arXiv 1504.050632015-04-20nucl-thnucl-ex

少核子基态的电磁结构

Electromagnetic Structure of Few-Nucleon Ground States

L. E. Marcucci, F. Gross, M. T. Pena, M. Piarulli, R. Schiavilla, I. Sick, A. Stadler, J. W. Van Orden, M. Viviani

备注：: 66 pages, 23 figures, topical review submitted to J. Phys. G: Nucl. Part. Phys
DOI：: 10.1088/0954-3899/43/2/023002

摘要：

氢和氦同位素的实验形状因子，从这些系统的弹性电子散射测量的截面和极化观测值的最新全球分析中提取，与三种不同理论方法中获得的预测进行比较：第一种是基于现实的相互作用和电流，包括相对论修正第二种方法依赖于手征有效场论对原子核中强相互作用和电磁相互作用的描述（标记为$χ$ EFT）;第三个利用完全相对论处理核动力学的协变旁观者理论（标记为CST）。对于低于$Q \lesssim 5$ fm $^{-1}$的动量转移，在所有三种方法中，实验数据和理论结果之间都有令人满意的一致性。然而，在$Q \gtrsim 5$ fm $^{-1}$，特别是在氘核的情况下，动力学的相对论处理是必要的，就像在CST中所做的那样。氘核$A$结构函数的实验数据扩展到$Q \simeq 12$ fm $^{-1}$，并且这些数据与CST结果之间的密切一致性表明，即使在这种极端的运动学状态下，也没有证据表明来自短距离夸克和胶子自由度的新效应。

英文摘要：

Experimental form factors of the hydrogen and helium isotopes, extracted from an up-to-date global analysis of cross sections and polarization observables measured in elastic electron scattering from these systems, are compared to predictions obtained in three different theoretical approaches: the first is based on realistic interactions and currents, including relativistic corrections (labeled as the conventional approach); the second relies on a chiral effective field theory description of the strong and electromagnetic interactions in nuclei (labeled $χ$EFT); the third utilizes a fully relativistic treatment of nuclear dynamics as implemented in the covariant spectator theory (labeled CST). For momentum transfers below $Q \lesssim 5$ fm$^{-1}$ there is satisfactory agreement between experimental data and theoretical results in all three approaches. However, at $Q \gtrsim 5$ fm$^{-1}$, particularly in the case of the deuteron, a relativistic treatment of the dynamics, as is done in the CST, is necessary. The experimental data on the deuteron $A$ structure function extend to $Q \simeq 12$ fm$^{-1}$, and the close agreement between these data and the CST results suggests that, even in this extreme kinematical regime, there is no evidence for new effects coming from quark and gluon degrees of freedom at short distances.

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