Disconnected contributions to the spin of the nucleon
Disconnected contributions to the spin of the nucleon
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DOI：
10.1103/physrevd.92.114517
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发表时间：
2015-08
影响因子：
5
通讯作者：
A. Chambers;R. Horsley;A. Schiller;H. Stüben;D. Pleiter;D. Pleiter;J. Zanotti;H. Perlt;Y. Nakamura;P. Rakow;G. Schierholz;R. Young
中科院分区：
文献类型：
--
作者：
A. Chambers;R. Horsley;A. Schiller;H. Stüben;D. Pleiter;D. Pleiter;J. Zanotti;H. Perlt;Y. Nakamura;P. Rakow;G. Schierholz;R. Young
质子的自旋分解是强子物理学中一个长期关注的话题。格子QCD在计算夸克自旋的关联贡献方面取得了很大的成功。然而，必须涉及胶子和奇异夸克贡献的完整计算仍然存在一些挑战。这些“不相关”的贡献通常涉及隐藏在大统计背景下的小信号，并依赖于计算密集的随机技术。在这项工作中，我们演示了如何使用Feynman-Hellmann方法来计算这样的量，通过测量由于对QCD作用的人为修改而引起的质子能量的移动。在470 MeV的介子质量下，我们发现了一个统计上显著的非零结果，即不连通的夸克自旋对质子的贡献约为-5%。
The spin decomposition of the proton is a long-standing topic of much interest in hadronic physics. Lattice QCD has had much success in calculating the connected contributions to the quark spin. However, complete calculations, which necessarily involve gluonic and strange-quark contributions, still present some challenges. These "disconnected" contributions typically involve small signals hidden against large statistical backgrounds and rely on computationally intensive stochastic techniques. In this work we demonstrate how a Feynman-Hellmann approach may be used to calculate such quantities, by measuring shifts in the proton energy arising from artificial modifications to the QCD action. We find a statistically significant non-zero result for the disconnected quark spin contribution to the proton of about -5% at a pion mass of 470 MeV.