核理论

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[1] arXiv:2505.23920 [中文pdf, pdf, html, 其他]

标题： 基于AI辅助的$^{28}$Si$^*$ $\rightarrow$ 7$α$裂变数据解析 显示英文标题

标题： AI-Assisted analysis of $^{28}$Si$^*$ $\rightarrow$ 7$α$ break-up data

Theodoros Depastas, Aldo Bonasera, Joe Natowitz

评论： 9页，9幅图

主题： 核理论 (nucl-th)

中等质量的$\alpha$-共轭核预计会拥有具有高角动量的奇特类似环形共振。 在$^{28}$硅$^*$中寻找这些状态是 Cao 及其同事以及 Hannaman 及其同事发表的两项关于周边$^{28}$硅 +$^{12}$碳反应的实验研究的主要内容。 在这项工作中，我们开发了一种基于人工智能（AI）的机器学习方法，利用高斯混合模型（GMM）来分析现有的实验和理论数据。 此外，我们还使用混合$\alpha$-团簇（H$\alpha$C）模型研究了该反应。在所有检查的数据中，我们的结果显示存在一种接近预测的环状状态的潜在结构。 显示英文摘要

Mid-weight $\alpha$-conjugate nuclei are predicted to possess exotic toroid-like resonances with high angular momenta. The search for these states in $^{28}$Si$^*$ is the main point of two published experimental investigations of the peripheral $^{28}$Si + $^{12}$C reaction by Cao and collaborators and by Hannaman and collaborators. In this work, we develop a novel Artificial Intelligence (AI)-based machine learning method utilizing the Gaussian Mixture Model (GMM) to analyze available experimental and theoretical data. We additionally study the reaction with the Hybrid $\alpha$-Cluster (H$\alpha$C) model. In all the examined data our results suggest the presence of underlying structure which is close to that predicted for toroidal states.

[2] arXiv:2505.24104 [中文pdf, pdf, html, 其他]

标题： 具有超子组分的原中子星的径向与非径向振荡 显示英文标题

标题： Radial and Non-Radial Oscillations of Protoneutron Stars with Hyperonic Composition

Prashant Thakur, Adamu Issifu, Ishfaq Ahmad Rather, Y. Lim, Tobias Frederico

评论： 18页，12幅图，6张表格

主题： 核理论 (nucl-th) ; 高能天体物理现象 (astro-ph.HE)

本文研究了新生中子星（PNS）从炽热且富含中微子的初始状态，经历去轻子化过程，演化到低温催化态时的径向和非径向振荡。状态方程（EoS）采用基于密度相关的相对论平均场框架建模，恒星演化通过熵和轻子分数的变化来表征。既考虑了核子成分也考虑了超子成分。 使用牛顿近似法和完整广义相对论方法计算了非径向$f$-模式和$p_1$-模式的振荡。 初始阶段被困住的中微子最初增加了$f$-模式的牛顿近似误差，在去轻子化过程中这一误差减小，并在冷态阶段再次上升。 相比之下，由于压力和密度梯度的演变，$p_1$-模式的误差在中间阶段达到峰值。 超子的存在适度提高了两种模式下的振荡频率。 现有的关于$f$-模式频率和阻尼时间的普适关系缺乏对于PNS模型的独立性，这促使我们寻找一个更稳健的关系。 特别是，我们提出的涉及转动惯量和$\tilde{\eta}$的普适关系在所有演化阶段表现出强烈的吻合性，为天琴座地震学提供了温度敏感且模型无关的尺度。 此外，还研究了不同状态方程下$1.4,M_\odot$质量PNS的径向振荡。 我们的结果显示，位移（$\xi$）和压力扰动（$\eta$）的分布对热状态、组成和致密性非常敏感。由于方程-of-state 的软化，超子星表现出更高的频率、改变的节点结构以及更强的压力扰动。核子模型与超子模型之间频率分裂（$\Delta \nu_n$）和基频（$\nu_0$）的差异提供了清晰的观测诊断，可用于探测PNS内部并限制高密度物质的方程-of-state。 显示英文摘要

