Nuclear Β-decay Research Articles

Quasi-particle–vibration coupling approach for nuclear β-decay

The study of β-decay is important to answer open questions in physics and astrophysics; however, theoretical predictions of the associated half-lives are still plagued by uncertainties. In this short review, we argue that a reliable model for this study is nuclear density functional theory (DFT), complemented by further specific correlations; the quasi-particle–vibration coupling (QPVC) model has been successful in predicting half-lives in a number of spherical nuclei, and its extension to deformed systems should be envisioned. Some remaining open questions are addressed.

Radiative corrections to neutron and nuclear β-decays: a serious kinematics problem in the literature

We report a serious kinematics problem in the bremsstrahlung photon part of the order-α outer (model independent) radiative correction calculations for those neutron (and nuclear beta) decay observables (like electron-neutrino correlation parameter measurement) where the proton (recoil particle) is detected. The so-called neutrino-type radiative correction calculations, which fix the neutrino direction in the bremsstrahlung photon integrals, use 3-body decay kinematics to connect the unobserved neutrino direction with the observed electron and proton (recoil particle) momenta. But the presence of the bremsstrahlung photon changes the kinematics from 3-body to 4-body one, and the accurate information about the recoil particle momentum is lost due to the integration with respect to the photon momentum. Therefore the application of the abovementioned 3-body decay kinematics connection for the radiative correction calculations, rather prevalent in the literature, is not acceptable. We show that the correct, so-called recoil-type radiative correction calculations, which fix the proton (recoil particle) momentum instead of the neutrino direction and use rather involved analytical, semianalytical or Monte Carlo bremsstrahlung integration methods, result usually in much larger corrections than the incorrect neutrino-type analytical methods.

Quantitative analysis of an ECR Ar plasma structure by X-ray spectroscopy at high spatial resolution

In the frame of the PANDORA_Gr3 project, aiming at measuring for the first time in-plasma nuclear β-decays of astrophysical interest, an innovative multi-diagnostic approach to correlate plasma parameters to nuclear activity has been proposed [1–3]. This is based on several detectors and techniques (optical emission spectroscopy, RF systems, interferopolarimetry) and here we focus on high resolution spatially-resolved X-ray spectroscopy, performed by means of a X-ray pin-hole camera setup sensitive in the 0.5–20 keV energy domain. We present measurements on an Ar plasma heated by Electron Cyclotron Resonance at the ECR-plasma lab of ATOMKI-Debrecen. The achieved spatial and energy resolution were 0.5 mm and 300 eV at 8 keV, respectively [4]. The new algorithm of analysis for single-photon-counted images has been developed allowing an investigation in High-Dynamic-Range (HDR) mode. Hence a spatially resolved quantitative characterization of plasma vs. plasma walls emitted spectra was done; the investigated electrons are the ones crucial for in-plasma ionization. Both stable and turbulent plasma regimes can be investigated.

Nuclear β-decays in plasmas: how to correlate plasma density and temperature to the activity

Magnetized plasmas in compact traps may become experimental en-vironments for the investigation of nuclear beta-decays of astrophysical inter-est. In the framework of the project PANDORA (Plasmas for Astrophysics, Nuclear Decays Observation and Radiation for Archaeometry) the research ac-tivities are devoted to demonstrate the feasibility of an experiment aiming atmeasuring lifetimes of radionuclides of astrophysical interest when changing the charge state distribution of the in-plasma ions and the other plasma param- eters such as density and temperature. This contribution describes the multidi-agnostics setup now available at INFN-LNS, which allows unprecedented in-vestigations of magnetoplasmas properties in terms of density, temperature and charge state distribution (CSD). The setup includes an interfero-polarimeter for total plasma density measurement, a multi-X-ray detectors system for X-ray spectroscopy (including time resolved spectroscopy), an X-ray pin-hole camera for high-resolution 2D space resolved spectroscopy, a two-pin plasma-chamber immersed antenna for the detection of plasma radio-self-emission, and differ- ent spectrometers for the plasma-emitted visible light characterization. The setup is also suitable for other studies of astrophysical interest, such as turbulent plasma regimes dominated by the so-called Cyclotron Maser Instability, which is a typical kinetic turbulence occurring in astrophysical objects like magnetized stars, brown dwarfs, etc. A description of recent results about plasma parame- ters characterization in quiescent and turbulent Electron Cyclotron Resonance-heated plasmas will be given.

