Newly observed exotic doubly charmed meson $T^{+}_{cc}$

Abstract

In this work, we treat the newly observed doubly charmed four-quark state $ T_{cc}^{+}$ as an axial-vector tetraquark with content $cc\overline{u} \overline{d}$, and calculate its spectroscopic parameters and width. The mass and current coupling of the tetraquark $T_{cc}^{+}$ are found by means of the QCD two-point sum rule method by taking into account quark, gluon and mixed condensates up to dimension $10$. The width of the $T_{cc}^{+}$ is evaluated using partial widths of decay processes $T_{cc}^{+} \to \widetilde{ T}\pi ^{0}$ and $T_{cc}^{+} \to T_{cc;\overline{u}\overline{u}}^{0}\pi ^{+}$ , where $\widetilde{T}=cc\overline{u}\overline{d}$ and $T_{cc;\overline{u} \overline{u}}^{0}$ are scalar tetraquarks. To compute the partial width of the first process, we apply the QCD three-point sum rule approach and extract numerical value of the strong coupling $g$ that corresponds to the vertex $T_{cc}^{+}\widetilde{T}\pi ^{0}$. The width of the second decay is estimated using isospin symmetry and the prediction obtained for the first channel. Our results for the mass $m=(3868\pm 124)~\mathrm{MeV}$ and width $ \Gamma=(489\pm 92)~\mathrm{keV}$ of the tetraquark $T_{cc}^{+}$ are in a nice agreement with recent measurements of the LHCb collaboration.