X(3872) Relevant DD̅^* Scattering in N_f=2 Lattice QCD

We study the S-wave DD̅^*(I=0) scattering at four different pion masses m_π ranging from 250 MeV to 417 MeV from N_f=2 lattice QCD. A bound state near the DD̅^* threshold likely exists even after considering the possible left-hand cut effect due to the one pion exchange interaction. At m_π≈ 417 MeV where the effective range expansion is valid, the compositeness of the bound state is X≈ 1 and indicates a predominant DD̅^* component. This state may correspond to X(3872). On the other hand, our results of the finite volume energies also hint at the existence of a 1^++ resonance below 4.0 GeV with a width around 60 MeV.