Doubly charm tetraquark channel with isospin 1 from lattice QCD

Abstract

Experimentally, the doubly charm tetraquark channel ccq¯q¯ with q=u, d features an exotic hadron, Tcc, with isospin I=0 near the DD* threshold, while no peak was observed for I=1. We present a lattice QCD study of this channel with I=1, JP=1+, and mπ≃280 MeV. Finite-volume energies calculated across five charm quark masses consistently feature a positive energy shift with respect to noninteracting energies, indicating repulsive interaction at energies near the threshold. These energies are used to compute the DD* scattering amplitude using both the standard Lüscher method and the recently proposed effective field theory-based approach in the plane wave basis, which incorporates the long-range interactions and the left-hand cut. Both analyses render a small negative scattering length and a scattering amplitude that does not feature any poles in the energy region near the DD* threshold, in line with the LHCb results. We identify that the Wick contraction, resembling t-channel isovector-vector meson exchanges between D and D*, plays a key role in distinguishing between the I=0 and I=1 channels, leading to repulsion in the I=1 and attraction in the I=0 channel. Published by the American Physical Society 2025