Speaker
Description
We investigate the pole structure of the (T_{cs}) resonance in a coupled-channel quark model. The model space is separated into a compact four-quark sector (P) and a two-meson continuum sector (Q={DK,D^\ast K^\ast}). Compact seed states are calculated using constituent-quark Hamiltonians with two-body one-gluon-exchange interactions and possible instanton-induced or three-body two-gluon-exchange terms. The continuum sector includes the long-range part of the pion-exchange, while the compact-continuum transition is treated within a generalized non-orthogonal framework.
The physical pole positions are obtained by eliminating the continuum sector and solving the resulting energy-dependent pole equation on the appropriate Riemann sheets. We trace the pole trajectories as a function of the compact-continuum coupling strength and examine the roles of the (D^\ast K^\ast) threshold, the finite (K^\ast) width, and the compact seed structure. The seed-1 trajectory is found to be particularly sensitive to the (D^\ast K^\ast) channel and can be shifted toward the (T_{cs0}(2870)) energy region. We also find additional companion-like solutions, suggesting that non-orthogonality and hidden rearrangement components of the compact basis may play a nontrivial role in the coupled-channel pole structure.