Tue·Jun 15, 2021Tuesday·June 15, 2021

1. 01*

   Expanding Nuclear Physics Horizons with the Gamma Factory

   Dmitry Budker🇩🇪 · Julian C. Berengut🇦🇺 · Victor V. Flambaum🇦🇺 · Mikhail Gorchtein🇩🇪 · Junlan Jin🇨🇳 · Felix Karbstein🇩🇪 · Mieczyslaw Witold Krasny🇫🇷 · Yuri A. Litvinov🇩🇪 · Adriana Pálffy🇩🇪 · Vladimir Pascalutsa🇩🇪 · Alexey Petrenko🇷🇺 · Andrey Surzhykov🇩🇪 and 4 other authors

   The Gamma Factory (GF) is an ambitious proposal, currently explored within the CERN Physics Beyond Colliders program, for a source of photons with energies up to $\approx 400$MeV and photon fluxes (up to $\approx 10^{17}$ photons per second) exceeding those of the currently available gamma sources by orders of magnitude. The high-energy (secondary) photons are produced via resonant scattering of the primary laser photons by highly relativistic partially-stripped ions circulating in the accelerator. The secondary photons are emitted in a narrow cone and the energy of the beam can be monochromatized, eventually down to the $\approx 1$ ppm level, via collimation, at the expense of the photon flux. This paper surveys the new opportunities that may be afforded by the GF in nuclear physics and related fields.

   nucl-exhep-exnucl-thphysics.acc-ph+1Annalen Phys.(2022)·42 citations
2. 02*

   ${}^{159}$Dy electron-capture: a strong new candidate for neutrino mass determination

   Z. Ge🇫🇮 · T. Eronen🇫🇮 · K. S. Tyrin🇷🇺 · J. Kotila🇫🇮 · J. Kostensalo🇫🇮 · D. A. Nesterenko🇫🇮 · O. Beliuskina🇫🇮 · R. de Groote🇫🇮 · A. de Roubin🇫🇷 · S. Geldhof🇫🇮 · W. Gins🇫🇮 · M. Hukkanen🇫🇮 and 12 other authors

   { The ground-state to ground-state electron-capture $Q$ value of ${}^{159}$Dy ($3/2^{-}$) has been measured directly utilizing the double Penning trap mass spectrometer JYFLTRAP. A value of 364.73(19)~keV was obtained from a measurement of the cyclotron frequency ratio of the decay parent ${}^{159}$Dy and the decay daughter ${}^{159}$Tb ions using the novel phase-imaging ion-cyclotron resonance technique. The $Q$ values for allowed Gamow-Teller transition to $5/2^{-}$ and the third-forbidden unique transition to $11/2^{+}$ state with excitation energies of 363.5449(14)~keV and 362.050(40)~keV in ${}^{159}$Tb were determined to be 1.18(19) keV and 2.68(19) keV, respectively. The high-precision $Q$ value of transition $3/2^{-}\to 5/2^{-}$ from this work, revealing itself as the lowest electron-capture $Q$ value, is utilized to unambiguously characterise all the possible lines that are present in its electron capture spectrum. { We performed atomic many-body calculations for both transitions to determine electron-capture probabilities from various atomic orbitals, and found an order of magnitude enhancement in the event rates near the end-point of energy spectrum in the transition to the $5/2^{-}$ nuclear excited state, which can become very interesting once the experimental challenges of identifying decays into excited states are overcome. The transition to the $11/2^{+}$ state is strongly suppressed and found unsuitable for measuring the neutrino mass. These results show that the electron capture in the ${}^{159}$Dy atom, going to the $5/2^{-}$ state of the ${}^{159}$Tb nucleus, %\textcolor{red} {is a new candidate which may open the way to determine the electron-neutrino mass in the sub-eV region by studying EC. Further experimental feasibility studies, including coincidence measurements with realistic detectors, will be of great interest.} }

   nucl-exPRL(2021)·34 citations
3. 03*

   A Concept for Polarized ${}^3$He Targets for High Luminosity Scattering Experiments in High Magnetic Field Environments

   James Maxwell🇺🇸 · Richard Milner🇺🇸

   We present the conceptual design of a polarized ${}^3$He target to be used for high luminosity scattering experiments within high magnetic field environments. This two-cell target will take advantage of advancements in optical pumping techniques at high magnetic field to create 60% longitudinally polarized ${}^3$He gas in a pumping cell within a uniform magnetic field above 1 T. By transferring the polarized gas to cryogenic target cell, the gas density is increased to create a target thickness suitable for high luminosity applications. We discuss the general design of this scheme, and plans for its application in Jefferson Lab's CLAS12 detector.

