Ab initio calculation of the neutron-proton mass difference
Ab initio calculation of the neutron-proton mass difference
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DOI：
10.1126/science.1257050
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发表时间：
2015-03-27
期刊：
影响因子：
56.9
通讯作者：
Toth, B. C.
中科院分区：
文献类型：
--
作者：
Borsanyi, Sz.;Durr, S.;Toth, B. C.
原子的存在和稳定性依赖于中子比质子更大的事实。测得的质量差异仅为两个质量平均值的0.14%。稍小或稍大的值将导致一个截然不同的宇宙。在这里，我们证明这种差异是由电磁和质量同位旋破坏效应之间的竞争造成的。我们使用四种非简并威尔逊费米子进行了晶格量子色动力学和量子电动力学计算，并以 300 千电子伏的精度计算了中子-质子质量分裂，这比 0 x 5 标准偏差大。我们还确定了 Sigma、Xi、D 和 Xi(cc) 同位旋多重态的分裂，在某些情况下超出了实验测量的精度。
The existence and stability of atoms rely on the fact that neutrons are more massive than protons. The measured mass difference is only 0.14% of the average of the two masses. A slightly smaller or larger value would have led to a dramatically different universe. Here, we show that this difference results from the competition between electromagnetic and mass isospin breaking effects. We performed lattice quantum-chromodynamics and quantum-electrodynamics computations with four nondegenerate Wilson fermion flavors and computed the neutron-proton mass-splitting with an accuracy of 300 kilo-electron volts, which is greater than 0 by 5 standard deviations. We also determine the splittings in the Sigma, Xi, D, and Xi(cc) isospin multiplets, exceeding in some cases the precision of experimental measurements.