Mon·Jul 17, 2023Monday·July 17, 2023

1. 01*

   Level Structures of ${}^{56,58}$Ca Cast Doubt on a doubly magic ${}^{60}$Ca

   S. Chen🇨🇳 · F. Browne🇯🇵 · P. Doornenbal🇯🇵 · J. Lee🇨🇳 · A. Obertelli🇩🇪 · Y. Tsunoda🇯🇵 · T. Otsuka🇯🇵 · Y. Chazono🇯🇵 · G. Hagen🇺🇸 · J.D. Holt🇨🇦 · G.R. Jansen🇺🇸 · K. Ogata🇯🇵 and 71 other authors

   Gamma decays were observed in ${}^{56}$Ca and ${}^{58}$Ca following quasi-free one-proton knockout reactions from ${}^{57,59}$Sc beams at $\approx 200$ MeV/nucleon. For ${}^{56}$Ca, a $\gamma$ ray transition was measured to be 1456(12) keV, while for ${}^{58}$Ca an indication for a transition was observed at 1115(34) keV. Both transitions were tentatively assigned as the $2_1^{+}\to 0_{gs}^{+}$ decays, and were compared to results from ab initio and conventional shell-model approaches. A shell-model calculation in a wide model space with a marginally modified effective nucleon-nucleon interaction depicts excellent agreement with experiment for $2_1^{+}$ level energies, two-neutron separation energies, and reaction cross sections, corroborating the formation of a new nuclear shell above the $N$ = 34 shell. Its constituents, the $0f_{5/2}$ and $0g_{9/2}$ orbitals, are almost degenerate. This degeneracy precludes the possibility for a doubly magic ${}^{60}$Ca and potentially drives the dripline of Ca isotopes to ${}^{70}$Ca or even beyond.

   nucl-exnucl-thPLB(2023)·21 citations
2. 02*

   Nuclear Level Density and $\gamma$-ray Strength Function of ${}^{67}\mathrm{Ni}$ and the impact on the i-process

   V. W. Ingeberg🇳🇴 · S. Siem🇳🇴 · M. Wiedeking🇿🇦 · A. Choplin🇧🇪 · S. Goriely🇧🇪 · L. Siess🇧🇪 · K. J. Abrahams🇿🇦 · K. Arnswald🇩🇪 · F. Bello Garrote🇳🇴 · D. L. Bleuel🇺🇸 · J. Cederkäll · T. L. Christoffersen🇳🇴 and 20 other authors

   Proton-$\gamma$ coincidences from $(\mathrm{d},\mathrm{p})$ reactions between a ${}^{66}\mathrm{Ni}$ beam and a deuterated polyethylene target have been analyzed with the inverse-Oslo method to find the nuclear level density (NLD) and $\gamma$-ray strength function ($\gamma$SF) of ${}^{67}\mathrm{Ni}$. The ${}^{66}\mathrm{Ni}(n,\gamma )$ capture cross section has been calculated using the Hauser-Feshbach model in TALYS using the measured NLD and $\gamma$SF as constraints. The results confirm that the ${}^{66}\mathrm{Ni}(n,\gamma )$ reaction acts as a bottleneck when relying on one-zone nucleosynthesis calculations. However, the impact of this reaction is strongly dampened in multi-zone models of low-metallicity AGB stars experiencing i-process nucleosynthesis.

   nucl-exastro-ph.SRnucl-thPRC(2025)·9 citations
3. 03*

   Measurement of $\Lambda$ hyperon spin-spin correlations in p+p collisions by the STAR experiment

   Jan Vanek (for the STAR Collaboration)🇺🇸

   Polarization of $\Lambda$ hyperons has been observed in various collision systems over a wide range of collision energies over the last 50 years since its discovery in Fermilab in the 70's. The existing experimental and theoretical techniques were not able to provide a conclusive answer about the origin of the polarization. In these proceedings, we discuss the possibility to use a new experimental method which utilizes measurement of $\Lambda \bar{\Lambda }$, $\Lambda \Lambda$, and $\bar{\Lambda }\bar{\Lambda }$ pair spin-spin correlations. With this new approach, it should be possible to distinguish if the polarization originates from early stage effects, such as initial state parton spin correlation, or if it is a final state effect originating from hadronization. Furthermore we, study the feasibility to perform this measurement in $p+p$ collisions at $\sqrt{s}=200$~GeV collected by STAR in 2012 which should provide sufficient statistics of $\Lambda \bar{\Lambda }$, $\Lambda \Lambda$, and $\bar{\Lambda }\bar{\Lambda }$ pairs to perform this measurement.

