-
C. E. Aalseth,
III F. T. Avignone,
R. L. Brodzinski,
S. Cebrian,
E. Garcia,
D. Gonzales,
W. K. Hensley,
I. G. Irastorza,
I. V. Kirpichnikov,
A. A. Klimenko, [......],
V. S. Pogosov,
J. Puimedon, J. H. Reeves,
M. L. Sarsa,
A. A. Smolnikov,
A. S. Starostin,
A. G. Tamanyan,
A. A. Vasenko,
S. I. Vasiliev,
J. A. Villar
[show abstract]
[hide abstract]
ABSTRACT: This paper is a response to the preceding Comment by Klapdor-Kleingrothaus, Dietz, and Krivosheina. The criticisms are confronted, and the questions raised are answered. We demonstrate that the lower limit quoted by IGEX, T1/20ν(76Ge)≥1.57×1025 yr, is correct and that there was no “arithmetical error” as claimed in the “Critical View” article.
Phys. Rev. D. 10/2004; 70(7).
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D. Gonzalez,
J Morales,
S. Cebrian,
E. Garcia,
I. G. Irastorza,
A Morales,
A. Ortiz de Solorzano,
J. Puimedon,
M. L. Sarsa,
J. A. Villar, [......],
H. S. Miley, J. H. Reeves,
I. V. Kirpichnikov,
A. A. Klimenko,
S. B. Osetrov,
A. A. Smolnikov,
A. A. Vasenko,
S. I. Vasiliev,
V. S. Pogosov,
A. G. Tamanyan
[show abstract]
[hide abstract]
ABSTRACT: The IGEX experiment has been operating enriched germanium detectors in the Canfranc Underground Laboratory (Spain) in a search for the neutrinoless double decay of 76Ge. The implementation of Pulse Shape Discrimination techniques to reduce the radioactive background is described in detail. This analysis has been applied to a fraction of the IGEX data, leading to a rejection of ~60 % of their background, in the region of interest (from 2 to 2.5 MeV), down to ~0.09 c/(keV kg y).
03/2003;
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I. G. Irastorza,
A Morales,
C. E. Aalseth,
F. T. Avignone III,
R. L. Brodzinski,
J. M. Carmona,
S. Cebrian,
E. Garcia,
I. V. Kirpichnikov,
A. A. Klimenko, [......],
S. B. Osetrov,
V. S. Pogosov,
J. Puimedon, J. H. Reeves,
M. L. Sarsa,
A. A. Smolnikov,
A. G. Tamanyan,
A. A. Vasenko,
S. I. Vasiliev,
J. A. Villar
[show abstract]
[hide abstract]
ABSTRACT: One IGEX 76Ge double-beta decay detector is currently operating in the Canfranc Underground Laboratory in a search for dark matter WIMPs, through the Ge nuclear recoil produced by the WIMP elastic scattering. In this talk we report on the on-going efforts to understand and eventually reject the background at low energy. These efforts have led to the improvement of the neutron shielding and to partial reduction of the background, but still the remaining events are not totally identified. A tritium contamination or muon-induced neutrons are considered as possible sources, simulations and experimental test being still under progress. According to the success of this study we comment the prospects of the experiment as well as those of its future extension, the GEDEON dark matter experiment.
12/2002;
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C. E. Aalseth,
F. T. Avignone III,
R. L. Brodzinski,
S. Cebrian,
E. Garcia,
D. Gonzalez,
W. K. Hensley,
I. G. Irastorza,
I. V. Kirpichnikov,
A. A. Klimenko, [......],
V. S. Pogosov,
J. Puimedon, J. H. Reeves,
M. L. Sarsa,
A. A. Smolnikov,
A. S. Starostin,
A. G. Tamanyan,
A. A. Vasenko,
S. I. Vasiliev,
J. A. Villar
[show abstract]
[hide abstract]
ABSTRACT: 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: $T_{1/2}(0\nu)> 1.57 \times 10^{25}$ yr (90% C.L.). This corresponds to an upper bound in the Majorana neutrino mass parameter,$<m_{\nu}>$, between 0.33 eV and 1.35 eV, depending on the choice of theoretical nuclear matrix elements used in the analysis.
