Mon·Dec 9, 2019Monday·December 9, 2019

1. 01*

   $E0$ transition strength in stable Ni isotopes

   L.J. Evitts🇨🇦 · A.B. Garnsworthy🇨🇦 · T. Kibedi🇦🇺 · J. Smallcombe🇨🇦 · M.W. Reed🇦🇺 · A.E. Stuchbery🇦🇺 · G.J. Lane🇦🇺 · T.K. Eriksen🇦🇺 · A. Akber🇦🇺 · B. Alshahrani · M. de Vries · M.S.M. Gerathy🇦🇺 and 12 other authors

   Excited states in ${}^{58,60,62}$Ni were populated via inelastic proton scattering at the Australian National University as well as via inelastic neutron scattering at the University of Kentucky Accelerator Laboratory. The Super-e electron spectrometer and the CAESAR Compton-suppressed HPGe array were used in complementary experiments to measure conversion coefficients and $\delta (E2/M1)$ mixing ratios, respectively, for a number of $2^{+}\to 2^{+}$ transitions. The data obtained were combined with lifetimes and branching ratios to determine $E0$, $M1$, and $E2$ transition strengths between $2^{+}$ states. The $E0$ transition strengths between $0^{+}$ states were measured using internal conversion electron spectroscopy and compare well to previous results from internal pair formation spectroscopy. The $E0$ transition strengths between the lowest-lying $2^{+}$ states were found to be consistently large for the isotopes studied.

   nucl-exPRC(2019)·11 citations
2. 02*

   Electromagnetic properties of ${}^{21}$O for benchmarking nuclear Hamiltonians

   S. Heil🇩🇪 · M. Petri🇩🇪 · K. Vobig🇩🇪 · D. Bazin🇺🇸 · J. Belarge · P. Bender · B. A. Brown🇺🇸 · R. Elder · B. Elman · A. Gade🇺🇸 · T. Haylett · J. D. Holt🇨🇦 and 16 other authors

   The structure of exotic nuclei provides valuable tests for state-of-the-art nuclear theory. In particular electromagnetic transition rates are more sensitive to aspects of nuclear forces and many-body physics than excitation energies alone. We report the first lifetime measurement of excited states in ${}^{21}$O, finding ${\tau }_{1/2^{+}}=420_{-32}^{+35}{\text{(stat)}}_{-12}^{+34}\text{(sys)}$\,ps. This result together with the deduced level scheme and branching ratio of several $\gamma$-ray decays are compared to both phenomenological shell-model and ab initio calculations based on two- and three-nucleon forces derived from chiral effective field theory. We find that the electric quadrupole reduced transition probability of $\mathrm{B}(E2;1/2^{+}\to 5/2_{g.s.}^{+})=0.71_{-0.06-0.06}^{+0.07+0.02}$~e${}^2$fm${}^4$, derived from the lifetime of the $1/2^{+}$ state, is smaller than the phenomenological result where standard effective charges are employed, suggesting the need for modifications of the latter in neutron-rich oxygen isotopes. We compare this result to both large-space and valence-space ab initio calculations, and by using multiple input interactions we explore the sensitivity of this observable to underlying details of nuclear forces.

   nucl-exnucl-thPLB(2020)·13 citations
3. 03*

   Spectroscopy of ${}^{196}$Hg using Digital INGA at VECC, Kolkata

   S. Das🇮🇳 · S. Chatterjee🇮🇳 · S. Samanta · R. Raut🇮🇳 · S. S. Ghugre · A. K. Sinha · S. Bhattacharya🇮🇳 · S. Nandi · R. Banik🇮🇳 · G. Mukherjee🇮🇳 · S. Bhattacharyya🇮🇳 · S. Ali🇺🇸 and 4 other authors

   Spectroscopic investigation of the ${}^{196}$Hg (Z=80, N=116) was carried out using the Indian National Gamma Array (INGA) setup at the Variable Energy Cyclotron Centre (VECC), Kolkata. Analysis of the acquired data led to the identification of new $\gamma$-ray transitions and levels in the excitation pattern of the nucleus along with the spin-parity assignments thereof. The latter were either previously absent or had been tentatively identified. Theoretical interpretation of the level structure obtained from these efforts can be pursued with appropriate model calculations.

