Decay Probability Ratio of Pentaquark Θ State

The pentaquark state of Θ+(uudds) has been observed to decay with two decay modes: Θ+ → nK+ and Θ+ → pK0. The decay probability ratio of the two decay modes is studied with general symmetry consideration of isospin, spin, and parity. We arrive at a result of the ratio Γ(Θ →nK) Γ(Θ+→pK0) = (α−β) 2 (α+β)2 (1 k2 )2L+1, which is valid for the Θ+ state to be a pure isoscalar or isovector state, or an isotensor state with mixture of isoscalar and isovector components with coefficients α and β. The dependence on spin and parity of the pentaquark Θ+ state is found to be small due to small difference between the center of mass decay momenta k1 and k2 of the two decay modes. Future experimental results about the decay probability ratio may provide information about the isospin configuration of the pentaquark Θ+ state.