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

We study the S-wave DD̄^*(I=0) scattering at four different pion masses m_π ranging from 250 MeV to 417 MeV from Nf=2 lattice QCD. A bound state near the DD̄^* 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 DD̄^* 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.