03/2002;
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The Majorana Collaboration: C. E. Aalseth,
D Anderson,
F. T. Avignone III,
A. Barabash,
T.W. Bowyer,
R. L. Brodzinski,
V. Brudanin,
J. I. Collar,
P. J. Doe,
S. Egorov, [......],
V. Sandukovsky,
E. Smith,
V. Stekhanov,
R. C. Thompson,
W. Tornow,
V. Umatov,
R. A. Warner,
J Webb,
J. Wilkerson,
A Young
[show abstract]
[hide abstract]
ABSTRACT: The Majorana Experiment is a next-generation Ge-76 double-beta decay search. It will employ 500 kg of Ge, isotopically enriched to 86% in Ge-76, in the form of 200 detectors in a close-packed array for high granularity. Each crystal will be electronically segmented, with each region fitted with pulse-shape analysis electronics. A half-life sensitivity is predicted of 4.2e27 y or < 0.02-0.07 eV, depending on the nuclear matrix elements used to interpret the data.
02/2002;
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I. G. Irastorza,
A Morales,
C. E. Aalseth,
F. T. Avignone III,
R. L. Brodzinski,
S. Cebrian,
E. Garcia,
I. V. Kirpichnikov,
A. A. Klimenko,
H. S. Miley, [......],
S. B. Osetrov,
V. S. Pogosov,
J. Puimedon, J. H. Reeves,
M. L. Sarsa,
A. A. Smolnikov,
A. G. Tamanyan,
A. A. Vasenko,
S. I. Vasiliev,
J. A. Villar
[show abstract]
[hide abstract]
ABSTRACT: One IGEX 76Ge double-beta decay detector is currently operating in the Canfranc Underground Laboratory in a search for dark matter WIMPs, through the Ge nuclear recoil produced by the WIMP elastic scattering. A new exclusion plot has been derived for WIMP-nucleon spin-independent interactions. To obtain this result, 40 days of data from the IGEX detector (energy threshold 4 keV), recently collected, have been analyzed. These data improve the exclusion limits derived from all the other ionization germanium detectors in the mass region from 20 GeV to 200 GeV, where a WIMP supposedly responsible for the annual modulation effect reported by the DAMA experiment would be located. The new IGEX exclusion contour enters, by the first time, the DAMA region by using only raw data, with no background discrimination, and excludes its upper left part. It is also shown that with a moderate improvement of the detector performances, the DAMA region could be fully explored.
12/2001;
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A Morales,
C. E. Aalseth,
F. T. Avignone III,
R. L. Brodzinski,
S. Cebrian,
E. Garcia,
I. G. Irastorza,
I. V. Kirpichnikov,
A. A. Klimenko,
H. S. Miley, [......],
S. B. Osetrov,
V. S. Pogosov,
J. Puimedon, J. H. Reeves,
M. L. Sarsa,
A. A. Smolnikov,
A. G. Tamanyan,
A. A. Vasenko,
S. I. Vasiliev,
J. A. Villar
[show abstract]
[hide abstract]
ABSTRACT: One IGEX 76Ge double-beta decay detector is currently operating in the Canfranc Underground Laboratory in a search for dark matter WIMPs, through the Ge nuclear recoil produced by the WIMP elastic scattering. A new exclusion plot, has been derived for WIMP-nucleon spin-independent interactions. To obtain this result, 40 days of data from the IGEX detector (energy threshold E \~ 4 keV), recently collected, have been analyzed. These data improve the exclusion limits derived from all the other ionization germanium detectors in the mass region from 20 GeV to 200 GeV, where a WIMP supposedly responsible for the annual modulation effect reported by the DAMA experiment would be located. The new IGEX exclusion contour enters, by the first time, the DAMA region by using only raw data, with no background discrimination, and excludes its upper left part. It is also shown that with a moderate improvement of the detector performances, the DAMA region could be fully explored.
