Thu·Jun 10, 2021Thursday·June 10, 2021

1. 01*

   Evidence against the wobbling nature of low-spin bands in ${}^{135}$Pr

   B. F. Lv🇨🇳 · C. M. Petrache🇫🇷 · E. A. Lawrie🇿🇦 · S. Guo🇨🇳 · A. Astier🇫🇷 · E. Dupont🇫🇷 · K. K. Zheng🇨🇳 · H. J. Ong🇨🇳 · J. G. Wang🇨🇳 · X. H. Zhou🇨🇳 · Z. Y. Sun🇨🇳 · P. Greenlees🇫🇮 and 27 other authors

   The electromagnetic character of the $\Delta I=1$ transitions connecting the one- to zero-phonon and the two- to one-phonon wobbling bands should be dominated by an $E2$ component, due to the collective motion of the entire nuclear charge. In the present work it is shown, based on combined angular correlation and linear polarization measurements, that the mixing ratios of all analyzed connecting transitions between low-lying bands in ${}^{135}$Pr interpreted as zero-, one-, and two-phonon wobbling bands, have absolute values smaller than one. This indicates predominant $M1$ magnetic character, which is incompatible with the proposed wobbling nature. All experimental observables are instead in good agreement with quasiparticle-plus-triaxial-rotor model calculations, which describe the bands as resulting from a rapid re-alignment of the total angular momentum from the short to the intermediate nuclear axis.

   nucl-exPLB(2022)·23 citations
2. 02*

   Improving the particle identification of radioactive isotope beams at the RIBLL2 separator

   Fang Fang🇨🇳 · Shuwen Tang🇨🇳 · Shitao Wang🇨🇳 · Xueheng Zhang🇨🇳 · Zhiyu Sun🇨🇳 · Yuhong Yu🇨🇳 · Duo Yan🇨🇳 · Shuya Jin🇨🇳 · Yixuan Zhao🇨🇳 · Shaobo Ma🇨🇳 · Yongjie Zhang🇨🇳

   To improve the ability of particle identification of the RIBLL2 separator at the HIRFL-CSR complex, a new high-performance detector for measuring fragment starting time and position at the F1 dispersive plane has been constructed and installed, and a method for achieving precise Bh̊o} determination has been developed using the experimentally derived ion-optical transfer matrix elements from the measured position and ToF information. Using the high-performance detectors and the precise Bh̊o} determination method, the fragments produced by the fragmentation of 78Kr at 300 MeV/nucleon were identified clearly at the RIBLL2-ETF under full momentum acceptance. The atomic number Z resolution of {\sigma}Z~0.19 and the mass-to-charge ratio A/Q resolution of {\sigma}A/Q~5.8e-3 were obtained for the 75As33+ fragment. This great improvement will increase the collection efficiency of exotic nuclei, extend the range of nuclei of interest from the A<40 mass region up to the A~80 mass region, and promote the development of radioactive nuclear beam experiments at the RIBLL2 separator.

   ↳ physics.ins-detnucl-exNucl.Phys.Rev.(2022)·5 citations
3. 03*

   Wigner SU(4) symmetry, clustering, and the spectrum of ${}^{12}$C

   Shihang Shen🇩🇪 · Timo A. Lähde🇩🇪 · Dean Lee🇺🇸 · Ulf-G. Meißner🇩🇪

   We present lattice calculations of the low-lying spectrum of ${}^{12}$C using a simple nucleon-nucleon interaction that is independent of spin and isospin and therefore invariant under Wigner's SU(4) symmetry. We find strong signals for all excited states up to $\sim 15$~MeV above the ground state, and explore the structure of each state using a large variety of $\alpha$ cluster and harmonic oscillator trial states, projected onto given irreducible representations of the cubic group. We are able to verify earlier findings for the $\alpha$ clustering in the Hoyle state and the second $2^{+}$ state of ${}^{12}$C. The success of these calculations to describe the full low-lying energy spectrum using spin-independent interactions suggest that either the spin-orbit interactions are somewhat weak in the ${}^{12}$C system, or the effects of $\alpha$ clustering are diminishing their influence. This is in agreement with previous findings from {\it ab initio} shell model calculations.

   ↳ nucl-thhep-lathep-phnucl-exEPJA(2021)·23 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.