On the basis of assuming that the narrow state X(3872) is a molecule state consisting of D0andˉD*0, we apply the Mandelstam generalization of the Gell–Mann–Low method to calculate the matrix element of quark current between the heavy meson states described by Bether–Salpeter wave function. In calculation of the matrix element of quark current the operator product expansion is used in order to include the nonperturbative contribution of the vacuum condensates. In this scheme we calculate the mass of X(3872). We believe that this scheme is closer to QCD than the previous work.
On the basis of assuming that the narrow state X(3872) is a molecule state consisting of D0 and D*0, we apply the Mandelstam generalization of the Ge11-Mann-Low method to calculate the matrix element of quark current between the heavy meson states described by Bether-Salpeter wave function. In calculation of the matrix element of quark current the operator product expansion is used in order to include the nonperturbative contribution of the vacuum condensates. In this scheme we calculate the mass of X(3872). We believe that this scheme is closer to QCD than the previous work.