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

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: T _1/2(0ν)>1.57×10²⁵ yr (90% C.L.). This corresponds to an upper bound on the Majorana neutrino mass parameter, 〈m _ν〉, between 0.33 eV and 1.35 eV depending on the choice of theoretical nuclear matrix elements used in the analysis.     

Final results of the EDELWEISS-II WIMP search using a 4-kg array of cryogenic germanium detectors with interleaved electrodes

The EDELWEISS-II Collaboration has completed a direct search for WIMP dark matter with an array of ten 400-g cryogenic germanium detectors in operation at the Laboratoire Souterrain de Modane. The combined use of thermal phonon sensors and charge collection electrodes with an interleaved geometry enables the efficient rejection of γ-induced radioactivity as well as near-surface interactions. A total effective exposure of 384 kg d has been achieved, mostly coming from fourteen months of continuous operation. Five nuclear recoil candidates are observed above 20 keV, while the estimated background is 3.0 events. The result is interpreted in terms of limits on the cross-section of spin-independent interactions of WIMPs and nucleons. A cross-section of 4.4×¹⁰−8 pb is excluded at 90%CL for a WIMP mass of 85 GeV. New constraints are also set on models where the WIMP-nucleon scattering is inelastic.     

On the investigation of possible systematics in WIMP annual modulation search

An investigation of the WIMP annual modulation signature is in progress at the Gran Sasso National Laboratory of the I.N.F.N. by means of the kg NaI(Tl) DAMA set-up; the results obtained during four annual cycles have already been published. In this paper we will further address in some details the main arguments, which have allowed us to exclude known systematic effects as a possible source of the annual modulation observed in the rate at very low energy. In particular, the (more recently released) data of the DAMA/NaI-3 and DAMA/NaI-4 running periods are considered as quantitative examples. Received: 26 September 2000 / Published online: 27 November 2000     

Dark matter search with CRESST cryogenic detectors

Results of the CRESST experiment at Gran Sasso using 262-g sapphire calorimeters with tungsten phase transition thermometers are presented. Calibration and analysis methods are described. Data taken in 2000 have been used to place limits on WIMP dark matter particles in the Galactic halo. The sapphire detectors are especially sensitive to low-mass WIMPs with spin-dependent interaction and improve on existing limits in this region.     

Speed limitation of Ge far-infrared photoconductive detectors

The speed of Ge submillimetre detectors is investigated with the aid of a pulsed n-InSb Landau emitter. A rise-time of 2.2 nsec with a responsivity of about 10 V/W is achieved for a sample containing 2 × 10¹⁵ donors and 1.2 × 10¹⁵ acceptors per cm³ at an applied electric field of 32 V/cm. The risetime can be further shortened to 0.5 nsec by reducing the bias electric field. From the observation that the capture cross-section does not decrease appreciably with increasing impurity concentration up to 2 × 10¹⁵ impurities per cm³ we conclude that no speed limitation occurs for Ge submillimetre detectors down to rise-times of about 10⁻¹⁰sec.     

New results from exposures of CR-39 nuclear track detectors

Six stacks of nuclear track detectors were exposed in December 1994 to ²⁰⁷Pb⁸²⁺ ions of 158 A GeV at the CERN-SPS. Each stack was made of CR39 sheets placed after a target. The CR39 was manufactured by the Intercast Europe Co. of Parma (Italy). The exposures were carried out at normal incidence to an average density of 400 ions/cm². The main purpose of the exposures was the calibration of the CR39 nuclear track detector used in a large area detector to search for magnetic monopoles (experiment MACRO at the Gran Sasso Laboratory). We compare the response of CR39 of different production batches in different etching conditions. The results indicate no relevant aging effect for the CR39 made more than 5 years ago. The first result of a “long period” investigation of possible fading effects for the CR39 is also presented.     

First search for gravitational wave bursts with a network of detectors

We report the initial results from a search for bursts of gravitational radiation by a network of five cryogenic resonant detectors during 1997 and 1998. This is the first significant search with more than two detectors observing simultaneously. No gravitational wave burst was detected. The false alarm rate was lower than 1 per 10(4) yr when three or more detectors were operating simultaneously. The typical threshold was H approximately 4x10(-21) Hz-1 on the Fourier component at approximately 10(3) Hz of the gravitational wave strain amplitude. New upper limits for amplitude and rate of gravitational wave bursts have been set.     

New results on first integrals of lagrangian systems

First integrals of second order systems are obtained if one lagrangian function is known. When two lagrangian functions are known the results of Hojman and Harleston are obtained.     

Segmented HPGe detectors for the search of neutrinoless double beta-decay

Neutrinoless double beta-decay (0vbb-decay) is the most promising approach to distinguish between the possibilities of a Dirac or a Majorana nature of neutrinos. Additionally, a measurement of the half-life of 0vbb-decay can give information on the absolute mass scale of neutrinos. At the moment HPGe detectors yield the most sensitive limits on this Lepton-number violating process. The segmentation of HPGe detectors increases the experimental sensitivity by allowing the reconstruction of event topologies. The successful operation of prototype detectors submerged in cryoliquid demonstrates the viability of this experimental approach.     

