$T_{cc}$ and Hidden Charm Tetraquarks $1^{+}$ and $0^{+}$in QCD sum rules and Heavy-Quark Spin Symmetry

In this work, $T_{cc}$ double charm tetraquark and $1^{+}$ and $0^{+}$ hidden charm tetraquarks are studied within the QCD sum rules framework. In the heavy-quark limit, the $1^{+}$ and $0^{+}$ tetraquarks are degenerate and the difference in their masses is an $1\mathrm{/}{m}_c$ effect. It is shown that, although the uncertainty in the mass predictions of each of these hadrons is $\mathcal{O}(100\mathrm{M}\mathrm{e}\mathrm{V})$, when the mass differences are studied, the uncertainty is reduced to less than $\mathcal{O}(10\mathrm{M}\mathrm{e}\mathrm{V})$. Hence, it is concluded that if one of the exotic hadrons is observed and its mass is used as input, the masses of the other hadrons can be determined with a precision of $\mathcal{O}(10\mathrm{M}\mathrm{e}\mathrm{V})$ using the QCD sum rules method.