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Title: Calm multi-baryon operators

Publication Date:
Research Org.:
Brookhaven National Laboratory (BNL), Upton, NY (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Nuclear Physics (NP) (SC-26); RIKEN
OSTI Identifier:
Report Number(s):
RBRC-1259; BNL-203296-2018-CPPJ
DOE Contract Number:
Resource Type:
Resource Relation:
Conference: 35th International Symposium on Lattice Field Theory (Lattice 2017), Granada, Spain , 6/18/2017 - 6/24/2017
Country of Publication:
United States

Citation Formats

Berkowitz, Evan, and Rinaldi, Enrico. Calm multi-baryon operators. United States: N. p., 2017. Web.
Berkowitz, Evan, & Rinaldi, Enrico. Calm multi-baryon operators. United States.
Berkowitz, Evan, and Rinaldi, Enrico. Sun . "Calm multi-baryon operators". United States. doi:.
title = {Calm multi-baryon operators},
author = {Berkowitz, Evan and Rinaldi, Enrico},
abstractNote = {},
doi = {},
journal = {},
number = ,
volume = ,
place = {United States},
year = {Sun Jun 18 00:00:00 EDT 2017},
month = {Sun Jun 18 00:00:00 EDT 2017}

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  • The construction of the operators and correlators required to determine the excited baryon spectrum is presented, with the aim of exploring the spatial and spin structure of the states while minimizing the number of propagator inversions. The method used to construct operators that transform irreducibly under the symmetries of the lattice is detailed, and the properties of example operators is studied using domain-wall fermion valence propagators computed on MILC asqtad dynamical lattices.
  • We present results for ground and excited-state nucleon masses in quenched lattice QCD using anisotropic lattices. Group theoretical constructions of local and nonlocal straight-link irreducible operators are used to obtain suitable sources and sinks. Matrices of correlation functions are diagonalized to determine the eigenvectors. Both chi-square fitting and Bayesian inference with an entropic prior are used to extract masses from the correlation functions in a given channel. We observe clear separation of the excited state masses from the ground state mass. States of spin >= 5/2 have been isolated by use of G{sub 2} operators.
  • The design and implementation of large sets of spatially extended baryon operators for use in lattice simulations are described. The operators are constructed to maximize overlaps with the low-lying states of interest, while minimizing the number of sources needed in computing the required quark propagators.
  • The effects of Gaussian quark-field smearing and analytic stout-link smearing on the correlations of gauge-invariant extended baryon operators are studied. Gaussian quark-field smearing substantially reduces contributions from the short wavelength modes of the theory, while stout-link smearing significantly reduces the noise from the stochastic evaluations. The use of gauge-link smearing is shown to be crucial for baryon operators constructed of covariantly-displaced quark fields. Preferred smearing parameters are determined for a lattice spacing a_s ~ 0.1 fm.
  • Energies for excited light baryons are computed in quenched QCD with a pion mass of 490 MeV. Operators used in the simulations include local operators and the simplest nonlocal operators that have nontrivial orbital structures. All operators are designed with the use of Clebsch-Gordan coefficients of the octahedral group so that they transform irreducibly under the group rotations. Matrices of correlation functions are computed for each irreducible representation, and then the variational method is applied to separate mass eigenstates. We obtained 17 states for isospin 1/2 and 11 states for isospin 3/2 in various spin-parity channels including J{sup P}=5/2{sup {+-}}.more » The pattern of the lowest-lying energies from each irrep is discussed. We use anisotropic lattices of volume 24{sup 3} x 64 with temporal lattice spacing a{sub t}{sup -1}=6.05 GeV with renormalized anisotropy xi=3.0.« less