Mon·May 11, 2020Monday·May 11, 2020

1. 01*

   Coulomb excitation of the $\left|T_z\right|=\frac{1}{2}$, $A=23$ mirror pair

   J. Henderson🇨🇦 · G. Hackman🇨🇦 · P. Ruotsalainen · J. D. Holt🇨🇦 · S. R. Stroberg🇺🇸 · C. Andreoiu · G. C. Ball🇨🇦 · N. Bernier🇨🇦 · M. Bowry · R. Caballero-Folch · S. Cruz🇨🇦 · A. Diaz Varela🇨🇦 and 14 other authors

   Background: Electric-quadrupole ($E2$) strengths relate to the underlying quadrupole deformation of a nucleus and present a challenge for many nuclear theories. Mirror nuclei in the vicinity of the line of $N=Z$ represent a convenient laboratory for testing deficiencies in such models, making use of the isospin-symmetry of the systems. Purpose: Uncertainties associated with literature $E2$ strengths in \textsuperscript{23}Mg are some of the largest in $T_z=\left|\frac{1}{2}\right|$ nuclei in the $sd$-shell. The purpose of the present work is to improve the precision with which these values are known, to enable better comparison with theoretical models. Methods: Coulomb-excitation measurements of ${}^{23}$Mg and ${}^{23}$Na were performed at the TRIUMF-ISAC facility using the TIGRESS spectrometer. They were used to determine the $E2$ matrix elements of mixed $E2$/$M1$ transitions. Results: Reduced $E2$ transition strengths, $B(E2)$, were extracted for \textsuperscript{23}Mg and \textsuperscript{23}Na. Their precision was improved by factors of approximately six for both isotopes, while agreeing within uncertainties with previous measurements. Conclusions: A comparison was made with both shell-model and {\it ab initio} valence-space in-medium similarity renormalization group calculations. Valence-space in-medium similarity-renormalization-group calculations were found to underpredict the absolute $E2$ strength - in agreement with previous studies.

   nucl-exnucl-thPRC(2022)·19 citations
2. 02*

   Precision measurement of the $E2$ transition strength to the 2${}_1^{+}$ state of ${}^{12}$C

   A. D'Alessio · T. Mongelli · M. Arnold · S. Bassauer · J. Birkhan · M. Hilcker · T. Hüther · J. Isaak · L. Jürgensen · T. Klaus · P. von Neumann-Cosel · N. Pietralla and 7 other authors

   The form factor of the electromagnetic excitation of ${}^{12}$C to its 2${}_1^{+}$ state was measured at extremely low momentum transfers in an electron scattering experiment at the S-DALINAC. A combined analysis with the world form factor data results in a reduced transition strength $B(E2;2_1^{+}\to 0_1^{+})=7.63(19)$ e${}^2$fm${}^4$ with an accuracy improved to 2.5\%. In-Medium-No Core Shell Model results with interactions derived from chiral effective field theory are capable to reproduce the result. A quadrupole moment $Q(2_1^{+})=5.97(30)$ efm${}^2$ can be extracted from the strict correlation with the $B((E2)$ strength emerging in the calculations.

   nucl-exnucl-thPRC(2020)·16 citations
3. 03*

   Evolution of the dipole polarizability in the stable tin isotope chain

   S. Bassauer (1) · P. von Neumann-Cosel (1)🇩🇪 · P.-G. Reinhard (2)🇩🇪 · A. Tamii (3)🇯🇵 · S. Adachi (3) · C. A. Bertulani (4)🇺🇸 · P. Y. Chan (3) · G. Colò (5)🇮🇹 · A. D'Alessio (1) · H. Fujioka (6)🇯🇵 · H. Fujita (3) · Y. Fujita (3)🇯🇵 and 27 other authors

   The dipole polarizability of stable even-mass tin isotopes 112,114,116,118,120,124 was extracted from inelastic proton scattering experiments at 295 MeV under very forward angles performed at RCNP. Predictions from energy density functionals cannot account for the present data and the polarizability of 208Pb simultaneously. The evolution of the polarizabilities in neighboring isotopes indicates a kink at 120Sn while all model results show a nearly linear increase with mass number after inclusion of pairing corrections.

   nucl-exnucl-thPLB(2020)·28 citations
4. 04*

   Static quadrupole moments of nuclear chiral doublet bands

   Q. B. Chen🇩🇪 · N. Kaiser🇩🇪 · Ulf-G. Meißner🇩🇪 · J. Meng🇨🇳

   The static quadrupole moments (SQMs) of nuclear chiral doublet bands are investigated for the first time taking the particle-hole configuration $\pi (1h_{11/2})\otimes \nu (1h_{11/2}{)}^{-1}$ with triaxial deformation parameters in the range $260^{\circ }\le \gamma \le 270^{\circ }$ as examples. The behavior of the SQM as a function of spin $I$ is illustrated by analyzing the components of the total angular momentum. It is found that in the region of chiral vibrations the SQMs of doublet bands are strongly varying with $I$, whereas in the region of static chirality the SQMs of doublet bands are almost constant. Hence, the measurement of SQMs provides a new criterion for distinguishing the modes of nuclear chirality. Moreover, in the high-spin region the SQMs can be approximated by an analytic formula with a proportionality to $\cos \gamma$ for both doublet bands. This provides a way to extract experimentally the triaxial deformation parameter $\gamma$ for chiral bands from the measured SQMs.

   ↳ nucl-thnucl-exPLB(2020)·23 citations
5. 05*

   Monopole and dipole transitions of the cluster states of 18O

   T. Baba🇯🇵 · M. Kimura🇯🇵

   On the basis of an extended antisymmetrized molecular dynamics calculation, we study the cluster structure and the of the 0+ and 1- states of 18O. We discuss that several different kinds of cluster states appear in the excitation spectrum, and their monopole and dipole transitions are interesting fingerprints of unique cluster structure. We show that the monopole/dipole transitions are enhanced for the 14C+alpha cluster states, while they are hindered for the molecular-orbit state. We also point out that the ratio of the electric and isoscalar monopole transition strengths gives a good hint for the structure of the excited states.

   ↳ nucl-thnucl-exPRC(2020)·7 citations
6. 06*

   Dark Matter Capture by Atomic Nuclei

   Bartosz Fornal🇺🇸 · Benjamin Grinstein🇺🇸 · Yue Zhao🇺🇸

   We propose a new strategy to search for a particular type of dark matter via nuclear capture. If the dark matter particle carries baryon number, as motivated by a class of theoretical explanations of the matter-antimatter asymmetry of the universe, it can mix with the neutron and be captured by an atomic nucleus. The resulting state de-excites by emitting a single photon or a cascade of photons with a total energy of up to several MeV. The exact value of this energy depends on the dark matter mass. We investigate the prospects for detecting dark matter capture signals in current and future neutrino and dark matter direct detection experiments.

   ↳ hep-phhep-exnucl-exPLB(2020)·13 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.