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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 323 × 64 generated using the rational hybrid Monte Carlo algorithm at a = 0.081 fm and with Mπ = 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 2-state fit to data at multiple values of the source-sink separation tsep. We show that both methods can be tuned to significantly reduce excited-state contamination and discuss their relative advantages and cost effectiveness. As a result, a detailed analysis of the size of source smearing used in the calculation of quark propagators and the range of values of tsep needed to demonstrate convergence of the isovector charges of the nucleon to the tsep → ∞ estimates is presented.
Authors:
 [1] ;  [1] ;  [1] ;  [2] ;  [3] ;  [4] ;  [5] ;  [6] ;  [7] ;  [6] ;  [4] ;  [4] ;  [4]
  1. Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
  2. New Mexico State Univ., Las Cruces, NM (United States)
  3. Johannes Gutenberg-Univ. Mainz, Mainz (Germany)
  4. Thomas Jefferson National Accelerator Facility (TJNAF), Newport News, VA (United States)
  5. Univ. of California, Berkeley, CA (United States)
  6. Massachusetts Inst. of Technology (MIT), Cambridge, MA (United States)
  7. College of William and Mary, Williamsburg, VA (United States)
Publication Date:
OSTI Identifier:
1343699
Report Number(s):
LA-UR--16-20524
Journal ID: ISSN 2470-0010; PRVDAQ
Grant/Contract Number:
AC52-06NA25396
Type:
Accepted Manuscript
Journal Name:
Physical Review D
Additional Journal Information:
Journal Volume: 93; Journal Issue: 11; Journal ID: ISSN 2470-0010
Publisher:
American Physical Society (APS)
Research Org:
Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
Sponsoring Org:
USDOE
Contributing Orgs:
Nucleon Matrix Elements (NME) Collaboration
Country of Publication:
United States
Language:
English
Subject:
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS atomic and nuclear physics