The reactions K-p → π-+Σ+-(1385) at 4.2 GeV/c

The reactions K-p → π-Σ+(1385) and K-p → π+Σ-(1385) are studied at 4.2 GeV/c incident momentum using data from a high statistics bubble chamber experiment corresponding to approximately 80 events/μb. The total and differential cross sections are presented. Amplitude analyses are performed and the complete Σ+-(1385) helicity spin density matrices are extracted. The results are compared with the predictions of the additive quark model and exchange degeneracy. A substantial cross section is observed for the reaction K-p → π+Σ-(1385) in the forward direction, which implies exotic meson quantum numbers in the t-channel. One possible interpretation of this process provides an explanation for the small but significant violations of the additive quark model predictions observed in the reaction K-p → π-Σ+(1385) at low four-momentum transfer. In the backward direction unnatural parity exchange is shown to give a larger contribution to K-p → Σ-(1385)π+ than natural parity exchange. (Auth.)