Recently LHCb experimental group find an exotic state $T^+_{ cc}$ from the process $p\bar{ p} \to D^0D^0\pi^+ + X$. A key question is if it is just a molecule or may have confined tetraquark ingredient. To investigate this, different methods are taken, including two channel ($D^{ *+}D^0$ and $D^{ *0}D^+$) K-matrix unitarization and single channel Flatt\'e-like parametrization method analysed by pole counting rule and spectral density function sum rule. It demonstrates that $T^+_{ cc}$ is a molecular state, though the possibility that there may exist elementary ingredient can not be excluded, by rough analysis on its production rate.
Categories: hep-ph