Measurement of the Coherent Dissociation Reactionp+A→pπ+π−+A

The coherent reaction $p+A\to p{\pi }^{+}{\pi }^{-}+A$ was measured at 22.5 and 15.3 GeV in order to study diffraction dissociation free from normal Regge exchange background. Glauber-model analysis yields a $\mathrm{pN}\to N^{*}N$ signal in good agreement with $\mathrm{pp}$ scattering. Through the model it is found that ${\sigma }_T\left(N^{*}N\right)$ decreases rapidly from 36±3 mb for $M\left(N^{*}\right)=1.4\mathrm{}$ GeV to 18±4 mb for $M>~1.7$ GeV and that $\alpha \left(N^{*}N\right)\sim -0.5\mathrm{}$ for $M<\mathrm{}1.7\mathrm{}$ GeV.