skip to main content
OSTI.GOV title logo U.S. Department of Energy
Office of Scientific and Technical Information

Title: Quark spin content of the proton, hyperon semileptonic decays, and the decay width of the {theta}{sup +} pentaquark

Abstract

Using the exisiting experimental data for hyperon semileptonic decays and the flavor-singlet axial-vector charge g{sub A}{sup (0)} from polarized deep inelastic scattering of the proton, we derive the decay width of the {theta}{sup +} pentaquark baryon. We take into account the effects of flavor SU(3) symmetry breaking within the framework of the chiral quark-soliton model. All dynamical parameters of the model are fixed by using the five experimental hyperon semileptonic decay constants and flavor-singlet axial-vector charge. We obtain the numerical results of the decay width of the {theta}{sup +} pentaquark baryon as a function of the pion-nucleon sigma term {sigma}{sub {pi}}{sub N} and investigate the dependence of the decay width of the {theta}{sup +} on the g{sub A}{sup (0)}, varying the g{sub A}{sup (0)} within the range of the experimental uncertainty. We demonstrate that the combined values of all known semileptonic decays with the generally accepted value of g{sub A}{sup (0)}{approx_equal}0.3 for the proton are compatible with a small decay width {gamma}{sub {theta}}{sub KN} of the {theta}{sup +} pentaquark, i.e. {gamma}{sub {theta}}{sub KN}{<=}1 MeV.

Authors:
;  [1];  [2]
  1. Institut fuer Theoretische Physik II, Ruhr-Universitaet Bochum, D-44780 Bochum (Germany)
  2. Department of Physics, and Nuclear Physics and Radiation Technology Institute (NuRI), Pusan National University, 609-735 Busan (Korea, Republic of)
Publication Date:
OSTI Identifier:
21020476
Resource Type:
Journal Article
Resource Relation:
Journal Name: Physical Review. D, Particles Fields; Journal Volume: 75; Journal Issue: 9; Other Information: DOI: 10.1103/PhysRevD.75.094004; (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; CHIRALITY; DEEP INELASTIC SCATTERING; FLAVOR MODEL; HYPERONS; MEV RANGE; PARTICLE WIDTHS; PION-NUCLEON INTERACTIONS; PIONS; PROTONS; QUARKS; REST MASS; SEMILEPTONIC DECAY; SOLITONS; SPIN; SU-3 GROUPS

