Search NASA⌕ Search

SEARCH · Search NASA

Results for “nuclear parity”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 217 records · Page 12
All sourcesNASA NTRSDOE OSTI
DOE OSTI2024

Global fit of electron and neutrino elastic scattering data to determine the strange quark contribution to the vector and axial form factors of the nucleon

We present a global fit of neutral-current elastic (NCE) neutrino-scattering data and parity-violating electron-scattering (PVES) data with the goal of determining the strange quark contribution to the vector and axial form factors of the proton. Previous fits of this form included data from a variety of PVES experiments (PVA4, HAPPEx, G0, SAMPLE) and the NCE neutrino and anti-neutrino data from BNL E734. These fits did not constrain the strangeness contribution to the axial form factor G A s ( Q 2 ) at low Q 2 very well because there was no NCE data for Q 2 < 0.45 GeV 2 . Our new fit includes for the first time MiniBooNE NCE data from both neutrino and antineutrino scattering; this experiment used a hydrocarbon target and so a model of the neutrino interaction with the carbon nucleus was required. Three different nuclear models have been employed: a relativistic Fermi gas model, the superscaling approximation model, and a spectral function model. We find a tremendous improvement in the constraint of G A s ( Q 2 ) at low Q 2 compared to previous work, although more data is needed from NCE measurements that focus on exclusive single-proton final states, for example from MicroBooNE. Published by the American Physical Society 2024

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2022

Precision Determination of the Neutral Weak Form Factor of Ca 48

In this work, we report a precise measurement of the parity-violating asymmetry $A_{\rm PV}$ in the elastic scattering of longitudinally polarized electrons from $^{48}{\rm Ca}$. We measure $A_{\rm PV} =2668\pm 106\ {\rm (stat)}\pm 40\ {\rm (syst)}$ parts per billion, leading to an extraction of the neutral weak form factor $F_{\rm W} (q=0.8733$ fm$^{-1}) = 0.1304 \pm 0.0052 \ {\rm (stat)}\pm 0.0020\ {\rm (syst)}$ and the charge minus the weak form factor $F_{\rm ch} - F_{\rm W} = 0.0277\pm 0.0055$. The resulting neutron skin thickness $R_n-R_p=0.121 \pm 0.026\ {\rm (exp)} \pm 0.024\ {\rm (model)}$~fm is relatively thin yet consistent with many model calculations. The combined CREX and PREX results will have implications for future energy density functional calculations and on the density dependence of the symmetry energy of nuclear matter.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2026

Nuclear Structure and Decay Data for A=169 Isobars

Experimental data pertaining to all nuclei with mass number A=169 (Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Hf, Ta, W, Re, Os, Ir, Pt) have been evaluated. Level schemes from both radioactive decay and reaction studies are presented, along with associated tables of experimental data and adopted properties for levels and γ rays. The present evaluation for A=169 supersedes the 2008 evaluation, 2008Ba31, by C.M. Baglin. A few highlights of this evaluation: More extensive work on ε decay from 169W is needed and new experimental work will be required to resolve a discrepancy between the J π values deduced for a 180-keV level in 169Ta based on extensive band structure from (HI,xnγ) work (J π =1/2−) and TDPAD measurements (J=5/2). Low lying states of 169Os were studied via fine structure of 173Pt α decay in 2014ThZZ. The Eαs feeding the g.s. of 169Os in 2008Ba31 are separated well into two consistent groups to feed the g.s. and the newly proposed state at 34.84 keV. Based on the studies of 2014ThZZ and 2021Zh52, the g.s. spin-parity assignment of 169Os has been proposed to be (7/2−) from (5/2−). The 169Ir g.s. half-life and alpha emission branching reported in 2012Th13 from 173Au α decay measurements are preferred over the values in 2005Sc22. The reported half-life value in 2005Sc22 for 169Ir g.s. is discrepant and the research work was carried out in the same lab of 2012Th13.

Basunia, M Shamsuzzoha↗
DOE OSTI2022

Half-life measurement of the 199-keV isomeric state in Ga 76

Background: Isomeric states in atomic nuclei are a sensitive probe of their underlying microscopic structure and can be used to study the evolution of shell structure far from stability. Recent studies have identified and provided detailed spectroscopy of isomers in neutron-rich nuclei with Z = 28-50. Isomeric states in the odd-odd gallium isotopes have been reported for all gallium isotopes from A = 72 to A = 80 with the exception of 76 Ga. Purpose: The purpose of this experiment was to observe short-lived isomeric states in the vicinity of 78 Ni. Methods: In-beam fragmentation of a 86 Kr primary beam at the National Superconducting Cyclotron Laboratory produced radioactive ions which were delivered to and deposited in a Ce Br 3 scintillator coupled to a position-sensitive photomultiplier tube. Beta-delayed γ rays were measured by ancillary HPGe clover and LaBr 3 detectors which surrounded the implantation detector. Results: The previously observed J π = 1 + , 199-keV level in 76 Ga, populated following the β decay of 76 Zn, was identified as isomeric with a half-life of 34(1) stat. (8) sys. ns. Shell-model calculations suggest this state is formed by the coupling of protons in negative-parity configurations to 1/2 - neutron configurations. Transition strengths assuming a ground-state spin of J = 2 and J = 3 were determined from the experimental data.