11/2001;
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A Morales,
F. T. Avignone III,
R. L. Brodzinski,
S. Cebrian,
E. Garcia,
D. Gonzalez,
I. G. Irastorza,
H. S. Miley,
J Morales,
A. Ortiz de Solorzano,
J. Puimedon, J. H. Reeves,
M. L. Sarsa,
S. Scopel,
J. A. Villar
[show abstract]
[hide abstract]
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. 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 axion-photon coupling obtained from the analysis of the data looking for a Primakoff axion-to-photon conversion and Bragg scattering inside the crystal.
02/2001;
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I. G. Irastorza,
A Morales,
C. E. Aalseth,
F. T. Avignone III,
R. L. Brodzinski,
S. Cebrian,
E. Garcia,
D. Gonzalez,
W. K. Hensley,
H. S. Miley,
J Morales,
A. Ortiz de Solorzano,
J. Puimedon, J. H. Reeves,
M. L. Sarsa,
S. Scopel,
J. A. Villar
[show abstract]
[hide abstract]
ABSTRACT: Two germanium detectors are currently operating in the Canfranc Underground Laboratory at 2450 m.w.e looking for WIMP dark matter. One is a 2 kg 76Ge IGEX detector (RG-2) which has an energy threshold of 4 keV and a low-energy background rate of about 0.3 c/keV/kg/day. The other is a small (234 g) natural abundance Ge detector (COSME), of low energy threshold (2.5 keV) and an energy resolution of 0.4 keV at 10 keV which is looking for WIMPs and for solar axions. The analysis of 73 kg-days of data taken by COSME in a search for solar axions via their photon Primakoff conversion and Bragg scattering in the Ge crystal yields a 95% C.L. limit for the axion-photon coupling g < 2.8 10^-9 GeV^-1. These data, analyzed for WIMP searches provide an exclusion plot for WIMP-nucleon spin-independent interaction which improves previous plots in the low mass region. On the other hand, the exclusion plot derived from the 60 kg-days of data from the RG-2 IGEX detector improves the exclusion limits derived from other ionization (non thermal) germanium detector experiments in the region of WIMP masses from 30 to 100 GeV recently singled out by the reported DAMA annual modulation effect.
12/2000;
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[show abstract]
[hide abstract]
ABSTRACT: 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.
Physics of Atomic Nuclei 06/2000; 63(7):1264-1267. · 0.57 Impact Factor
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C. E. Aalseth,
F. T. Avignone,
R. L. Brodzinski,
S. Cebrian,
D. Gonzáles,
E. García,
W. K. Hensley,
I. G. Irastorza,
I. V. Kirpichnikov,
A. A. Klimenko, [......],
J. Puimedón, J. H. Reeves,
M. L. Sarsa,
S. Scopel,
A. A. Smolnikov,
A. S. Starostin,
A. G. Tamanyan,
A. A. Vasenko,
S. I. Vasiliev,
J. A. Villar
[show abstract]
[hide abstract]
ABSTRACT: 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.
Physics of Atomic Nuclei 06/2000; 63(7):1225-1228. · 0.57 Impact Factor
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C. E. Aalseth,
F. T. Avignone,
R. L. Brodzinski,
S. Cebrian,
D. Gonzáles,
E. García,
W. K. Hensley,
I. G. Irastorza,
I. V. Kirpichnikov,
A. A. Klimenko, [......],
J. Puimedón, J. H. Reeves,
M. L. Sarsa,
S. Scopel,
A. A. Smolnikov,
A. S. Starostin,
A. G. Tamanyan,
A. A. Vasenko,
S. I. Vasiliev,
J. A. Villar
[show abstract]
[hide abstract]
ABSTRACT: To search for cold dark matter (CDM) particles, the data from two (Ge-76 and Ge-natural) detectors, fabricated in the first
phase of the IGEX collaboration, were accumulated and analyzed for a period from May 1995 to May 1999. The use of effective
passive and active shielding together with pulse shape discrimination allowed us to perform long-term measurements with an
energy threshold of 2 keV at a level of the residual background 0.1 counts/(kg keV d). New restrictions on masses of weakly
interacting massive particles and the cross section of their elastic scattering on nuclei have been obtained from the data
corresponding to 810 d of live time. The derived exclusion plots compete with the best bounds obtained so far. Annual modulations
of the CDM signal have been also investigated. It is shown that the planned operation of all IGEX detectors (at Canfranc and
Baksan) with the recently achieved low-energy thresholds gives a chance to achieve the DAMA annual modulation sensitivity
region in a nearest future.
