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

TL;DR

This paper employs QCD sum rules to analyze the Z^+(4430) meson as a D*D_1 molecule, accurately predicting its mass and extending the analysis to similar mesons Z_s and Z_bb.

Contribution

It provides the first QCD sum rule analysis of Z^+(4430) as a D*D_1 molecule and predicts masses for its strange and bottom counterparts.

Findings

Predicted Z^+(4430) mass as 4.40 GeV, matching experimental data.

Estimated Z_s mass at 4.70 GeV, likely a broad state.

Predicted Z_bb mass at 10.74 GeV, consistent with quark models.

Abstract

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 $m_Z=(4.40\pm0.10) \GeV$ 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 $m_{Z_{s}}= (4.70\pm 0.06) {\rm GeV}$, 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 $m_{Z_{bb}}= (10.74\pm 0.12) {\rm GeV}$, in agreement with quark model predictions.