59 ≤ A ≤ 89↗
DOE OSTI2025

Trends in actinide electronic structure revealed from asymmetric, isostructural transuranic metallocenes

The study of actinide electronic structure and bonding within rigorously controlled environments is fundamental to advancing nuclear applications. Here, we report a new set of isostructural actinide organometallics; An(COT big ) 2 , (An = Th, U, Np, and Pu), where COT big is the bulky 1,4-bis(triphenylsilyl)-substituted cyclooctatetraenyl dianion (1,4-(Ph 3 Si) 2 C 8 H 6 ) 2 -. The actinide(IV) metallocene sandwiches have a clam-shell structure, offering a new molecular symmetry to explore f-orbital contributions in bonding. Combined experimental and computational studies reveal that An(COT big ) 2 complexes strongly differ from the previously published coplanar An(COT) 2 sandwiches due to the bent geometry and electron-withdrawing nature of the substituents. While COT big displays comparatively weaker electron donation, the low-energy f-f transitions in An(COT big ) 2 have increased molar absorptivity consistent with the removal of the parity selection rule and better energetic matching between ligand and actinide 5f orbitals as the series is traversed. For Pu(COT big ) 2 , covalent mixing of donor 5f metal orbitals and the ligand-π orbitals is especially strong.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2023

Liouvillian dynamics of the open Schwinger model: String breaking and kinetic dissipation in a thermal medium

Understanding the dynamics of bound state formation is one of the fundamental questions in confining quantum field theories such as Quantum Chromodynamics (QCD). One hadronization mechanism that has garnered significant attention is the breaking of a string initially connecting a fermion and an antifermion. Deepening our understanding of real-time string-breaking dynamics with simpler, lower dimensional models like the Schwinger model can improve our understanding of the hadronization process in QCD and other confining systems found in condensed matter and statistical systems. Here in this paper, we consider the string-breaking dynamics within the Schwinger model and investigate its modification inside a thermal medium, treating the Schwinger model as an open quantum system coupled to a thermal environment. Within the regime of weak coupling between the system and environment, the real-time evolution of the system can be described by a Lindblad evolution equation. We analyze the Liouvillian gaps of this Lindblad equation and the time dependence of the system’s von Neumann entropy. We observe that the late-time relaxation rate decreases as the environment correlation length increases. Moreover, when the environment correlation length is infinite, the system exhibits two steady states, one in each of the sectors with definite charge-conjugation-parity (CP) quantum numbers. For parameter regimes where an initial string breaks in vacuum, we observe a delay of the string breaking in the medium, due to kinetic dissipation effects. Conversely, in regimes where an initial string remains intact in vacuum time evolution, we observe string breaking (melting) in the thermal medium. We further discuss how the Liouvillian dynamics of the open Schwinger model can be simulated on quantum computers and provide an estimate of the associated Trotter errors.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2025

Yrast structures of 98 Nb and 99 Mo

Neutron-rich nuclei in the A ≈ 100 mass region are interesting due to a rapid shape transition, especially pronounced in the Zr isotopes, and more recently observed in Nb isotopes. 98 Nb, with only one proton and one neutron outside the subshell closure nucleus of 96 Zr, is amenable to shell model calculations. To further examine the rapid shape transition the yrast structure of 98 Nb was established in this work. This was the only yrast structure missing from all immediate neighbors to 96 Zr. The yrast structure of 98 Nb was studied in the fission of the compound systems formed in three heavy-ion induced reactions, 24 Mg (134.5 MeV) + 173 Yb, 23 Na (129 MeV) + 176 Yb, and 18 O (91 MeV) + 208 Pb. Prompt γ-ray spectroscopy was accomplished using the Gammasphere array. Excitation energies up to 3 MeV were observed for the first time in 98 Nb. The yrast structure above the previously known (5) + isomer was established. In the process of studying 98 Nb the yrast structure of positive-parity states in 99 Mo was extended to 3.7 MeV excitation energy, the previously-known 99 Nb level scheme was enriched, and two new levels were added in the level scheme of 97 Zr. The coupling of the odd proton occupying the g 9/2 orbital to the yrast states in the core nucleus of 97 Zr can account for all observed states in 98 Nb. The yrast structure for the positive-parity states of 99 Mo is compared to the deformed ground-state bands of the 101 Ru isotone and of 98,100 Mo.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2024

