1. Indirect dark matter search with YBJ-AS Observatory
Outline
Introduction
Status of ground-based observations
Data analysis with AS experiment
Results
5. Conclusions
Wu hanrong on behalf of YBJ-ASg collaboration

2. Indirect Dark Matter search Astrophysics : Dark matter halo
Gamma-ray flux from WIMP annihilation:
Particle Physics
From Observation

3. Target of indirect search
Galactic Halo
external galaxies
galaxy clusters
substructures
Galactic Center(GC)
Local Group galaxies
Mini-spikes around IMBH

4. Indirect DM search—ground based observatory
IACT arrays
Advantage: Good angular resolution; gamma/hadron discrimination
Disadvantage: limited FOV and duty cycle
Advantage: large FOV, 90% duty cycle
Disadvantage: no good gamma/hadron identifintification
EAS arrays

6. Data analysis with AS experiment

7. Tibet AS Observatory a.s.l. 4300 m (YBJ , Tibet) 606g/cm2
Large field of view
Duty cycle (>90%)
Mode Energy: ASγ(~3TeV)
ARGO
ASγ

8. Schematic map of the array and data using in analysis
Tibet-II
Tibet-IIIB4
Run period
space
Mode Energy
Angular resolution
area
Tibet-III ~
7.5m
~3TeV
~0.90
~22050m2
Statistic (after selection): ~1.86*10^10

9. analysis method Equal 迭代
This method is developed to fit simultaneously the relative cosmic ray intensity from all directions over the sky. The principle is that at any moment, for all directions , if we scale down(or up) the observed event number by divide them by their relative CR intensity, then statistically, those scaled observed event number in an zenith belt should be equal anywhere.Here we define relative CR. Intensity as I. So, for some moment, at some zenith angle,we get an on-source window, and then we obtain some off-sources window with the same shape, the same size and the same zenith angle as on-source window, For the on source window, there are observed event number Non and relative intensity Ion, according for off-sources, Noff and Ioff.then statistically, Non/Ion and the average value of Noff/Ioff should be approximately equal, so a ki-square function can be built, this is for some certain direction and on-source window, and then for all direction and all moment, in the same way, we can get all ki-square function and then sum them,so a large ki-square function is constructed.by minimizing the function, we can get CR relative Intensity at all directions.

10. 全天图以及M31显著性
1.M31(10.7,41.3)
Non:
Noff:
Nexc:
Significance: 0.97
M31
2. No high siginificant point (>5sigma) except known source crab and Mrk421 is detected

11. 1. 90%C.L. limit— M31

12. 2. 90%C.L. limit— substructure
Significance for BKG
Significance for BKG+DM signal

13. 2. 90%C.L. limit— substructure
preliminary

14. Conclusions
Detect no any substructure in the field of YBJ ASgamma observatory
Detect no DM from M31
90% C.L. upper limit on “thermally averaged annihilation cross section” between 10^-19cm^3s^-1 and 10^-22cm^3s^-1 is given
Future search, ARGO-YBJ(~300GeV)

15. Thanks!

16. 1. 90%C.L. Flux limit— M31 90%C.L. flux limit： DM spectrum
From Observation
Monte Carlo

17. 2. 90%C.L. Flux limit— substructure
-----Number of substructure for 800 toy MC trials
BKG
BKG+DM signal