Model-independent confirmation of theZ(4430)−state

The decay ${B}^{0}\ensuremath{\rightarrow}\ensuremath{\psi}(2S){K}^{+}{\ensuremath{\pi}}^{\ensuremath{-}}$ is analyzed using $3\text{ }\text{ }{\mathrm{fb}}^{\ensuremath{-}1}$ of $pp$ collision data collected with the LHCb detector. A model-independent description of the $\ensuremath{\psi}(2S)\ensuremath{\pi}$ mass spectrum is obtained, using as input the $K\ensuremath{\pi}$ mass spectrum and angular distribution derived directly from data, without requiring a theoretical description of resonance shapes or their interference. The hypothesis that the $\ensuremath{\psi}(2S)\ensuremath{\pi}$ mass spectrum can be described in terms of $K\ensuremath{\pi}$ reflections alone is rejected with more than $8\ensuremath{\sigma}$ significance. This provides confirmation, in a model-independent way, of the need for an additional resonant component in the mass region of the $Z(4430{)}^{\ensuremath{-}}$ exotic state.