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

LHCb Collaboration

Research output: Contribution to journalArticle (Academic Journal)peer-review


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 $1^+$.
Original languageEnglish
Pages (from-to)222002
Number of pages9
JournalPhysical Review Letters
Issue number22
Publication statusPublished - 6 Jun 2014

Bibliographical note

10 pages, 4 figures


  • hep-ex

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