Evidence for unnatural spin-parity states of (K ππ) 0 in the charge-exchange reaction K-p→( overlineK0π +π -) n

A partial-wave analysis of the (K ππ) ⁰ system produced in the charge exchange reaction K^-p→( overlineK⁰π ⁺π ^-) n has been made in the mass range 1.04 ⩽ M (K ππ) < 1.56 GeV c data at 8, 10 and 16 GeV/ c. It was found that in about {2}/{3} of the cases, the (K ππ) ⁰ system is produced in states of unnatural spin-parity, namely J^P = 0 ^- and 1 ⁺; the rest is in the natural spin-parity state J^P = 2 ⁺ state is consistent with being all K ^∗ (1420). The unnatural spin-parity states are produced mostly (∼ 80% of the events) by natural parity exchange. The facts that unnatural spin-parity states are produced in this non-diffractive channel, with J^P = 1 ⁺ dominant, and that the exchange responsible for their production is mostly of natural parity, are similar to what was found for the charged (K ππ) ^- system in the diffractive reaction K ^-p→(K ππ) ^-p. However, the absolute value and the energy dependence of the cross sections are very different in the two cases.