Partial γ-ray production cross sections for (n,xnγ) reactions in natural argon at 1-30 MeV

Background: Neutron-induced backgrounds are a significant concern for experiments that require extremely low levels of radioactive backgrounds such as direct dark matter searches and neutrinoless double-β decay experiments. Unmeasured neutron scattering cross sections are often accounted for incorrectly in Monte Carlo simulations.Purpose: The purpose of this article is to determine partial γ-ray production cross sections for (n,xnγ) reactions in natural argon for incident neutron energies between 1 and 30 MeV.Methods: The broad-spectrum neutron beam at the Los Alamos Neutron Science Center (LANSCE) was used used for the measurement. Neutron energies were determined using time of flight, and resulting γ rays from neutron-induced reactions were detected using the GErmanium Array for Neutron Induced Excitations (GEANIE).Results: Partial γ-ray cross sections were measured for six excited states in 40Ar and two excited states in 39Ar. Measured (n,xnγ) cross sections were compared to the talys and CoH3 nuclear reaction codes.Conclusions: These new measurements will help to identify potential backgrounds in neutrinoless double-β decay and dark matter experiments that use argon as a detection medium or shielding. The measurements will also aid in the identification of neutron interactions in these experiments through the detection of γ rays produced by (n,xnγ) reactions

Extended search for the invisible axion with the axion dark matter experiment

This Letter reports on a cavity haloscope search for dark matter axions in the Galactic halo in the mass range 2.81–3.31μeV. This search utilizes the combination of a low-noise Josephson parametric amplifier and a large-cavity haloscope to achieve unprecedented sensitivity across this mass range. This search excludes the full range of axion-photon coupling values predicted in benchmark models of the invisible axion that solve the strong CP problem of quantum chromodynamics

The MAJORANA experiment: An ultra-low background search for neutrinoless double-beta decay

The observation of neutrinoless double-beta decay would resolve the Majorana nature of the neutrino and could provide information on the absolute scale of the neutrino mass. The initial phase of the MAJORANA experiment, known as the DEMONSTRATOR, will house 40 kg of Ge in an ultra-low background shielded environment at the 4850' level of the Sanford Underground Laboratory in Lead, SD. The objective of the DEMONSTRATOR is to determine whether a future 1-tonne experiment can achieve a background goal of one count per tonne-year in a narrow region of interest around the 76Ge neutrinoless double-beta decay peak

Bayesian analysis of a future β\beta decay experiment's sensitivity to neutrino mass scale and ordering

International audienceBayesian modeling techniques enable sensitivity analyses that incorporate detailed expectations regarding future experiments. A model-based approach also allows one to evaluate inferences and predicted outcomes, by calibrating (or measuring) the consequences incurred when certain results are reported. We present procedures for calibrating predictions of an experiment's sensitivity to both continuous and discrete parameters. Using these procedures and a new Bayesian model of the β-decay spectrum, we assess a high-precision β-decay experiment's sensitivity to the neutrino mass scale and ordering for one assumed design scenario. We find that such an experiment could measure the electron-weighted neutrino mass within ∼40 meV after 1 year (90% credibility). Neutrino masses >500 meV could be measured within ≈5 meV. Using only β decay and external reactor neutrino data, we find that next-generation β-decay experiments could potentially constrain the mass ordering using a two-neutrino spectral model analysis. By calibrating mass ordering results, we identify reporting criteria that can be tuned to suppress false ordering claims. In some cases, a two-neutrino analysis can reveal that the mass ordering is inverted, an unobtainable result for the traditional one-neutrino analysis approach

Viterbi decoding of CRES signals in Project 8

International audienceCyclotron radiation emission spectroscopy (CRES) is a modern approach for determining charged particle energies via high-precision frequency measurements of the emitted cyclotron radiation. For CRES experiments with gas within the fiducial volume, signal and noise dynamics can be modelled by a hidden Markov model. We introduce a novel application of the Viterbi algorithm in order to derive informational limits on the optimal detection of cyclotron radiation signals in this class of gas-filled CRES experiments, thereby providing concrete limits from which future reconstruction algorithms, as well as detector designs, can be constrained. The validity of the resultant decision rules is confirmed using both Monte Carlo and Project 8 data

Cyclotron Radiation Emission Spectroscopy of Electrons from Tritium Beta Decay and 83m^{83\rm m}Kr Internal Conversion

International audienceProject 8 has developed a novel technique, Cyclotron Radiation Emission Spectroscopy (CRES), for direct neutrino mass measurements. A CRES-based experiment on the beta spectrum of tritium has been carried out in a small-volume apparatus. We provide a detailed account of the experiment, focusing on systematic effects and analysis techniques. In a Bayesian (frequentist) analysis, we measure the tritium endpoint as $18553^{+18}_{-19}$ ($18548^{+19}_{-19}$) eV and set upper limits of 155 (152) eV (90% C.L.) on the neutrino mass. No background events are observed beyond the endpoint in 82 days of running. We also demonstrate an energy resolution of $1.66\pm0.19$ eV in a resolution-optimized magnetic trap configuration by measuring $^{83\rm m}$Kr 17.8-keV internal-conversion electrons. These measurements establish CRES as a low-background, high-resolution technique with the potential to advance neutrino mass sensitivity

Tritium Beta Spectrum and Neutrino Mass Limit from Cyclotron Radiation Emission Spectroscopy

The absolute scale of the neutrino mass plays a critical role in physics at every scale, from the particle to cosmological. Measurements of the tritium endpoint spectrum have provided the most precise direct limit on the neutrino mass scale. In this Letter, we present advances by Project 8 to the Cyclotron Radiation Emission Spectroscopy (CRES) technique culminating in the first frequency-based neutrino mass limit. With only a cm$^3$-scale physical detection volume, a limit of $m_\beta$<180 eV is extracted from the background-free measurement of the continuous tritium beta spectrum. Using $^{83{\rm m}}$Kr calibration data, an improved resolution of 1.66$\pm$0.16 eV (FWHM) is measured, the detector response model is validated, and the efficiency is characterized over the multi-keV tritium analysis window. These measurements establish the potential of CRES for a high-sensitivity next-generation direct neutrino mass experiment featuring low background and high resolution

The MAJORANA demonstrator: A search for neutrinoless double-beta decay of germanium-76

The observation of neutrino less double-beta decay would show that neutrinos are Majorana particles and provide information on neutrino mass. Attaining sensitivities for neutrino masses in the inverted hierarchy region requires large, tonne scale detectors with extremely low backgrounds, at the level of 10(-')(3) counts keV(-')(1) t(-')(1) y(-')(1) or lower in the region of the signal. The MAJORANA collaboration is constructing the DEMONSTRATOR, an array consisting of 40 kg of p-type point contact germanium detectors, at least half of which will be enriched to 86% in (76)Ge. The primary aim is to show the feasibility for a future tonne scale measurement. With a sub-keV energy threshold, the array should also be able to search for light WIMP dark matter. This paper presents a brief update on the status of constructing the DEMONSTRATOR including an electroforming facility that is now operating underground at the Sanford Underground Research Facility