SOURCES: a code for calculating (α,n), spontaneous fission, and delayed neutron sources and spectra

Wilson, W.B.; Perry, R.T.; Charlton, William; Parish, T.A.; Shores, Erik F.

doi:10.1093/rpd/nci260

Cited by 78 publications

(99 citation statements)

References 14 publications

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“…capture on 63 Cu and 65 Cu in the copper components, and on 136 Xe in the LXe). A simulation using a simplified experimental geometry and employing the FLUKA [22,23] and SOURCES [24] software packages is used to generate neutrons, track and thermalize them. The resulting neutron capture rates are used as input to the Geant4-based [20] EXO-200 simulation package [9], with the respective ncapture γ-spectra produced based upon ENSDF information [25] for the given nuclides.…”

Section: Investigation and Determination Of Systematic Errorsmentioning

confidence: 99%

Search for Majorana neutrinos with the first two years of EXO-200 data

2014

Nature

386

318

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Many extensions of the Standard Model of particle physics suggest that neutrinos should be Majorana-type fermions, but this assumption is difficult to confirm. Observation of neutrinoless double-beta decay (0νββ), a spontaneous transition that may occur in several candidate nuclei, would verify the Majorana nature of the neutrino and constrain the absolute scale of the neutrino mass spectrum. Recent searches carried out with 76 Ge (GERDA experiment) and 136 Xe (KamLAND-Zen and EXO-200 experiments) have established the lifetime of this decay to be longer than 10 25 yr, corresponding to a limit on the neutrino mass of 0.2-0.4 eV. Here we report new results from EXO-200 based on 100 kg·yr of 136 Xe exposure, representing an almost fourfold increase from our earlier published datasets. We have improved the detector resolution at the 136 Xe double-betadecay Q-value to σ/E = 1.53% and revised the data analysis. The obtained half-life sensitivity is 1.9 · 10 25 yr, an improvement by a factor of 2.7 compared to previous EXO-200 results. We find no statistically significant evidence for 0νββ decay and set a half-life limit of 1.1 · 10 25 yr at 90% CL. The high sensitivity holds promise for further running of the EXO-200 detector and future 0νββ decay searches with nEXO. Majorana fermions, a class of neutral spin-1/2 particles described by 2-component spinors, have been an element of quantum field theory since its inception [1,2]. Electrons and other spin-1/2 elementary particles with distinct antiparticles, however, are described by 4-component Dirac spinors. Majorana quasiparticles may have been observed in condensed matter systems [3] where neutrality is achieved through the collective action of electrons and holes. Among the known elementary particles, only neutrinos are Majorana fermion candidates, owing to their intrinsic neutrality. Confirmation of this property would imply the non-conservation of lepton number, an additive quantum number that, unlike charge or color, is not related to any known gauge symmetry. As yet, lepton number has been empirically found to be conserved. Neutrinos are also remarkable for their small, yet finite, masses [4] that are generally difficult to explain, but arise naturally in many extensions [5,6] of the Standard Model of particle physics (SM). A generic consequence of many such extensions is that neutrinos should be of the Majorana variety.The most sensitive probe for Majorana neutrinos is a nuclear process known as neutrinoless double-beta decay (0νββ), whereby a nucleus decays by emitting two electrons and nothing else, while changing its charge by two units [7]. A related double-beta decay process, known as two-neutrino double-beta decay (2νββ), is allowed by the SM and has been observed in many nuclei, 136 Xe among them [8,9]. It provides, however, no direct information on the Majorana/Dirac question. The exotic 0νββ can be distinguished from the 2νββ by measuring the sum energy of the two electrons that is peaked at the Q-value for the former and is a continuum for the latter....

