QCD sum rules study of the meson Z^+(4430)

Abstract

We use QCD sum rules to study the recently observed meson $Z^{+}(4430)$, considered as a $D^{\ast }{D}_1$ 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 $m_Z=(4.40\pm 0.10)\text{GeV}$ in a very good agreement with the experimental value. We also make predictions for the analogous mesons $Z_s$ and $Z_{bb}$ considered as $D_s^{\ast }{D}_1$ and $B^{\ast }{B}_1$ molecules respectively. For $Z_s$ we predict $m_{Z_s}=(4.70\pm 0.06)\mathrm{GeV}$, which is above the $D_s^{\ast }{D}_1$ threshold, indicating that it is probably a very broad state and, therefore, difficult to be experimentally seen. For $Z_{bb}$ we predict $m_{Z_{bb}}=(10.74\pm 0.12)\mathrm{GeV}$, in agreement with quark model predictions.

Comments: 2 new figures included. version accepted for publication in Phys. Lett. B