This paper explores radial and non-radial oscillations of protoneutron stars (PNSs) as they evolve from hot, neutrino-rich configurations through deleptonization to cold, catalyzed states. The equation of state (EoS) is modeled using a density-dependent relativistic mean-field framework, with stellar evolution characterized by changes in entropy and lepton fraction. Both nucleonic and hyperonic compositions are considered. Non-radial $f$- and $p_1$-mode oscillations are computed using both the Cowling approximation and full general relativity. Trapped neutrinos initially increase the error of the Cowling approximation for $f$-modes, which decreases during deleptonization and rises again in the cold phase. In contrast, $p_1$-mode errors peak during intermediate stages due to evolving pressure and density gradients. The emergence of hyperons modestly raises oscillation frequencies in both modes. Existing universal relations for $f$-mode frequency and damping time lack model independence for PNSs, motivating a more robust relation. In particular, our proposed universal relation involving the moment of inertia and $\tilde{\eta}$ shows strong agreement across all evolutionary phases, offering a temperature-sensitive, model-independent scaling for asteroseismology. Radial oscillations of a $1.4,M_\odot$ PNS are also studied for different EoSs. Our results show that displacement ($\xi$) and pressure perturbation ($\eta$) profiles are highly sensitive to thermal state, composition, and compactness. Hyperonic stars show higher frequencies, altered node structures, and stronger pressure perturbations due to EoS softening. Differences in frequency separation $\Delta \nu_n$ and fundamental frequency $\nu_0$ between nucleonic and hyperonic models provide clear observational diagnostics for probing PNS interiors and constraining the dense matter EoS.

[3] arXiv:2505.24121 [中文pdf, pdf, html, 其他]

标题： 无中微子双贝塔衰变的次领头阶预测 显示英文标题

标题： Next-to-leading-order prediction for the neutrinoless double-beta decay

Y. L. Yang, P. W. Zhao

评论： 6页，5个图，被物理评论快报接受

主题： 核理论 (nucl-th) ; 高能物理 - 实验 (hep-ex) ; 高能物理 - 现象学 (hep-ph) ; 核实验 (nucl-ex)

无中微子双贝塔衰变（$0\nu\beta\beta$）是两个中子$nn \rightarrow ppee$的基本亚过程，也是原子核中$0\nu\beta\beta$衰变的一部分。 为了确定候选核在大规模$0\nu\beta\beta$搜索中的核矩阵元的短程贡献，需要精确了解$nn \rightarrow ppee$振幅。 本文中，我们报告了 nn\rightarrow ppee 振幅的第一个次领头阶预测，并进行了贝叶斯不确定性量化。 这是由于相对论性手征有效场理论的发展，该理论在次领头阶之前不需要未知的接触项。 该理论通过无参数方式重现了关于两核子散射中电荷无关性和电荷对称性破缺贡献的可用数据，从而得到验证。 目前的工作朝着解决与$0\nu\beta\beta$搜索相关的理论计算中核矩阵元的不确定性迈出了重要一步。 显示英文摘要

The neutrinoless double-beta decay ($0\nu\beta\beta$) of two neutrons$nn \rightarrow ppee$ is the elementary subprocess of $0\nu\beta\beta$ decay in nuclei. Accurate knowledge of the $nn \rightarrow ppee$ amplitude is required to pin down the short-range contributions in the nuclear matrix elements of the candidate nuclei for large-scale $0\nu\beta\beta$ searches. In this Letter, we report the first next-to-leading-order prediction of the nn \rightarrow ppee amplitude, with Bayesian uncertainty quantification. This is made possible by the development of the relativistic chiral effective field theory, in which no unknown contact term is required up to next-to-leading order. The theory is validated by reproducing in a parameter-free way the available data on the charge independence and charge symmetry breaking contributions in the two-nucleon scattering. The present work makes an essential step towards addressing the uncertainty in the theoretical calculations of the nuclear matrix elements relevant for $0\nu\beta\beta$ searches.

