Mon·Jun 3, 2024Monday·June 3, 2024

1. 01*

   Simultaneous impacts of nuclear shell structure and collectivity on $\beta$ decay: Evidence from ${}^{80}$Ga${}_{49}$

   R. Li🇫🇷 · D. Verney🇫🇷 · G. De Gregorio🇮🇹 · R. Mancino🇩🇪 · I. Matea🇫🇷 · L. Coraggio🇮🇹 · N. Itaco.🇮🇹 · M. N. Harakeh🇳🇱 · C. Delafosse🇫🇮 · F. Didierjean🇫🇷 · L. A. Ayoubi🇫🇮 · H. Al Falou🇱🇧 and 23 other authors

   The Gamow-Teller strength distribution covering the entire $\beta$-decay window, up to 10.312(4) MeV, of ${}^{80g+m}$Ga was measured for the first time in photo fission of UC${}_x$ induced by a 50 MeV electron beam. The new data show significant enhancement in the high-energy region with a jump structure. Simultaneously, the $\gamma$ deexciting behavior of $\beta$-populated states presents a competition between deexcitation to 2${}_1^{+}$ [${\beta }_2$ = 0.155(9)] and to 2${}_2^{+}$ [${\beta }_2$ = 0.053${}_{0.009}^{0.008}$)] in ${}^{80}$Ge. To understand these data, we performed a realistic shell-model calculation and systematic analysis of log $ft$ ratios between precursors' $\beta$ decay to 2${}_2^{+}$ and to 2${}_1^{+}$ of Ga isotopes. We conclude that these phenomena evidence simultaneous impacts of nuclear shell structure and collectivity on $B$(GT) distribution and therefore the half-life of the precursor.

   nucl-exPRC(2025)·5 citations
2. 02*

   Recent Highlights from STAR BES Phase II

   Dylan Neff (for the STAR Collaboration)🇫🇷

   The second phase of the RHIC Beam Energy Scan (BES-II) was conducted between 2019 and 2021. High statistics data was collected by the STAR experiment for Au+Au collisions at $\sqrt{s_{NN}}$ from 7.7 to 27 GeV in collider mode and from 3 to 13.7 GeV in fixed target mode. A selection of results from the various BES-II analyses are presented here to showcase the wide range of physics accessible.

   nucl-ex0 citations
3. 03*

   Probing the nature of the QCD phase transition with higher-order net-proton number fluctuation and local parton density fluctuation measurements at RHIC-STAR

   Dylan Neff (for the STAR Collaboration)🇺🇸

   The moments of proton and net-proton multiplicity distributions are observables expected to be sensitive to the QCD critical point and the nature of the QCD phase transition from QGP to hadron gas. Hyper-order cumulants are measured in wide centrality bins in STAR BES-I data and found to be qualitatively consistent with trends predicted by lattice QCD which finds a cross-over phase transition at low ${\mu }_{\text{B}}$. Data collected at $\sqrt{s_{NN}}=3$ GeV in BES-II exhibit trends opposite of those observed in higher energy collisions which may suggest the dominance of hadronic interactions at this energy. The variance of proton multiplicity distributions in azimuthal partitions is measured to search for signals of clustering indicative of a first-order phase transition. A strong dependence on the event multiplicity is observed. This dependence is independent of energy in AMPT while in STAR data a significant trend with energy is observed.

   nucl-exEPJ Web Conf.(2024)·0 citations
4. 04*

   ${}^{242m}$Am isomer yield in ${}^{243}$Am$(n,2n)$ reaction

   V.M. Maslov

   The reaction 243 Am (n, 2n) populates the T of 16 hours ground state 242 g Am with J of 1 or the 242 m Am isomer state J of 5 with T of 141 years. The former state 242 g Am mostly beta decays to 242 Cm, or transmutes to 242 Pu via electron capture. The absolute yield of 242 g Am is compatible with the measured data, estimated by the alpha activity of 242 Cm by Norris in 1983. The branching ratio defined by the ratio of the populations of the lowest intrinsic states of 242 Am. Calculated yields of ground 242 g Am and isomer 242 m Am states of the residual nucleus 242 Am are used to predict the relative yield of isomer. These populations defined by the gamma decay of the excited states, described by the standard kinetic equation. The ordering of the low and high spin states is different in case of 236 Np and 242 Am nuclei, that explains different shapes of relative yields near the (n, 2n) reaction threshold, though the excitation energy dependences are similar. Data of 243 Am (n, F) at 5 MeV and 15 MeV by Drapchinsky in 2004, support calculated 243Am (n,xnf) prefission neutron contribution to prompt fission neutron spectra and calculated exclusive neutron spectra of 243 Am (n, 2n) feeding the 242 g Am and isomer 242 m Am states.

   nucl-exnucl-th0 citations
5. 05*

   First evidence for chiral wobbling of triaxial nuclei

   S. Frauendorf

   The appearance of wobbling motion and chirality in rotating triaxial nuclei is explained. The discovery of a new mode, chiral wobbling, in ${}^{74}$Br, is commented.

   ↳ nucl-thnucl-exNucl.Sci.Tech.(2024)·2 citations
6. 06*

   Methodology for Analyzing Proton Multiplicity Fluctuations with Azimuthal Partitions in Heavy-Ion Collisions

   Dylan Neff🇺🇸 · Zhongling Ji🇺🇸 · Roli Esha🇺🇸 · Gang Wang🇺🇸 · Huan Huang🇺🇸

   A primary objective in high-energy heavy-ion collisions is to investigate the phase transition between confined and deconfined color matter. Complementary to the cumulants of conserved charges integrated over the full azimuth, we introduce a novel experimental approach to explore particle fluctuations in azimuthal partitions, which are potentially sensitive to the first-order phase transition in heavy-ion collisions. We evaluate proton multiplicity ($N_w$) fluctuations in azimuthal partitions of width $w$ to quantitatively estimate the clustering tendency among these protons. The $\Delta {\sigma }^2$ observable is defined as the normalized difference between the variance of the $N_w$ distribution and the binomial baseline. We demonstrate the feasibility and characteristics of this observable through simulations using the AMPT and MUSIC+FIST models. We also use a Gaussian correlation model to illustrate that the dependence of $\Delta {\sigma }^2$ on $w$ can be parameterized to accurately extract the strength and the range of the input interaction among protons.

   ↳ nucl-thhep-phnucl-exPRC(2024)·1 citation

* 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.