1. Yue, Qian @ Yongpyung, Korea
Prospects of Dark Matter Search with an Ultra-Low Threshold Germanium Detector
Yue, Yongpyung, Korea

2. matter  0.3  baryon  0.01-0.03  lum  0.003 
Components of the Universe:
matter  0.3 
baryon  
lum  
Note: Dark Matter is the dominant component of the
universe. Main part of it is Non-baryonic.

3. ...... Massive neutrinos WIMP (Weekly Interactive Massive Particles )
Neutralino
(Lightest super-symmetric particle)
Axion
......

4. Direct Detection of WIMPs

5. The basic conditions of WIMP detector :
High detection efficiency
High pure target material
Good shielding
Good PSD capability
Low threshold

6. Principles of direct detection:
ER : the recoil energy
E0 : the most probable incident energy of a dark matter particle of
mass MD
r : a kinematical factor
R : the event rate ( 1/KeV · Day · Kg )
R0 : the total event rate ( 1/Day · Kg )

7. The possible mass range of WIMPs:
1 — 1000 GeV c-2
Typical recoil energies are in the range keV.
So good shielding is necessary to eliminate nuclear recoils from neutrons produced by cosmic ray muons.
Methods of discriminating between nuclear recoils and electrons

8. The right-hand side is considerably complicated owing to the following corrections.
a Detector on the Earth, in orbit around sun, and solar system moving
through the Galaxy.
b The Quenching Factor.
c The target may consist of more than one elements.
d Instrumental resolution and threshold effects.
e SD & SI
f Form factor

9. Take account all of these factors:
vmax = vescape
= 650km/s

10. The thresholds are
a few keV!
Corresponding to the ~10GeV mass limit measurable!

11. CRESST: Spin-independent 262g Sapphire detector
The lowest threshold gotten until now! 500keV
Cryogenic bolometer!

12. Our Detector:
HPGe detector
Target mass: 5g
Threshold?
100eV
100eV

13. Our estimated results:
Target mass: 5g
QF: 0.25
Counts rate: 0.1 /keV·kg·day
Threshold: 100KeV

14. ? Our expected results: 5g mass + 0.1cpd 5g mass +0.01cpd

15. Problem:
Background Level--- How good?
Experimental site! --- more suitable?
Try larger detector mass!