Wed·Sep 15, 2021Wednesday·September 15, 2021

1. 01*

   Evidence for enhanced neutron-proton correlations from the level structure of the $N=Z+1$ nucleus ${}_{43}^{87}$Tc${}_{44}^{}$

   X. Liu🇨🇳 · B. Cederwall🇸🇪 · C. Qi🇸🇪 · R. A. Wyss🇸🇪 · Ö. Aktas🇸🇪 · A. Ertoprak🇸🇪 · W. Zhang🇸🇪 · E. Clément🇫🇷 · G. de France🇫🇷 · D. Ralet🇫🇷 · A. Gadea🇪🇸 · A. Goasduff🇮🇹 and 60 other authors

   The low-lying excited states in the neutron-deficient $N=Z+1$ nucleus ${}_{43}^{87}$Tc${}_{44}^{}$ have been studied via the fusion-evaporation reaction ${}^{54}$Fe(${}^{36}$Ar, $2n1p$)${}^{87}$Tc at the Grand Accélérateur National d'Ions Lourds (GANIL), France. The AGATA spectrometer was used in conjunction with the auxiliary NEDA, Neutron Wall, and DIAMANT detector arrays to measure coincident prompt $\gamma$-rays, neutrons, and charged particles emitted in the reaction. A level scheme of ${}^{87}$Tc from the (9/2${}_{g.s.}^{+}$) state to the (33/2${}_1^{+}$) state was established based on 6 mutually coincident $\gamma$-ray transitions. The constructed level structure exhibits a rotational behavior with a sharp backbending at $\hslash \omega \approx 0.50$ MeV. A decrease in alignment frequency and increase in alignment sharpness in the odd-mass isotonic chains around $N=44$ is proposed as an effect of the enhanced isoscalar neutron-proton interactions in odd-mass nuclei when approaching the $N=Z$ line.

   nucl-exnucl-thPRC(2021)·7 citations
2. 02*

   Proton decays from $\alpha$-unbound states in ${}^{22}$Mg and the ${}^{18}$Ne($\alpha ,p_0$)${}^{21}$Na cross section

   J. W. Brümmer🇿🇦 · P. Adsley🇿🇦 · T. Rauscher🇨🇭 · F. D. Smit🇿🇦 · C. P. Brits🇿🇦 · M. Köhne🇿🇦 · N. A. Khumalo🇿🇦 · K. C. W. Li🇿🇦 · D. J. Marín-Lámbarri🇿🇦 · N. J. Mukwevho🇿🇦 · F. Nemulodi🇿🇦 · R. Neveling🇿🇦 and 6 other authors

   This paper examines the ${}^{18}$Ne($\alpha ,p_0$)${}^{21}$Na cross-section relevant in X-ray bursts. The study was performed with the K600 magnetic spectrometer in coincidence with the CAKE, a silicon detector array, at iThemba LABS in Cape Town, South Africa. A 100-MeV proton beam was impinged on a ${}^{24}$Mg target to study the ${}^{24}$Mg($p,t$)${}^{22}$Mg reaction. The triton ejectiles were momentum-analysed with the magnetic spectrometer and proton decays from the ${}^{22}$Mg recoil nucleus to the ground state of ${}^{21}$Na and various excited states thereof were detected with the CAKE. In doing so, we were able to compare our results to previous direct and indirect measurements of the ${}^{18}$Ne($\alpha ,p$)${}^{21}$Na reaction.

   nucl-exPRC(2023)·3 citations
3. 03*

   First Direct Measurement of an Astrophysical p-Process Reaction Cross Section Using a Radioactive Ion Beam

   G. Lotay🇬🇧 · S. A. Gillespie🇨🇦 · M. Williams · T. Rauscher🇨🇭 · M. Alcorta · M. Amthor · C. A. Andreoiu · D. Baal · G. C. Ball · S. S. Bhattacharjee🇨🇦 · H. Behnamian · V. Bildstein🇨🇦 and 26 other authors

   We have performed the first direct measurement of the 83Rb(p,g) radiative capture reaction cross section in inverse kinematics using a radioactive beam of 83Rb at incident energies of 2.4 and 2.7 A MeV. The measured cross section at an effective relative kinetic energy of Ecm = 2.393 MeV, which lies within the relevant energy window for core collapse supernovae, is smaller than the prediction of statistical model calculations. This leads to the abundance of 84Sr produced in the astrophysical p process being higher than previously calculated. Moreover, the discrepancy of the present data with theoretical predictions indicates that further experimental investigation of p-process reactions involving unstable projectiles is clearly warranted.

   nucl-exPRL(2021)·17 citations
4. 04*

   Machine-learning-based identification for initial clustering structure in relativistic heavy-ion collisions

   Junjie He🇨🇳 · Wan-Bing He🇨🇳 · Yu-Gang Ma🇨🇳 · Song Zhang🇨🇳

   $\alpha$-clustering structure is a significant topic in light nuclei. A Bayesian convolutional neural network (BCNN) is applied to classify initial non-clustered and clustered configurations, namely Woods-Saxon distribution and three-$\alpha$ triangular (four-$\alpha$ tetrahedral) structure for ${}^{12}$C (${}^{16}$O), from heavy-ion collision events generated within a multi-phase transport (AMPT) model. Azimuthal angle and transverse momentum distributions of charged pions are taken as inputs to train the classifier. On multiple-event basis, the overall classification accuracy can reach $95\%$ for ${}^{12}$C/${}^{16}$O + ${}^{197}$Au events at $\sqrt{S_{NN}}=$ 200 GeV. With proper constructions of samples, the predicted deviations on mixed samples with different proportions of both configurations could be within $5\%$. In addition, setting a simple confidence threshold can further improve the predictions on the mixed dataset. Our results indicate promising and extensive possibilities of application of machine-learning-based techniques to real data and some other problems in physics of heavy-ion collisions.

   ↳ hep-phnucl-exnucl-thPRC(2021)·38 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.