Abstract
We present a detailed analysis of methods to reduce statistical errors and excited-state contamination in the calculation of matrix elements of quark bilinear operators in nucleon states. All the calculations were done on a -flavor ensemble with lattices of size generated using the rational hybrid Monte Carlo algorithm at and with . The statistical precision of the data is improved using the all-mode-averaging method. We compare two methods for reducing excited-state contamination: a variational analysis and a 2-state fit to data at multiple values of the source-sink separation . We show that both methods can be tuned to significantly reduce excited-state contamination and discuss their relative advantages and cost effectiveness. A detailed analysis of the size of source smearing used in the calculation of quark propagators and the range of values of needed to demonstrate convergence of the isovector charges of the nucleon to the estimates is presented.
12 More- Received 29 March 2016
DOI:https://doi.org/10.1103/PhysRevD.93.114506
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