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Nuclear Theory·nucl-th

Monday·August 18, 2025

6 papers—3 primary·3 cross-listed

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  1. 01

    Nonflow suppression in flow analysis with a maximum likelihood estimator

    Chong Ye🇨🇳 · Wei-Liang Qian🇨🇳 · Cesar A. Bernardes🇧🇷 · Sandra S. Padula🇧🇷 · Rui-Hong Yue🇨🇳 · Yutao Xing🇧🇷 · Takeshi Kodama🇧🇷

    We show that the maximum likelihood estimator (MLE) is an effective tool for mitigating non-flow effects in flow analysis. To this end, one constructs two toy models that simulate non-flow contributions corresponding to particle decay and momentum conservation, respectively. The performance of MLE is analyzed by comparing it against standard approaches such as particle correlation and event plane methods. For both cases, MLE is observed to provide a reasonable estimate of the underlying flow harmonics, and in particular, its performance can be further improved when the specific form of the likelihood in the presence of non-flow can be assessed. The dependencies of extracted flow harmonics on the multiplicity of individual events and the total number of events are analyzed. Additionally, it is shown that the proposed approach performs efficiently in addressing deficiencies in detector acceptance. These findings suggest MLE as a compelling alternative to standard methods for flow analysis.

    nucl-thPRC(2026)·1 citation
  2. 02

    Low-lying level structures in Lu

    N Susshma · S Deepa · K Vijay Sai · R Gowrishankar

    The well-tested empirical two quasiparticle rotor model calculations are used to characterize low-lying isomers in the odd-odd nucleus Lu. Physically admissible 2qp bandheads are obtained to construct the low-energy level structure of the nucleus, assign spin-parity (J), orbital configuration, and level energies (E), for the gs and the two reported isomers. The spin-parity and orbital configuration of the 1.5 min isomer are confirmed to be J= 4\{5/2[402] 3/2[521]\}. Its level energy has been estimated to be E 62 keV. The 1.9 min isomer is characterized for the first time with J= 6\{9/2[514] 3/2[521]\} and energy E 157 keV. Based on these assignments, individual -decay branches of gs and the two isomers to the daughter levels in Yb are proposed. The study is extended to neighboruing isotopes Lu. A short-lived isomer, tentatively proposed in a previous study of Lu, is identified as J= 6\{7/2[404] 5/2[402]\} with energy E 52 keV. The energy of the J=3 isomer in Lu, currently listed with large uncertainty, is deduced as E 100 keV significantly improving its value.

    nucl-thPRC(2026)·0 citations
  3. 03

    Highly efficient nuclear population transfer through physics-informed neural networks

    Jing Liu · Fu-Quan Dou

    Nuclear coherent population transfer (NCPT) offers numerous potential applications, particularly in next-generation nuclear clocks and nuclear batteries. However, the realization of high fidelity, fast operation, and low energy consumption in NCPT remains so far challenging. Here, we employ physics-informed neural networks (PINNs) to the population transfer in an open three-level nuclear system with spontaneous emission. The method embeds the system's control equations and boundary conditions into the loss function, thereby enabling the automatic learning of optimal laser pulse sequences that drive highly efficient population transfer. We take a short-lived excited state of and a long-lived state of as representative examples, and systematically compare the performance of the PINNs approach with three conventional control strategies. We show that PINNs can achieve higher transfer efficiency with smaller pulse areas and shorter durations across different lifetime regimes. Our results provide a new perspective to overcome the lifetime limitation and enhance the efficiency of nuclear state transfer.

    nucl-thPRC(2026)·1 citation

Affiliations

first authorsco-authorsvia INSPIRE