310 research outputs found

    MERGING THE 21ST CENTURY INTO A GILDED AGE, FORTUNE 500 BOARDROOM

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    Polychrome, gilded, and embossed leather was considered an attractive covering for decorative furnishings and walls in American Gilded Age mansions. These specialty European leathers originally crafted in the 17th and 18th century were either repurposed in the 19th century for the American market or, new versions of them were crafted following evolving 19th century technologies. By the 21st century, with a decreased demand for these decorative leathers, the craft traditions had become a forgotten art. The 2003 decision to replace 1,400 square feet of polychromed embossed leather in a gilded age boardroom presented an opportunity to visit the atelier to discuss and document the decorative finishing process. This presentation shares through a photo essay how one workshop has revived this traditional craft for the 21st century marketplace. Decorated leathers are produced using a combination of traditional techniques and contemporary materials. The presentation will also address how these leathers were prepared and mounted for long-term preservation needs using current materials and methods

    Background free search for neutrinoless double beta decay with GERDA Phase II

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    The Standard Model of particle physics cannot explain the dominance of matter over anti-matter in our Universe. In many model extensions this is a very natural consequence of neutrinos being their own anti-particles (Majorana particles) which implies that a lepton number violating radioactive decay named neutrinoless double beta (0νββ0\nu\beta\beta) decay should exist. The detection of this extremely rare hypothetical process requires utmost suppression of any kind of backgrounds. The GERDA collaboration searches for 0νββ0\nu\beta\beta decay of 76^{76}Ge (^{76}\rm{Ge} \rightarrow\,^{76}\rm{Se} + 2e^-) by operating bare detectors made from germanium with enriched 76^{76}Ge fraction in liquid argon. Here, we report on first data of GERDA Phase II. A background level of 103\approx10^{-3} cts/(keV\cdotkg\cdotyr) has been achieved which is the world-best if weighted by the narrow energy-signal region of germanium detectors. Combining Phase I and II data we find no signal and deduce a new lower limit for the half-life of 5.310255.3\cdot10^{25} yr at 90 % C.L. Our sensitivity of 4.010254.0\cdot10^{25} yr is competitive with the one of experiments with significantly larger isotope mass. GERDA is the first 0νββ0\nu\beta\beta experiment that will be background-free up to its design exposure. This progress relies on a novel active veto system, the superior germanium detector energy resolution and the improved background recognition of our new detectors. The unique discovery potential of an essentially background-free search for 0νββ0\nu\beta\beta decay motivates a larger germanium experiment with higher sensitivity.Comment: 14 pages, 9 figures, 1 table; ; data, figures and images available at http://www.mpi-hd.mpg/gerda/publi

    Limits on uranium and thorium bulk content in GERDA Phase I detectors

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    Internal contaminations of 238^{238}U, 235^{235}U and 232^{232}Th in the bulk of high purity germanium detectors are potential backgrounds for experiments searching for neutrinoless double beta decay of 76^{76}Ge. The data from GERDA Phase~I have been analyzed for alpha events from the decay chain of these contaminations by looking for full decay chains and for time correlations between successive decays in the same detector. No candidate events for a full chain have been found. Upper limits on the activities in the range of a few nBq/kg for 226^{226}Ra, 227^{227}Ac and 228^{228}Th, the long-lived daughter nuclides of 238^{238}U, 235^{235}U and 232^{232}Th, respectively, have been derived. With these upper limits a background index in the energy region of interest from 226^{226}Ra and 228^{228}Th contamination is estimated which satisfies the prerequisites of a future ton scale germanium double beta decay experiment.Comment: 2 figures, 7 page

    2νββ2\nu\beta\beta decay of 76^{76}Ge into excited states with GERDA Phase I

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    Two neutrino double beta decay of 76^{76}Ge to excited states of 76^{76}Se has been studied using data from Phase I of the GERDA experiment. An array composed of up to 14 germanium detectors including detectors that have been isotopically enriched in 76^{76}Ge was deployed in liquid argon. The analysis of various possible transitions to excited final states is based on coincidence events between pairs of detectors where a de-excitation γ\gamma ray is detected in one detector and the two electrons in the other. No signal has been observed and an event counting profile likelihood analysis has been used to determine Frequentist 90\,\% C.L. bounds for three transitions: 0g.s.+21+{0^+_{\rm g.s.}-2^+_1}: T1/22ν>T^{2\nu}_{1/2}>1.61023\cdot10^{23} yr, 0g.s.+01+{0^+_{\rm g.s.}-0^+_1}: T1/22ν>T^{2\nu}_{1/2}>3.71023\cdot10^{23} yr and 0g.s.+22+{0^+_{\rm g.s.}-2^+_2}: T1/22ν>T^{2\nu}_{1/2}>2.31023\cdot10^{23} yr. These bounds are more than two orders of magnitude larger than those reported previously. Bayesian 90\,\% credibility bounds were extracted and used to exclude several models for the 0g.s.+01+{0^+_{\rm g.s.}-0^+_1} transition

    Results on ββ\beta\beta decay with emission of two neutrinos or Majorons in 76^{76}Ge from GERDA Phase I

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    A search for neutrinoless ββ\beta\beta decay processes accompanied with Majoron emission has been performed using data collected during Phase I of the GERmanium Detector Array (GERDA) experiment at the Laboratori Nazionali del Gran Sasso of INFN (Italy). Processes with spectral indices n = 1, 2, 3, 7 were searched for. No signals were found and lower limits of the order of 1023^{23} yr on their half-lives were derived, yielding substantially improved results compared to previous experiments with 76^{76}Ge. A new result for the half-life of the neutrino-accompanied ββ\beta\beta decay of 76^{76}Ge with significantly reduced uncertainties is also given, resulting in T1/22ν=(1.926±0.095)1021T^{2\nu}_{1/2} = (1.926 \pm 0.095)\cdot10^{21} yr.Comment: 3 Figure

    Limit on the Radiative Neutrinoless Double Electron Capture of 36^{36}Ar from GERDA Phase I

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    Neutrinoless double electron capture is a process that, if detected, would give evidence of lepton number violation and the Majorana nature of neutrinos. A search for neutrinoless double electron capture of 36^{36}Ar has been performed with germanium detectors installed in liquid argon using data from Phase I of the GERmanium Detector Array (GERDA) experiment at the Gran Sasso Laboratory of INFN, Italy. No signal was observed and an experimental lower limit on the half-life of the radiative neutrinoless double electron capture of 36^{36}Ar was established: T1/2>T_{1/2} > 3.6 ×\times 1021^{21} yr at 90 % C.I.Comment: 7 pages, 3 figure
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