  A large correlation of production and decay planes of
(\pi^-\pi^+\pi^-)-system in dissociation of $\pi^-$-beam 40 GeV/c on nuclear
targets was observed. The dependence of the correlation on atomic number,
Feynmann variable and transversal momentum as well as on invariant mass of the
pion triple and neutral pion pair were investigated. It was shown that the
phenomenon has a clear dynamic origin and resembles the single spin asymmetry
behavior.
