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Register a new userThe meson $Z^+(4430)$ as a tetraquark state
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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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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 suggest that the recently discovered charm-strange meson D_sJ(2632), with unusual properties, could be a cyptoexotic tetraquark baryonium state cdd_bars_bar. We predict other four narrow states, as Regge recurrences of D_sJ(2632), below the possible baryon-antibaryon thresholds.
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.
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 $1^+$.
We propose to describe the heavy and exotic tetraquark state as a holographic molecule by binding the lightest heavy-light meson $(0^-, 1^-)$ multiplet to a flavored sphaleron in the bulk of the Witten-Sakai-Sugimoto model. The strongly bound tetraquark state emerges as an Efimov state with a binding energy that is comparable to that reported in recent lattice simulations and standard quark model estimates for bottom. Our construction finds charm and mixed charm-bottom tetraquark states to be also bound. The unique feature of these states stems from the fact that they are perhaps the first manifestation of the Efimov bound state mechanism in the hadronic world.
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