Citation Formats

Yang, Ghil-Seok, Goeke, Klaus, and Kim, Hyun-Chul. Quark spin content of the proton, hyperon semileptonic decays, and the decay width of the {theta}{sup +} pentaquark. United States: N. p., 2007. Web. doi:10.1103/PHYSREVD.75.094004.
Yang, Ghil-Seok, Goeke, Klaus, & Kim, Hyun-Chul. Quark spin content of the proton, hyperon semileptonic decays, and the decay width of the {theta}{sup +} pentaquark. United States. doi:10.1103/PHYSREVD.75.094004.
Yang, Ghil-Seok, Goeke, Klaus, and Kim, Hyun-Chul. Tue . "Quark spin content of the proton, hyperon semileptonic decays, and the decay width of the {theta}{sup +} pentaquark". United States. doi:10.1103/PHYSREVD.75.094004.
@article{osti_21020476,
title = {Quark spin content of the proton, hyperon semileptonic decays, and the decay width of the {theta}{sup +} pentaquark},
author = {Yang, Ghil-Seok and Goeke, Klaus and Kim, Hyun-Chul},
abstractNote = {Using the exisiting experimental data for hyperon semileptonic decays and the flavor-singlet axial-vector charge g{sub A}{sup (0)} from polarized deep inelastic scattering of the proton, we derive the decay width of the {theta}{sup +} pentaquark baryon. We take into account the effects of flavor SU(3) symmetry breaking within the framework of the chiral quark-soliton model. All dynamical parameters of the model are fixed by using the five experimental hyperon semileptonic decay constants and flavor-singlet axial-vector charge. We obtain the numerical results of the decay width of the {theta}{sup +} pentaquark baryon as a function of the pion-nucleon sigma term {sigma}{sub {pi}}{sub N} and investigate the dependence of the decay width of the {theta}{sup +} on the g{sub A}{sup (0)}, varying the g{sub A}{sup (0)} within the range of the experimental uncertainty. We demonstrate that the combined values of all known semileptonic decays with the generally accepted value of g{sub A}{sup (0)}{approx_equal}0.3 for the proton are compatible with a small decay width {gamma}{sub {theta}}{sub KN} of the {theta}{sup +} pentaquark, i.e. {gamma}{sub {theta}}{sub KN}{<=}1 MeV.},
doi = {10.1103/PHYSREVD.75.094004},
journal = {Physical Review. D, Particles Fields},
number = 9,
volume = 75,
place = {United States},
year = {Tue May 01 00:00:00 EDT 2007},
month = {Tue May 01 00:00:00 EDT 2007}
}
  • In this article, we take the point of view that the pentaquark state {theta}{sup +}(1540) has negative parity, and choose the diquark-triquark type interpolating current to calculate the strong coupling constant g{sub {theta}}{sub NK} in the QCD sum rules approach. Our numerical results indicate the values of the strong coupling constant g{sub {theta}}{sub NK} are very small, |g{sub {theta}}{sub NK}|=0.175{+-}0.084, and the width is {gamma}{sub {theta}}<4 MeV, which can explain the narrow width {gamma}{<=}10 MeV naturally.
  • We report on a high-statistics search for the {theta}(1540){sup +} resonance in {sigma}{sup -}-nucleus collisions at 340 GeV/c. No evidence for this resonance was found in our data sample which contains 13 million K{sub s}{sup 0}{yields}{pi}{sup +}{pi}{sup -} decays above background. For the decay channel {theta}{sup +}{yields}K{sub s}{sup 0}p and the kinematic range x{sub F}> 0.05, we find the production cross section to be BR({theta}{sup +}{yields}K{sub s}{sup 0}p){sigma}{sub 0}<1.8 {mu}b per nucleon at 99% C.L.
  • We calculate the width of the {theta}{sup +}(1540) pentaquark in a relativistic model in which the pentaquark is considered to be composed of a scalar diquark and a spin 1/2 triquark. We consider both positive and negative parity for the pentaquark. There is a single parameter in our model which we vary and which describes the size of the pentaquark. If the pentaquark size is somewhat smaller than that of the nucleon, we find quite small widths for the pentaquark of about 1 MeV or less. Our model of confinement plays an important role in our analysis and makes itmore » possible to use Feynman diagrams to describe the decay of the pentaquark.« less
  • The data on the reactions K{sup +}Xe {sup {yields}}K{sup 0{gamma}}X and K{sup +}Xe {sup {yields}}K{sup +{gamma}}X, obtained with the bubble chamber DIANA, have been analyzed for possible radiative decays of the {Theta}{sup +}(1540) baryon: {Theta}{sup +} {sup {yields}}K{sup 0}p{gamma} and {Theta}{sup +} {sup {yields}}K{sup +}n{gamma}. No signals have been observed, and we derive the upper limits {Gamma}({Theta}{sup +} {sup {yields}}K{sup 0}p{gamma})/{Gamma}({Theta}{sup +} {sup {yields}}K{sup 0}p) < 0.032 and {Gamma}({Theta}{sup +} {sup {yields}}K{sup +}n{gamma})/{Gamma}({Theta}{sup +} {sup {yields}}K{sup +}n{gamma}) < 0.041 which, using our previous measurement of {Gamma}({Theta}{sup +} {sup {yields}}KN) = 0.39 {+-} 0.10 MeV, translate to {Gamma}({Theta}{sup +} {sup {yields}}K{supmore » 0}p{gamma}) < 8 keV and {Gamma}({Theta}{sup +} {sup {yields}}K{sup +}n{gamma}) < 11 keV at 90% confidence level. We have also measured the cross sections of K{sup +}-induced reactions involving emission of a neutral pion: {sigma}(K{sup +}n {sup {yields}}K{sup 0}p{pi}{sup 0}) = 68 {+-} 18 {mu}b and {sigma}(K{sup +}N {sup {yields}}K{sup +}N{pi}{sup 0}) = 30 {+-} 8 {mu}b for incident K{sup +} momentum of 640 MeV.« less
  • We investigate the {ital B} and {ital D} mesons in the relativistic quark model by applying the variational method with the Gaussian wave function. We calculate the Fermi momentum parameter {ital p}{sub {ital F}}, and obtain {ital p}{sub {ital F}}=0.50{minus}0.54 GeV, which is almost independent of the input parameters {alpha}{sub {ital s}}, {ital m}{sub {ital b}}, {ital m}{sub {ital c}}, and {ital m}{sub {ital sp}}. We then calculate the ratio {ital f}{sub {ital B}}/{ital f}{sub {ital D}}, and obtain a result which is larger, by a factor of about 1.3, than {radical}{ital M}{sub {ital D}}/{ital M}{sub {ital B}} given bymore » the naive nonrelativistic analogy. This result is in a good agreement with the recent lattice calculations. We also calculate the ratio ({ital M}{sub {ital B}{sup {asterisk}}}{minus}{ital M}{sub {ital B}})/({ital M}{sub {ital D}{sup {asterisk}}}{minus}{ital M}{sub {ital D}}). In these calculations the wave function at the origin {psi}(0) is essential. We also determine {ital p}{sub {ital F}} by comparing the theoretical prediction of the ACCMM model with the lepton energy spectrum of {ital B}{r_arrow}{ital e}{nu}{ital X} from the recent ARGUS analysis, and find that {ital p}{sub {ital F}}=0.27{plus_minus}{sub 0.27}{sup 0.22} GeV, when we use {ital m}{sub {ital c}}=1.5 GeV. However, this experimentally determined value of {ital p}{sub {ital F}} is strongly dependent on the value of the input parameter {ital m}{sub {ital c}}. {copyright} {ital 1996 The American Physical Society.}« less