P. Agnes et al. (DarkSide Collaboration) M. Wójcik, G. Zuzel & K. Pelczar

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http://dx.doi.org/10.1103/PhysRevD.93.081101

Abstract

Liquid argon is a bright scintillator with potent particle identification properties, making it an attractive target for direct-detection dark matter searches. The DarkSide-50 dark matter search here reports the first WIMP search results obtained using a target of low-radioactivity argon. DarkSide-50 is a dark matter detector, using a two-phase liquid argon time projection chamber, located at the Laboratori Nazionali del Gran Sasso. The underground argon is shown to contain Ar39 at a level reduced by a factor (1.4±0.2)×103 relative to atmospheric argon. We report a background-free null result from (2616±43)  kg d of data, accumulated over 70.9 live days. When combined with our previous search using an atmospheric argon, the 90% C.L. upper limit on the WIMP-nucleon spin-independent cross section, based on zero events found in the WIMP search regions, is 2.0×10−44  cm2 (8.6×10−44  cm2, 8.0×10−43  cm2) for a WIMP mass of 100  GeV/c2 (1  TeV/c2, 10  TeV/c2).

Applied Radiation and Isotopes 81 (2013) 146–150

M. Misiaszek a), K. Pelczar a), M. Wójcik a), G. Zuzel a) & M. Laubenstein b)

a) M. Smoluchowski Institute of Physics, Jagiellonian University, Reymonta 4, PL-30-059 Kraków, Poland
b) Laboratori Nazionali del Gran Sasso, INFN, S.S. 17/bis km 18+910, Assergi(AQ), I-67100 Italy

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http://dx.doi.org/10.1016/j.apradiso.2013.03.006

Abstract

Results of alpha spectrometric measurements deep underground and above ground with and without active veto show that the underground measurement of thick samples is the most sensitive method due to significant reduction of the muon-induced background. In addition, the polonium diffusion for some samples requires an appropriate selection of an energy region in the registered spectrum. On the basis of computer simulations the best counting conditions are selected for a thick lead sample in order to optimize the detection limit.

Applied Radiation and Isotopes 81 (2013) 81–86

Guillaume Lutter a), Mikael Hult a), Gerd Marissens a), Erica Andreotti a), Ulf Rosengård a), Marcin Misiaszek b), Ayhan Yüksela c) & Namik Sahina d)

a) European Commission, DG JRC, Institute for Reference Materials and Measurements (IRMM), Retieseweg 111, 2440 Geel, Belgium
b) Smoluchowski Institute of Physics, Jagiellonian University, ul. Reymonta 4, PL-30-059 Krakow, Poland
c) TAEK-CNAEM, Turkish Atomic Energy Authority, Istanbul, Turkey
d) TAEK-SANAEM, Turkish Atomic Energy Authority, Ankara,Turkey

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http://dx.doi.org/10.1016/j.apradiso.2013.03.079

Abstract

The newest development in IRMM’s underground analytical facility is a large lead shield lined with copper that is versatile and can host several detectors of different types. The characteristics and the background performance of the shield are described for four different detector configurations involving HPGe-detectors and NaI-detectors. The shield has been designed to swap detectors, while still maintaining a low background. This enables testing of detectors for other experiments and optimisation of detection limits for specific radionuclides in different projects.

doi:10.1088/1475-7516/2012/05/015

G. Bellini et al. (Borexino Collaboration) M. Wójcik, G. Zuzel, M. Misiaszek

Download http://iopscience.iop.org/1475-7516/2012/05/015

Abstract
We have measured the muon flux at the underground Gran Sasso National Laboratory (3800 m w.e.) to be (3.41±0.01)⋅10⁻⁴m⁻²s⁻¹ using four years of Borexino data. A modulation of this signal is observed with a period of (366±3) days and a relative amplitude of (1.29±0.07)%. The measured phase is (179±6) days, corresponding to a maximum on the 28^th of June. Using the most complete atmospheric data models available, muon rate fluctuations are shown to be positively correlated with atmospheric temperature, with an effective coefficient α_T = 0.93±0.04. This result represents the most precise study of the muon flux modulation for this site and is in good agreement with expectations.

J. S. E. Wieslander,1,2 J. Suhonen,2 T. Eronen,2 M. Hult,1 V.-V. Elomaa,2 A. Jokinen,2 G. Marissens, M. Misiaszek,3 M. T. Mustonen,2 S. Rahaman,2 C. Weber,2 and J. Äystö2

1)EC-JRC-IRMM, Institute for Reference Materials and Measurements, Retieseweg 111, B-2440 Geel, Belgium
2)Department of Physics, P.O. Box 35 (YFL), FIN-40014 University of Jyväskylä, Finland
3)Marian Smoluchowski Institute of Physics, Jagiellonian University, ul. Reymonta 4, 30-059 Krakow, Poland

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Abstract

The ground-state-to-ground-state Qbeta- value of 115In was determined to 497.68(17) keV using a high-precision Penning trap facility at the University of Jyväskylä, Finland. From this, a Qbeta- value of 0.35(17) keV was obtained for the rare beta- decay to the first excited state of 115Sn at 497.334(22) keV. The partial half-life was determined to 4.1(6)×1020 yr using ultra low-background gamma-ray spectrometry in an underground laboratory. Theoretical modeling of this 2nd-forbidden unique beta- transition was also undertaken and resulted in Qbeta-=57_-12⁺¹⁹ eV using the measured half-life. The discrepancy between theory and experiment could be attributed to atomic effects enhanced by the low Q value. The present study implies that this transition has the lowest Q value of any known nuclear beta decay.

J.S. Elisabeth Wieslander a, d, Mikael Hult a, Joël Gasparro a, Gerd Marissens a, Marcin Misiaszek b and Werner Preusse a, c

a) EC-JRC-IRMM, Institute for Reference Materials and Measurements, Retieseweg 111, B-2440 Geel, Belgium
b) M. Smoluchowski Institute of Physics, Jagiellonian University, ul. Reymonta 4, 30-059 Krakow, Poland
c) Saxon State Laboratories for Environmental Radioactivity, Dresdner Street 183, D-09131 Chemnitz, Germany
d) Department of Physics, P.O. Box 35 (YFL), FIN-40014 University of Jyväskylä, Finland

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Abstract

The technical details and performance of the newly developed Sandwich spectrometer for ultra low-level γ-ray spectrometry are presented. The spectrometer, which consists of two HPGe detectors, an active muon shield and a lead/copper shield with a convenient and rapid opening mechanism, is located in an underground laboratory at a depth of 500 m water equivalent. The data is collected in list mode, which enables off-line data analysis to identify muon-induced events and possible Ge detector crosstalk due to Compton scattering. The background count-rate from 40 to 2700 keV normalised to the mass of the Ge crystals is 220 day−1 kg−1