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At least 1,099 records · Page 61
All sourcesNASA NTRSDOE OSTI
DOE OSTI2021

Boson Fermion Nucleus Explanation for Violation of Parity in the Radioactive Decay of Cobalt-60: Monograph #12

In 1957, Chien-Shuing Wu subjected cobalt-60 to supercooled temperatures and a strong magnetic field while measuring radioactive decay. This experiment showed violation of parity— a long-held, fundamental precept in physics stating that nuclear radioactive-decay emission flux will not vary in the solid angle about the nucleus. During Wu’s experiment, beta particles (electrons) exhibited asymmetry, preferentially exiting the cobalt-60 nuclei in the polar region opposite the applied magnetic field. Gamma-ray emissions were anisotropic, preferring to exit the nucleus around the equatorial region. The boson fermion nucleus (BFN) explains the origins of these observed phenomena, where the nuclear structure is pinned in the strong magnetic field with minimal motion in supercooled conditions, while beta particles and gamma rays are emitted from specific locations within the nuclear structure.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2023

Collaborative Research Towards a tonne-scale bolometer-based neutrinoless double beta decay experiment (Final Report)

Cryogenic bolometers are an excellent technology for neutrinoless double beta decay searches owing to their very high energy resolution and potential for high radiopurity. The current most advanced large-scale experiment using these detectors is the Cryogenic Underground Observatory for Rare Events (CUORE). The largest source of background in CUORE is degraded alpha particles, emitted from shallow depths of the detector holders, which can deposit a thermal energy signature similar to neutrinoless double beta decay. To mitigate this background, the CUPID concept (CUORE Upgrade with Particle IDentification) proposes to use scintillating cryogenic detectors. Detecting both the scintillation light and the thermal signal allows discrimination between alpha particle events and beta/gamma events. We report on the design and execution of R&D tests to optimize the design of the single detector module, in particular the scintillation light collection efficiency at cryogenic temperatures.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2022

Calculation of β- and double β-decay rates in nuclei [Poster]

The knowledge of how neutrinos interact in nuclei is critical to an understanding of finite nuclei, neutrino physics and also to astrophysical environments like neutron stars and supernovae. Within this project we studied how nuclei decay through the emission of a neutrino and a lepton, i.e. β-decay. We implemented realistic treatments of many-nucleon correlations and currents to enable high-precision studies of neutrino physics.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2022

Engineering Evaluation of Barium Buildup in a Decayed CsCl Sealed Source and Potential Impact for Cesium Release from a Breached Source

For more than 50 years, radioactive 137 Cs has been a major source material for radioactive sealed sources, usually constructed as cesium chloride (CsCl) salt loaded into double-walled, stainless-steel capsules. A complication develops as 137 Cs decays to 137 Ba since this process creates a strongly reducing environment inside the capsule. A potential hazard exists if the capsule is breached and air ingress induces rapid exothermic oxidation, and this mechanism is suspected to be responsible for the well-known contamination incident at the Harbor View facility in Washington state. For this study, many thermodynamic evaluations were performed to assess the internal state of capsules after several decades of decay and to describe the potential oxidation if the capsule contents were to suddenly be exposed to air. Results suggest that reduction of impurities such as Cu, Fe, Pb, and Cr to metal will occur. If these impurities are lacking, it is possible that even Ba metal will form. In most cases, rapid oxidation can occur, and the exothermic reactions are sufficient to vaporize portions of the contents, which would include the remaining 137 Cs.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2022

Impact of Irradiation and Decay Time on Chemical Speciation in Uranyl Sulfate Solution

