Investigating different structures of the Z_{b}(10610) and Z_{b}(10650)

Abstract

The recently observed narrow resonance $Z_b(10610)$ is examined with the assumptions both as a $B^{\ast }\bar{B}$ molecular state and a $[bd][\bar{b}\bar{u}]$ tetraquark state with quantum numbers $I^G{J}^P=1^{+}{1}^{+}$. Possible interpolating currents are constructed to describe the $Z_b(10650)$ as an axial-vector $B^{\ast }{\bar{B}}^{\ast }$ molecular state or a $[bd][\bar{b}\bar{u}]$ tetraquark state. Using QCD sum rules (QCDSR), we consider contributions up to dimension six in the operator product expansion (OPE) at the leading order in ${\alpha }_s$. The mass is obtained as $(10.44\pm 0.23)GeV$ for molecular state and $(10.50\pm 0.19)GeV$ for tetraquark state, both of which coincide with the $Z_b(10610)$. The results $m_{B^{\ast }{\bar{B}}^{\ast }}=(10.45\pm 0.31)GeV$ and $m_{[bd][\bar{b}\bar{u}]}=(10.48\pm 0.33)GeV$ are consistent with the $Z_b(10650)$.

Comments: 17 pages, 9 figures