Quark spin content of the proton, hyperon semileptonic decays, and the decay width of the Θ+ pentaquark

Using the exisiting experimental data for hyperon semileptonic decays and the flavor-singlet axial-vector charge gA(0) from polarized deep inelastic scattering of the proton, we derive the decay width of the Θ+ 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 Θ+ pentaquark baryon as a function of the pion-nucleon sigma term ΣπN and investigate the dependence of the decay width of the Θ+ on the gA(0), varying the gA(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 gA(0)≅0.3 for the proton are compatible with a small decay width ΓΘKN of the Θ+ pentaquark, i.e. ΓΘKN≤1 MeV