A pH-1, 200-g U/L, highly enriched uranyl sulfate solution was neutron-irradiated using an accelerator-driven neutron source (the Universal Neutron Irradiator, UNI) to fission U-235 under conditions similar to those used by SHINE to produce Mo-99 in a subcritical assembly. We completed a series of five uranyl sulfate irradiations to assess the impact of irradiation and decay time on uranium precipitation and iodine speciation in solution. The duration of each irradiation was increased in order, with the shortest irradiation taking 2.9 hours and the longest, 64.5 hours. A total of 9.5E16 U-235 nuclei were fissioned in all irradiations, and a maximum fission power density of 0.26 W/mL was reached in the final irradiation. We observed no evidence of uranyl peroxide or other precipitates, demonstrating that the addition of Fe 2+ to a final Fe concentration of 200 ppm in the target solution was successful at preventing precipitation under representative irradiation conditions. Nonvolatile I - was found to be the dominant (>70%) iodine species in solution, both immediately after irradiation and after days to weeks of decay time.

38 RADIATION CHEMISTRY, RADIOCHEMISTRY, AND NUCLEA↗
DOE OSTI2023

Muon Decay Study at NSRL

A muon is an unstable subatomic particle, classified as a lepton according to the Standard Model. Muons are charged leptons with 1/2 spin. They were discovered by Neddermeyer and Anderson from hadronic cosmic ray showers. Figure 1 provides a visual representation of a cosmic ray shower in Earth’s atmosphere. At a height of 50 000 m in the atmosphere, a primary cosmic ray (mainly protons, helium, a heavy nucleus or a gamma ray) interacts with a gas molecule. The striking of a gas molecule creates a cosmic ray shower, where the energy of the primary particle is distributed among many secondary particles and gamma rays. With each interaction, the cosmic ray particles in the shower lose energy but distribute this energy among a higher number of particles. From the initial interaction, primarily heavy nuclei and pions are generated. Heavy nuclei will interact with gas molecules to produce protons, gamma rays, electrons and pions. The dominant decay mode of neutral pions is to two gamma rays, while charged pions decay to a muon and a neutrino (equation 1): $π^+ → µ^+$ + $\overline ν$ $_µ$; $π → µ$ $^-$ + $\overline v$ $_µ$.

43 PARTICLE ACCELERATORS↗
DOE OSTI2024

Nuclear Structure and Decay Data for A=230

The experimental reaction and decay studies producing nuclei in the A=230 mass chain have been reviewed. Data on elements from radon (Z=86) to americium (Z=95) are included, and level and decay schemes are presented for these nuclides. This work supersedes the previous evaluation for this mass chain (2012Br12).

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2024

Nuclear structure of 157 Sm via β – decay of 157 Pm

Excited states of the neutron-rich nucleus 157 Sm were populated through the β – decay of 157 Pm, which has a tentatively assigned ground-state spin and parity of J π = (5/2 – ). Over 30 levels have been observed, 16 of which are new, and over 45 new γ-ray transitions have been placed in the level scheme. An evolution in the ground-state configurations for N = 95 nuclei from 5/2 – [523] (Er/Yb), to 5/2 + [642] (Dy), to 3/2 – [521] (Sm/Gd) can be explained based on increasing deformation from Z = 70 to Z = 62 and the fact that these three orbitals are energetically close to each other at deformations near β 2 ≈ 0.25 – 0.3. Tentative spin and parity assignments are made for most of the states below 1500 keV based on the decay properties of the levels and using excitation-energy systematics of the various orbitals observed in N = 95 nuclei.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2025

Early Career Award: Single Molecule Fluorescence Imaging for a Background-Free Neutrinoless Double Beta Decay Search

This project aimed to develop a suite of novel technologies targeted at detecting individual barium ions produced in neutrinoless double beta decays of 136 Xe, as part of the NEXT program of gaseous xenon detectors. We realized novel molecules which could sense Ba 2+ ions in dry conditions; new microscopy techniques operable in dry noble gases, including the required operating conditions of xenon at 10 bar pressure; and new radiofrequency ion transport methods (developed both theoretically and experimentally) that can transport ions in dense xenon gas. Together, these developments represent a major advance toward a background-free neutrinoless double beta decay experiment based on single molecule fluorescence imaging of Ba 2+ daughter ions.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2025

Pion and Kaon decays from lattice QCD and |Vud|, |Vus|

We review lattice calculations of the form factors for Kaon semileptonic decays and the leptonic decay constants of Kaons and Pions. We discuss the determinations of the CKM matrix elements $|V_{ud}|$ and $|V_{us}|$ using the form factors and experimental results. We use the CKM matrix elements to test first-row unitarity of the CKM matrix.