   nucl-ex0 citations
4. 04*

   Current status of LEGEND: Searching for Neutrinoless Double-Beta Decay in ${}^{76}$Ge: Part I

   I.S. Guinn🇺🇸 · J.M. López-Castaño🇺🇸

   Neutrinoless double-beta decay($0\nu \beta \beta$) decay is a hypothetical process that violates lepton number, and whose observation would unambiguously indicate that neutrinos are Majorana fermions. In the standard inverted-ordering neutrino mass scenario, the minimum possible value of m${}_{\beta \beta }$ corresponds to a half-life around 10${}^{28}$ yr for $0\nu \beta \beta$ decay in ${}^{76}$Ge, which is the target of the next generation of experiments. The current limits of GERDA and \textsc{Majorana Demonstrator} indicate a half-life higher than 10${}^{26}$ yr. These experiments use high-purity germanium (HPGe) detectors that are highly-enriched in ${}^{76}$Ge. They have achieved the best intrinsic energy resolution and the lowest background rate in the signal search region among all $0\nu \beta \beta$ experiments. Taking advantage of these successes, a new international collaboration - the Large Enriched Germanium Experiment for Neutrinoless $\beta \beta$ Decay (LEGEND) - has been formed to build a ton-scale experiment with discovery potential covering the inverse-ordering neutrino mass range in a decade, following a phased approach. This first part of LEGEND proceedings describes GERDA and \textsc{Majorana Demonstrator} capabilities and the general plan of LEGEND to reach the goal, while the second part is focused in the status of the first stage of LEGEND, LEGEND-200.

   nucl-exPoS(2019)·0 citations
5. 05*

   Current status of LEGEND: Searching for Neutrinoless Double-Beta Decay in 76Ge: Part II

   J.M. López-Castaño🇺🇸 · I. Guinn🇺🇸

   Neutrinoless double-beta decay (0$\nu \beta \beta$) decay is a hypothetical process that violates lepton number, and whose observation would unambiguously indicate that neutrinos are Majorana fermions. In the standard inverted-ordering neutrino mass scenario, the minimum possible value of mbb corresponds to a half-life around 10${}^{28}$ yr for 0$\nu \beta \beta$ decay in ${}^{76}$Ge, which is the target of the next generation of experiments. The current limits of GERDA and MAJORANA DEMONSTRATOR indicate a half-life higher than 10${}^{26}$ yr. These experiments use high-purity germanium (HPGe) detectors that are highly enriched in ${}^{76}$Ge. They have achieved the best intrinsic energy resolution and the lowest background rate in the signal search region among all 0nbb experiments. Taking advantage of these successes, a new international collaboration - the Large Enriched Germanium Experiment for Neutrinoless bb Decay (LEGEND) - has been formed to build, following a phased approach, a ton-scale experiment with discovery potential covering the inverse-ordering neutrino mass range in a decade. The first part of LEGEND proceedings describes GERDA and MAJORANA DEMONSTRATOR capabilities and the general plan of LEGEND to reach the goal, while this second part is focused in the status of the first stage of LEGEND, LEGEND-200.

   nucl-exhep-exPoS(2019)·3 citations
6. 06*

   A practical guide to using the AngCor package

   Philip Adsley🇫🇷 · Kevin Li · Harshna Jivan🇿🇦 · Luke Morris · Luna Pellegri🇿🇦

   This guide contains brief, practically oriented instructions for the use of the AngCor package for computing angular correlations following nuclear reactions. This guide serves as a lasting reference for the AngCor package and complements the GitHub repository for the AngCor code.

   nucl-ex1 citation
7. 07*

   Microscopic cluster study of the 10Be and 11Be nuclei

   Pierre Descouvemont🇧🇪 · Naoyuki Itagaki🇯🇵

   We use a microscopic multicluster model to investigate the structure of ${}^{10}$Be and of ${}^{11}$Be. These nuclei are described by $\alpha +\alpha +n+n$ and $\alpha +\alpha +n+n+n$ configurations, respectively, within the Generator Coordinate Method (GCM). The 4- and 5-body models raise the problem of a large number of generator coordinates (6 for ${}^{10}$Be and 9 for ${}^{11}$Be), which requires specific treatment. We address this issue by using the Stochastic Variational Method (SVM), which is based on an optimal choice of the basis functions, generated randomly. The model provides good energy spectra for low-lying states of both nuclei. We also compute rms radii and densities, as well as electromagnetic transition probabilities. We analyze the structure of ${}^{10}$Be and of ${}^{11}$Be by considering energy curves, where one of the generator coordinates is fixed during the minimization procedure.

