1. The Heidelberg Dark Matter Search Experiment
Laura Baudis
Stanford University

2. The HDMS collaboration
MPI fuer Kernphysik, Heidelberg
Group of Prof. H.V. Klapdor-Kleingrothaus

3. The HDMS detectors WIMP 2 HPGe detectors in one cryostat system
inner: WIMP target
outer: active veto
against multiple Comptons
passive Ge shield
gamma

4. Some detector properties
Property
Inner Detector
Outer Detector
Crystal type
p-type
n-type
Mass [g]
202
2111
Active vol [cc] 37
383
Diameter [mm]
35.2
84.4
Length [mm]
40.3
86.2
Op. bias [V]
+ 2500
-1500
300 keV
(1332 keV) [keV]
1.2 (1.87)
3.2 (4.45)
Threshold [keV]
2.0
7.5

5. Cross talk between detectors
linear correlation:
correction offline
kio = /-
0.43 x 10-4
koi = /-
0.27 x 10-3

6. Cross talk induced error
compare zero energy
resolutions:
inner: no effect
outer: from 0.3% to
0.4% at 1332 keV

7. The HDMS detector

8. HDMS in Gran Sasso
prototype: March 98-July 99

9. Performance @ GS stable running over ~ 15 months
individual runs ~ 0.9 d
checked daily: leakage current
nitrogen flow
overall trigger
individual count rate, etc
weekly: calibration with 133Ba, 152Eu-232Th source

10. Outer detector: 363 raw live-d
68Ge, 57Co, 58Co, 54Mn, 60Co, 65Zn, 137Cs, 238U, 232Th, 40K

11. Inner detector: 363 raw live-d
68Ge, 54Mn, 57Co, 60Co, 210Pb, 212Pb, 214Pb, 40K

12. Background model MC simulation of dominant backgrd.
sources with extended GEANT3.21

13. Inner: low energy spectrum
68Ga X-ray
49Ti,
55Mn
cross talk?

14. Structure at 32 keV: cross talk?

15. Anticoincidence between inner and outer
Eth for anticoincidence: 3 sigma away from zero
threshold
[keV]
FWHM/2.35
inner
2.0
0.40
outer
7.5
1.42 3s
1.2 keV
4.3 keV
keV: factor 4.3
11-40 keV: 0.2 events/kg d keV
keV: 0.07 events/kg d keV

16. HDMS prototype limits only last 49 d of data taking: 9.9 kg d
2-30 keV: 0.5 events/kg y keV
L. Baudis et al., PRD63,2000

17. 73Ge-HDMS: full scale inner crystal replaced by 73Ge crystal
sensitive to spin-dependent interactions
70Ge de-enriched by factor >50
new copper holder system
no soldering of contacts
installed in GS: August 2000
working well
first analysis: fall 2001?
expectation: test DAMA with
independent technique and raw data

18. HDMS goal
Based on: 0.07 events/kg d keV in keV region

19. Conclusions HDMS prototype worked well
limits competitive to other Ge experiments
73Ge-HDMS installed in August 2000
first 73Ge detector!
first data to be analyzed soon...
independent test of DAMA region
sensitive to spin-dependent interaction
however, increase of target mass improbable
no sensitivity to a WIMP signature