X (3872) Relevant DD^* Scattering in Nf=2 Lattice QCD

We study the S-wave DD^* (I=0) scattering at four different pion masses m_ ranging from 250 MeV to 417 MeV from Nf=2 lattice QCD. A bound state near the DD^* threshold likely exists even after considering the possible left-hand cut effect due to the one pion exchange interaction. At m_ 417 MeV where the effective range expansion is valid, the compositeness of the bound state is X 1 and indicates a predominant DD^* 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.