Evidence for $Z_c^{\pm }(3900)$ in semi-inclusive decays of $b$-flavored hadrons

We present evidence for the exotic charged charmonium-like state $Z_c^{\pm }(3900)$ in semi-inclusive weak decays of $b$-flavored hadrons. The signal is correlated with a $J\mathrm{/}\psi {\pi }^{+}{\pi }^{-}$ system in the invariant mass range 4.2$-$4.7~GeV and includes the sequential process $b$-quark hadron $\to Y(4260)+$ anything, $Y(4260) \rightarrow Z_c^{\pm}(3900) \pi^{\mp}$,$Z_c^{\pm}(3900) \rightarrow J/\psi \pi^{\pm}$. The study is based on $10.4\mathrm{f}{\mathrm{b}}^{-1}$ of $p\bar{p}$ collision data collected by the D0 experiment at the Fermilab Tevatron collider.