Observations of hyperon-nucleus systems produced on ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$ and ${}_{}{}^7{}_{}{}^{}\mathrm{Li}$ targets using the (${\mathrm{K}}^{\mathrm{-}}$,${\pi }^{+}$) reaction at 715 MeV/c

The hypernuclear systems ${\Sigma }^{\mathrm{-}}$${+}^{11}$B and ${\Sigma }^{\mathrm{-}}$${+}^6$He were produced by the ($K^{\mathrm{-}}$,${\pi }^{+}$) reaction on targets on ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$ (graphite) and ${}_{}{}^7{}_{}{}^{}\mathrm{Li}$ using 715 MeV/c incident kaons. Spectra were measured at reaction angles of 4° and 12° to investigate the momentum transfer dependence. A decay detector surrounded the target to provide a decay mode tag. Data were analyzed with and without this tag. The resulting spectra for the ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$ target are similar to previous results with the exception that the narrow structure reported in the stopped $K^{\mathrm{-}}$ experiments is not confirmed. The spectra do show enhancements over phase space near the thresholds of the Σ plus core hole states which are created when a proton in the target is converted into a Σ. The decay mode cut shows a correlation between sigma-lambda conversion and this structure. No evidence of narrow states in either hypernucleus is observed in either the tagged or untagged data.