A. M. Bakalyarov

Latest results from the HEIDELBERG-MOSCOW double beta decay experiment

Abstract:New results for the double beta decay of 76Ge are presented. They are extracted from data obtained with the HEIDELBERG-MOSCOW experiment, which operates five enriched 76Ge detectors in an extreme low-level environment in the Gran Sasso underground laboratory. The two-neutrino-accompanied double beta decay is evaluated for the first time for all five detectors with a statistical significance of 47.7 kg y resulting in a half-life of T1/22ν = [1.55±0.01(stat)+0.19-0.15(syst)]×1021 y. The lower limit on the half-life of the 0νββ decay obtained with pulse shape analysis is T1/20ν > 1.9×1025(3.1×1025) y with 90% C.L. (68% C.L.) (with 35.5 kg y). This results in an upper limit of the effective Majorana-neutrino mass of 0.35 eV (0.27 eV) using the matrix elements of A. Staudt et al.s work (Europhys. Lett. 13, 31 (1990)). This is the most stringent limit at present from double beta decay. No evidence for a majoron-emitting decay mode is observed.

LIMITS ON THE MAJORANA NEUTRINO MASS IN THE 0.1 EV RANGE

The Heidelberg-Moscow experiment gives the most stringent limit on the Majorana neutrino mass. After 24 kg yr of data with pulse shape measurements, we set a lower limit on the half-life of the neutrinoless double beta decay in 76Ge of T_1/2 > 5.7 * 10^{25} yr at 90% C.L., thus excluding an effective Majorana neutrino mass greater than 0.2 eV. This allows to set strong constraints on degenerate neutrino mass models.

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

Measurement of the Double-Beta Decay Half-Life and Search for the Neutrinoless Double-Beta Decay of

{}^{76}\mathrm{Ge}

^{48}{\rm Ca}

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.

with the NEMO-3 Detector

The NEMO-3 experiment at the Modane Underground Laboratory has investigated the double-

New half life limits for the? ? 2v+0v decay of76Ge to the excited states of76Se from the Heidelberg-Moscow ?? experiment

\beta

Status of the Germanium Detector Array (GERDA) in the search of neutrinoless ββ decays of 76Ge at LNGS

decay of

Production, characterization and operation of 76Ge enriched BEGe detectors in GERDA: GERDA Collaboration - eScholarship

^{48}{\rm Ca}