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Type: Journal article
Title: Isolating excited states of the nucleon in lattice QCD
Author: Mahbub, M.
Cass, A.
Kamleh, W.
Lasscock, B.
Leinweber, D.
Williams, A.
Citation: Physical Review. D. Particles, Fields, Gravitation and Cosmology, 2009; 80(5):054507-1-054507-11
Publisher: American Physical Soc
Issue Date: 2009
ISSN: 1550-7998
Statement of
M. S. Mahbub, Alan Ó. Cais, Waseem Kamleh, B. G. Lasscock, Derek B. Leinweber, and Anthony G. Williams (CSSM Collaboration)
Abstract: We discuss a robust projection method for the extraction of excited-state masses of the nucleon from a matrix of correlation functions. To illustrate the algorithm in practice, we present results for the positive parity excited states of the nucleon in quenched QCD. Using eigenvectors obtained via the variational method, we construct an eigenstate-projected correlation function amenable to standard analysis techniques. The method displays its utility when comparing results from the fit of the projected correlation function with those obtained from the eigenvalues of the variational method. Standard nucleon interpolators are considered, with 2×2 and 3×3 correlation matrix analyses presented using various combinations of source-smeared, sink-smeared, and smeared-smeared correlation functions. Using these new robust methods, we observe a systematic dependency of the extracted nucleon excited-state masses on source- and sink-smearing levels. To the best of our knowledge, this is the first clear indication that a correlation matrix of standard nucleon interpolators is insufficient to isolate the eigenstates of QCD.
Rights: ©2009 American Physical Society
RMID: 0020092825
DOI: 10.1103/PhysRevD.80.054507
Appears in Collections:Physics publications

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