Unraveling the nature of the novel and tetraquark candidates
P.G. Ortega🇪🇸 · D.R. Entem🇪🇸 · F. Fernandez🇪🇸 · J. Segovia🇪🇸
Using proton-proton collisions at centre-of-mass energies , , and TeV, with a total integrated luminosity of , the LHCb collaboration has performed amplitude analyses of the , and decays, observing that new and resonances are required in order to explain the experimental data. These signals could be the first observation of tetraquark candidates that do not contain a heavy quark-antiquark pair; in fact, they consist of four different flavours of quarks, one of which is a doubly charged open-charm state. We present herein an analysis of the and states, which is an extension of our recently published study of similar exotic candidates. Our theoretical framework is a constituent-quark-model-based coupled-channels calculation of and tetraquark sectors for and structures, respectively. We explore the nature, and pole position, of the singularities that appear in the scattering matrix with spin-parity quantum numbers: , , and . The constituent quark model has been widely used in the heavy quark sector, and thus all model parameters are already constrained from previous works. This makes our predictions robust and parameter-free. We find many singularities in the solution of various scattering-matrix problems which are either virtual states or resonances, but not bound states. Some of them fit well with the experimental observations of the spin-parity, mass and width of and candidates, and thus tentative assignments are made; however, with caution, because the experimental Breit-Wigner parameters are related to the pole characteristics.