Evidence for Splitting in theQRegion ofK+π+π−Mass

Abstract

We observe a splitting in the $K^{+}{\pi }^{+}{\pi }^{-}$ mass spectrum in $K^{+}d$ interactions at $9 \frac{\mathrm{GeV}}{c}$. We find a mass of $1243\pm 8 \frac{\mathrm{MeV}}{c^2}$ and a width of ${70}_{-18\mathrm{}}^{+26\mathrm{}}$ for the lower mass state, and a mass of 1344 ± 8 and a width of less than $60 \frac{\mathrm{MeV}}{c^2}$ for the higher mass state. The isospin of both states is determined to be ½. The results can be interpreted as evidence for the mixing of two $J^P=1^{+} K^{*}$ states.