论文标题
关于质子和中子之间的质量差异
On the mass difference between proton and neutron
论文作者
论文摘要
Cottingham公式以虚拟康普顿散射幅度来表达粒子质量的电磁部分。在大的光子矩时，这种振幅由与自旋0和自旋2的算子相关的短距离奇异性主导。在质子和中子之间的差异，手性对称性抑制了自旋0项。尽管角积分完全消除了自旋2奇异性，但在Cottingham公式的标准分解中出现的各种零件确实会采取此类贡献。这些方法渐近性非常缓慢，因为相关的威尔逊系数只会偏离对数。我们以从头算避免了领先的Spin 2贡献的方式重写公式。使用Reggeon优势遵循的总和规则，对E.M.的数值评估。质子和中子之间的质量差异的一部分产生$ m_ {qed}^{p-n} = 0.58 \ pm 0.16 \，$ mev。结果表明，与弹性相比，非弹性贡献很小。
The Cottingham formula expresses the electromagnetic part of the mass of a particle in terms of the virtual Compton scattering amplitude. At large photon momenta, this amplitude is dominated by short distance singularities associated with operators of spin 0 and spin 2. In the difference between proton and neutron, chiral symmetry suppresses the spin 0 term. Although the angular integration removes the spin 2 singularities altogether, the various pieces occurring in the standard decomposition of the Cottingham formula do pick up such contributions. These approach asymptotics extremely slowly because the relevant Wilson coefficients only fall off logarithmically. We rewrite the formula in such a way that the leading spin 2 contributions are avoided ab initio. Using a sum rule that follows from Reggeon dominance, the numerical evaluation of the e.m. part of the mass difference between proton and neutron yields $m_{QED}^{p-n}=0.58\pm 0.16\,$MeV. The result indicates that the inelastic contributions are small compared to the elastic ones.
