Observation of a Narrow Antibaryon State at 2.26 ${\mathrm{G}\mathrm{e}\mathrm{V}/\mathit{c}}^2$

We report evidence, from a study of multihadron final states produced in the wide-band photon beam at Fermilab, for the production of a new antibaryon state which decays into $\overline{\Lambda }{\pi }^{-}{\pi }^{-}{\pi }^{+}$. The mass of this state is 2.26 ± 0.01 ${\mathrm{G}\mathrm{e}\mathrm{V}/\mathit{c}}^2$ and its decay width is less than 75 ${\mathrm{M}\mathrm{e}\mathrm{V}/\mathit{c}}^2$. We also report evidence of a state of higher mass (∼2.5 ${\mathrm{G}\mathrm{e}\mathrm{V}/\mathit{c}}^2$) which decays into the state at 2.26 ${\mathrm{G}\mathrm{e}\mathrm{V}/\mathit{c}}^2$.