# Observation of the resonant character of the $Z(4430)^-$ state

Abstract : Resonant structures in $B^0\to\psi'\pi^-K^+$ decays are analyzed by performing a four-dimensional fit of the decay amplitude, using $pp$ collision data corresponding to $\rm 3 fb^{-1}$ collected with the LHCb detector. The data cannot be described with $K^+\pi^-$ resonances alone, which is confirmed with a model-independent approach. A highly significant $Z(4430)^-\to\psi'\pi^-$ component is required, thus confirming the existence of this state. The observed evolution of the $Z(4430)^-$ amplitude with the $\psi'\pi^-$ mass establishes the resonant nature of this particle. The mass and width measurements are substantially improved. The spin-parity is determined unambiguously to be $1^+$.
Document type :
Journal articles

http://hal.in2p3.fr/in2p3-00975399
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Submitted on : Tuesday, April 8, 2014 - 3:34:33 PM
Last modification on : Sunday, June 26, 2022 - 12:01:11 PM

### Citation

R. Aaij, Y. Amhis, S. Barsuk, O. Callot, J. He, et al.. Observation of the resonant character of the $Z(4430)^-$ state. Physical Review Letters, American Physical Society, 2014, 112, pp.222002. ⟨10.1103/PhysRevLett.112.222002⟩. ⟨in2p3-00975399⟩

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