The Majorana Collaboration is operating an array of high purity Ge detectors to search for neutrinoless double-β decay in ^{76}Ge. The Majorana Demonstrator comprises 44.1 kg of Ge detectors (29.7 kg enriched in ^{76}Ge) split between two modules contained in a low background shield at the Sanford Underground Research Facility in Lead, South Dakota. Here we present results from data taken during construction, commissioning, and the start of full operations. We achieve unprecedented energy resolution of 2.5 keV FWHM at Q_{ββ} and a very low background with no observed candidate events in 9.95 kg yr of enriched Ge exposure, resulting in a lower limit on the half-life of 1.9×10^{25}  yr (90% C.L.). This result constrains the effective Majorana neutrino mass to below 240-520 meV, depending on the matrix elements used. In our experimental configuration with the lowest background, the background is 4.0_{-2.5}^{+3.1}  counts/(FWHM t yr).

An ultralow background spectrometer is used as a detector of cold dark matter candidates from the halo of our galaxy Using a realistic model for the galactic halo, large regions of the mass-cross section space are excluded for important halo component particles. In particular, a halo dominated by heavy standard Dirac neutrinos (taken as an example of particles with spm-lndependent Z ° exchange interactions) with masses between 20 GeV and 1 TeV is excluded. The local density of heavy standard Dirac neutrinos is <0.4 GeV/cm 3 for masses between 17.5 GeV and 2 5 TeV, at the 68% confidence level.Galactic rotation curves suggest that most of the matter in the universe is non-luminous [ 1 ]. A variety of arguments suggest that this matter may be nonbaryonic [2]. This letter discusses the use of an ultralow background germanium spectrometer as a detector of cold dark matter particles interacting with Ge nuclei. Since only 73Ge, with a natural abundance of 7.8%, has a non-zero spin, our best bounds apply to spin-independent (s.i.) interactions. Bounds on dark matter candidates coupling to baryons through Z ° exchange, like stable massive Dirac neutrinos [ 3 ] and scalar neutrinos [4], are presented. Our results exclude a halo dominated by particles with scattering cross section 0"Sl =O'weak with masses 20 GeV ~m~< 1 TeV (their local density is <0.4 GeV/cm 3 for 17.5 GeV ~m~<2.5 TeV at the 68% confidence level) and apply to s.i. reactions in the range of O "SI ~ 10--10"weak to 0 "Sl ~ 10 .28 cm 2 (for which the dark matter particles would be stopped in the earth's On leave of absence from Department of Physics, University of Rome II, Via Orazlo Ralmondo, 1-00173 Rome, Italy crust before arriving at the detector) where 0"weak is the weak scattering cross section of a standard heavy Dirac neutrino from a Ge nucleus. This range includes neutral technibaryons, recently proposed as dark matter candidates [5], having cross sections -~ 100weak , which are, therefore, excluded for masses larger than 16 GeV. The 73Ge in the detector with s = 9/2, allows us to obtain a bound on particles with spin-dependent (s.d.) interactions, which case applies to particles in the range a---4 s a 10 O'~,ea k to O',~, 10 -28 cm 2 (where O' weakSd" corresponds to a standard heavy Majorana neutrino).The measurement of the nuclear recoil, due to the scattering of heavy weakly interacting massive partides (WIMPs), requires a detector with a low energy threshold and excellent background rejection [6][7][8].In this paper, the use of a germanium diode detector to search for dark matter is discussed. The low band gap (0.69 eV at 77 K) and high efficiency for converting electronic energy loss to electron-hole (e-h) pairs (2.96 eV per e-h pair at 77 K) make germanium detectors probably the best existing detectors 0370-2693/87/$ 03.50

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 1.94 kg yr of data from the 1 kg DEMOS detector in Sierra Grande, Argentina, yields a new laboratory bound by an axion-photon coupling of g agg , 2.7 3 10 29 GeV 21 , independent of axion mass up to ϳ1 keV. [S0031-9007(98)07812-0] PACS numbers: 14.80. Mz, 96.60.Vg Early QCD theories predicted a particle with the quantum numbers of the h meson, but with a mass close to that of the pion. A term added to the QCD Lagrangian to ameliorate this so-called U(1) problem violated CP invariance in strong interactions and implied a neutron electric-dipole moment about 10 9 times larger than the experimental upper bound [1]. Peccei and Quinn [2] introduced a new field causing strong CP violation to vanish dynamically. Subsequently, Weinberg [3,4] and Wilczek [5] demonstrated that the Peccei-Quinn mechanism generates a Nambu-Goldstone boson, the axion, that couples to a two-photon vertex via a coupling g agg . Axion production via the Primakoff effect occurs when a photon couples to a charge via a virtual photon, producing an axion. Detection can occur by observing photons resulting from axions coupling to electrical charges via virtual photons.The dense volume of photons and charges in the sun or any star produces conditions for axion production. The Ge detector then can act as the axion-photon converter and detector. When the characteristic wavelength of the axion satisfies a Bragg condition in the single crystal Ge detector, photon production would occur with an expected temporal pattern depending on the changing relative directions between the vectors from the solar core and the crystalline planes.Extensive reviews of axion phenomenology and their effects on stellar evolution have been given by Raffelt [6,7] who gives a bound of 10 210 GeV 21 on the coupling of axions to the two-photon vertex from the population of red giant stars. A detailed treatment of solar axions and of a proposed method of detecting them was given by van Bibber et al. [8]. Details of a theory for searching for axions with germanium detectors were recently given by Creswick et al. [9]. The objective is to detect solar axions through their coherent Primakoff conversion into photons in the lattice of a germanium crystal when the incident angle satisfies the Bragg condition. The detection rates in various energy windows are correlated with the relative orientations of the detector and the sun [9]. This correlation results in a distinctive, unique signature of the axion. In this Letter, the results of a search using a 1 kg, ultralow background germanium detector installed in the HIPARSA iron mine in Sierra Grande, Argentina, at 410 24 00 S and 65 ± 22 0 W are presented. A description of the experimental setup and detector spectrum was given earlier by Di Gregori...

We comment on the recent claim for the experimental observation of neutrinoless doublebeta decay. We discuss several limitations in the analysis provided in that paper and conclude that there is no basis for the presented claim.

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Abstract. The 8.4 Tesla, 10 m long transverse magnetic field of a twin aperture LHC bending magnet can be utilized as a macroscopic coherent solar axion-to-photon converter. Numerical calculations show that the integrated time of alignment with the Sun would be 33 days per year with the magnet on a tracking table capable of ±5 o in the vertical direction and ±40 o in the horizontal direction. The existing lower bound on the axion-to-photon coupling constant can be improved by a factor between 30 and 100 in 3 years, i.e., g aγγ < ∼ 9 · 10 −11 GeV −1 for axion masses < ∼ 1 eV. This value falls within the existing open axion mass window. The same set-up can simultaneously search for lowand high-energy celestial axions, or axion-like particles, scanning the sky as the Earth rotates and orbits the Sun.

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

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 [1,2]. 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 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 axionphoton coupling obtained from the analysis of the data looking for a Primakoff axion-to-photon conversion and Bragg scattering inside the crystal. PACS: 95.35+d; 14.80.Mz