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Section: Investigation and Determination Of Systematic Errorsmentioning

confidence: 99%

Search for Majorana neutrinos with the first two years of EXO-200 data

2014

Nature

386

318

View full text Add to dashboard Cite

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“…For alumina, such as is used for the construction of the insulator in this model of resistor, the total neutron yield (due to the high cross-section (α,n) reaction involving 27 Al) for the 238 U chain in equilibrium is calculated using the SOURCES4A software [30]. The soft- Table 6: Calculated contaminations for a sample of resistors screened using both Chaloner and Lunehead.…”

Section: Significant Disequilibrium At 210 Pbmentioning

confidence: 99%

Low-background gamma spectroscopy at the Boulby Underground Laboratory

Scovell

Meehan²,

Araújo

et al. 2018

Astroparticle Physics

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The Boulby Underground Germanium Suite (BUGS) comprises three low-background, high-purity germanium detectors operating in the Boulby Underground Laboratory, located 1.1 km underground in the north-east of England, UK. BUGS utilises three types of detector to facilitate a high-sensitivity, high-throughput radio-assay programme to support the development of rare-event search experiments. A Broad Energy Germanium (BEGe) detector delivers sensitivity to low-energy gamma-rays such as those emitted by 210 Pb and 234 Th. A Small Anode Germanium (SAGe) well-type detector is employed for efficient screening of small samples. Finally, a standard p-type coaxial detector provides fast screening of standard samples. This paper presents the steps used to characterise the performance of these detectors for a variety of sample geometries, including the corrections applied to account for cascade summing effects. For low-density materials, BUGS is able to radio-assay to specific activities down to 3.6 mBq kg −1 for 234 Th and 6.6 mBq kg −1 for 210 Pb both of which have uncovered some significant equilibrium breaks in the 238 U chain. In denser materials, where gamma-ray self-absorption increases, sensitivity is demonstrated to specific activities of 0.9 mBq kg −1 for 226 Ra, 1.1 mBq kg −1 for 228 Ra, 0.3 mBq kg −1 for 224 Ra, and 8.6 mBq kg −1 for 40 K with all upper limits at a 90% confidence level. These meet the requirements of most screening campaigns presently under way for rare-event search experiments, such as the LUX-ZEPLIN (LZ) dark matter experiment. We also highlight the ability of the BEGe detector to probe the X-ray fluorescence region which can be important to identify the presence of radioisotopes associated with neutron production; this is of particular relevance in experiments sensitive to nuclear recoils.

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“…Neutrons originating from the Th and U decay chains were simulated for each material in the setup (lead, polyethylene, copper). The primary energy spectra of the neutrons was generated using the SOURCES4C package [74][75][76], which computes the neutron spectra due to spontaneous fission and (α, n) reactions of alphas from the full decay chains within the matrix material. The neutrons were propagated through all materials, eventually creating NRs in the Ge and Si detectors.…”

Section: Radiogenic Background Estimatementioning

confidence: 99%

Improved WIMP-search reach of the CDMS II germanium data

Agnese¹,

Anderson²,

Asai³

et al. 2015

Phys. Rev. D

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CDMS II data from the 5-tower runs at the Soudan Underground Laboratory were reprocessed with an improved charge-pulse fitting algorithm. Two new analysis techniques to reject surfaceevent backgrounds were applied to the 612 kg days germanium-detector WIMP-search exposure. An extended analysis was also completed by decreasing the 10 keV analysis threshold to ∼5 keV, to increase sensitivity near a WIMP mass of 8 GeV/c 2 . After unblinding, there were zero candidate events above a deposited energy of 10 keV and 6 events in the lower-threshold analysis. This yielded minimum WIMP-nucleon spin-independent scattering cross-section limits of 1.8×10 −44 and 1.18×10 −41 cm 2 at 90% confidence for 60 and 8.6 GeV/c 2 WIMPs, respectively. This improves the previous CDMS II result by a factor of 2.4 (2.7) for 60 (8.6) GeV/c 2 WIMPs.PACS numbers: 95.35.+d, 95.30.Cq, 85.25.Oj, 29.40.Wk

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SOURCES: a code for calculating (α,n), spontaneous fission, and delayed neutron sources and spectra

Cited by 78 publications

References 14 publications

Search for Majorana neutrinos with the first two years of EXO-200 data

Search for Majorana neutrinos with the first two years of EXO-200 data

Low-background gamma spectroscopy at the Boulby Underground Laboratory

Improved WIMP-search reach of the CDMS II germanium data

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