Isolating excited states of the nucleon in lattice QCD

Journal Article · Tue Sep 01 04:00:00 EDT 2009 · Physical Review. D, Particles Fields

DOI:https://doi.org/10.1103/PHYSREVD.80.054507· OSTI ID:21322611

Mahbub, M S ^[1]; Cais, Alan O; Kamleh, Waseem; Lasscock, B G; Leinweber, Derek B; Williams, Anthony G ^[1]

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1. Special Research Centre for the Subatomic Structure of Matter, Adelaide, South Australia 5005 (Australia) and Department of Physics, University of Adelaide, South Australia 5005 (Australia)

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 2x2 and 3x3 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.

• OSTI ID: 21322611
• Journal Information: Physical Review. D, Particles Fields, Journal Name: Physical Review. D, Particles Fields Journal Issue: 5 Vol. 80; ISSN PRVDAQ; ISSN 0556-2821
• Country of Publication: United States
• Language: English

Related Subjects

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS
ALGORITHMS
CORRELATION FUNCTIONS
CORRELATIONS
EIGENSTATES
EIGENVALUES
EIGENVECTORS
EXCITED STATES
EXTRACTION
MASS
NUCLEONS
PARITY
QUANTUM CHROMODYNAMICS
VARIATIONAL METHODS