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Title: Positive and negative-parity flavor-octet baryons in coupled QCD sum rules

Abstract

We apply the method of the QCD sum rule, in which positive- and negative-parity baryons couple with each other, to the flavor-octet hyperons and investigate the parity splittings. We also reexamine the nucleon in the method, which was studied in our previous paper, by carefully choosing the Borel weight. Both in the nucleon and hyperon channels the obtained sum rules turn out to have a very good Borel stability and also have a Borel window, an energy region in which the OPE converges and the pole contribution dominates over the continuum contribution. The predicted masses of the positive- and negative-parity baryons reproduce the experimental ones fairly well in the {lambda} and {sigma} channels, if we assign the {lambda}(1670) and the {sigma}(1620) to the parity partners of the {lambda} and the {sigma}, respectively. This implies that the {lambda}(1405) is not the parity partner of the {lambda} and may be a flavor-singlet or exotic state. In the {xi} channel, the sum rule predicts the mass of the negative-parity state to be about 1.8 GeV, which leads to two possibilities; one is that the observed state with the closest mass, {xi}(1690), is the parity partner and the other is that the parity partnermore » is not yet found but exists around 1.8 GeV.« less

Authors:
; ; ;  [1];  [2];  [2];  [2]
  1. Kokugakuin University, Higashi, Shibuya, Tokyo 150-8440 (Japan)
  2. (Japan)
Publication Date:
OSTI Identifier:
21010986
Resource Type:
Journal Article
Resource Relation:
Journal Name: Physical Review. D, Particles Fields; Journal Volume: 75; Journal Issue: 3; Other Information: DOI: 10.1103/PhysRevD.75.034010; (c) 2007 The American Physical Society; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS; BARYON OCTETS; FLAVOR MODEL; GEV RANGE; LAMBDA-1405 BARYONS; LAMBDA-1670 BARYONS; NUCLEONS; PARITY; QUANTUM CHROMODYNAMICS; SIGMA BARYONS; SUM RULES; XI-1690 BARYONS