   nucl-exhep-ex6 citations
4. 04*

   Experimental determination of the ${}^3$He($\alpha$,$\gamma$)${}^7$Be reaction cross section above the ${}^7$Be proton separation threshold

   Á. Tóth · T. Szücs🇭🇺 · T. N. Szegedi🇭🇺 · Gy. Gyürky🇭🇺 · Z. Halász🇭🇺 · G. G. Kiss🇭🇺 · Zs. Fülöp

   The ${}^3$He($\alpha$,$\gamma$)${}^7$Be reaction plays a major role both in the BBN producing the majority of the primordial ${}^7$Li, and in the pp-chain, where it is the branching point. As a few-nucleon system, this reaction is often used to validate ab-initio theoretical calculations and/or test R-matrix theory and code implementations. For the latter, experimental data in an extended energy range is of crucial importance to test the fit and extrapolation capabilities of the different codes. The ${}^3$He($\alpha$,$\gamma$)${}^7$Be reaction cross section has been measured by several groups up to the first resonance ($E_{c.m.}\approx 3$ MeV) in the reaction. However, only one dataset exists above the ${}^7$Be proton separation threshold measured in a narrow energy range ($E_{c.m.}=4.0-4.4$ MeV). In this work we extend the available experimental capture cross section database to the energy range of known ${}^7$Be levels. The activation method was used. The experiment was performed using a thin-window gas cell with two high-purity Al foils as entrance and exit windows. The activity of the ${}^7$Be nuclei implanted in the exit/catcher foil was measured by detecting the yield of the emitted $\gamma$~rays using shielded high-purity germanium detectors. New experimental ${}^3$He($\alpha$,$\gamma$)${}^7$Be reaction cross section data were obtained for the first time in the $E_{c.m.}=4.3-8.3$ MeV energy region. The new dataset with about 0.2 MeV step covers the energy range of known levels and particle separation thresholds. No prominent structures are observer around the ${}^7$Be levels. The reaction cross section is slowly increasing with increasing energy. Above the ${}^6$Li$+p_1$ threshold, a decrease starts in the cross section trend. The overall structure of the cross section suggest a broad resonance peaking around $E_x=7.5$ MeV ${}^7$Be excitation energy, with a width of 8 MeV.

   nucl-exPRC(2023)·10 citations
5. 05*

   Degaussing Procedure and Performance Enhancement by Low-Frequency Shaking of a 3-Layer Magnetically Shielded Room

   Fabian Allmendinger · Benjamin Brauneis · Werner Heil🇩🇪 · Ulrich Schmidt

   We report on the performance of a Magnetically Shielded Room (MSR) intended for next level ${}^3$He/${}^{129}$Xe co-magnetometer experiments which require improved magnetic conditions. The MSR consists of three layers of Mu-metal with a thickness of 3 mm each, and one additional highly conductive copper-coated aluminum layer with a thickness of 10 mm. It has a cubical shape with an walk-in interior volume with an edge length of 2560 mm. An optimized degaussing (magnetic equilibration) procedure using a frequency sweep with constant amplitude followed by an exponential decay of the amplitude will be presented. The procedure for the whole MSR takes 21 minutes and measurements of the residual magnetic field at the center of the MSR show that $|B|<1$ nT can be reached reliably. The chosen degaussing procedure will be motivated by online hysteresis measurements of the assembled MSR and by Eddy current simulations showing that saturation at the center of the Mu-metal layer is reached. Shielding Factors can be improved by a factor $\approx 4$ in all directions by low frequency (0.2 Hz), low current (1 A) shaking of the outermost Mu-metal layer.

   ↳ physics.ins-dethep-exnucl-exphysics.app-phRev.Sci.Instrum.(2023)·2 citations
6. 06*

   Nuclear Physics in the Era of Quantum Computing and Quantum Machine Learning

   J.E. García-Ramos🇪🇸 · A. Sáiz🇪🇸 · J.M. Arias🇪🇸 · L. Lamata🇪🇸 · P. Pérez-Fernández🇪🇸

   In this paper, the application of quantum simulations and quantum machine learning to solve low-energy nuclear physics problems is explored. The use of quantum computing to deal with nuclear physics problems is, in general, in its infancy and, in particular, the use of quantum machine learning in the realm of nuclear physics at low energy is almost nonexistent. We present here three specific examples where the use of quantum computing and quantum machine learning provides, or could provide in the future, a possible computational advantage: i) the determination of the phase/shape in schematic nuclear models, ii) the calculation of the ground state energy of a nuclear shell model-type Hamiltonian and iii) the identification of particles or the determination of trajectories in nuclear physics experiments.

   ↳ quant-phnucl-exnucl-thAdv.Quantum Technol.(2025)·19 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.