Two-pole structure of the D0⁎(2400)

The so far only known charmed non-strange scalar meson is dubbed as D0⁎(2400) in the Review of Particle Physics. We show, within the framework of unitarized chiral perturbation theory, that there are in fact two (I=1/2,JP=0+) poles in the region of the D0⁎(2400) in the coupled-channel Dπ, Dη and DsK¯ scattering amplitudes. With all the parameters previously fixed, we predict the energy levels for the coupled-channel system in a finite volume, and find that they agree remarkably well with recent lattice QCD calculations. This successful description of the lattice data is regarded as a strong evidence for the two-pole structure of the D0⁎(2400). With the physical quark masses, the poles are located at (2105−8+6−i102−12+10) MeV and (2451−26+36−i134−8+7) MeV, with the largest couplings to the Dπ and DsK¯ channels, respectively. Since the higher pole is close to the DsK¯ threshold, we expect it to show up as a threshold enhancement in the DsK¯ invariant mass distribution. This could be checked by high-statistic data in future experiments. We also show that the lower pole belongs to the same SU(3) multiplet as the Ds0⁎(2317) state. Predictions for partners in the bottom sector are also given.