Calculation of mass of Y(4140) by introducing mixed molecule state in quark model

Using the general form of the Bethe–Salpeter wave functions for the bound states consisting of two vector fields given in our previous work, we investigate the molecular state composed of Ds⁎+Ds⁎−. However, for the SU(3) symmetry the component Ds⁎+Ds⁎− is coupled with the other components D⁎0D¯⁎0 and D⁎+D⁎−D⁎+D⁎−. Then we interpret the internal structure of the observed Y(4140)Y(4140) state as a mixed state of pure molecule states D⁎0D¯⁎0, D⁎+D⁎−D⁎+D⁎− and Ds⁎+Ds⁎− with quantum numbers JP=0+JP=0+. In this paper, the operator product expansion is used to introduce the nonperturbative contribution from the vacuum condensates into the interaction between two heavy mesons. The calculated mass of Y(4140)Y(4140) is consistent with the experimental value, and we conclude that it is a more reasonable scenario to explain the structure of Y(4140)Y(4140) as a mixture of pure molecule states.