A central question in exotic-hadron physics is their internal structure whether these states are loosely bound hadronic molecules or compact multiquark configurations. To shed light on this issue, we develop a model that incorporates mixing between hadronic-molecular and compact multiquark components. We then apply this framework to the specific case of the $T_{cc}(3875{)}^{+}$ and analyze the peak structure in the $D^0{D}^0{\pi }^{+}$ invariant-mass spectrum reported by LHCb. We find that the model admits three solutions of comparable fit quality that can account for the $T_{cc}(3875{)}^{+}$. One solution corresponds to a predominantly compact tetraquark configuration. The other two solutions imply a molecular $T_{cc}(3875{)}^{+}$: (1) the $T_{cc}(3875{)}^{+}$ is a $D^{*+}{D}^0$ molecule and an additional $D^{*0}{D}^{+}$ molecular state appears; (2) the $T_{cc}(3875{)}^{+}$ is a $D^{*0}{D}^{+}$ molecule and an additional $D^{*+}{D}^0$ molecular state is found below the $D^0{D}^0{\pi }^{+}$ threshold. These molecular states are not simple $I=0$ states, but mixtures of $I=0$ and $I=1$ states. We show that all three scenarios are also consistent with the experimentally observed near-threshold $D^0{D}^0$ and $D^0{D}^{+}$ invariant-mass distributions.

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• Hadron-hadron interactions
• Multiquark bound states
• Exotic mesons