[4] arXiv:2505.24485 [中文pdf, pdf, html, 其他]

标题： 中子星物质的中微子发射 显示英文标题

标题： Neutrino emission from neutron star matter

Omar Benhar, Lucas Tonetto

评论： 受邀论文，已被接受在《International Journal of Modern Physics E》上发表

主题： 核理论 (nucl-th)

新形成的中子星的温度被认为高达$10^{11}$~K，对应的热能约为$10$~MeV。 经过时间$t \sim 50 \ {\rm s}$，核物质中的中微子平均自由程超过典型恒星半径 R~$\sim$~10 公里，中微子发射成为主要的能量损失机制，最终将温度降至$\sim10^{8}$~K。 中微子还在决定恒星内部物质组成方面发挥关键作用，该组成主要由中子、质子和轻子的电荷中性混合物构成，在$\beta$-平衡下存在。 本文介绍了核物质中核子弱相互作用的入门知识，并简要回顾了中子星核心发生的中微子发射反应。 基于该领域近期进展，分析了标准理论处理热效应和动力学效应所涉及的近似方法，并概述了未来发展的前景。 显示英文摘要

The temperature of a newly formed neutron star is believed to be as high as $10^{11}$~K, corresponding to a thermal energy of about $10$ MeV. After a time $t \sim 50 \ {\rm s}$, the neutrino mean free path in nuclear matter exceeds the typical star radius, R~$\sim$~10 Km, and neutrino emission becomes the dominant mechanism of energy loss, eventually bringing the temperature down to $\sim10^{8}$~K. Neutrinos also play a critical role in determining the composition of matter in the star interior, consisting primarily of a charge-neutral mixture of neutrons, protons and leptons in $\beta$-equilibrium. This article provides an introduction to the weak interactions of nucleons in nuclear matter, as well as a concise review of the neutrino emission reactions taking place in the neutron star core. The approximations involved in the standard theoretical treatment of thermal and dynamical effects are analysed in the light of the recent progress of the field, and the prospects for future developments are outlined.

[5] arXiv:2505.24753 [中文pdf, pdf, html, 其他]

标题： 重离子双电荷交换反应作为双体跃迁密度的探针 显示英文标题

标题： Heavy Ion Double Charge Exchange Reactions as Probes for Two-Body Transition Densities

Jessica I.Bellone, Maria Colonna, Danilo Gambacurta, Horst Lenske

主题： 核理论 (nucl-th)

由二阶核子-核子相互作用诱导的碰撞重离子双电荷交换（DCE）反应表明，可以访问相互作用核中的互补DCE跃迁的两体跃迁密度。引入了相应的两体算符，并以s通道相互作用形式处理二阶畸变波反应振幅。理论结果应用于能量为$T_{lab}=270$MeV 的$^{18}O+{}^{76}Se\to {} ^{18}Ne+{}^{76}Ge$反应，其中$^{76}Ge$是无中微子双贝塔衰变的候选者。 显示英文摘要

Collisional heavy ion double charge exchange (DCE) reactions, induced by second order nucleon-nucleon interactions, are shown to provide access to the two-body transition densities of the complementary DCE transitions in the interacting nuclei. Corresponding two-body operators are introduced, treating the second order distorted wave reaction amplitude in the s-channel interaction form. The theoretical results are applied to the reaction $^{18}O+{}^{76}Se\to {} ^{18}Ne+{}^{76}Ge$ at $T_{lab}=270$~MeV, being $^{76}Ge$ a candidate for neutrino--less double beta decay.

替换提交 (展示 1 之 1 条目 )

[6] arXiv:2505.24674 (替换) [中文pdf, pdf, html, 其他]

标题： 关于低能区$ππ$和$πN$散射研究的最新进展综述 显示英文标题

标题： A review on recent progresses in the study of low energy $ππ$ and $πN$ scatterings

Qu-Zhi Li, Zhiguang Xiao, Han-Qing Zheng

评论： 投稿至EPJST，13页，7幅图

主题： 高能物理 - 现象学 (hep-ph) ; 高能物理 - 格点 (hep-lat) ; 核理论 (nucl-th)

我们总结了关于$\pi\pi$和$\pi N$散射的新结果。这些结果包括发现一个质量低于核子质量的负宇称核子极点，以及随着π介子质量变化时$f_0(500)$的极点轨迹。这些结果来源于模型无关的色散分析。我们还基于$O(N)$ $\sigma$ 模型和$N/D$方法研究了$f_0(500)$的热性质。 显示英文摘要

We summarize new results on the studies of $\pi\pi$ and $\pi N$ scatterings. They include the finding of a negative-parity nucleon pole with a mass lower than the nucleon mass, and the pole trajectory of $f_0(500)$ with respect to varying pion masses. The results are obtained from model-independent dispersion analyses. We also study the thermal properties of $f_0(500)$ based on the $O(N)$ $\sigma$ model and $N/D$ method.