Simone, J. N. [Fermilab] (ORCID:0000000185153337)↗
DOE OSTI2026

Search for Dark Showers from Higgs Boson Decays Through the Photon Portal

One of the primary goals of the CMS detector is to find particles beyond the standard model. We present a search for dark showers produced from decays of the Higgs boson using collision data from the CMS experiment at the LHC. These dark showers then decay into jets made entirely of photons, which we can observe in the detector. Thus, our analysis focuses on reconstructing and analyzing these jets and maximizing signal selection efficiency for data from the Monte Carlo simulation. The photon signature of dark jets can then be confirmed via an invariant-mass distribution of these two photon jets. If found, these particles would provide evidence of physics theories beyond the Standard Model.

MacMullin, Alexandra [Skidmore Coll.]↗
DOE OSTI2023

$B$-meson semileptonic decays with highly improved staggered quarks

We present an update of the Fermilab Lattice and MILC Collaborations project to compute the form factors for semileptonic $B_{(s)}$-meson decays. Our calculation uses the highly improved staggered quark (HISQ) action for sea and valence quarks, and ensembles with up, down, strange, and charm quarks in the sea. Using a highly improved action with the MILC Collaboration's gauge ensembles with lattice spacings down to $a\approx0.03$ fm, allows the heavy valence quarks to be treated with the same discretization as the light and strange quarks. This unified treatment of the valence quarks allows for absolutely normalized vector currents, bypassing the need for perturbative matching, which has been a source of uncertainty in previous calculations of $B$-meson decay form factors by our collaboration. All preliminary form-factor results are blinded.

Lytle, Andrew↗
DOE OSTI2025

Nuclear Matrix Elements for Neutrinoless Double-Beta Decay

Neutrinoless double-beta decay ($0\nu\beta\beta$) is a rare hypothesised process that, if discovered, would establish that the neutrino is Majorana, that is, it is its own antiparticle. Interpretation of experimental results relies on knowledge of nuclear matrix elements, whose large model uncertainty is the limiting factor in comparing measured (bounds on) half-lives to the neutrino mass. Nuclear effective field theory and lattice QCD have the potential to compute these matrix elements with better control over uncertainties, enhancing the discovery potential of next-generation $0\nu\beta\beta$ experiments. This work will survey various lattice QCD double-beta decay calculations and discuss their implications.

Grebe, Anthony V. [Fermilab] (ORCID:00000003103201↗
DOE OSTI2025

Form factors for semi-leptonic $B_{(s)} \to D_{(s)}^∗\ell \nu_\ell$ decays

Semileptonic $B_{(s)}$ decays are of great phenomenological interestbecause they allow to extract CKM matrix elements or test lepton flavouruniversality. Taking advantage of existing data, we explore extractingform factors for vector final states using the narrow widthapproximation. Based on RBC/UKQCD's set of 2+1 flavour gauge fieldensembles with Shamir domain-wall fermion and Iwasaki gauge fieldaction, we study semileptonic $B_{(s)}$ decays using domain-wallfermions for light, strange and charm quarks, whereas bottom quarks aresimulated with the relativistic heavy quark (RHQ) action. Exploratoryresults for $B_s \to D_s^* \ell \nu_\ell$ are presented.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2022

