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Register a new userExperimental constraints on the spin and parity of the Z(4430)+
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We perform a full amplitude analysis of B0 -> psi K+ pi- decays, with psi -> mu+ mu- or e+ e-, to constrain the spin and parity of the Z(4430)-. The J^P=1+ hypothesis is favored over the 0-, 1-, 2- and 2+ hypotheses at the levels of 3.4 sigma, 3.7 sigma, 4.7 sigma and 5.1 sigma, respectively. The analysis is based on a 711 fb^-1 data sample that contains 772x10^6 B B pairs, collected at the Y(4S) resonance by the Belle detector at the asymmetric-energy e+ e- collider KEKB.
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The X(3872) and Z(4430) are candidates of tetraquark state with a ccbar pair. We present results from Belle recently updated for the mass, branching fractions etc. in different production/decay processes of the X(3872). Results from a Dalitz analysis for B --> Z(4430) K --> psi pi^+- K are also presented.
Resonant structures in $B^0topsipi^-K^+$ 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 $Z(4430)^-topsipi^-$ component is required, thus confirming the existence of this state. The observed evolution of the $Z(4430)^-$ amplitude with the $psipi^-$ mass establishes the resonant nature of this particle. The mass and width measurements are substantially improved. The spin-parity is determined unambiguously to be $1^+$.
The decay $B^0to psi(2S) K^+pi^-$ 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 $Kpi$ 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 $Kpi$ 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.
We use QCD sum rules to study the recently observed meson $Z^+(4430)$, considered as a $D^*D_1$ molecule with $J^{P}=0^{-}$. We consider the contributions of condensates up to dimension eight and work at leading order in $alpha_s$. We get $m_Z=(4.40pm0.10) GeV$ in a very good agreement with the experimental value. We also make predictions for the analogous mesons $Z_{s}$ and $Z_{bb}$ considered as $D_s^*D_1$ and $B^*B_1$ molecules respectively. For $Z_{s}$ we predict $m_{Z_{s}}= (4.70pm 0.06) {rm GeV}$, which is above the $D_s^*D_1$ threshold, indicating that it is probably a very broad state and, therefore, difficult to be experimentally seen. For $Z_{bb}$ we predict $m_{Z_{bb}}= (10.74pm 0.12) {rm GeV}$, in agreement with quark model predictions.
We test the validity of the QCD sum rules applied to the meson $Z^+(4430)$, by considering a diquark-antidiquark type of current with $J^{P}=0^{-}$ and with $J^{P}=1^{-}$. We find that, with the studied currents, it is possible to find an acceptable Borel window. In such a Borel window we have simultaneously a good OPE convergence and a pole contribution which is bigger than the continuum contribution. We get $m_Z=(4.52pm0.09)GeV$ and $m_Z=(4.84pm0.14)GeV$ for the currents with $J^{P}=0^{-}$ and $J^{P}=1^{-}$ respectively. We conclude that the QCD sum rules results favors $J^{P}=0^{-}$ quantum numbers for the $Z^+(4430)$ meson.
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