2009/05/31 by M. Selim Mahbub, M. S. Mahbub, Alan Ò Cais +6 · 1 citation
Physics and Astronomy · #Eigenvalues and eigenvectors #Excited state #High-Energy Particle Collisions Research #Lattice QCD #Nucleon #Particle physics #Particle physics theoretical and experimental studies #Physics #Quantum Chromodynamics and Particle Interactions #Quantum chromodynamics #Quantum electrodynamics #Quantum mechanics #Statistical physics #Variational method #hep-lat
paper · pdf · doi:10.1103/physrevd.80.054507
published as Phys.Rev.D80:054507,2009 · May 2009.13pp, Minor changes and references added
openalex publication_date 2009/09/23 · arxiv created 2009/09/30 · arxiv updated 2010/04/28 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/05
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\ifmmode×\else\texttimes\fi2 and 3\ifmmode×\else\texttimes\fi3 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.