Fundamental Neutron Physics: Theory and Analysis

The goal of the proposed research is the study of the possible manifestations of new physics beyond the Standard model in fundamental neutron physics, with emphasis on fundamental symmetries and "exotic'' interactions. The main part of the research will be focused on theoretical support of the search for Time Reversal Invariance Violation (TRIV) in neutron nuclei scattering. The existence of our universe, and the prevalence of matter over antimatter, requires TRIV (the impossibility of going from the past to the future). However, the source of TRIV in the Standard model is not strong enough to explain why our universe exists. Thus, the observation of large TRIV effects will be a clear signal of new physics. The proposed research topics include calculations of Parity Violating (PV) and TRIV effects in neutron nuclei scattering on different targets, and the study of the possible manifestations of new physics in neutron-decays, neutron-antineutron oscillations, and in interactions of ultra-cold neutrons with nuclei. This research will provide theoretical support to the ongoing experimental programs related to the search for TRIV in neutron scattering at Los Alamos National Laboratory and J-PARC (Japan), and will contribute in the efforts in searching for new physics in fundamental neutron physics experiments at the Oak Ridge National Laboratory, and at other national and international neutron research centers.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2021

Electric dipole moments of three-nucleon systems in the pionless effective field theory

We calculate the electric dipole moments (EDMs) of three-nucleon systems at leading order in pionless effective field theory. The one-body contributions that arise from permanent proton and neutron EDMs and the two-body contributions that arise from charge-parity-odd nucleon-nucleon interactions are taken into account. Neglecting the Coulomb interaction, we consider the triton and 3 He, and also investigate them in the Wigner-SU(4) symmetric limit. We also calculate the electric dipole form factor and find numerically that the momentum dependence of the electric dipole form factor in the Wigner limit is, up to an overall constant (and numerical accuracy), the same as the momentum dependence of the charge form factor. Finally, we study the cutoff dependence of these observables and find that they are properly renormalized.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2025

Parity-Doubled Nucleons Can Rapidly Cool Neutron Stars

In confined hadronic matter, the spontaneous breaking and restoration of chiral symmetry can be described by considering nucleons, 𝑁 + ⁡(939), and excited states of opposite parity, 𝑁 − ⁡(1535). In a cold, dense hadronic phase where chiral symmetry remains spontaneously broken, direct Urca decay processes involving the 𝑁 − are possible, e.g., 𝑁 − → 𝑁 + + 𝑒 − + $\bar{𝜈}_𝑒$. Here, we show that at low temperature and moderate densities, because the 𝑁 − are much heavier than the 𝑁 + , such cooling dominates over standard 𝑁 + direct Urca processes. This provides a strong astrophysical signature of the pattern of chiral symmetry restoration in neutron stars.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2021

Axial and pseudoscalar form factors from charged current quasielastic neutrino-nucleon scattering

We study the scattering of neutrinos on polarized and unpolarized free nucleons, and also the polarization of recoil particles in these scatters. In contrast to electromagnetic processes, the parity-violating weak interaction gives rise to large spin asymmetries at leading order. Future polarization measurements could provide independent access to the proton axial structure and allow the first extraction of the pseudoscalar form factor from neutrino data without the conventional partially conserved axial current (PCAC) ansatz and assumptions about the pion-pole dominance. The pseudoscalar form factor can be accessed with precise measurements with muon (anti)neutrinos of a few hundreds MeV of energy or with tau (anti)neutrinos. The axial form factor can be extracted from scattering measurements using accelerator neutrinos of all energies.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2020

Non-cancellation of the parity anomaly in the strong-field regime of QED 2+1

Quantum fluctuations lead to an anomalous violation of parity symmetry in quantum electrodynamics for an even number of spatial dimensions. While the leading parity-odd electric current vanishes in vacuum, we uncover a non-cancellation of the anomaly for strong electric fields with distinct macroscopic signatures. We perform real-time lattice simulations with fully dynamical gauge fields and Wilson fermions in 2 + 1 space-time dimensions. In the static field limit, relevant at early times, we solve the problem analytically. Our results point out the fundamental role of quantum anomalies for strong-field phenomena, relevant for a wide range of condensed matter and high-energy applications, but also for the next generation of gauge theory quantum simulators.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2020

