1. Detecting dark matter through line emission
a suggestion for the Chinese space station
Guoming Chen
IHEP, CAS
Sep. 23, 2008
2019/4/17
Guoming CHEN

2. What to detect in space? Charged particles: AMS Gamma ray: GLAST
2019/4/17
Guoming CHEN

3. γray from neutralino annihilation
smoke gun
evidence
Mχ=1.5TeV
Line emission:
large acceptance
excellent energy resolution
2019/4/17
Guoming CHEN

4. Where to detect? advantage disadvantage Galactic Center
large statistics
Background
foreground
Sub-halo
background free
large No. of subs
low statistics per subhalo
Satellite
low background
low statistics
Extra galactic
good statistics
background
2019/4/17
Guoming CHEN
Jan Conrad

5. Strategy To detect dark matter through line emission
To scan the full sky, mostly depending on sub-halos
Different from normal gamma ray detector, this one emphasizes on acceptance, energy resolution and particle ID.
2019/4/17
Guoming CHEN

6. Detector concept design (High Energy Gamma Ray detector, HEGARD)
50mm thick plastic rubber
Tungsten 1000*1000*3.5mm3
Scintillator fiber 5*5*1000mm3
20 radiation lengths
Lithium Glass 20*20*5mm3
Plastic Scintillator 10*10*1200mm3
2019/4/17
Guoming CHEN

7. One layer of the ECAL
One layer = one radiation length, 20 layers in total
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Guoming CHEN

8. take 1m2 scenario as an example
Weight and Acceptance
ECAL size naked detector support area geo. factor
m kg kg m m2sr
0.71x
1.00x
1.40x
1.73x
take 1m2 scenario as an example
2019/4/17
Guoming CHEN

9. MC simulation
Hits level
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Guoming CHEN

10. Energy measurement
From 30GeV to 4TeV , energy resolution better than 2%
(leakage corrected)
scale
energy resolution
deviation from linearity
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Guoming CHEN

11. Shower shape difference on γ/p
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Guoming CHEN

12. 2019/4/17
Guoming CHEN

13. Boost decision tree output
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Guoming CHEN

14. γeff. vs. p eff.
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Guoming CHEN

15. γ/e separation
Veto efficiency , i.e., only 10-4 electron can contaminate gamma
The problem is gamma efficiency
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Guoming CHEN

16. Backlash
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Guoming CHEN

17. backlash property
Back scattering particles include both electrons and gammas, gammas dominate
Energy mostly less than 2MeV
energy of backlash gamma
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Guoming CHEN

18. Backlash identification
Using plastic rubber to absorb electrons in the backlash
For the gammas：
1）ID with position 2）ID with energy y
gamma efficiency:92%
at 200GeV, Ex>1MeV,
Ey>1MeV x x
光子效率：〉95%
2019/4/17
Guoming CHEN

19. HEGARD concept size 112x112x40 cm3 weight 2000kg
power consumption 500W
time resolution 1ns
area 1m2
geometry factor 3m2sr
gamma energy measurement 30GeV—4TeV
energy resolution 2%
angular resolution 0.5o
proton rejection 10-7
electron rejection 10-4
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Guoming CHEN

20. ISS orbit simulation
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Guoming CHEN

21. effective time in one year survey
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Guoming CHEN

22. backgrounds astro-ph/0510714v2 1996A&A..120C.465M 2019/4/17
Guoming CHEN

23. Theoretical calculation bu X.J. Bi
416GeV
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Guoming CHEN

24. One year sensitivity
HEGARD
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Guoming CHEN

25. Conclusion It is able to detect dark matte through line emission
The proposed detector has large acceptance, excellent energy resolution and excellent particle ID.
It is able to detect dark matte
through line emission
2019/4/17
Guoming CHEN

26. Thank you You are welcome to give any criticism,
comments, and improvements of the design.
And you more than welcome to offer collaboration.
2019/4/17
Guoming CHEN

27. backup
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Guoming CHEN

28. 电磁量能器事例数 能量 (GeV) 50 100 200 500 1000 2000 4000 总和 电子 10k 5k 50k 光子质子
300k
298k
227k
170k
163k
1.498M
2019/4/17
Guoming CHEN