标题： 使用混合插值器研究格点上核子结构中的激发态效应 显示英文标题

标题： Excited-state effects in nucleon structure on the lattice using hybrid interpolators

摘要： 在格点QCD计算中，找到一种能够降低激发态效应的方法，且计算成本较低，这将非常有用。 我们探索了在变分基中使用包含非平凡胶子激发态的混合插值算符，并与具有调整平滑宽度的标准插值算符一起使用。 使用场强张量的clover离散化，可以使用与标准计算相同数量的夸克传播子来执行标准和混合插值算符的固定线性组合计算，这使得这是一种成本效益高的选项。 我们发现，通过求解广义特征值问题优化的这种插值算符，可以减少两点关联函数中的激发态贡献。 然而，在需要计算核子矩阵元的三点关联函数中，效果是混合的：对于某些矩阵元，如张量电荷，激发态效应被抑制，而对于其他矩阵元，如轴向电荷，它们却被增强。 结果表明，变分方法并不能保证在渐近区域之外减少激发态的净贡献，并表明使用一个能够分离所有相关低能态的大插值算符基可能很重要。 显示英文摘要

摘要： It would be very useful to find a way of reducing excited-state effects in lattice QCD calculations of nucleon structure that has a low computational cost. We explore the use of hybrid interpolators, which contain a nontrivial gluonic excitation, in a variational basis together with the standard interpolator with tuned smearing width. Using the clover discretization of the field strength tensor, a calculation using a fixed linear combination of standard and hybrid interpolators can be done using the same number of quark propagators as a standard calculation, making this a cost-effective option. We find that such an interpolator, optimized by solving a generalized eigenvalue problem, reduces excited-state contributions in two-point correlators. However, the effect in three-point correlators, which are needed for computing nucleon matrix elements, is mixed: for some matrix elements such as the tensor charge, excited-state effects are suppressed, whereas for others such as the axial charge, they are enhanced. The results illustrate that the variational method is not guaranteed to reduce the net contribution from excited states except in its asymptotic regime, and suggest that it may be important to use a large basis of interpolators capable of isolating all of the relevant low-lying states.