Wed·Feb 16, 2022Wednesday·February 16, 2022

1. 01*

   Direct determination of the atomic mass difference of the pairs ${}^{76}$As-${}^{76}$Se and ${}^{155}$Tb-${}^{155}$Gd rules out ${}^{76}$As and ${}^{155}$Tb as possible candidates for electron (anti)neutrino mass measurements

   Z. Ge🇫🇮 · T. Eronen🇫🇮 · A. de Roubin🇫🇷 · J. Kostensalo🇫🇮 · J. Suhonen🇫🇮 · D. A. Nesterenko🇫🇮 · O. Beliuskina🇫🇮 · R. de Groote🇫🇮 · C. Delafosse🇫🇮 · S. Geldhof🇫🇮 · W. Gins🇫🇮 · M. Hukkanen🇫🇮 and 10 other authors

   The first direct determination of the ground-state-to-ground-state $Q$ values of the ${\beta }^{-}$ decay ${}^{76}$As $\to$ ${}^{76}$Se and the electron-capture decay ${}^{155}$Tb $\to$ ${}^{155}$Gd was performed utilizing the double Penning trap mass spectrometer JYFLTRAP. By measuring the atomic mass difference of the decay pairs via the phase-imaging ion-cyclotron-resonance (PI-ICR) technique, the $Q$ values of ${}^{76}$As $\to$ ${}^{76}$Se and ${}^{155}$Tb $\to$ ${}^{155}$Gd were determined to be 2959.265(74) keV and 814.94(18) keV, respectively. The precision was increased relative to earlier measurements by factors of 12 and 57, respectively. The new $Q$ values are 1.33 keV and 5 keV lower compared to the values adopted in the most recent Atomic Mass Evaluation 2020. With the newly determined ground-state-to-ground-state $Q$ values combined with the excitation energy from $\gamma$-ray spectroscopy, the $Q$ values for ground-state-to-excited-state transitions ${}^{76}$As (ground state) $\to$ ${}^{76}$Se${}^{\ast }$ (2968.4(7) keV) and ${}^{155}$Tb (ground state) $\to$ ${}^{155}$Gd${}^{\ast }$ (815.731(3) keV) were derived to be -9.13(70) keV and -0.79(18) keV. Thus we have confirmed that both of the ${\beta }^{-}$-decay and EC-decay candidate transitions are energetically forbidden at a level of at least 4$\sigma$, thus definitely excluding these two cases from the list of potential candidates for the search of low-$Q$-value ${\beta }^{-}$ or EC decays to determine the electron-(anti)neutrino mass.

   nucl-exPRC(2022)·12 citations
2. 02*

   Application of complex transition density to nuclear reaction and effect of phase factor

   T. Furumoto🇯🇵

   Complex transition density can be constructed by a nuclear structure model with a complex basis and/or complex coefficient. In general, the complex transition density is converted to the real one with phase factor. In this study, we apply the complex transition density directly to the microscopic reaction model. We compare with scattering cross sections calculated with the real and complex transition densities in the frameworks of the optical model, the distorted wave Born approximation, and the coupled-channel (CC) calculation, respectively. In addition, we investigate the dependence of the phase factor for the transition density in the elastic and inelastic cross sections. The effect of the phase factor on the elastic and inelastic cross sections can be seen in the CC calculation. Finally, we found an important role of the phase factor in the nuclear elastic and inelastic scatterings.

   ↳ nucl-thnucl-ex0 citations
3. 03*

   Simulation of the RIBRAS Facility with GEANT4

   L.E. Tamayose🇧🇷 · J.C. Zamora🇧🇷 · G.F. Fortino🇧🇷 · D. Flechas🇨🇴

   A Geant4 simulation code was developed to perform realistic simulations of the RIBRAS facility. A second order expansion of a finite solenoid field was included to describe the beam optics with a good precision. A systematic study of coil currents for several magnetic rigidities and focal points was performed. Parameterizations of the coil currents for single and dual mode operations were obtained. Dedicated routines were developed to simulate the mechanism of direct reactions involving two and three particles in the final state. The present simulations were employed to investigate the feasibility of a Solenoidal Spectrometer with the RIBRAS facility. Our first results indicate that the concept can be applied in the RIBRAS system under certain conditions. Forthcoming studies both from simulations and experiment are already under development.