Positron Emission Intensity in the Decay of 86 gY for Use in Dosimetry Studies

The β + -emitting radionuclide 86 gY (t 1/2 = 14.7 h) forms a matched-pair with the β – -emitting therapeutic radionuclide 90Y (t 1/2 = 2.7 d) for theranostic application in medicine. This approach demands a precise knowledge of the positron emission probability of the PET nuclide which was until recently rather uncertain for 86 gY. In this work, an 86 gY source of high radionuclidic purity was prepared and a direct measurement of the positron emission intensity per 100 decay of the parent (hereafter “positron emission intensity”) was performed using high-resolution HPGe detector γ-ray spectroscopy. The electron capture intensity was also determined as an additional check by measuring the K α and K β X-rays of energies 14.1 and 15.8 keV, respectively, using a low energy HPGe detector. From those measurements, normalized values of 27.2 ± 2.0% for β + -emission and 72.8 ± 2.0% for EC were obtained. These results are in excellent agreement with values recently reported in the literature based on a detailed decay scheme study.

61 RADIATION PROTECTION AND DOSIMETRY↗
DOE OSTI2021

Role of Parallel Solenoidal Electric Field on Energy Conversion in 2.5D Decaying Turbulence with a Guide Magnetic Field

We perform 2.5D particle-in-cell simulations of decaying turbulence in the presence of a guide (out-of-plane) background magnetic field. The fluctuating magnetic field initially consists of Fourier modes at low wavenumbers (long wavelengths). With time, the electromagnetic energy is converted to plasma kinetic energy (bulk flow+thermal energy) at the rate per unit volume of J· E for current density J and electric field E. Such decaying turbulence is well known to evolve toward a state with strongly intermittent plasma current. Here we decompose the electric field into components that are irrotational, E ir , and solenoidal (divergence-free), E so . E ir is associated with charge separation, and J · E ir is a rate of energy transfer between ions and electrons with little net change in plasma kinetic energy. Therefore, the net rate of conversion of electromagnetic energy to plasma kinetic energy is strongly dominated by J · E so , and for a strong guide magnetic field, this mainly involves the component E so,∥ parallel to the total magnetic field B. We examine various indicators of the spatial distribution of the energy transfer rate J ∥ · E so,∥ , which relates to magnetic reconnection, the best of which are (1) the ratio of the out-of-plane electric field to the in-plane magnetic field, (2) the out-of-plane component of the nonideal electric field, and (3) the magnitude of the estimate of current helicity.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2026

Shake-up and shake-off spectra in the electron capture decay of atomic $^7$Be

The most stringent laboratory-based experimental limits on the existence of sub-MeV sterile neutrinos are currently set by decay spectroscopy of radioactive $^7$Be embedded into superconducting sensors. The systematic uncertainties are dominated by the modeling of the electron shake-up and shake-off spectra that are not based on state-of-the-art atomic theory and do not include electron correlations or relativistic effects. We have used the multiconfiguration Dirac-Fock formalism to obtain correlated wavefunctions ab initio and compute all single and double shake processes in the electron capture decay of atomic $^7$Be. The simulations can explain some but not all of the observed spectral features, likely because the wave functions are modified by the Ta sensor material that the $^7$Be is embedded into. The new models also show that the L/K electron capture ratio of $^7$Be in Ta has previously been slightly underestimated revising the previous value of 0.070(7) to a new value of 0.0756(20).

Atomic Physics (physics.atom-ph)↗
DOE OSTI2026

Massive right-handed neutrinos in $\bar{B} \to D^* τ\bar X$ decay

We explore signatures of a massive right-handed neutrino (RHN) in angular distributions of $\bar{B} \to D^* (\to D π) τ(\to πν_τ) \bar X$ decays, where $X$ is an invisible state. We assume the new physics is described by the standard model effective field theory extended with an RHN in the MeV-GeV mass range. We calculate for the first time the full differential distributions in terms of the visible final states, including the decay of the $τ$ lepton. We evaluate the sensitivity of various distributions to the new physics operators.

FOS: Physical sciences↗