The scalar exotic resonances X(3915), X(3960), X_0(4140)

Abstract

The scalar resonances X(3915), X(3960), X_0(4140) are considered as exotic four-quark states: cqbar{c} bar{q}, csbar{c} bar{s}, csbar{c}bar{s}, while the X(3863) is proved to be the cbar{c}, 2,^3P_0 state. The masses and the widths of these resonances are calculated in the framework of the Extended Recoupling Model, where a four-quark system is formed inside the bag and has relatively small size (lesssim 1.0 fm). Then the resonance X(3915) appears due to the transitions: J/psi omega into D^{*+}D^{*-} (or D^{*0}bar{D}^{*0}) and back, while the X(3960) is created due to the transitions D_s^+D_s^- into J/psi phi and back, and the X_0(4140) is formed in the transitions J/psi phi into D_s^{*+}D_s^{*-} and back. The characteristic feature of the recoupling mechanism is that this type of resonances can be predominantly in the S-wave decay channels and has J^P=0^+. In two-channel case the resonance occurs to be just near the lower threshold, while due to coupling to third channel (like the cbar{c} channel) it is shifted up and lies by (20–30) MeV above the lower threshold. The following masses and widths are calculated: M(X(3915))=3920 MeV, Gamma (X(3915))=20 MeV; M(X(3960))=3970 MeV, Gamma (X(3960)=45(5) MeV, M(X_0(4140))= 4120(20) MeV, Gamma (X_0(4140))=100 MeV, which are in good agreement with experiment.