We perform a study of the $X(3872)$ lineshape using the data samples of $e^+e^-\to\gamma X(3872)$, $X(3872)\to D^0\bar{ D}^0 \pi^0$ and $\pi^+\pi^- J/\psi$ collected with the BESIII detector. The effects of the coupled-channels and the off-shell $D^{ *0}$ are included in the parameterization of the lineshape. The lineshape mass parameter is obtained to be $M_{ X}=(3871.63\pm 0.13^{ +0.06}_{ -0.05})$ MeV. Two poles are found on the first and second Riemann sheets corresponding to the $D^{ *0}\bar{ D}^0$ branch cut. The pole location on the first sheet is much closer to the $D^{ *0}\bar{ D}^0$ threshold than the other, and is determined to be $7.04\pm0.15^{ +0.07}_{ -0.08}$ MeV above the $D^0\bar{ D}^0\pi^0$ threshold with an imaginary part $-0.19\pm0.08^{ +0.14}_{ -0.19}$ MeV.
Categories: hep-ex