Mon·Jan 1, 2024Monday·January 1, 2024

1. 01*

   Population of tetraneutron continuum in reactions of ${}^8$He on deuterium

   I.A. Muzalevskii🇷🇺 · N.B. Shulgina🇷🇺 · A.A. Bezbakh🇷🇺 · V. Chudoba · S.A. Krupko🇷🇺 · S.G. Belogurov🇷🇺 · D. Biare · I.A. Egorova · A.S. Fomichev🇷🇺 · E.M. Gazeeva🇷🇺 · A.V. Gorshkov🇺🇸 · L.V. Grigorenko🇷🇺 and 20 other authors

   Search for the population of the low-energy continuum of a tetraneutron system was performed for reactions of the ${}^8$He beam on a deuterium target. These studies are based on the data [I.A. Muzalevskii \textit{et al.}, Phys.\ Rev.\ C \textbf{103}, 044313 (2021)], previously used for the studies of ${}^7$H and ${}^6$H in the ${}^2\text{H}{(}^8\text{He},{}^3\text{He}{)}^7$H and ${}^2\text{H}{(}^8\text{He},{}^4\text{He}{)}^6$H reactions. Evidence for a hump in the ${}^4$n continuum at $3.5\pm 0.7$ and $3.2\pm 0.8$ MeV was observed in the ${}^2$H(${}^8$He,${}^6$Li)${}^4$n and ${}^2$H(${}^8$He,${}^3$He)${}^7$H${\to }^3$H+${}^4$n reactions, respectively. The observed statistics is quite low (6 events and up to 40 events) corresponding to very low cross sections of few microbarns or tens of microbarns. The background conditions for the ${}^2$H(${}^8$He,${}^6$Li)${}^4$n reaction are shown to be good, favoring the physical nature of the observed events. The ${}^2$H(${}^8$He,${}^3$He)${}^7$H${\to }^3$H+${}^4$n process transforms to the ${}^2$H(${}^8$He,${}^6$Li${}^{\ast }{)}^{4}n$ reaction in the limit of the highest ${}^7$H decay energies. The population of the low-energy region in the ${}^4$n spectrum is found to be perfectly correlated with the population of the lowest ${}^6$Li state in the ${}^3$He+${}^3$H continuum with $E^{\ast }=18$ MeV. Theoretical calculations of ${}^8$He in a five-body $\alpha$+$4n$ and of ${}^4$n in a four-body hyperspherical models are presented. The ${}^8$He wave function is shown to contain strong specific correlations, which may give rise to very low-energy structures in tetraneutron continuum in extreme-peripheral reaction scenarios.

   nucl-exnucl-thPRC(2025)·7 citations
2. 02*

   Low-energy structure and $\beta$ decay properties of neutron-rich nuclei in the region of a shape phase transition

   Kosuke Nomura🇯🇵

   The low-energy structure and $\beta$ decay properties of the neutron-rich even-mass nuclei near the neutron number $N=60$ that are experimentally of much interest are investigated within the framework of the nuclear density functional theory and the interacting boson-fermion-fermion model. By using the results of the constrained self-consistent mean-field calculations based on the relativistic energy density functional, the interacting-boson Hamiltonian describing the even-even core nuclei, the boson-fermion, and the fermion-fermion interactions are determined. The Gamow-Teller transition strengths, with the corresponding operator being constructed without introducing further phenomenological adjustment, are computed by using the wave functions of the initial and final nuclei of the $\beta$ decay. The triaxial quadrupole potential energy surfaces computed for the $N=60$ even-even isotones suggest a pronounced $\gamma$ softness. The calculated energy spectra for the even-even and odd-odd nuclei in the Rb to Cd isotopic chains exhibit an abrupt change in nuclear structure around $N=60$, as suggested experimentally. The predicted $\beta$-decay $\log {}_{10}ft$ values underestimate the measured values for the nuclei with low $Z$ and with $N⩽60$, exhibit a rapid increase for $N>60$, reflecting the nuclear structure evolution, and agree rather well with the measured values for those nuclei with $Z$ being not far from the proton major shell closure $Z=50$. Sensitivity of the predicted $\beta$-decay properties to the model assumptions and parameters employed in the nuclear structure calculations is discussed, specifically, by comparing results obtained based on the different choices of the underlying energy density functional.

   ↳ nucl-thnucl-exPRC(2024)·8 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.