A. Ortiz de Solórzano

The IGEX Ge-76 neutrinoless double beta decay experiment: Prospects for next generation experiments

The International Germanium Experiment (IGEX) has analyzed 117 mole yr of 76Ge data from its isotopically enriched (86% 76Ge) germanium detectors. Applying pulse-shape discrimination (PSD) to the more recent data, the lower bound on the half-life for neutrinoless double-beta decay of 76Ge is:

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

T_{1/2}(0\nu)> 1.57 \times 10^{25}

Experimental Search for Solar Axions via Coherent Primakoff Conversion in a Germanium Spectrometer

yr (90% C.L.). This corresponds to an upper bound in the Majorana neutrino mass parameter,

First results of the ROSEBUD dark matter experiment

, between 0.33 eV and 1.35 eV, depending on the choice of theoretical nuclear matrix elements used in the analysis.

Recent results of the IGEX 76Ge double-beta decay experiment

Abstract A small, natural abundance, germanium detector (COSME) has been operating recently at the Canfranc Underground Laboratory (Spanish Pyrenees) in improved conditions of shielding and overburden with respect to a previous operation of the same detector (Nucl. Instrum. Meth. A 321 (1992) 410; Phys. Rev. D 51 (1995) 1458). An exposure of 72.7 kg day in these conditions has at present a background improvement of about one order of magnitude compared to the former operation of the detector. These new data have been applied to a direct search for weakly interacting massive particles (WIMPs) and solar axions. New WIMP exclusion plots improving the current bounds for low masses are reported. The paper also presents a limit on the axion–photon coupling obtained from the analysis of the data looking for a Primakoff axion-to-photon conversion and Bragg scattering inside the crystal.

Prospects of solar axion searches with crystal detectors

Results are reported of an experimental search for the unique, rapidly varying temporal pattern of solar axions coherently converting into photons via the Primakoff effect in a single crystal germanium detector when axions are incident at a Bragg angle with a crystalline plane. The analysis of 1.94thinspthinspkgthinspyr of data from the 1thinspthinspkg DEMOS detector in Sierra Grande, Argentina, yields a new laboratory bound by an axion-photon coupling of g{sub a{gamma}{gamma}}{lt}2.7{times}10{sup {minus}9} GeV{sup {minus}1} , independent of axion mass up to {approximately}1 keV . {copyright} {ital 1998} {ital The American Physical Society }

Pulse shape discrimination in the IGEX experiment

Abstract The IGEX Collaboration enriched 76 Ge double-beta decay detectors are currently operating in the Canfranc Underground Laboratory with an overburden of 2450 m.w.e. A recent upgrade has made it possible to use them in a search for WIMPs. A new exclusion plot, σ (m), has been derived for WIMP-nucleon spin-independent interaction. To obtain this result, 30 days of data from one IGEX detector, which has an energy threshold E thr ∼4 keV, have been considered. These data improve the exclusion limits derived from other ionization (non-thermal) germanium detector experiments in the ∼50 GeV DAMA region, and show that with a moderate improvement of the background below 10 keV, the DAMA region may be tested with an additional 1 kg-year of exposure.

The IGEX experiment reexamined: A response to the critique of Klapdor-Kleingrothaus, Dietz, and Krivosheina

Abstract ROSEBUD (Rare Objects SEarch with Bolometers UndergrounD) is an experiment which attempts to detect low mass weak interacting massive particles through their elastic scattering off Al and O nuclei. It consists of three small sapphire bolometers (of a total mass of 100 g) with NTD-Ge sensors in a dilution refrigerator operating at 20 mK in the Canfranc Underground Laboratory. We report in this paper the results of several runs (of about 10 days each) with successively improved energy thresholds, and the progressive background reduction obtained by improvement of the radiopurity of the components and subsequent modifications in the experimental assembly, including the addition of old lead shields. Mid-term plans and perspectives of the experiment are also presented.

Filtering microphonics in dark matter germanium experiments

The International Germanium Experiment (IGEX) has now analyzed 117 mol yr of data from its isotopically enriched (86% 76Ge) germanium detectors. Applying pulse shape discrimination (PSD) to the more recent data, the lower bound on the half-life for neutrinoless double-beta decay of 76Ge is deduced: T1/2(0ν)>1.57×1025 yr (90% C.L.). This corresponds to an upper bound on the Majorana neutrino mass parameter, 〈mν〉, between 0.33 eV and 1.35 eV depending on the choice of theoretical nuclear matrix elements used in the analysis.