发表机构
Idaho State University; Virginia Tech; Hampton Roads Academy; Texas A & M University - Kingsville; University of Zagreb, Faculty of Science; California State University, Los Angeles; William & Mary; Thomas Jefferson National Accelerator Facility; Instituto Nazionale di Fisica Nucleare, Sezione di Catania; Louisiana Tech University; Mississippi State University; University of Manitoba（爱达荷州立大学; 弗吉尼亚理工大学; 汉普顿路学院; 德克萨斯农工大学金斯维尔分校; 萨格勒布大学理学院; 洛杉矶加州州立大学; 威廉与玛丽学院; 托马斯·杰斐逊国家加速设施; 意大利国家核物理研究所卡塔尼亚分部; 路易斯安那理工大学; 密西西比州立大学; 曼尼托巴大学）
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
本文通过 PREX 和 CREX 实验测量宇称破坏电子散射不对称度，精确确定了 $^{208}$Pb 和 $^{48}$Ca 的中子皮厚度，并描述了相关实验与数据分析技术。
AI 中文摘要
我们在 PREX 和 CREX 实验中分别测量了 $^{208}$Pb 和 $^{48}$Ca 靶核上的宇称破坏弹性电子散射不对称度；这两个核都是双幻核，其激发态可以通过杰斐逊实验室 Hall A 的高分辨谱仪与基态区分开来。该不对称度在单个 $Q^2$ 值上提供了弱电荷形状因子的精确测定，并以相对干净且模型无关的方式确定了这两个核的中子半径。这是因为弱相互作用的 $Z^0$ 玻色子主要与中子耦合。较重的铅核具有中子过剩，其中子皮厚度可用来解释体相中子物质的性质。对于较轻的 $^{48}$Ca 核（同样富含中子），与微观核理论计算的比较对约束较差的 3 中子力敏感。提取的弱中性形状因子 $F_W(Q^2)$ 为：对于 $^{208}$Pb（来自 PREX-2），在 $Q = 0.3977 \mathrm{fm}^{-1}$ 处为 $0.368 \pm 0.013$；对于 $^{48}$Ca，在 $Q = 0.8733 \mathrm{fm}^{-1}$ 处为 $0.1304 \pm 0.0055$。计算得到的形状因子差 $(F_{ch}-F_W)(Q^2)$ 为：对于 $^{208}$Pb（来自 PREX-2），在 $Q = 0.3977 \mathrm{fm}^{-1}$ 处为 $0.041 \pm 0.013$；对于 $^{48}$Ca，在 $Q = 0.8733 \mathrm{fm}^{-1}$ 处为 $0.0277 \pm 0.0055$。在修正库仑畸变并利用核模型信息后，我们发现中子皮厚度为：结合 PREX-1 和 PREX-2 数据，$R^{208}_{\mathrm{skin}} = 0.283 \pm 0.071$ fm；$R^{48}_{\mathrm{skin}} = 0.121 \pm 0.035$ fm。本文完整描述了为精确测量这些微小不对称度而采用的专门实验和数据分析技术。
英文摘要
We have measured the parity-violating elastic electron scattering asymmetry in the PREX and CREX experiments on ${}^{208}$Pb and ${}^{48}$Ca respectively; these are both doubly-magic nuclei whose excited states can be discriminated from the ground state by the high resolution spectrometers in Hall A at Jefferson Lab. This asymmetry provides a precise determination of the weak charge form factor at one $Q^2$ and pins down the neutron radius in these two nuclei in a relatively clean and model-independent way. This is because the $Z^0$ boson of the weak interaction couples primarily to neutrons. The heavier lead nucleus, with a neutron excess, provides an interpretation of the neutron skin thickness in terms of properties of bulk neutron matter. For the lighter ${}^{48}$Ca nucleus, which is also rich in neutrons, comparisons to microscopic nuclear theory calculations are sensitive to poorly constrained 3-neutron forces. The weak neutral form factors $F_W(Q^2)$ were extracted to be $0.368 \pm 0.013$ at $Q = 0.3977 {\rm\ fm}^{-1}$ for $^{208}$Pb from PREX-2 and $0.1304 \pm 0.0055$ at $Q = 0.8733 {\rm\ fm}^{-1}$ for $^{48}$Ca. The form factor differences $(F_{ch}-F_W)(Q^2)$ were calculated to be $0.041 \pm 0.013$ at $Q = 0.3977 {\rm fm}^{-1}$ for $^{208}$Pb from PREX-2 and $0.0277 \pm 0.0055$ at $Q = 0.8733 {\rm fm}^{-1}$ for $^{48}$Ca. Correcting for Coulomb distortions and using nuclear model information, we find the neutron skin thicknesses to be $R^{208}_{\rm skin} = 0.283 \pm 0.071$ fm combining PREX-1 and PREX-2 and $R^{48}_{\rm skin} = 0.121 \pm 0.035$ fm. This paper provides a full description of the special experimental and data analysis techniques employed for precisely measuring these small asymmetries.
Comments51 pages, 43 figures