Multidiagnostics setups for magnetoplasmas devoted to astrophysics and nuclear astrophysics research in compact traps

Magnetized plasmas in compact trap may become experimental environments for the investigation of nuclear β-decays of astrophysical interest. In the framework of the project PANDORA (Plasmas for Astrophysics, Nuclear Decays Observation and Radiation for Archaeometry) the research activities are devoted to demonstrate the feasibility of an experiment aiming at correlating radionuclides lifetimes to the in-plasma ions charge state distribution (CSD). The paper describes the multidiagnostics setup now available at INFN-LNS, which allows unprecedented investigations of magnetoplasma properties in terms of density, temperature and CSD. The developed setup includes an interfero-polarimeter for total plasma density measurements, a multi-X-ray detectors system for X-ray spectroscopy (including time resolved spectroscopy), a X-ray pin-hole camera for high-resolution 2D space resolved spectroscopy and different spectrometers for the plasma-emitted visible light characterization. A description of recent results about plasma parameters characterization in quiescent and turbulent Electron Cyclotron Resonance-heated plasmas will be given. A complete characterization has been already performed, studying, in particular, the time evolution of X-ray spectra and the change of plasma morphology, including the balance between radiation originated in the plasma core and the one due to plasma losses. Finally, the experimental setup is going to be further upgraded in order to allow measurements of nuclear decays in magnetoplasmas.

Direct Search for keV-Sterile Neutrino in Nuclear Decay. Troitsk Nu-Mass (Scientific Summary)

We present a brief review of experimental status in searching for hypothetical sterile neutrino in nuclear decay in laboratory testing. The main idea is based on search for an additional small component in the β-spectrum or a shift in the internal electron conversion energy. For example, in a three-body β-decay it looks like a kink in the continuous spectrum shifted by the value of sterile neutrino mass from the spectrum endpoint. After a short general motivation for such a search we discuss the way how to find sterile neutrino in the nuclear β-decay and present the current status of upper limits on sterile neutrino mixing with electron antineutrino. The advantages and problems arising in the precise measurements of β-spectrum are demonstrated on the basis of the “Troitsk nu-mass” experiment by presenting the all measurement and analysis procedures in details. At the end we discuss the nearest future of such experiments.

Review of fundamental nuclear-geophysical researches in OSENU: i. standard beta decay theory elements and new cooperative electron-β-nuclear spectroscopy

This paper opens a series of publications, devoted to review of new results of the original nuclear-geophysical researches at the OSENU mathematics department and its laboratories (computational and quantum mathematics and mechanics, environmental radioactivity, nuclear geophysics). Primarily the first material will focus on fundamental issues that constitute the theoretical basis of the further applied nuclear-geophysical research. It is shortly presented a modern approach to computing the key parameters of the beta decay processes. There are discussed the cooperative electron β-nuclear processes in atoms and molecules, including the excitation, ionization, electronic rearrangement, induced by the nuclear reactions and β-decay. A few factors are taken into account: changing the integration limits in the Fermi function integral, energy corrections for different chemical substances, and the possibility of the bound β-decay or other exotic decay channels.

Neutrinoless double beta decay and nuclear environment

We show that the presence in the nuclear medium of lepton number violating four-fermion interactions of neutrinos with quarks from a decaying nucleus could account for an apparent incompatibility among the 0 νββ searches in the laboratory, the direct neutrino mass measurement with the nuclear β-decay and cosmological data.

