A 0 0 (980)-ƒ 0(980) mixing and spin asymmetry in the π− p→ηπ 0 n reaction

Abstract

The mass difference between the K+ and K0 mesons induces mixing of the a 0 0 (980) and f0(980) resonances. The mixing amplitude is large, on the order of \(m(m_{K^0 }^2 - m_{K^ + }^2 )^{1/2} \approx \sqrt \alpha m_K^2 \) near the \(K\bar K\) thresholds, and its phase changes sharply by 90°. A high-energy experiment on the π−p→η π 0n reaction in a polarized target is proposed. In this experiment, the presence of a 0 0 (980)−f0(980) mixing can be unambiguously and simply identified by the presence of a large jump in the azimuthal asymmetry of the cross section for production of the ηπ0 system in the S wave near the \(K\bar K\) thresholds. Our estimates of the magnitude of the polarization effect, which is expected to be observed in the experiment, are almost model-independent.