Coherent Production of theK−π+π−System inK−−dInteractions at 5.5 GeV/c

$K^{-}d$ interactions were studied at an incident momentum of 5.5 GeV/c in a 5-eV/μb exposure of the 30-in. deuterium bubble chamber at the Argonne Zero-Gradient Synchrotron. The dominant feature of the reaction $K^{-}d\to K^{-}{\pi }^{+}{\pi }^{-}d$ is ${\overline{K}}^{*}\mathrm{}\left(890\right)\mathrm{}$ production, although the low-mass enhancement, usually referred to as $d^{*}$, is also prominent in the $d{\pi }^{-}$ mass spectrum. The low momentum transfer to the deuteron imposed by coherent production strongly favors a $K\pi \pi$ mass in the region of the $Q$ enhancement. As is usually observed, the production and decay characteristics of the $K\pi \pi$ system are generally compatible with a $1^{+}$ spin-parity assignment. A study of the $K^{-}{\pi }^{+}$ system reveals an $s$-wave-$p$-wave interference similar to that observed in $K\pi$ scattering. The data are compared with the predictions of a double-Regge-pole model.