Resonant structures in B-0 -> psi'pi K--(+) decays are analyzed by performing a four-dimensional fit of the decay amplitude, using pp collision data corresponding to 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)(-) -> 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(+).
LHCb Collaboration Martínez Vidal, Fernando Oyanguren Campos, Arantza Ruiz Valls, Pablo Sánchez Mayordomo, Carlos 2014 Observation of the Resonant Character of the Z(4430)(-) State Physical Review Letters 112 22 222002-1 222002-9
