New limits on dark-matter weakly interacting particles from the Heidelberg-Moscow experiment

Abstract

New results after 0.69 kg yr of measurement with an enriched 76 Ge detector of the Heidelberg-Moscow experiment with an active mass of 2.758 kg are presented. An energy threshold of 9 keV and a background level of 0.042 counts/(kg d keV) in the energy region between 15 keV and 40 keV was reached. The derived limits on the WIMP-nucleon cross section are the most stringent limits on spin-independent interactions obtained to date by using essentially raw data without background subtraction.

Sensitivity plots for WIMP direct detection using the annual modulation signature

“…As expected, the sensitivity is roughly proportional to (MT) −1/2 . Figures 1-2 refer to Ge detectors with background b=0.01 cpd/kg/keV and energy thresholds E th =2 and 12 keV respectively (thresholds already obtained in the COSME [16] and Heidelberg-Moscow [11] experiments, respectively, and a background not far from that obtained by Heidelberg-Moscow and CDMS [13]). In Figure 3 the intermediate situation of a germanium detector with b=0.1 cpd/kg/keV and E th =4 keV is given (except from the assumption of flat background, the case depicted in Fig.…”

“…In this section we give a quantitative discussion of the sensitivity plots by considering different target materials: Ge, T eO 2 , N aI with quenching factors, experimental thresholds and resolutions summarized in Table II (they have been chosen in order to be indicative of running or planned experiments [5,[11][12][13][14]). For simplicity, in order to calculate the sensitivity plots, a flat background will be always assumed and in the following the index k of b k will be dropped.…”

First results from the Heidelberg dark matter search experiment

“…The evaluation for dark matter limits on the WIMP-nucleon cross section σ W−N scalar follows the method described in [7]. Because the cosmogenic radionuclides produced in the Ge crystals and in the surrounding copper have typical half-lives of 300 days, we consider only the last 49 d of measurement of the HDMS prototype.…”

Particle dark matter and solar axion searches with a small germanium detector at the Canfranc Underground Laboratory

“…This result is compared with the limit obtained with the previous data of COSME (thick dashed line) as well as a combined contour obtained from several previous germanium experiments [2,12,13] (thin dotted line) and two recent germanium results, IGEX-DM [10] (thin dashed line) and Heidelberg-Moscow [14] (thin dot-dashed line). All the curves have been computed from the raw data with the same set of assumptions (except for those for which a 0.25 quenching factor was not a good aproximation, for which an appropriate energy dependence has been used [14]). The DAMA region corresponding to its reported annual modulation effect [15] is also shown.…”

“…The thick dashed line shows the one from the previous running of the same detector [2] for comparison. Limits from a recent result of IGEX-DM experiment [10] (thin-dashed), from the Heidelberg-Moscow experiment [14] (dot-dashed) and from a combination of previous germanium experiments [2,12,13] (dots) are also shown. The closed region corresponds to the (3σ) annual modulation effect reported by the DAMA collaboration (including NaI-1,2,3,4 runnings) [15].…”