Physics of Atomic Nuclei 06/2000; 63(7):1268-1271. · 0.57 Impact Factor
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A Morales,
C. E. Aalseth,
F. T. Avignone III,
R. L. Brodzinski,
S. Cebrian,
E. Garcia,
D. Gonzalez,
W. K. Hensley,
I. G. Irastorza,
I. V. Kirpichnikov, [......],
V. S. Pogosov,
J. Puimedon, J. H. Reeves,
M. L. Sarsa,
S. Scopel,
A. A. Smolnikov,
A. G. Tamanyan,
A. A. Vasenko,
S. I. Vasiliev,
J. A. Villar
[show abstract]
[hide abstract]
ABSTRACT: The IGEX Collaboration enriched 76Ge 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 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 of ~4 keV, have been considered. These data improve the exclusion limits derived from other germanium diode 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.
03/2000;
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[show abstract]
[hide abstract]
ABSTRACT: An improved low-background cooled FET assembly for germanium spectroscopy has been designed and tested at PNNL. This assembly was designed to improve signal fidelity, improve physical reliability under thermal cycling, and optimize the temperature of the FET. While meeting these goals, the assembly must also contribute negligibly to the radioactive background of the detector system. Component and material screening for this system were accomplished with two different PNNL ultra-low level spectrometers. Thermal design was validated using a cold stage at a variety of temperatures. Its temperature dependence allowed us, in one case, to calibrate the resistive feedback element as a temperature sensor. Electronic response was measured and compared to existing low-background and commercial systems. The result is an electrical and physical package that is robust and useful for special applications such as pulse shape analysis and ultra-low background radiation detection
Nuclear Science Symposium, 1999. Conference Record. 1999 IEEE; 02/1999
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[show abstract]
[hide abstract]
ABSTRACT: Two measurements of the half-life of the 2 nu beta beta -decay of 76Ge are reported. One was made with the PNL-USC natural isotopic abundance germanium twin detectors. T12/2 nu =(1.12+-0.26+0.48)*1021 y (2 sigma ), and one with a Soviet-manufactured 0.25-kg Ge (Li) detector isotopically enriched to 85% in 76Ge, T12/2 nu (9.2+-0.4+0.7)*1020 y (2 sigma ). Both were measured in the same facility. These values are in good agreement with nuclear structure calculations and with an independent measurement by the ITEP-YPI collaboration.
Journal of Physics G Nuclear and Particle Physics 12/1998; 17(S):S181. · 4.18 Impact Factor
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D. Abriola,
F. T. Avignone III,
R. L. Brodzinski,
J. I. Collar,
D. E. Di Gregorio,
H. A. Farach,
E. Garcia,
A. O. Gattone,
C. K. Guerard,
F. Hasenbalg,
H Huck,
H. S. Miley,
A Morales,
J Morales,
A. Ortiz de Solorzano,
J. Puimedon, J. H. Reeves,
A. Salinas,
M. L. Sarsa,
J. A. Villar
[show abstract]
[hide abstract]
ABSTRACT: Data collected during three years with a germanium spectrometer at the Sierra Grande underground laboratory have been analyzed for distinctive features of annual modulation of the signal induced by WIMP dark matter candidates. The main motivation for this analysis was the recent suggestion by the DAMA/NaI Collaboration that a yearly modulation signal could not be rejected at the 90% confidence level when analyzing data obtained with a high-mass low-background scintillator detector. We performed two different analyses of the data: First, the statistical distribution of modulation-significance variables (expected from an experiment running under the conditions of Sierra Grande) was compared with the same variables obtained from the data. Second, the data were analyzed in energy bins as an independent check of the first result and to allow for the possibility of a crossover in the expected signal. In both cases no statistically significant deviation from the null result was found, which could support the hypothesis that the data contain a modulated component. A plot is also presented to enable the comparison of these results to those of the DAMA collaboration. Comment: New version accepted by Astroparticle Physics. Changes suggested by the referee about the theoretical prediction of rates are included. Conclusions remain unaffected. 14 pages, LaTeX, 7 figures. Uses epsfig macro
09/1998;
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[show abstract]
[hide abstract]
ABSTRACT: A fast digital oscilloscope based pulse shape discrimination (PSD) system has been tested with intrinsic germanium detectors
large enough to allow ionizing events which generate localized electron-hole pairs at a single site to be segregated from
those depositing energy at several different sites in the crystal. Drift velocities of the electrons and holes result in pulses
several hundred nanoseconds long. Since the electric field varies by almost a factor of 10 between the outer and inner surfaces,
collection of electrons and holes can frequently be dinstinguished, and pulses due to multi-site events can be distinguished
from single site events.
