The reactions K −p→ π∓Σ±(1385) at 4.2 GeV/ c

Abstract

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 ∼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.