QCD sum rules study of the $J^{PC}=1^{--}$ charmonium $Y$ mesons

TL;DR

This study uses QCD sum rules to analyze the nature of Y(4260), Y(4350), and Y(4660) mesons, exploring tetraquark and molecular configurations to match experimental data.

Contribution

It provides mass estimates for tetraquark and molecular models of the Y mesons, testing their compatibility with observed states, and concludes that Y(4260) is unlikely a tetraquark.

Findings

Y(4660) compatible with $(c\bar{c}s\bar{s})$ tetraquark

Y(4350) consistent with $D_{s0}\bar{D}_s^*$ molecule

Y(4260) not explained as a tetraquark in this model

Abstract

We use QCD sum rules to test the nature of the recently observed mesons Y(4260), Y(4350) and Y(4660), assumed to be exotic four-quark $(c\bar{c}q\bar{q})$ or $(c\bar{c}s\bar{s})$ states with $J^{PC}=1^{--}$. We work at leading order in $\alpha_s$, consider the contributions of higher dimension condensates and keep terms which are linear in the strange quark mass $m_s$. We find for the $(c\bar{c}s\bar{s})$ state a mass $m_Y=(4.65\pm 0.10)$ GeV which is compatible with the experimental candidate Y(4660), while for the $(c\bar{c}q\bar{q})$ state we find a mass $m_Y=(4.49\pm 0.11)$ GeV, which is higger than the mass of the experimental candidate Y(4350). With the tetraquark structure we are working we can not explain the Y(4260) as a tetraquark state. We also consider molecular $D_{s0}\bar{D}_s^*$ and $D_{0}\bar{D}^*$ states. For the $D_{s0}\bar{D}_s^*$ molecular state we get $m_{D_{s0}\bar{D}_s^*}=(4.42\pm 0.10)$ GeV which is consistent, considering the errors, with the mass of the meson Y(4350) and for the $D_{0}\bar{D}^*$ molecular state we get $m_{D_{0}\bar{D}^*}=(4.27\pm 0.10)$ GeV in excelent agreement with the mass of the meson Y(4260).