A new measurement of electron transverse polarization in polarized nuclear β-decay

The Mott polarimetry for T-violation (MTV) experiment tests time-reversal symmetry in polarized nuclear [Formula: see text]-decay by measuring an electron’s transverse polarization as a form of angular asymmetry in Mott scattering using a thin metal foil. A Mott scattering analyzer system developed using a tracking detector to measure scattering angles offers better event selectivity than conventional counter experiments. In this paper, we describe a pilot experiment conducted at KEK-TRIAC using a prototype system with a polarized 8Li beam. The experiment confirmed the sound performance of our Mott analyzer system to measure T-violating triple correlation (R correlation), and therefore recommends its use in higher-precision experiments at the TRIUMF-ISAC.

Quantum-chemical estimation of the relaxation of equilibrium structure upon radiochemical reactions of iodine-containing molecules and ions

Energy of vibrational relaxation E r upon nuclear β-decay of the Ph2I+, C2F3I, (C4v )- and (С2v )- C2B4H5I, (D 5d )-C2B10H10I2 iodine-containing compounds as well as undecafluorinated and hexachlorinated anions of iodocarba-closo-dodecaborane has been determined using the PBE0/SDD and MP2full/SDD quantum-chemical methods. Diphenyliodonium Ph2I+ is directly converted into PhXe+ and Ph+ cations pair. The PhXe+ cation can be stabilized via ortho-fluorination of the phenyl substituent.

Measurement of β-decay end point energy with planar HPGe detector

The β–γ coincidence measurement has been performed with a segmented planar Hyper-Pure Germanium (HPGe) detector and a single coaxial HPGe detector to determine the end point energies of nuclear β-decays. The experimental end point energies have been determined for some of the known β-decays in Rh106→Pd106. The end point energies corresponding to three weak branches in Rh106→Pd106 decay have been measured for the first time. The γ ray and β particle responses for the planar HPGe detector were simulated using the Monte Carlo based code GEANT3. The experimentally obtained β spectra were successfully reproduced with the simulation.

Precision measurements in nuclear ‐decay with LPCTrap

The experimental achievements and the current program with the LPCTrap device installed at the LIRAT beam line of the SPIRAL1‐GANIL facility are presented. The device is dedicated to the study of the weak interaction at low energy by means of precise measurements of the β−ν angular correlation parameter. Technical aspects as well as the main results are reviewed. The future program with new available beams is briefly discussed.

Direct neutrino mass determination: Status and prospects

More than 80 years after the prediction of their existence, there are still many open questions regarding the nature and properties of neutrinos. Among these questions is the issue of neutrino mass. While oscillation experiments have proven that neutrinos possess non-zero masses, these measurements cannot determine the absolute mass scale. Information on absolute neutrino masses can be deduced either from cosmological observations of large scale structure formation, from the search for neutrino-less double β-decay or from the study of the kinematics of weak decays. While the first two methods are subject to model dependencies or rather large systematical uncertainties, measurements based on the kinematics of nuclear β-decay or electron-capture reactions offer a model-independent way to determine the neutrino mass. This paper provides an overview of status and sensitivities of direct neutrino mass experiments currently under construction (KATRIN, MARE) or in development (Project 8, ECHO).

Superallowed Gamow–Teller decay of the doubly magic nucleus 100Sn

The shell structure of atomic nuclei is associated with 'magic numbers' and originates in the nearly independent motion of neutrons and protons in a mean potential generated by all nucleons. During β(+)-decay, a proton transforms into a neutron in a previously not fully occupied orbital, emitting a positron-neutrino pair with either parallel or antiparallel spins, in a Gamow-Teller or Fermi transition, respectively. The transition probability, or strength, of a Gamow-Teller transition depends sensitively on the underlying shell structure and is usually distributed among many states in the neighbouring nucleus. Here we report measurements of the half-life and decay energy for the decay of (100)Sn, the heaviest doubly magic nucleus with equal numbers of protons and neutrons. In the β-decay of (100)Sn, a large fraction of the strength is observable because of the large decay energy. We determine the largest Gamow-Teller strength so far measured in allowed nuclear β-decay, establishing the 'superallowed' nature of this Gamow-Teller transition. The large strength and the low-energy states in the daughter nucleus, (100)In, are well reproduced by modern, large-scale shell model calculations.

