Speaker
Description
In this talk, I will first present the $D^*D$ scattering results obtained using $(2+1)$-flavor lattice QCD simulations with a nearly physical pion mass of $m_\pi=146$ MeV, which is crucial for understanding the first doubly charmed tetraquark $T^+_{cc}$. Next, I will discuss the left-hand cut singularity, which has been recently pointed out to be relevant for analyzing $T^+_{cc}$. Special focus will be given on its origin in both non-relativistic and relativistic scatterings, how this singularity appears/disappears in the infinite/finite volume scattering, as well as its implications.