Calculated laser damage thresholds of Ge:Hg photoconductive detectors

Thermal damage in laser irradiated mercury-doped germanium detectors is investigated. Threshold levels of 10.6 μm laser radiation corresponding to onset of irreversible damage in Ge:Hg crystals are measured. The dependence of the damage thresholds on irradiaton time agrees favorably with thermal model predictions. Thresholds for both onset of irreversible damage and complete loss of photoresponse for Ge:Hg detectors are then calculated as a function of irradiation time, using parameters obtained from experimental results on laser damage in Ge:Hg crystals.     

New results in the search of quarks in matter by the magnetic levitation electrometer

The results of many runs performed levitating in succession several spheres without opening the levitation chamber show the existence of an additional (magneto-electric) force acting on the sphere. Ignoring this force in the analysis of the data produces “spurious” fractional charges.     

Results of the pilot experiment to search for inelastic interactions of WIMPs with 73Ge

A pilot search for the excitation of ⁷³Ge to the first excited state at 13.26 keV by spin-dependent interactions of Weakly Interacting Massive Particles (WIMPs) was performed. The first experimental results have been analyzed with a new method. The background for these reactions is ≤0.0012 events/(keV kg(⁷³Ge) d). Although there is no theory for E2 excitations by WIMPs, this very large suppression of the background may promise an enlarged version of this experiment to be competitive. It is appropriate to propose an experiment with several kg of enriched ⁷³Ge detectors based on these results.     

Current programs of search for gravitational waves by terrestrial detectors

We discuss the problem of of detection the gravitational radiation which could be produced by relativistic objects in the Universe. After a brief sketch of the detector world net the attention is concentrated on present programs of search for conceivable signals expected in the frame of modern astrophysics. It is concluded that the probability of succeeding with the modern generation of gravitational detectors, sensitive to the metric perturbation on the order of 10⁻²¹, is low. One of the ways to increase the probability is a search for “astro-gravity correlations” where a gravitational detector noise background is analysed referring to the data of gamma-ray and neutrino detectors. Author dedicates this article to Prof. Jiří Bičák’s 60th birthday.     

Compatibility of cast search with axionlike interpretation of PVLAS results

The PVLAS Collaboration has results that may be interpreted in terms of a light axionlike particle, while the CAST Collaboration has not found any signal of such particles. We propose a particle physics model with paraphotons and with a low energy scale in which this apparent inconsistency is circumvented.     

Recent results on the search of bound kaonic states in nuclei with FINUDA

An overview of the results achieved so far by the FINUDA experiment in the search of kaon–nuclear bound systems is presented.     

Decay of the first excited state at 13.3 keV in73Ge

Singles and coincidence measurements of the 13.3 keV transition of⁷³Ge are reported. The total andK conversion coefficients of this gamma-ray and the half-life of this level have been determined. The results are: α _T =1095±55; α _K =312±30;T _1/2=2.98±0.05 μs.     

First results of the search for neutrinoless double-beta decay with the NEMO 3 detector

The NEMO 3 detector, which has been operating in the Fréjus underground laboratory since February 2003, is devoted to the search for neutrinoless double-beta decay (beta beta 0v). The half-lives of the two neutrino double-beta decay (beta beta 2v) have been measured for 100Mo and 82Se. After 389 effective days of data collection from February 2003 until September 2004 (phase I), no evidence for neutrinoless double-beta decay was found from approximately 7 kg of 100Mo and approximately 1 kg of 82Se. The corresponding limits are T1/2(beta beta0v) > 4.6 x 10(23) yr for 100Mo and T1/2(beta beta 0v) > 1.0 x 10(23) yr for 82Se (90% C.L.). Depending on the nuclear matrix element calculation, the limits for the effective Majorana neutrino mass are < 0.7-2.8 e/v for 100Mo and < 1.7-4.9 eV for 82Se.     

Interpreting the LHC Higgs search results in the MSSM

Recent results reported by the ATLAS and CMS experiments on the search for a SM-like Higgs boson both show an excess for a Higgs mass near 125 GeV, which is mainly driven by the γγ   and ZZ^?$Z{Z}^{?}$ decay channels, but also receives some support from channels with a lower mass resolution. We discuss the implications of this possible signal within the context of the minimal supersymmetric Standard Model (MSSM), taking into account previous limits from Higgs searches at LEP, the Tevatron and the LHC. The consequences for the remaining MSSM parameter space are investigated. Under the assumption of a Higgs signal we derive new lower bounds on the tree-level parameters of the MSSM Higgs sector. We also discuss briefly an alternative interpretation of the excess in terms of the heavy CP-even Higgs boson, a scenario which is found to be still viable.