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

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 FWHM @ 300 keV (1332 keV) [keV] 1.2 (1.87) 3.2 (4.45) Threshold [keV] 2.0 7.5

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. 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 inner 2.0 0.40 outer 7.5 1.42 3s 1.2 keV 4.3 keV 40-100 keV: factor 4.3 11-40 keV: 0.2 events/kg d keV 40-100 keV: 0.07 events/kg d 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

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

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