A model-independent confirmation of the $Z(4430)^-$ state

TL;DR

This paper provides a model-independent confirmation of the $Z(4430)^-$ state by analyzing $B^0$ decays, showing that the observed spectrum cannot be explained solely by known $K o ext{reflection}$ effects.

Contribution

It introduces a model-independent method to confirm the $Z(4430)^-$ state, avoiding assumptions about resonance shapes or interference.

Findings

The $ ext{psi}(2S) o ext{pi}$ mass spectrum cannot be explained by $K o ext{reflection}$ alone.

The data reject the $K o ext{reflection}$ hypothesis with more than 8$\sigma$ significance.

Confirmation of the $Z(4430)^-$ as an exotic resonance.

Abstract

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