Wed·Mar 1, 2023Wednesday·March 1, 2023

1. 01*

   First observation of the $\beta$3$\alpha$p decay of ${}^{13}\mathrm{O}$ via $\beta$-delayed charged-particle spectroscopy

   Jack Bishop🇺🇸 · G.V. Rogachev🇺🇸 · S. Ahn🇰🇷 · M. Barbui🇺🇸 · S.M. Cha🇰🇷 · E. Harris🇺🇸 · C. Hunt🇺🇸 · C.H. Kim🇰🇷 · D. Kim🇰🇷 · S.H. Kim🇰🇷 · E. Koshchiy🇺🇸 · Z. Luo🇺🇸 and 7 other authors

   Background: The $\beta$-delayed proton-decay of ${}^{13}\mathrm{O}$ has previously been studied, but the direct observation of $\beta$-delayed $\alpha$+$\alpha$+$\alpha$+p decay has not been reported. Purpose: Observing rare 3$\alpha$+p events from the decay of excited states in ${}^{13}{\mathrm{N}}^{\star }$ allows for a sensitive probe of exotic highly-clustered configurations in ${}^{13}$N. Method: To measure the low-energy products following $\beta$-delayed 3$\alpha$p-decay, the TexAT Time Projection Chamber was employed using the one-at-a-time $\beta$-delayed charged-particle spectroscopy technique at the Cyclotron Institute, Texas A&M University. Results: A total of $1.9\times 10^5$ ${}^{13}\mathrm{O}$ implantations were made inside the TexAT Time Projection Chamber. 149 3$\alpha$+p events were observed yielding a $\beta$-delayed 3$\alpha +p$ branching ratio of 0.078(6)%. Conclusion: Four previously unknown $\alpha$-decaying states were observed, one with a strong ${}^9\mathrm{B}(g.s)+\alpha$ characteristic at 11.3 MeV, one with a ${}^9\mathrm{B}({\frac{1}{2}}^{+})+\alpha$ nature at 12.4 MeV, and another two that are dominated by ${}^9\mathrm{B}({\frac{5}{2}}^{+})+\alpha$ at 13.1 and 13.7 MeV. Population of the ${\frac{1}{2}}^{+}$ state in ${}^9\mathrm{B}$ has been unambiguously seen, cementing the predicted existence of the mirror-state based on the states observed in ${}^9\mathrm{Be}$.

   nucl-exPRL(2023)·9 citations
2. 02*

   N=16 magicity revealed at the proton drip-line through the study of 35Ca

   L. Lalanne🇫🇷 · O. Sorlin🇫🇷 · A. Poves🇪🇸 · M. Assié🇫🇷 · F. Hammache🇫🇷 · S. Koyama🇯🇵 · D. Suzuki🇯🇵 · F. Flavigny🇫🇷 · V. Girard-Alcindor🇫🇷 · A. Lemasson🇫🇷 · A. Matta🇫🇷 · T. Roger🇫🇷 and 18 other authors

   The last proton bound calcium isotope ${}^{35}$Ca has been studied for the first time, using the ${}^{37}$Ca($p,t$)${}^{35}$Ca two neutron transfer reaction. The radioactive ${}^{37}$Ca nuclei, produced by the LISE spectrometer at GANIL, interacted with the protons of the liquid hydrogen target CRYPTA, to produce tritons $t$ that were detected in the MUST2 detector array, in coincidence with the heavy residues Ca or Ar. The atomic mass of ${}^{35}$Ca and the energy of its first 3/2${}^{+}$ state are reported. A large $N=16$ gap of 4.61(11) MeV is deduced from the mass measurement, which together with other measured properties, makes ${}^{36}$Ca a doubly-magic nucleus. The $N=16$ shell gaps in ${}^{36}$Ca and ${}^{24}$O are of similar amplitude, at both edges of the valley of stability. This feature is discussed in terms of nuclear forces involved, within state-of-the-art shell model calculations. Even though the global agreement with data is quite convincing, the calculations underestimate the size of the $N=16$ gap in 36Ca by 840(110) keV.

   nucl-exPRL(2023)·27 citations
3. 03*

   Higgs response and pair condensation energy in superfluid nuclei

   Kengo Takahashi🇯🇵 · Yusuke Matsuda🇯🇵 · Masayuki Matsuo🇯🇵

   The pairing correlation in nuclei causes a characteristic excitation, known as the pair vibration, which is populated by the pair transfer reactions. Here we introduce a new method of characterizing the pair vibration by employing an analogy to the Higgs mode, which emerges in infinite superconducting/superfluid systems as a collective vibrational mode associated with the amplitude oscillation of the Cooper pair condensate. The idea is formulated by defining a pair-transfer probe, the Higgs operator, and then describing the linear response and the strength function to this probe. We will show that the pair condensation energy in nuclei can be extracted with use of the strength sum and the static polarizability of the Higgs response. In order to demonstrate and validate the method, we perform for Sn isotopes numerical analysis based the quasi-particle random phase approximation to the Skyrme-Hartree-Fock-Bogoliubov model. We discuss a possibility to apply this new scheme to pair transfer experiment.

   ↳ nucl-thcond-mat.supr-connucl-exPTEP(2023)·5 citations
4. 04*

   New perspectives on spectroscopic factor quenching from reactions

   Chloë Hebborn🇺🇸 · Filomena M. Nunes🇺🇸 · Amy E. Lovell🇺🇸

   The evolution of single-particle strengths as the neutron-to-proton asymmetry changes informs us of the importance of short- and long-range correlations in nuclei and has therefore been extensively studied for the last two decades. Surprisingly, the strong asymmetry dependence of these strengths and their extreme values for highly-asymmetric nuclei inferred from knockout reaction measurements on a target nucleus are not consistent with what is extracted from electron-induced, transfer, and quasi-free reaction data, constituting a two-decade old puzzle. This work presents the first consistent analysis of one-nucleon transfer and one-nucleon knockout data, in which theoretical uncertainties associated with the nucleon-nucleus effective interactions considered in the reaction models are quantified using a Bayesian analysis. Our results demonstrate that, taking into account these uncertainties, the spectroscopic strengths of loosely-bound nucleons extracted from both probes agree with each other and, although there are still discrepancies for deeply-bound nucleons, the slope of the asymmetry dependence of the single-particle strengths inferred from transfer and knockout reactions are consistent within $1\sigma$. Both probes are consistent with a small asymmetry dependence of these strengths. The uncertainties obtained in this work represent a lower bound and are already significantly larger than the original estimates.

   ↳ nucl-thnucl-exPRL(2023)·17 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.