Search for Y(4260) in $$B \rightarrow Y(4260) K$$ Decay Mode at Belle

Abstract

Y(4260) is an exotic charmonium-like state with \(4230\pm 8\) MeV/\(c^2\) mass and \(55\pm 19\) MeV width. The \(Y(4260)'\)s decay to \(J/\psi \pi \pi \) suggests, it to be a charmonium (\(c\bar{c}\)) meson. But its mass is not consistent with any of \(1^{--}\) \(c\bar{c}\) state. Several models have been proposed to explain the nature of Y(4260) including \(c\bar{c}g\) hybrid model, tetraquark, \(D_1D\), \(D^0D^*\) molecule, \(J/\psi f_0(980)\) molecule, and so on. This state is so interesting that a charged state \(Z_c(3900)\) is observed in its decay mode and \(Z_c(3900)\) is a tetraquark state. Some recent studies suggest Y(4260) be an admixture of tetraquark and charmonium state. It has been suggested that the structure of Y(4260) can be estimated if one measured branching fraction of \(B\rightarrow Y(4260)K\). Till now, this state has been only produced by ISR or \(e^+e^-\) annihilation. We search for \(B \rightarrow Y (4260)K\), where \(Y(4260) \rightarrow J/\psi \pi \pi \) decay mode using the full \(\Upsilon (4S)\) data collected by the Belle detector at the asymmetric KEKB \(e^+e^-\) collider.