Wed·Feb 28, 2018Wednesday·February 28, 2018

1. 01*

   Re-examining the transition into the N=20 island of inversion: structure of ${}^{30}$Mg

   B. Fernández-Domínguez🇪🇸 · B. Pietras🇬🇧 · W.N. Catford🇬🇧 · N.A. Orr🇫🇷 · M. Petri🇩🇪 · M. Chartier🇬🇧 · S. Paschalis🇬🇧 · N. Patterson🇬🇧 · J .S. Thomas🇬🇧 · M. Caamaño🇪🇸 · T. Otsuka🇯🇵 · A. Poves🇪🇸 and 25 other authors

   Intermediate energy single-neutron removal from ${}^{31}$Mg has been employed to investigate the transition into the N=20 island of inversion. Levels up to 5~MeV excitation energy in ${}^{30}$Mg were populated and spin-parity assignments were inferred from the corresponding longitudinal momentum distributions and $\gamma$-ray decay scheme. Comparison with eikonal-model calculations also permitted spectroscopic factors to be deduced. Surprisingly, the 0${}_2^{+}$ level in ${}^{30}$Mg was found to have a strength much weaker than expected in the conventional picture of a predominantly $2p-2h$ intruder configuration having a large overlap with the deformed ${}^{31}$Mg ground state. In addition, negative parity levels were identified for the first time in ${}^{30}$Mg, one of which is located at low excitation energy. The results are discussed in the light of shell-model calculations employing two newly developed approaches with markedly different descriptions of the structure of ${}^{30}$Mg. It is concluded that the cross-shell effects in the region of the island of inversion at Z=12 are considerably more complex than previously thought and that $np-nh$ configurations play a major role in the structure of ${}^{30}$Mg.

   nucl-exnucl-thPLB(2018)·18 citations
2. 02*

   Elliptic flow from Coulomb interaction and low density elastic scattering

   Yuliang Sun🇨🇳 · Qingfeng Li🇨🇳 · Fuqiang Wang🇺🇸

   In high energy heavy ion collisions and interacting cold atom systems, large elliptic flow anisotropies have been observed. For the large opacity ($\rho \sigma L\sim 10^3$) of the latter hydrodynamics is a natural consequence, but for the small opacity ($\rho \sigma L\sim 1$) of the former hydrodynamic description is questionable. To shed light onto the situation, we simulate the expansion of a low density Argon ion (or atom) system, initially trapped in an elliptical region, under the Coulomb interaction (or elastic scattering). Significant elliptic anisotropy is found in both cases, and the anisotropy depends on the initial spatial eccentricity and the density of the system. The results may provide insights into the physics of anisotropic flow in high energy heavy ion collisions and its role in the study of quantum chromodynamics.

   ↳ nucl-thnucl-exPRC(2018)·0 citations
3. 03*

   Spin-Isospin Properties of $N=Z$ Odd-Odd Nuclei from a Core+$pn$ Three-Body Model including Core Excitations

   Futoshi Minato🇯🇵 · Yusuke Tanimura🇫🇷

   For $N=Z$ odd-odd nuclei, a three-body model assuming two valence particles and an inert core can provide an understanding of pairing correlations in the ground state and spin-isospin excitations. However, since residual core-nucleon interactions can have a significant impact on these quantities, the inclusion of core excitations in the model is essential for useful calculation to be performed. The effect of core excitations must be included in order to gain a detailed understanding of both the ground state and spin-isospin properties of these systems. To this end, we include the vibrational excitation of the core nucleus in our model. We solve the three-body core-nucleon-nucleon problem including core vibrational states to obtain the nuclear ground state as well as spin-isospin excitations. The spin-isospin excitations are examined from the point of view of SU(4) multiplets. By including the effect of core excitation, several experimental quantities of $N=Z$ odd-odd nuclei are better described, and the root mean square distances between proton and neutron and that between the center of mass of proton and neutron and core nucleus increase. Large $B$($M1$) and $B$(GT) observed for ${}^{18}$F and ${}^{40}$Ca were explained in terms of the SU(4) symmetry. The core nucleus is meaningfully broken by the residual core-nucleon interactions, and various quantities concerning spin-isospin excitations as well as the ground state become consistent with experimental data. Including the core excitation in the three-body model is thus important for a more detailed understanding of nuclear structure.

   ↳ nucl-thnucl-exEPJA(2020)·3 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.