Possible Physical Mechanisms in the Galaxy to Cause Homochiral Biomaterials for Life

The origin of homochirality in life remains a mystery that some believe is essential for life, and which may result from chiral symmetry breaking interactions with galactic organic material.

Oxidation number: issues of its determination and range

The paper is aimed at the issues of oxidation state determination and limiting values. The possibility of existence of compounds containing an atom with the oxidation number beyond the current common values, i.e., below −IV and above +VIII are discussed. Three principal modes of preparation of compounds with the oxidation number exceeding VIII, electrochemical anodic oxidation, photoionization, and nuclear β-decay, are evaluated. Failure to prepare compounds containing an atom with the oxidation number below −IV is rationalized. The paper provides an opinion on uncertainties in oxidation state determination in three kinds of compounds: binary compounds, nitrosyl complexes, and compounds containing mutually bonded atoms of the same element. The questions are discussed from the viewpoint of correlation of “man-made” quantities and objective, experimentally obtainable data.

The WITCH experiment: Acquiring the first recoil ion spectrum

The standard model of the electroweak interaction describes β-decay in the well-known V–A form. Nevertheless, the most general Hamiltonian of a β-decay includes also other possible interaction types, e.g. scalar (S) and tensor (T) contributions, which are not fully ruled out yet experimentally. The WITCH experiment aims to study a possible admixture of these exotic interaction types in nuclear β-decay by a precise measurement of the shape of the recoil ion energy spectrum. The experimental set-up couples a double Penning trap system and a retardation spectrometer. The set-up is installed in ISOLDE/CERN and was recently shown to be fully operational. The current status of the experiment is presented together with the data acquired during the 2006 campaign, showing the first recoil ion energy spectrum obtained. The data taking procedure and corresponding data acquisition system are described in more detail. Several further technical improvements are briefly reviewed.

The LPCTrap for the measurement of the β- ν correlation in 6He

The application of traps to precision measurements of the β-ν angular correlation coefficient a in nuclear β-decay is pursued by several laboratories world wide. Various nuclear transitions are addressed and different trap devices are used. At GANIL, a novel transparent Paul trap (LPCTrap) has been built downstream from the SPIRAL source to determine a in the pure Gamow-Teller decay of 6He. This transition is driven by the axial-vector interaction. The forbidden tensor interaction may be observed through a precise measurement of a. The LPCTrap consists of an RFQ-Buncher, a transparent Paul trap, and the detection system. It is currently the only facility that uses a Paul trap with a novel geometry to perform high-precision nuclear physics experiments. All the elements have been tested and meet the requirements. In this contribution we give a short status report of the project underlining the highlights achieved so far.

Measurements of the βν angular correlation in nuclear β-decay

The angular correlation between the electron and the neutrino in nuclear β-decay constitutes a sensitive observable to search for exotic couplings in the weak interaction. This correlation provides also an alternative means to determine the ratio between the Gamow-Teller and Fermi contributions in mixed transitions. We describe here the progress of the LPCTrap experiment aiming to measure the βν angular correlation in the pure Gamow-Teller decay of 6He using a transparent Paul trap. We summarize also the status of similar experiments and projects.

Radiative tritium β-decay and the neutrino mass

The shape of the electron energy spectrum in 3H β-decay permits a direct assay of the absolute scale of the neutrino mass; a highly accurate theoretical description of the electron energy spectrum is necessary to the empirical task. We update Sirlin's calculation of the outer radiative correction to nuclear β-decay to take into account the non-zero energy resolution of the electron detector. In previous 3H β-decay studies the outer radiative corrections were neglected all together; only Coulomb corrections to the spectrum were included. This neglect artificially pushes mν2<0 in a potentially significant way. We present a computation of the theoretical spectrum appropriate to the extraction of the neutrino mass in the sub-eV regime.