Observations of hyperon-nucleus systems produced on 12C and 7Li targets using the (K-, pi +) reaction at 715 MeV/c.

The hypernuclear systems ${\ensuremath{\Sigma}}^{\mathrm{\ensuremath{-}}}$${+}^{11}$B and ${\ensuremath{\Sigma}}^{\mathrm{\ensuremath{-}}}$${+}^{6}$He were produced by the (${K}^{\mathrm{\ensuremath{-}}}$,${\ensuremath{\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\ifmmode^\circ\else\textdegree\fi{} and 12\ifmmode^\circ\else\textdegree\fi{} 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 ${K}^{\mathrm{\ensuremath{-}}}$ experiments is not confirmed. The spectra do show enhancements over phase space near the thresholds of the \ensuremath{\Sigma} plus core hole states which are created when a proton in the target is converted into a \ensuremath{\Sigma}. 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.