   ↳ nucl-thnucl-exPTEP·17 citations
8. 08*

   Rearrangement term in the nonlocal folding model of the nucleon optical potential

   Doan Thi Loan🇻🇳 · Dao T. Khoa🇻🇳 · Nguyen Hoang Phuc🇻🇳

   Based on the mean-field determination of the single-particle energy in nuclear matter that contains naturally a rearrangement term (RT) implied by the Hugenholtz-van Hove theorem, the folding model of the nucleon optical potential (OP) is extended to take into account the RT using the effective, density dependent CDM3Yn interaction. With the exchange part of the nucleon folded OP treated exactly in the Hartree-Fock manner, a compact nonlocal version of the folding model is suggested in the present work to determine explicitly the isospin-dependent, nonlocal central term of the nucleon OP. To solve the optical model (OM) equation with a complex nonlocal OP, the calculable $R$-matrix method is used to analyse the elastic neutron and proton scattering on ${}^{40,48}$Ca, ${}^{90}$Zr, and ${}^{208}$Pb targets at low energies. The inclusion of the RT into the folding model calculation of the nonlocal nucleon OP was shown to be essential for the overall good OM description of elastic nucleon scattering. To validate the nonlocal version of the folding model, the OM results given by the nonlocal folded nucleon OP are also compared with those given by the global parametrization of the nonlocal OP using the analytical nonlocal form factor suggested by Perey and Buck.

   ↳ nucl-thnucl-exJ.Phys.G(2020)·15 citations
9. 09*

   Monte Carlo simulations of the S-shaped neutron guide

   Luiz P. de Oliveira🇧🇷 · Alexandre P.S. Souza🇧🇷 · Fabiano Yokaichiya🇧🇷 · Frederico A. Genezini🇧🇷 · Margareth K.K.D. Franco🇧🇷

   Neutron transport along guides is governed by the Liouville theorem and the technology involved has advanced in recent decades. Computer simulations have proven to be useful tools in the design and conception of neutron guide systems in facilities. In this study, we use a Monte Carlo method to perform simulations for an S-shaped neutron guide with different dimensions for a Small-Angle Neutron Scattering (SANS) instrument, through the MCSTAS software. A wavelength cutoff is observed and shown to be dependent on the geometrical parameters of the guide. Results for the neutron flux at sample position are presented and a greater sensitivity of cutoffs concerning the curvatures of the guides than to their lengths is noticed. Our results are in agreement with those obtained from the Acceptance Diagram method and we analyze the beam divergence behavior along the S-shaped guide.

   ↳ physics.ins-detnucl-exnucl-thJINST(2020)·2 citations
10. 10*

    Proton-proton momentum correlation function as a probe of the high momentum tail of the nucleon momentum distribution

    Gao-Feng Wei🇨🇳 · Xi-Guang Cao🇨🇳 · Qi-Jun Zhi🇨🇳 · Xin-Wei Cao🇨🇳 · Zheng-Wen Long🇨🇳

    Within an improved transport model, we examine effects of the high momentum tail of the nucleon momentum distribution induced by short-range correlations on the proton-proton momentum correlation function in ${}^{197}$Au+${}^{197}$Au collisions at 400 MeV/nucleon. It is found that the proton-proton momentum correlation function from preequilibrium emissions responds sensitively to the presence as well as fraction of nucleons in the high momentum tail of the nucleon momentum distribution, but is almost robustly insensitive to other factors including the symmetry energy and the uncertainty of cutoff value of nucleon effective high momentum. In terms of the sensitivity and clearness, we propose that the proton-proton momentum correlation function from preequilibrium emissions can be as an effective probe of the high momentum tail of the nucleon momentum distribution.

    ↳ nucl-thnucl-exPRC(2020)·6 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.