A study of the ηπ0 system produced in the reaction π−p → π+π−4γ n at 18 GeV/c Original Research Article

The exclusive reaction π−p → ηπ0n, η → π+π−π0, π0 → 2γ at 18 GeV/c has been studied. A partial wave analysis has been performed on a sample of 18712 ηπ0n events. A mass dependent fit of the P+ and D+ waves and their relative phase gives evidence for a neutral exotic JPC = 1−+ state production, where C-parity is a good quantum number.