Speaker
Description
A coupled-channel approach is applied to the charged tetraquark state $T_{cc}$ discovered by the LHCb Collaboration and the lattice data. Special attention is paid to the three-body and left-hand cut for the physical and unphysical pion mass cases, respectively. We discuss the lattice data to stress a potentially strong impact of left-hand cuts from the one-pion exchange on the pole extraction for near-trehshold exotic states. In particular, if the left-hand cut is located close to the two-particle threshold, which happens naturally in the $DD^*$ system for the pion mass exceeding its physical value, the effective-range expansion is valid only in a very limited energy range up to the cut and as such is of little use to reliably extract the poles. Then, an accurate extraction of the pole locations requires the one-pion exchange to be implemented explicitly into the scattering amplitudes. Our findings are general and potentially relevant for a wide class of hadronic near-threshold states.
