Search for NarrowN¯NStates near Threshold

A missing-mass experiment in $\mathrm{pd}\to \mathrm{NX}$, where $X$ is the system whose mass $M_X$ is measured, was performed for interactions of antiprotons at rest and in flight below 500 MeV/c. The 4-standard-deviation upper limit for the production of narrow states, in the mass interval $M_X=1650-1930\mathrm{}$ MeV/${\mathit{c}}^2$, is 2 mb for annihilations in flight and 0.3% of the annihilations at rest.