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Title: Controlling excited-state contamination in nucleon matrix elements

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 2+1 flavor ensemble with lattices of size $$32^3 \times 64$$ generated using the rational hybrid Monte Carlo algorithm at $a=0.081$~fm and with $$M_\pi=312$$~MeV. 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 two-state fit to data at multiple values of the source-sink separation $$t_{\rm sep}$$. 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 $$t_{\rm sep}$$ needed to demonstrate convergence of the isovector charges of the nucleon to the $$t_{\rm sep} \to \infty $$ estimates is presented.
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Publication Date:
OSTI Identifier:
Report Number(s):
JLAB-THY-16-2285; DOE/OR/23177-3842; arXiv:1602.07737
Journal ID: ISSN 2470-0010; PRVDAQ
DOE Contract Number:
AC05-00OR22725; KA-1401020; AC05-06OR23177; SC0011090; FG02-96ER40965
Resource Type:
Journal Article
Resource Relation:
Journal Name: Physical Review D; Journal Volume: 93; Journal Issue: 11
Research Org:
Thomas Jefferson National Accelerator Facility, Newport News, VA (United States)
Sponsoring Org:
USDOE; USDOE Office of Science (SC), Nuclear Physics (NP) (SC-26)
Contributing Orgs:
Nucleon Matrix Elements (NME) Collaboration
Country of Publication:
United States