Study of the Reaction ${\pi }^{-}p\to {\pi }^{-}{\pi }^{-}{\pi }^{-}{\pi }^{+}{\pi }^{+}p$ at 3.9 $\frac{\mathrm{GeV}}{c}$

We have obtained 459 events of the type ${\pi }^{-}p\to {\pi }^{-}{\pi }^{-}{\pi }^{-}{\pi }^{+}{\pi }^{+}p$ at 3.9 $\frac{\mathrm{GeV}}{c}$. The cross section is found to be 0.115±0.011 mb. Strong ${\Delta }^{++}\mathrm{}\left(1236\right)\mathrm{}$ production is observed, along with the production of ${\rho }^0$ in association with the ${\Delta }^{++}\mathrm{}\left(1236\right)\mathrm{}$. A statistically significant ${A_1}^{-}$ signal is present. An anomalous enhancement is observed at 1.4-GeV ${\pi }^{+}{\pi }^{+}p$ mass which is mainly caused by the strong ${\Delta }^{++}\mathrm{}\left(1236\right)\mathrm{}$ production. No meaningful structure is seen in any of the four- or five-body invariant-mass spectra. The data have been fitted with a model of incoherent resonance production.