rays lost their directional information, and are nearly isotropic because of the influence of magnetic fields in the Milky Way.

Galactic Magnetic field

Cygnus

Gyromagnetic radius

3TeV 0.001pc (200AU)

Expected

Expected Amp= 0.0016

The statistic error 0.00026 ， 5σ rule out the Compton-Getting effect.

Celestial Cosmic Ray intensity map for 300 TeV

These results have an implication that cosmic rays in this energy range is still strongly deflected and randomized by the Galactic magnetic field in the local environment.

3)Corotaion of the low energy particles

Know anisotropy —— Compton-Getting effect III

The cosmic ray particles would co-rotate with the interplanetary magnetic field (IMF).

Know anisotropy —— Compton-Getting effect I

Δ I< I >

= ( + 2 ) v c　 cos

A.H. Compton and I.A. Getting, Phys. Rev. 47, 817(1935)L.J. Gleeson and W.I. Axford, Ap. Space Sci. 2, 431(1968)

1) The solar motion around the Galactic center j

8

E-Differential E spectrum :

V=220km/s,