Y. Ramachers

The Heidelberg-Moscow experiment: improved sensitivity for 76Ge neutrinoless double beta decay

Abstract The Heidelberg-Moscow experiment operates five enriched 76Ge detectors with 10.96 kg active mass in the Gran Sasso underground laboratory. After 28.7 kg y of measurement with a counting rate between 2000 keV and 2080 keV of 0.20 ± 0.01 cts/kg y keV we receive a lower limit on the neutrinoless double beta decay of 76Ge of T 1 2 (0 + → 0 + ) > 1.1 × 10 25 y (90% C.L.). This restricts the Majorana neutrino mass to 0.46 eV. Recently we achieved a reduction in the background counting rate by a factor of 3–5 within the energy region of the neutrinoless double beta decay by recording the differentiated preamplifier pulse shapes and doing an off-line analysis to distinguish between pointlike and multiple scattered interactions.

New limits on dark-matter WIMPs from the Heidelberg-Moscow experiment

New results after 0.69 kg yr of measurement with an enriched

Background and technical studies for GENIUS as a dark matter experiment

{}^{76}\mathrm{Ge}

PROPOSAL FOR A NEW GE-SEMICONDUCTOR DARK MATTER DETECTOR

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 cts/(kg d keV) in the energy region between 15 keV and 40 keV was reached. The derived limits on the weakly interacting massive particles--nucleon cross section are the most stringent limits on spin-independent interactions obtained to date by using essentially raw data without background subtraction.

Bounds on new Majoron models from the Heidelberg-Moscow experiment.

Abstract The GENIUS project is a proposal for a new dark matter detector, with an increased sensitivity of three orders of magnitude relative to existing direct dark matter detection experiments. We performed a technical study and calculated the main background sources for the relevant energy region in a detailed detector geometry. The achieved overall background level and detector performance confirm the outstanding potential of GENIUS as a powerful tool for the direct search of WIMPs in our Galaxy.

Dark matter search with the HDMS-experiment and the GENIUS project

Abstract We present a new proposal for a Ge-semiconductor dark matter detector. As will be shown the use of anti-coincidence between two Ge-detectors will drastically reduce the photon background which mainly limits the direct detection of hypothetical dark matter particles (WIMPs). We expect to improve WIMP cross section limits to a level comparable to planned cryogenic experiments.

Search for new physics with neutrinoless doubel beta decay

In recent years several new Majoron models were invented to avoid the shortcomings of the ordinary models while leading to observable decay rates in double {beta} experiments. We give the first experimental half-life bounds on double {beta} decays with new Majoron emission and derive bounds on the effective neutrino-Majoron couplings from the data of the {sup 76}Ge Heidelberg-Moscow experiment. While stringent half-life limits for all decay modes and the coupling constants of the ordinary models were obtained, small matrix elements and phase space integrals result in much weaker limits on the effective coupling constants of the new Majoron models. {copyright} {ital 1996 The American Physical Society.}

Search forNew Physics with Neutrinoless Double β Decay

Abstract We present a new Germanium Dark Matter Experiment. It consists of two HPGe-Detectors which are run in a unique configuration. The anticoincidence between the two detectors will further reduce the background that we achieve now in the Heidelberg-Moscow-Experiment and will allow to improve WIMP cross section limits to a level comparable to planned cryogenic experiments. This should also allow to test recently claimed positive evidence for dark matter by the DAMA experiment. We show first detector performances from the test period in the Heidelberg Low Level Laboratory and give a preliminary estimation for the background reduction efficiency. The HDMS experiment in being built up now in the Gran Sasso Underground Laboratory and will start taking data by the end of this year. For a substantial improvement of the WIMP-nucleon cross section limits, future dark matter experiments will have to be either massive direction-sensitive detectors or massive ton-scale detectors with almost zero background. A proposal for a high mass (1 ton) Ge experiment with a much further reduced background is the Heidelberg GENIUS experiment. GENIUS will be able to give a WIMP limit of the order 0.02 counts/day/kg and additionally to look for the annual modulation WIMP-signature by using raw data without subtraction.

Aspects of Dark Matter Direct Detection

Neutrinoless double beta decay (

High-purity germanium detector ionization pulse shapes of nuclear recoils, γ-interactions and microphonism

0\nu\beta\beta