   ↳ physics.ins-detnucl-exNucl.Instrum.Meth.A(2021)·6 citations
4. 04*

   Optimising Scintillating Neutron Detectors for Cosmic Ray Soil Moisture Monitoring

   J. P. Stowell🇬🇧 · S. J. Fargher · C. A. Steer · L. F. Thompson🇬🇧

   Cosmic Ray Neutron Sensing (CRNS) is a powerful technique that allows non-invasive monitoring of soil moisture on length scales well matched for agricultural applications. One factor limiting the use of the technique within industrial agriculture settings is the high initial cost of Helium-3 or BF3 tubes typically used for ground level neutron monitoring. This paper discusses the use of Geant4 to optimise an alternative scintillator based neutron detector that may be applicable for challenges where cost is a higher driving factor than temporal resolution.

   ↳ physics.ins-detnucl-exJINST(2021)·3 citations
5. 05*

   The Angular Correlations in the $e^{+}{e}^{-}$ Decay of Excited States in 8Be

   A.C Hayes🇺🇸 · J.L. Friar🇺🇸 · GM. Hale🇺🇸 · GT. Garvey🇺🇸

   Motivated by the recent observation of anomalous electron-positron angular correlations in the decay of the 18.15 MeV 1+ excited states in 8Be, we reexamine in detail the Standard Model expectations for these angular correlations. The 18.15 MeV state is above particle threshold, and several multipoles can contribute to its $e^{+}{e}^{-}$ decay. We present the general theoretical expressions for $e^{+}{e}^{-}$ angular distributions for nuclear decay by C0, C1, C2 M1, E1, and E2 multipoles, and we examine their relative contribution to the $e^{+}{e}^{-}$ decay of 8Be at 18.15 MeV. We find that this resonance is dominated by M1 and E1 decay, and that the ratio of M1 to E1 strength is a strong function of energy. This is in contract to the original analysis of the $e^{+}{e}^{-}$ angular distributions, where the M1/E1 ratio was assumed to be a constant over the energy region Ep = 0:8-1:2 MeV. We find that the existence of a `bump' in the measured angular distribution is strongly dependent on the assumed M1/E1 ratio, with the present analysis finding the measured large-angle contributions to the $e^{+}{e}^{-}$ angular distribution to be lower than expectation. Thus, in the current analysis we find no evidence for axion decay in the 18.15 MeV resonance region of 8Be.

   ↳ nucl-thhep-exhep-phnucl-exPRC(2022)·20 citations
6. 06*

   Interplay between pairing and triaxial shape degrees of freedom in Os and Pt nuclei

   K. Nomura🇭🇷 · D. Vretenar🇭🇷 · Z. P. Li🇨🇳 · J. Xiang

   The effect of coupling between pairing and quadrupole triaxial shape vibrations on the low-energy collective states of $\gamma$-soft nuclei is investigated using a model based on the framework of nuclear energy density functionals (EDFs). Employing a constrained self-consistent mean-field (SCMF) method that uses universal EDFs and pairing interactions, potential energy surfaces of characteristic $\gamma$-soft Os and Pt nuclei with $A\approx 190$ are calculated as functions of the pairing and triaxial quadrupole deformations. Collective spectroscopic properties are computed using a number-nonconserving interacting boson model (IBM) Hamiltonian, with parameters determined by mapping the SCMF energy surface onto the expectation value of the Hamiltonian in the boson condensate state. It is shown that, by simultaneously considering both the shape and pairing collective degrees of freedom, the EDF-based IBM successfully reproduces data on collective structures based on low-energy $0^{+}$ states, as well as $\gamma$-vibrational bands.

   ↳ nucl-thnucl-exPRC(2021)·11 citations
7. 07*

   $K_S^0$ meson production in inelastic $\text{p+p}$ interactions at 158 GeV/c beam momentum measured by NA61/SHINE at the CERN SPS

   A. Acharya🇵🇱 · H. Adhikary🇵🇱 · K.K. Allison🇺🇸 · N. Amin🇩🇪 · E.V. Andronov🇷🇺 · T. Antičić🇭🇷 · V. Babkin🇷🇺 · M. Baszczyk🇵🇱 · S. Bhosale🇵🇱 · A. Blonde · M. Bogomilov🇧🇬 · Y. Bondar🇵🇱 and 130 other authors

   The production of $K_S^0$ mesons in inelastic $\text{p+p}$ collisions at beam momentum 158 GeV/c ($\sqrt{s_{NN}}=17.3$ GeV) was measured with the NA61/SHINE spectrometer at the CERN Super Proton Synchrotron. Double-differential distributions were obtained in transverse momentum and rapidity. The mean multiplicity of $K_S^0$ was determined to be $0.162\pm 0.001(stat.)\pm 0.011(sys.)$. The results on $K_S^0$ production are compared with model predictions (EPOS 1.99, SMASH 2.0, PHSD and UrQMD 3.4 models) as well as with published world data.

   ↳ hep-exnucl-exEPJC(2022)·18 citations

* Reconstructed cohort: no mailing for this day survives in the archive. Papers are grouped by their submission times and arXiv's announcement cut-off, assuming announcement without delay; positions follow identifier order. Validated at ~91% exact-day agreement against the archived era.