Measurements of elastic electron scattering data within the past decade have highlighted two-photon exchange contributions as a necessary ingredient in theoretical calculations to precisely evaluate hydrogen elastic scattering cross sections. This correction can modify the cross section at the few percent level. In contrast, dispersive effects can cause significantly larger changes from the Born approximation. The purpose of this experiment is to extract the carbon-12 elastic cross section around the first diffraction minimum, where the Born term contributions to the cross section are small to maximize the sensitivity to dispersive effects. The analysis uses the LEDEX data from the high resolution Jefferson Lab Hall A spectrometers to extract the cross sections near the first diffraction minimum of \(^{12}\)C at beam energies of 362 MeV and 685 MeV. The results are in very good agreement with previous world data, although with less precision. The average deviation from a static nuclear charge distribution expected from linear and quadratic fits indicate a 30.6% contribution of dispersive effects to the cross section at 1 GeV. The magnitude of the dispersive effects near the first diffraction minimum of \(^{12}\)C has been confirmed to be large with a strong energy dependence and could account for a large fraction of the magnitude for the observed quenching of the longitudinal nuclear response. These effects could also be important for nuclei radii extracted from parity-violating asymmetries measured near a diffraction minimum.

中文翻译：

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弹性电子-核散射的色散校正：对中间能态的研究及其对核物质的影响

在过去十年中，对弹性电子散射数据的测量结果突出了两光子交换贡献，这是理论计算中精确评估氢弹性散射截面的必要成分。这种校正可以在几个百分比的水平上修改横截面。相比之下，色散效应会导致Born近似值的变化更大。该实验的目的是提取第一个衍射最小值附近的碳12弹性横截面，其中Born项对横截面的贡献很小，以最大程度地提高对色散效应的敏感性。该分析使用来自高分辨率Jefferson Lab Hall A光谱仪的LEDEX数据提取接近第一个衍射最小值\（^ {12} \）的横截面束能量为362 MeV和685 MeV的C。尽管精度较低，但结果与以前的世界数据非常吻合。线性和二次拟合预期的静态核电荷分布的平均偏差表明，在1 GeV处，横截面的色散效应占30.6％。已经证实，在接近第一个衍射最小值\（^ {12} \） C的情况下，色散效应的大小很大，并且具有很强的能量依赖性，并且可以在观察到的纵向核猝灭中占很大一部分响应。对于从衍射最小附近测量的违反奇偶校验的不对称中提取的核半径，这些影响也可能很重要。