The Heidelberg Dark Matter Search Experiment
Laura Baudis
Stanford University
The HDMS collaboration
MPI fuer Kernphysik, Heidelberg
Group of Prof. H.V. Klapdor-Kleingrothaus
The HDMS detectors
2 HPGe detectors in one cryostat system
inner: WIMP target
outer: active veto
against multiple Comptons passive Ge shield
WIMP
gamma
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
FWHM @ 300 keV (1332 keV) [keV]
1.2 (1.87) 3.2 (4.45)
Threshold [keV] 2.0 7.5
Some detector properties
Cross talk between detectors
linear correlation:
correction offline kio = 0.00375 +/- 0.43 x 10-4 koi = 0.12850 +/- 0.27 x 10-3
Cross talk induced error
compare zero energy resolutions:
inner: no effect
outer: from 0.3% to 0.4% at 1332 keV
The HDMS detector
HDMS in Gran Sasso
prototype: March 98-July 99
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
Outer detector: 363 raw live-d
68Ge, 57Co, 58Co, 54Mn, 60Co, 65Zn, 137Cs, 238U, 232Th, 40K
Inner detector: 363 raw live-d
68Ge, 54Mn, 57Co, 60Co, 210Pb, 212Pb, 214Pb, 40K
Background model
MC simulation of dominant backgrd.
MC simulation of dominant backgrd.
sources with extended GEANT3.21 sources with extended GEANT3.21
Inner: low energy spectrum
68Ga X-ray
49Ti, 55Mn
cross talk?
Structure at 32 keV: cross talk?
Anticoincidence between inner and outer
Eth for anticoincidence: 3 sigma away from zero threshold
[keV]
FWHM/2.35 [keV]
inner 2.0 0.40
outer 7.5 1.42
40-100 keV: factor 4.3
11-40 keV: 0.2 events/kg d keV 40-100 keV: 0.07 events/kg d keV
3
1.2 keV 4.3 keV
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
73
Ge-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
HDMS goal
Based on: 0.07 events/kg d keV in 2 - 30 keV region
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
