Evidence for a narrow dip structure at 1.9 GeV/c$^2$ in $3π^+ 3π^- $ diffractive photoproduction

A narrow dip structure has been observed at 1.9 GeV/c$^2$ in a study of diffractive photoproduction of the $~3\pi^+3\pi^-$ final state performed by the Fermilab experiment E687.