   ↳ physics.acc-phnucl-exphysics.comp-phphysics.ins-detBraz.J.Phys.(2022)·2 citations
4. 04*

   In-medium $\Lambda$ isospin impurity from charge symmetry breaking in the ${}_{\Lambda }^4\mathrm{H}-{}_{\Lambda }^4\mathrm{He}$ mirror hypernuclei

   M. Schäfer🇮🇱 · N. Barnea🇮🇱 · A. Gal🇮🇱

   The $\Lambda$ separation energies in the mirror hypernuclei ${}_{\Lambda }^4\mathrm{H}-{}_{\Lambda }^4\mathrm{He}$ exhibit large charge symmetry breaking (CSB). Analyzing this CSB within pionless effective field theory while using partially conserved baryon-baryon SU(3) flavor symmetry, we deduce a $\Lambda -{\Sigma }^0$ induced in-medium admixture amplitude ${\mathcal{A}}_{I=1}\approx 1.5\%$ in the dominantly isospin $I=0$ $\Lambda$ hyperon. Our results confirm the free-space value ${\mathcal{A}}_{I=1}^{(0)}$ inferred directly within the SU(3) baryon octet by Dalitz and von-Hippel in 1964 and reaffirmed in a recent QCD+QED lattice calculation. Furthermore, exploring the consequences of SU(3) flavor symmetry on the $\Lambda$-nucleon interaction, we find that CSB is expected to impact the $S=1$ and $S=0$ spin channels in opposite directions, with the latter dominating by an order of magnitude. These observations explain a recent deduction of $\Lambda$-nucleon CSB strengths.

   ↳ nucl-thhep-phnucl-exPRC(2022)·13 citations
5. 05*

   Theoretical description of pygmy (dipole) resonances

   Edoardo G. Lanza · Andrea Vitturi🇮🇹

   Stable and unstable nuclei with neutron excess ($N>Z$) show - in the isovector dipole transition strength distribution - a small hump around the neutron emission threshold energy known as Pygmy Dipole Resonance (PDR). One of its main features is the isospin mixing allowing the experimental studies with both isovector and isoscalar probes. Different theoretical approaches and methodologies are used to deduce the characteristics of the PDR. In this Chapter, the various mean-field theories and their extensions, devoted to understand and reproduce the strength distribution of these low-lying dipole states, are summarised. Special attention is dedicated to the calculations of the inelastic cross section, aspect that is particularly important in the investigation with isoscalar probes, such as $\alpha$-particles or ${}^{17}$O. The relevance of the radial form factors is presented in relation to the inelastic cross-section calculations.

   ↳ nucl-thnucl-ex1 citation
6. 06*

   Pulse-shape discrimination in water-based scintillators

   Michael J. Ford🇺🇸 · Natalia P. Zaitseva · M. Leslie Carman · Steven A. Dazeley🇺🇸 · Adam Bernstein🇺🇸 · Andrew Glenn🇺🇸 · Oluwatomi A. Akindele🇺🇸

   This work describes a class of liquid scintillators that contain mostly water (>50 wt. % of the entire composition) and can discriminate between interactions induced by neutrons and gamma rays. By balancing the interface interactions between the components of the formulation, these scintillators form emulsions that can be thermodynamically stable. This approach, which considers a quantity known as the hydrophilic-lipophilic difference, requires consideration of the salinity and temperature as well as characterization of the surfactants and oil phase. Emulsions comprised of water and various oils were characterized first. Then, the effect of scintillating dyes in the oil phase was considered, followed by the construction of partial phase diagrams of the emulsions. For transparent oil-in-water emulsions with a single phase, the scintillation light yield and properties of pulse-shape discrimination were measured. The best performing scintillators contained 33 wt. % of a scintillating oil phase and exhibited a light yield that was as high as 18% of the light yield of a commercially available liquid scintillator that does not contain water (EJ-309). These water-based liquid scintillators exhibited a figure of merit of neutron/gamma ray discrimination as high as 1.79 at about 1500 keVee.

   ↳ physics.ins-detnucl-exNucl.Instrum.Meth.A(2022)·14 citations
7. 07*

   Digital Signal Analysis based on Convolutional Neural Networks for Active Target Time Projection Chambers

   G.F. Fortino🇧🇷 · J.C. Zamora🇧🇷 · L.E. Tamayose🇧🇷 · N.S.T. Hirata · V. Guimaraes🇧🇷

   An algorithm for digital signal analysis using convolutional neural networks (CNN) was developed in this work. The main objective of this algorithm is to make the analysis of experiments with active target time projection chambers more efficient. The code is divided in three steps: baseline correction, signal deconvolution and peak detection and integration. The CNNs were able to learn the signal processing models with relative errors of less than 6\%. The analysis based on CNNs provides the same results as the traditional deconvolution algorithms, but considerably more efficient in terms of computing time (about 65 times faster). This opens up new possibilities to improve existing codes and to simplify the analysis of the large amount of data produced in active target experiments.

   ↳ eess.SPcs.LGnucl-exphysics.comp-ph+2Nucl.Instrum.Meth.A(2022)·2 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.