Searching for low-lying multi-particle thresholds in lattice spectroscopy

Journal Article · Sat Mar 15 00:00:00 EDT 2014 · Annals of Physics (New York)

DOI:https://doi.org/10.1016/J.AOP.2014.01.004· OSTI ID:22224310

Mahbub, M. Selim ^[1]; Kamleh, Waseem ^[1]; Williams, Anthony G. ^[1]

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1. Special Research Centre for the Subatomic Structure of Matter, School of Chemistry and Physics, The University of Adelaide, SA, 5005 (Australia)

We explore the Euclidean-time tails of odd-parity nucleon correlation functions in a search for the S-wave pion–nucleon scattering-state threshold contribution. The analysis is performed using 2+1 flavor 32{sup 3}×64 PACS-CS gauge configurations available via the ILDG. Correlation matrices composed with various levels of fermion source/sink smearing are used to project low-lying states. The consideration of 25,600 fermion propagators reveals the presence of more than one state in what would normally be regarded as an eigenstate-projected correlation function. This observation is in accord with the scenario where the eigenstates contain a strong mixing of single and multi-particle states but only the single particle component has a strong coupling to the interpolating field. Employing a two-exponential fit to the eigenvector-projected correlation function, we are able to confirm the presence of two eigenstates. The lower-lying eigenstate is consistent with a Nπ scattering threshold and has a relatively small coupling to the three-quark interpolating field. We discuss the impact of this small scattering-state contamination in the eigenvector projected correlation function on previous results presented in the literature. -- Highlights: • Correlation-matrix projected correlators reveal more than one state contributing. • Results are associated with strong mixing of single and multi-particle states in QCD. • A two-exponential fit confirms the presence of two QCD eigenstates. •The lower-lying eigenstate is consistent with a nucleon–pion scattering threshold. •The impact of this small contamination on the higher-lying state is examined.

• OSTI ID: 22224310
• Journal Information: Annals of Physics (New York), Vol. 342; Other Information: Copyright (c) 2014 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved.; Country of input: International Atomic Energy Agency (IAEA); ISSN 0003-4916
• Country of Publication: United States
• Language: English

Related Subjects

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS
CORRELATION FUNCTIONS
EIGENSTATES
EIGENVECTORS
EUCLIDEAN SPACE
FLAVOR MODEL
NUCLEONS
PARITY
PERTURBED ANGULAR CORRELATION
QUANTUM CHROMODYNAMICS
QUARKS
S WAVES
SCATTERING
STRONG-COUPLING MODEL