Tue·Oct 15, 2024Tuesday·October 15, 2024

1. 01*

   Measurement of Quadrupole Deformation using E$2$ and M$1+$E$2$ Transitions in Heavy Isotopes in the Mass Range of $150<A<250$

   Prajwal MohanMurthy🇺🇸 · Lixin Qin🇨🇳 · Jeff A. Winger🇺🇸

   The measurement of a permanent electric dipole moment (EDM) in atoms is crucial for understanding the origins of CP-violation. However, accurate interpretation of the EDM in systems involving deformed isotopes requires the characterization of their deformation. While nuclear deformation is indicated in various structure models, there is substantial mutual disagreement between the theoretical models or between theoretical models and experimental values. Nuclear E$2$ transitions allow access to quantify quadrupole deformation, but these transitions are often mixed with M$1$ transitions. Both E$2$ and M$1$ transitions are well characterized by Weisskopf estimates, which rely on a single-particle approximation, but deviate due to collective nuclear deformations. Previously, Weisskopf estimates were only available for the mass range $A<150$, and in this work we have extended the Weisskopf estimates of both E$2$ and M$1$ transition lifetimes to the mass range of $150\le A\le 250$. We comprehensively studied the deviation of E$2$ and M$1+$E$2$ transition lifetimes from the newly established Weisskopf estimates in $91$ candidate isotopes, by comparing the transition lifetimes of the candidate isotopes to their nearest even-even counterparts, whose E$2$ transition strengths are very well understood. Estimates of collective nuclear quadrupole deformation in $67$ of these isotopes were thus obtained, either from E$2$ or M$1+$E$2$ transition lifetimes. In $32$ cases they were obtained from both types of transitions independently, and are mutually consistent, as well as following the trends established in theory. We thereby identify the isotopes ${}^{223,225}$Fr, ${}^{221,223}$Ra, ${}^{223,225,227}$Ac and ${}^{229}$Pa, where EDM measurements are foreseen and information on nuclear deformation is needed, for which no measurement of nuclear quadrupole deformation has been made.

   nucl-exnucl-thPoS(2025)·0 citations
2. 02*

   Chiral symmetry breaking, chiral partners, and the $K_1$ and $K^{\ast }$ in medium

   Su Houng Lee🇰🇷

   We clarify the concept of chiral partners. For a vector meson, the isospin-zero and hypercharge-zero state in the flavor octet mixes with the flavor singlet state. Since the flavor singlet vector meson does not have a chiral partner, the mixed $\omega$ and $\varphi$ mesons will not have chiral partners. This means that even when chiral symmetry is restored, these mesons will not become degenerate with their corresponding parity partners. On the other hand, the $K_1$ and $K^{\ast }$ mesons are chiral partners, and both have widths smaller than 100 MeV. Therefore, we emphasize that studying these mesons in environments where chiral symmetry is restored is particularly important for understanding the effect of chiral symmetry restoration on chiral partners and their masses.

   ↳ hep-phnucl-exnucl-thJ.Subatomic Part.Cosmol.(2024)·2 citations
3. 03*

   Role of the tensor force in induced fission of 240Pu

   Yun Huang🇨🇳 · Xiang-Xiang Sun🇨🇳 · Lu Guo

   Results: We find that the tensor force affects the height of fission barriers and the double-humped structure of fission path of 240Pu. On the PES, the fission valley becomes larger in the (Q20, Q30) plane, and the triaxial deformation is suppressed around the outer barrier after considering the tensor force. Incorporating the tensor force into the dynamical process enhances the difference in shape evolution between two asymmetric channels. More interestingly, the charge distribution from TDHF with double PNP calculations shows a strong odd-even effect after including the tensor force. In addition, the total mass and charge distributions of fission fragments show a slight shift towards larger asymmetry and are more consistent with the experiments when tensor components are included. We also find that the tensor force enhances energy gaps of the deformed shells for heavy fragments. Moreover, the TKEs of fragments are in accord with the experiments, and after incorporating the tensor force, we observe a higher concentration of the calculated TKEs for heavy fragments at Z = 52 and Z = 56. Conclusions: The tensor force plays a role in both static and dynamical processes in nuclear fission, improving the accuracy of theoretical descriptions within the current framework. Our calculations have shown that the fission-barrier height with SLy5t is closer to the empirical value than that of SLy5. Additionally, the inclusion of the tensor force not only manifests the odd-even effect in charge distribution but also improves the description of total mass and charge distributions.

   ↳ nucl-thnucl-exPRC(2024)·8 citations
4. 04*

   Simplified Efficiency Calibration Methods for Scintillation Detectors Used in Nuclear Remediation

   Victor V. Golovko

   Our study introduces innovative methods to address waste reduction and enhance resource efficiency in nuclear cleanup processes. We focus on sustainable nuclear technology, aligning with goals for cleaner production and environmental protection. We developed two novel methods, termed "oversimplified" and "simplified," for easily determining the photopeak efficiency of NaI(Tl) scintillation detectors. These methods, along with a "general" solution method, were validated with calibrated radioactive sources such as 241Am, 57Co, 133Ba, 137Cs, and 60Co, and were used to commission a NaI(Tl) scintillation detector system at Chalk River Laboratories (CRL) for nuclear remediation. The system demonstrated high accuracy, making it suitable for screening unstable isotopes at contaminated sites. This screening tool significantly reduces the number of soil samples requiring detailed characterization, thereby lowering operational costs. The NaI(Tl) detector system was calibrated for near-contact geometry, which is commonly used at CRL. Detection limits were established for this configuration. By improving the efficiency calibration of scintillation detectors, our study advances sustainable nuclear remediation practices, promoting environmental sustainability and cleaner production processes.

   ↳ physics.ins-detnucl-exJournal of Cleaner Production(2024)·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.