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Title: The Nc dependencies of baryon masses: Analysis with Lattice QCD and Effective Theory

Abstract

Baryon masses at varying values of Nc and light quark masses are studied with Lattice QCD and the results are analyzed in a low energy effective theory based on a combined framework of the 1/Nc and Heavy Baryon Chiral Perturbation Theory expansions. Lattice QCD results for Nc=3, 5 and 7 obtained in quenched calculations, as well as results for unquenched calculations for Nc=3, are used for the analysis. The results are consistent with a previous analysis of Nc=3 LQCD results, and in addition permit the determination of sub-leading in 1/Nc effects in the spin-flavor singlet component of the baryon masses as well as in the hyperfine splittings.

Authors:
 [1];  [2];  [1]
  1. JLAB
  2. University of Colorado
Publication Date:
Research Org.:
Thomas Jefferson National Accelerator Facility, Newport News, VA (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Nuclear Physics (NP) (SC-26)
OSTI Identifier:
1136853
Report Number(s):
JLAB-THY-14-1866; DOE/OR/23177-3040; arXiv:1404.2301
FG02-04ER41290; NSF PHY-0855789; NSF PHY-1307413
DOE Contract Number:
AC05-06OR23177
Resource Type:
Journal Article
Resource Relation:
Journal Name: Physical Review D; Journal Volume: 90; Journal Issue: 01
Country of Publication:
United States
Language:
English

Citation Formats

Calle Cordon, Alvaro C., DeGrand, Thomas A., and Goity, Jose L. The Nc dependencies of baryon masses: Analysis with Lattice QCD and Effective Theory. United States: N. p., 2014. Web. doi:10.1103/PhysRevD.90.014505.
Calle Cordon, Alvaro C., DeGrand, Thomas A., & Goity, Jose L. The Nc dependencies of baryon masses: Analysis with Lattice QCD and Effective Theory. United States. doi:10.1103/PhysRevD.90.014505.
Calle Cordon, Alvaro C., DeGrand, Thomas A., and Goity, Jose L. Tue . "The Nc dependencies of baryon masses: Analysis with Lattice QCD and Effective Theory". United States. doi:10.1103/PhysRevD.90.014505. https://www.osti.gov/servlets/purl/1136853.
@article{osti_1136853,
title = {The Nc dependencies of baryon masses: Analysis with Lattice QCD and Effective Theory},
author = {Calle Cordon, Alvaro C. and DeGrand, Thomas A. and Goity, Jose L.},
abstractNote = {Baryon masses at varying values of Nc and light quark masses are studied with Lattice QCD and the results are analyzed in a low energy effective theory based on a combined framework of the 1/Nc and Heavy Baryon Chiral Perturbation Theory expansions. Lattice QCD results for Nc=3, 5 and 7 obtained in quenched calculations, as well as results for unquenched calculations for Nc=3, are used for the analysis. The results are consistent with a previous analysis of Nc=3 LQCD results, and in addition permit the determination of sub-leading in 1/Nc effects in the spin-flavor singlet component of the baryon masses as well as in the hyperfine splittings.},
doi = {10.1103/PhysRevD.90.014505},
journal = {Physical Review D},
number = 01,
volume = 90,
place = {United States},
year = {Tue Jul 01 00:00:00 EDT 2014},
month = {Tue Jul 01 00:00:00 EDT 2014}
}
  • We investigate the quark mass dependence of baryon masses in 2+1 flavor lattice QCD using SU(3) heavy baryon chiral perturbation theory up to one-loop order. The baryon mass data used for the analyses are obtained for the degenerate up-down quark mass of 3 to 24 MeV and two choices of the strange quark mass around the physical value. We find that the SU(3) chiral expansion fails to describe both the octet and the decuplet baryon data if phenomenological values are employed for the meson-baryon couplings. The SU(2) case is also examined for the nucleon. We observe that higher order termsmore » are controlled only around the physical point. We also evaluate finite size effects using SU(3) heavy baryon chiral perturbation theory, finding small values of order 1% even at the physical point.« less
  • We apply black-box methods, i.e. where the performance of the method does not depend upon initial guesses, to extract excited-state energies from Euclidean-time hadron correlation functions. In particular, we extend the widely used effective-mass method to incorporate multiple correlation functions and produce effective mass estimates for multiple excited states. In general, these excited-state effective masses will be determined by finding the roots of some polynomial. We demonstrate the method using sample lattice data to determine excited-state energies of the nucleon and compare the results to other energy-level finding techniques.
  • We apply black-box methods, i.e. where the performance of the method does not depend upon initial guesses, to extract excited-state energies from Euclidean-time hadron correlation functions. In particular, we extend the widely used effective-mass method to incorporate multiple correlation functions and produce effective mass estimates for multiple excited states. In general, these excited-state effective masses will be determined by finding the roots of some polynomial. We demonstrate the method using sample lattice data to determine excited-state energies of the nucleon and compare the results to other energy-level finding techniques.
  • The excited baryon masses are analyzed in the framework of the 1/Nc expansion using the available physical masses and also the masses obtained in lattice QCD for different quark masses. The baryon states are organized into irreducible representations of SU(6) x O(3), where the [56,l P=0⁺] ground state and excited baryons, and the [56,2 +] and [70}},1 -] excited states are analyzed. The analyses are carried out to order O(1/N c) and first order in the quark masses. The issue of state identifications is discussed. Numerous parameter independent mass relations result at those orders, among them the well known Gell-Mann-Okubomore » and Equal Spacing relations, as well as additional relations involving baryons with different spins. It is observed that such relations are satisfied at the expected level of precision. The main conclusion of the analysis is that qualitatively the dominant physical effects are similar for the physical and the lattice QCD baryons.« less