Khuri-Treiman equations for 3$π$ decays of particles with spin

Khuri-Treiman equations have proven to be a useful theoretical tool in the analysis of three-body decays, especially into the 3$π$ final state. In this work we present in full detail the necessary generalization of the formalism to study the decays of particles with arbitrary spin, parity, and charge conjugation. To this extent, we find it most convenient to work with helicity amplitudes instead of the so-called invariant amplitudes, especially when dealing with the unitarity relations. The isobar expansions in the three possible ( s-, t-, and u- ) final channels are related with the appropriate crossing matrices. We pay special attention to the kinematical singularities and constraints of the helicity amplitudes, showing that these can be derived by means of the crossing matrix.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2022

Multiparticle-hole excitations in nuclei near N = Z = 20: $^{41}$K

This experimental study of high-spin structure near the N = Z = 20 region focuses on 41 K and also reports three newly observed γ transitions in 41 Ca from the same reaction. High-spin states were populated using the 26 Mg( 18 O, p2nγ) 41 K and 26 Mg( 18 O, 3nγ) 41 Ca reactions at a beam energy of 50 MeV at the Florida State University John D. Fox Superconducting Linear Accelerator Laboratory, employing the FSU high-purity germanium detector array. The level scheme of 41 K was extended to 12325 keV, possibly up to J π = 25/2 − or 27/2 + , by means of 25 new γ-ray transitions, and that of 41 Ca to 9916 keV. Linear polarization and angular-distribution measurements were used to provide spin and parity information for several states in the 41 K decay scheme. The results are compared with spsdpf cross-shell shell-model calculations using the FSU interaction. Configurations involving zero or one nucleon promoted from the sd to the fp shell reproduce the energies of many known states reasonably well, while multi-particle excitations reveal a more complex interplay of single-particle motion, collective pairing, and deformation, posing an interesting challenge for future theoretical work.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2023

Updated analysis of the Er 170 ( p , t ) Er 168 reaction data

More than 200 states up to 4.1 MeV excitation have been populated in 168 Er with the 170 Er ( p , t ) reaction at 25 MeV incident energy. About 80 of these states, with 0 + and 2 + assignments, were reported in a previous publication [D. Bucurescu et al., Phys. Rev. C 73, 064309 (2006)]. Here, the present work considerably enriches the knowledge of this nucleus. A multistep coupled-channels analysis of the angular distributions is now presented for all the states observed in this experiment. Spin and parity values between 0 + and 7 - are newly assigned for more than 100 states. For the states already reported in the ENSDF database with J π values there is a good agreement with our values. The 168 Er nucleus remains one of the best experimentally known nuclei for states with low and medium spins below 4 MeV excitation energy, representing a challenge for future microscopic structure model calculations aiming to disentangle the contributions of different excitation degrees of freedom.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2022

High-Gradient Wien Spin Rotators at Jefferson Lab

Nuclear physics experiments performed in the Continuous Electron Beam Accelerator Facility (CEBAF) at Jefferson Laboratory (JLab) require spin manipulation of electron beams. Two Wien spin rotators in the injector keV region are essential at CEBAF to establish longitudinal polarization at the end station target, and to flip the polarization direction by ? rad to rule out false asymmetries. In a Wien filter, the homogeneous and independent electric and magnetic fields, along with the velocity vectors of the electrons that traverse it, form a mutually orthogonal system. The magnitude of the electrostatic field, established by biasing two highly-polished electrodes, defines the desired spin angle at the target yet deviates the beam trajectory due to the Lorentz force. The beam trajectory in the Wien is then re-established by adjusting the magnetic field, induced by an electromagnet encasing the device vacuum chamber. This contribution describes the evolution design and high voltage testing of Wien filters for spin manipulation at increased beam energies in the keV injector region, required by high precision parity violation experiments like MOLLER.

Palacios Serrano, G. G.↗
DOE OSTI2022

High-Gradient Wien Spin Rotators at Jefferson Lab

Nuclear physics experiments performed in the Continuous Electron Beam Accelerator Facility (CEBAF) at Jefferson Laboratory (JLab) require spin manipulation of electron beams. Two Wien spin rotators in the injector keV region are essential at CEBAF to establish longitudinal polarization at the end station target, and to flip the polarization direction by ? rad to rule out false asymmetries. In a Wien filter, the homogeneous and independent electric and magnetic fields, along with the velocity vectors of the electrons that traverse it, form a mutually orthogonal system. The magnitude of the electrostatic field, established by biasing two highly-polished electrodes, defines the desired spin angle at the target yet deviates the beam trajectory due to the Lorentz force. The beam trajectory in the Wien is then re-established by adjusting the magnetic field, induced by an electromagnet encasing the device vacuum chamber. This contribution describes the evolution design and high voltage testing of Wien filters for spin manipulation at increased beam energies in the keV injector region, required by high precision parity violation experiments like MOLLER.

Palacios Serrano, G. G.↗