Journal of Radioanalytical and Nuclear Chemistry 06/1998; 233(1):119-125. · 1.52 Impact Factor
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A. O. Gattone,
D. Abriola,
F T Avignone,
R. L. Brodzinski,
J. I. Collar,
R. J. Creswick,
D. E. Di Gregorio,
H. A. Farach,
C K Guérard,
F. Hasenbalg,
H Huck,
H. S. Miley,
A Morales,
J Morales,
S. Nussinov,
A. Ortiz de Solórzano, J. H. Reeves,
J. A. Villar,
K. Zioutas
[show abstract]
[hide abstract]
ABSTRACT: A new technique has been used to search for solar axions using a single crystal germanium detector. It exploits the coherent conversion of axions into photons when their angle of incidence satisfies a Bragg condition with a crystalline plane. The analysis of approximately 1.94 kg.yr of data from the 1-kg DEMOS detector in Sierra Grande, Argentina, yields a new laboratory bound on axion-photon coupling of g_{a,\gamma\gamma}<2.7\times 10^{-9} GeV^{-1} independent of axion mass up to \sim 1 keV.
01/1998;
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F T Avignone,
D. Abriola,
R. L. Brodzinski,
J. I. Collar,
R. J. Creswick,
D. E. DiGregorio,
H. A. Farach,
A. O. Gattone,
C. K. Guerard,
F. Hasenbalg,
H Huck,
H. S. Miley,
A Morales,
J Morales,
S. Nussinov,
A. Ortiz de Solorzano, J. H. Reeves,
J. A. Villar,
K. Zioutas
[show abstract]
[hide abstract]
ABSTRACT: 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. This conversion is predicted when axions are incident at a Bragg angle with a crystalline plane. The analysis of approximately 1.94 kg.yr of data from the 1 kg DEMOS detector in Sierra Grande, Argentina, yields a new laboratory bound on axion-photon coupling of $g_{a\gamma \gamma} < 2.7\cdot 10^{-9}$ GeV$^{-1}$, independent of axion mass up to ~ 1 keV. Comment: RevTeX, 11 pages, figures can be obtained by fax from Juan.Collar@cern.ch. Submitted to Phys. Lett. B
08/1997;
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[show abstract]
[hide abstract]
ABSTRACT: Laboratory tests have established the feasibility of using neutron activation of copper as a means for measuring the moisture in Hanford`s high-level radioactive waste tanks. The performance of the neutron activation technique to measure moisture is equivalent to the neutron moisture gauges or neutron logs commonly used in commercial well-logging. The principle difference is that the activation of {sup 64}Cu (t{sub 1/2} = 12.7 h) replaces the neutron counters used in moisture gauges or neutron logs. For application to highly radioactive waste tanks, the Cu activation technique has the advantage that it is insensitive to very strong gamma radiation fields or high temperatures. In addition, this technique can be deployed through tortuous paths or in confined spaces such as within the bore of a cone penetrometer. However, the results are not available in ``real-time``. The copper probe`s sensitivity to moisture was measured using simulated tank waste of known moisture content. This report describes the preparation of the simulated waste mixtures and the experiments performed to demonstrate the capabilities of the neutron activation technique. These experiments included determination of the calibration curve of count rate versus moisture content using a single copper probe, measurement of the calibration curve based on ``near-field `` to ``far-field`` counting ratios using a multiple probe technique, and profiling the activity of the copper probe as a function of the vertical height within a simulated waste barrel.
09/1995;
