Diffractive dissociationn→pπ−π0induced by 12-GeV/cK−mesons

Abstract

A sample of 198 events, corresponding to a cross section of 110 \ifmmode\pm\else\textpm\fi{} 15 \ensuremath{\mu}b, has been isolated of the baryon-diffractive-dissociation process $n\ensuremath{\rightarrow}p{\ensuremath{\pi}}^{\ensuremath{-}}{\ensuremath{\pi}}^{0}$ for three-body masses less than 2.5 ${\mathrm{G}\mathrm{e}\mathrm{V}/\mathit{c}}^{2}$. These dissociations are induced by 12-GeV/c ${K}^{\ensuremath{-}}$ mesons. To isolate this process from background, it is necessary to observe the final-state proton explicitly by its ionization in the bubble chamber. The three-body mass spectrum seems different from that of the $n{\ensuremath{\pi}}^{+}{\ensuremath{\pi}}^{\ensuremath{-}}$ neutron diffractive breakup. A ${\ensuremath{\Delta}}^{0}$ signal is seen as well as possible ${N}_{1470}^{*}$, but no clear ${\ensuremath{\Delta}}^{+}$ is observed. The angular distribution of the proton in the $p{\ensuremath{\pi}}^{+}{\ensuremath{\pi}}^{\ensuremath{-}}$ rest frame indicates that a multiperipheral mechanism is present.