Very recently, the LHCb Collaboration reported the doubly charmed tetraquark state $T_{cc}^{+}$ below the $D^{*+}{D}^0$ threshold about 273 keV. As a very near-threshold state, its long-distance structure is very important. In the molecular scheme, we relate the coupling constants of $T_{cc}^{+}$ with $D^{*0}{D}^{+}$ and $D^{*+}{D}^0$ to its binding energy and mixing angle of two components with a coupled-channel effective field theory. With the coupling constants, we investigate the kinetically allowed strong decays $T_{cc}^{+}\to D^0{D}^0{\pi }^{+}$, $T_{cc}^{+}\to D^{+}{D}^0{\pi }^0$ and radiative decays $D^{+}{D}^0\gamma$. Our results show that the decay width of $T_{cc}^{+}\to D^0{D}^0{\pi }^{+}$ is the largest one, which is just the experimental observation channel. Our theoretical total strong and radiative widths are in favor of the $T_{cc}^{+}$ as a $|D^{*+}{D}^0⟩$ dominated bound state. The total strong and radiative width in the single channel limit and isospin singlet limit are given as ${59.7}_{-4.4}^{+4.6}\mathrm{keV}$ and ${46.7}_{-2.9}^{+2.7}\mathrm{keV}$, respectively. Our calculation is cutoff-independent and without prior isospin assignment. The absolute partial widths and ratios of the different decay channels can be used to test the structure of $T_{cc}^{+}$ state when the updated experimental results are available.

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• Bound states
• Effective field theory
• Particle decays
• Mesons