Quark spin content of the proton, hyperon semileptonic decays, and the decay width of the ${\Theta }^{+}$ pentaquark

Abstract

Using the exisiting experimental data for hyperon semileptonic decays and the flavor-singlet axial-vector charge $g_A^{(0)}$ from polarized deep inelastic scattering of the proton, we derive the decay width of the ${\Theta }^{+}$ 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 ${\Theta }^{+}$ pentaquark baryon as a function of the pion-nucleon sigma term ${\Sigma }_{\pi N}$ and investigate the dependence of the decay width of the ${\Theta }^{+}$ on the $g_A^{(0)}$, varying the $g_A^{(0)}$ within the range of the experimental uncertainty. We demonstrate that the combined values of all known semileptonic decays with the generally accepted value of $g_A^{(0)}\approx 0.3$ for the proton are compatible with a small decay width ${\Gamma }_{\Theta KN}$ of the ${\Theta }^{+}$ pentaquark, i.e. ${\Gamma }_{\Theta KN}\le 1$ MeV.

11 pages, 2 figures. Title has been changed, some of the text has been modified, and more references have been added. The final version accepted for publication in Phys. Rev. D

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• Axial-vector transitions and strong decays of the baryon antidecuplet in the self-consistent SU(3) chiral quark-soliton model
• Axial current matrix elements and pentaquark decay widths in chiral soliton models
• Magnetic and axial-vector transitions of the baryon antidecuplet
• On the Decay of Soliton Excitations