Citation Formats

Kondo, Yoshihiko, Morimatsu, Osamu, Nishikawa, Tetsuo, Kanada-En'yo, Yoshiko, Institute of Particle and Nuclear Studies, High Energy Accelerator Research Organization, 1-1, Ooho, Tsukuba, Ibaraki, 305-0801, Department of Physics, Tokyo Institute of Technology, 2-12-1, Oh-Okayama, Meguro, Tokyo 152-8551, and Yukawa Institute for Theoretical Physics, Kyoto University, Kyoto 606-8502. Positive and negative-parity flavor-octet baryons in coupled QCD sum rules. United States: N. p., 2007. Web. doi:10.1103/PHYSREVD.75.034010.
Kondo, Yoshihiko, Morimatsu, Osamu, Nishikawa, Tetsuo, Kanada-En'yo, Yoshiko, Institute of Particle and Nuclear Studies, High Energy Accelerator Research Organization, 1-1, Ooho, Tsukuba, Ibaraki, 305-0801, Department of Physics, Tokyo Institute of Technology, 2-12-1, Oh-Okayama, Meguro, Tokyo 152-8551, & Yukawa Institute for Theoretical Physics, Kyoto University, Kyoto 606-8502. Positive and negative-parity flavor-octet baryons in coupled QCD sum rules. United States. doi:10.1103/PHYSREVD.75.034010.
Kondo, Yoshihiko, Morimatsu, Osamu, Nishikawa, Tetsuo, Kanada-En'yo, Yoshiko, Institute of Particle and Nuclear Studies, High Energy Accelerator Research Organization, 1-1, Ooho, Tsukuba, Ibaraki, 305-0801, Department of Physics, Tokyo Institute of Technology, 2-12-1, Oh-Okayama, Meguro, Tokyo 152-8551, and Yukawa Institute for Theoretical Physics, Kyoto University, Kyoto 606-8502. Thu . "Positive and negative-parity flavor-octet baryons in coupled QCD sum rules". United States. doi:10.1103/PHYSREVD.75.034010.
@article{osti_21010986,
title = {Positive and negative-parity flavor-octet baryons in coupled QCD sum rules},
author = {Kondo, Yoshihiko and Morimatsu, Osamu and Nishikawa, Tetsuo and Kanada-En'yo, Yoshiko and Institute of Particle and Nuclear Studies, High Energy Accelerator Research Organization, 1-1, Ooho, Tsukuba, Ibaraki, 305-0801 and Department of Physics, Tokyo Institute of Technology, 2-12-1, Oh-Okayama, Meguro, Tokyo 152-8551 and Yukawa Institute for Theoretical Physics, Kyoto University, Kyoto 606-8502},
abstractNote = {We apply the method of the QCD sum rule, in which positive- and negative-parity baryons couple with each other, to the flavor-octet hyperons and investigate the parity splittings. We also reexamine the nucleon in the method, which was studied in our previous paper, by carefully choosing the Borel weight. Both in the nucleon and hyperon channels the obtained sum rules turn out to have a very good Borel stability and also have a Borel window, an energy region in which the OPE converges and the pole contribution dominates over the continuum contribution. The predicted masses of the positive- and negative-parity baryons reproduce the experimental ones fairly well in the {lambda} and {sigma} channels, if we assign the {lambda}(1670) and the {sigma}(1620) to the parity partners of the {lambda} and the {sigma}, respectively. This implies that the {lambda}(1405) is not the parity partner of the {lambda} and may be a flavor-singlet or exotic state. In the {xi} channel, the sum rule predicts the mass of the negative-parity state to be about 1.8 GeV, which leads to two possibilities; one is that the observed state with the closest mass, {xi}(1690), is the parity partner and the other is that the parity partner is not yet found but exists around 1.8 GeV.},
doi = {10.1103/PHYSREVD.75.034010},
journal = {Physical Review. D, Particles Fields},
number = 3,
volume = 75,
place = {United States},
year = {Thu Feb 01 00:00:00 EST 2007},
month = {Thu Feb 01 00:00:00 EST 2007}
}
  • Correlators of the octet baryons in the hot pion gas are studied in the framework of the QCD sum rule. The condensates appearing in the OPE side of the correlators become [ital T] dependent through the interaction with thermal pions. We present an explicit demonstration that the [ital O]([ital T][sup 2]) dependence of the condensates is completely compensated by the change of the pole residue and the [pi]+[ital B][r arrow][ital B][prime] scattering effect in the spectral functions. Therefore, the baryon masses are constant to this order, although [l angle][ital [bar u]u][r angle][sub [ital T]][congruent][l angle][ital [bar u]u][r angle][sub 0](1[minus][ital T][supmore » 2]/8[ital f][sub [pi]][sup 2]), which is consistent with the chiral symmetry constraint by Leutwyler and Smilga.« less
  • In this work, the strong coupling constants of the octet baryons to the K and {pi} mesons are studied within the Light Cone QCD sum rule method. It is well known that in the SU(3){sub f} limit, these couplings can be expressed in terms of only 2 constants, so called F and D constants. In this work, the SU(3){sub f} symmetry violating effects are also studied and it is shown that all the coupling constants can be expressed in terms of four analytical functions of the quark parameters.
  • Sum rules are derived relating Dirac mean square radii and anomalous magnetic moments of various couples of the ground state 1/2{sup +} octet baryons with the convergent integral of the difference of hadron photoproduction total cross-sections on the baryons. The chain of inequalities for corresponding total cross-sections has been found from those sum rules.
  • The coupling constants of K and {pi} mesons with the octet baryons are studied in light cone QCD sum rules taking into account SU(3){sub f} flavor symmetry breaking effects, but keeping the SU(2) isospin symmetry intact. It is shown that, in the SU(3){sub f} flavor symmetry breaking case, all of the couplings can be written in terms of four universal functions instead of F and D couplings which exist in the SU(3){sub f} symmetry case. A comparison of our results of kaon and pion-baryon couplings with existing theoretical and experimental results in the literature is performed.
  • A comprehensive study is made for the magnetic moments of octet baryons in the method of QCD sum rules. A complete set of QCD sum rules is derived using the external-field method and generalized interpolating fields. For each member, three sum rules are constructed from three independent tensor structures. They are analyzed in conjunction with the corresponding mass sum rules. The performance of each of the sum rules is examined using the criteria of operator product expansion convergence and ground-state dominance, along with the role of the transitions in intermediate states. Individual contributions from the u, d, and s quarksmore » are isolated and their implications in the underlying dynamics are explored. Valid sum rules are identified and their predictions are obtained. The results are compared with experiment and previous calculations.« less