1. Dark Matter Search With an Ultra-low Threshold Germanium Detector proposed by Tsinghua University Seoul National University Academia Sinica
Qian Yue
Tsing Hua University
OSAKA

2. The evidences of Dark Matter
How much darkmatter are there
Inthis universal?
Many evidence from cosmology and astroparticle support this argument: Universe
When the star of a spiral galaxy circle around the center of this galaxy, the speed of this star should be the expected cure accoding to the Newton gravitation principle. But it is not same with the result of observation. One possible explanation is the existence of lots of dark matter.
The direct evidence of Dark Matter exist:
Rotation Curve for the spiral galaxy
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3. WIMP (Weekly Interactive Massive Particles )
Dark Matter is the dominant component of the universe. Main part of it is Non-baryonic. There are some dark matter candidate:
Massive neutrinos
WIMP (Weekly Interactive Massive Particles )
(Typical energy region: 1~1000GeV)
Axion
......
Massive neutrino has mass and oscillation supported by SNO results and Super-Kamiokande
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4. Experiments: The Principle of WIMP Direct Detection running or
under construction
fluorine
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5. Some Foundation of WIMP Detection
The possible mass range of WIMPs:
1 — 1000 GeV c-2
Typical recoil energies are keV.
Expected event rate ~ 1/kg/day or less
The spectrum of recoils expected decrease with energy exponentially.
Neutron source: (alpha, n) Uranium decay chain
R : event rate
R0: total event rate
E0: most probable incident kinematic energy
r : kinematic factor, 4MDMT/(MD+MT)2
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6. How to obtain the -m scatter plot?
Many correction has been do for the calculation of -m scatter plot(QF, Maxwell, SI&SD,Form factor et al.)
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7. Present Status of WIMP detection
SI interaction only!
The thresholds are
a few keV!
Corresponding to
the ~10GeV mass
limit measurable!
This is the gotten results. Some projections show very promising and more stringent results.
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8. CRESST: lowest threshold
Cryogenic bolometer!
Spin-independent
262g Sapphire detector
The lowest threshold gotten until now!
500keV
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9. Our Proposal
Where is the position for a small experimental collaboration like us?
Until now, there is no experiment to give some promising results in this region
Our Idea: using low-threshold detector to “find” low-mass WIMP
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10. Experimental Site:
YangYang
YangYang
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11. Cosmic Ray Level on-site!
Experimental Site:
Underground 700m Y2L Laboratory.
Cosmic-ray Level:
five-order less than outside Lab.
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12. Our detector 5g Ge detector Shielding APN04 @ OSAKA
Until now, purest material is Germanium. And Lowest background has been achieved by Ge detector.
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13. Energy Threshold of Detector
less than 100eV after PSD
PSD Parameter: for every current shape
Manganese54, 22Ti (titanium)
100eV
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14. Electronics and DAQ DAQ based on Linux system 500MHz DIGITIZER
2 CHANNELS / BOARD
32us RECORDED/EVENT
Programmable trigger
logic & optional zero
suppression on-board
DAQ based on Linux system
VME CONTROLLER
USB2 INTERFACE
OPTIONAL Transfer
10 Mbytes/s data transfer
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15. How to Do the Calibration?
1. Gamma/electron calibration series of low energy /X-ray source & Beta source for ultra low X-ray(?) 2. Neutron Calibration (A) neutron source calibration (B) Accelerator neutron source
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16. Neutron Beam Test
To select the recoil events by scattering angle and to reduce the background level by coincidence
To obtain low energy recoiled events and do the QF measurement.
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17. The Projection of Our expriment
Our estimated results:
Target mass: 5g
QF: 0.25
Counts rate: 1 /keV·kg·day
Threshold: 100 eV
Upgrade to 1kg Ge
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18. Low energy recoiled sample obtained by neutron beam test (How low?)
Problem:
Low energy recoiled sample obtained by neutron beam test (How low?)
Simulation for prototype detector(5g) &
1kg detector array
Background Level--- How good?
Check on-site!
Detector upgrade 1Kg (Multi-detector Array)
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19. Time Table
2004.1~ Preparation of the detector and shielding (Passive and Active)
~ Run1with 5g detector
~ detector upgrade to 1kg
~ ? Run2 with 1kg detector
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20. Collaboration Tsing Hua university (Engineering Physics Dept.)
Seoul National University
(Dark matter research center)
Taiwan AS(TEXONO group)
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21. Thanks for your attention!
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