Study the structure of X(3872) from its lineshape

We fit the invariant mass distribution of $X(3872)\to J\mathrm{/}\psi {\pi }^{+}{\pi }^{-}$ from LHCb using the propagator for S-wave near-threshold states in effective field theory. In this way, we can directly determine the $Z$ which measures the projection of the bound state on the compact state in $X(3872)$. Consequently, the structure of $X(3872)$ can be elucidated. Moreover, the fitting result also can describe well the data for $X(3872)\to D^0{\bar{D}}^{0\ast }$ from Belle experiment, which demonstrate the reliability of our fitting. The fitting indicates that $Z$ is a non-vanishing value within error, which supports that $X(3872)$ has a compact short-distant core.