Tue·Jan 31, 2023Tuesday·January 31, 2023

1. 01*

   New isomeric transition in ${}^{36}$Mg: Bridging the N=20 and N=28 islands of inversion

   M. Madurga🇺🇸 · J.M. Christie🇺🇸 · Z. Xu🇧🇪 · R. Grzywacz🇺🇸 · A. Poves🇪🇸 · T. King🇺🇸 · J.M. Allmond🇺🇸 · A. Chester🇨🇦 · I. Cox🇺🇸 · J. Farr🇺🇸 · I. Fletcher · J. Heideman🇺🇸 and 11 other authors

   We observed a new isomeric gamma transition at 168 keV in ${}^{36}$Mg, with a half-life of T${}_{1/2}$=[130-500]$(\pm 40){(}_{-20}^{+800}{)}_{sys}$ ns. We propose that the observed transition de-excites a new 0${}^{+}$ isomeric state and populates the previously known first 2${}^{+}$ state. The existence of this isomer is consistent with the predictions of the large-scale shell model calculations of ${}^{36}$Mg using the sdpf-u-mix interaction. The observed excitation energy of the second 0${}^{+}$ state is caused by the small energy separation between two prolate-deformed configurations where the intruder configuration corresponds to two neutron excitations from the {\it sd} to the {\it pf} shell. Within this interpretation, ${}^{36}$Mg becomes the crossing point between nuclei in which ground state deformed/superdeformed configurations are caused by the dominance of N=20 intruders (${}^{32,34}$Mg) and nuclei where deformed configurations are associated with N=28 intruders (${}^{38}$Mg and beyond). We found the lack of three-body monopole corrections in other effective interactions results in a predominance of N=20 intruder configurations past ${}^{38}$Mg incompatible with our observation. We conclude that ${}^{36}$Mg bridges the N=20 and N=28 islands of inversion, forming the so-called Big Island of Deformation.

   nucl-exnucl-thPRC(2024)·3 citations
2. 02*

   Difference between signal and background of the chiral magnetic effect relative to spectator and participant planes in isobar collisions at $\sqrt{s_{{}_{\mathrm{NN}}}}=200$ GeV

   Bang-Xiang Chen🇨🇳 · Xin-Li Zhao🇨🇳 · Guo-Liang Ma🇨🇳

   The search for the chiral magnetic effect (CME) in relativistic heavy-ion collisions helps us understand the $\mathcal{C}\mathcal{P}$ symmetry breaking in strong interactions and the topological nature of the QCD vacuum. Since the background and signal of the CME have different correlations with the spectator and participant planes, a two-plane method has been proposed to extract the fraction of the CME signal inside the CME observable of $\Delta \gamma$ from the experimental measurements relative to the two planes. Using a multiphase transport model with different strengths of the CME, we reexamine the two-plane method in isobar collisions at $\sqrt{s_{{}_{\mathrm{NN}}}}=200$ GeV. The ratios of the CME signals and the elliptic flow backgrounds relative to the two different planes are found to be different, which is inconsistent with the assumptions made in the current experimental measurements. This difference arises from the decorrelation effect of the chiral magnetic effect relative to the spectator and participant planes caused by final state interactions. Our finding suggests that the current experimental measurements may overestimate the fraction of the CME signal in the CME observable in the final state of relativistic heavy-ion collisions.

   ↳ nucl-thhep-phnucl-exPRC(2024)·9 citations
3. 03*

   A new dynamical mechanism of incomplete fusion in heavy-ion collision

   A.K. Nasirov (1,2)🇷🇺 · B.M. Kayumov (2,3) · O.K. Ganiev (2,4,5) · G.A. Yuldasheva (2) ((1) Joint Institute for Nuclear Research, Dubna, Russia, (2) Institute of Nuclear Physics, Uzbekistan Academy of Sciences, Tashkent, (3) New Uzbekistan University, Tashkent, Uzbekistan, (4) School of Engineering, Akfa University, Tashkent, Uzbekistan, (5) Faculty of Physics, National University of Uzbekistan, 100174 Tashkent, Uzbekistan)

   The incomplete fusion has been proved as the formation and emission of the $\alpha$ particle by the increase in the rotational energy of the very mass-asymmetric dinuclear system. The results of the dinuclear system model have confirmed that the incomplete fusion in heavy-ion collisions occurs at a large orbital angular momentum ($L>30\hslash$) due to the strong increase of the intrinsic fusion barrier.

   ↳ nucl-thnucl-exPLB(2023)·16 citations
4. 04*

   Exploring Current Constraints on Antineutrino Production by ${}^{241}$Pu and Paths Towards the Precision Reactor Flux Era

   Yoshi Fujikake🇺🇸 · Bryce Littlejohn🇺🇸 · Ohana B. Rodrigues🇺🇸 · Pranava Teja Surukuchi🇺🇸

   By performing global fits to inverse beta decay (IBD) yield measurements from existing neutrino experiments based at highly ${}^{235}$U enriched reactor cores and conventional low-enriched cores, we explore current direct bounds on neutrino production by the sub-dominant fission isotope ${}^{241}$Pu. For this nuclide, we determine an IBD yield of ${\sigma }_{241}$ = 8.16 $\pm$ 3.47 cm${}^2$/fission, a value (135 $\pm$ 58)% that of current beta conversion models. This constraint is shown to derive from the non-linear relationship between burn-in of ${}^{241}$Pu and ${}^{239}$Pu in conventional reactor fuel. By considering new hypothetical neutrino measurements at high-enriched, low-enriched, mixed-oxide, and fast reactor facilities, we investigate the feasible limits of future knowledge of IBD yields for ${}^{235}$U, ${}^{238}$U, ${}^{239}$Pu, ${}^{241}$Pu, and ${}^{240}$Pu. We find that the first direct measurement of the ${}^{240}$Pu IBD yield can be performed at plutonium-burning fast reactors, while a suite of correlated measurements at multiple reactor types can achieve precision in direct ${}^{238}$U, ${}^{239}$Pu, and ${}^{241}$Pu yield knowledge that meets or exceeds that of current theoretical predictions.

   ↳ hep-phnucl-exnucl-thPRD(2023)·3 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.