An analysis of the K+π+π− system produced in 10 GeV/c K+ coherent interactions on nuclei

The coherent production process K+-nucleus→K+π+π−-nucleus has been analysed at 10 GeV/c, in a heavy liquid bubble chamber. Evidence for a coherent process is obtained from the momentum transfer distribution; the cross section is 2.12 ± 0.36 mb per nucleus. The K+π+π−, mass distribution of the coherent events shows abundant production of the so-called Q+ state, with a cross section of 1.70 ± 0.30 mb per nucleus. A Dalitz plot analysis of the K+π+π− system indicates JP=1+ for the Q+ with a high probability. The predominant decay is K∗π with some contribution of Kϱ. The density matrix elements for Q+ -production have been studied.