We present results on the large 𝑁c scaling of meson-meson scattering amplitudes. We work in a theory with 𝑁f = 4 degenerate quark flavors and run lattice simulations with 𝑁c = 3 − 6 and pion mass 𝑀𝜋 ≈ 590MeV. We focus on three different scattering channels, two of which have the same quantum numbers as some tetraquark candidates recently found at LHCb. Finite-volume energies are extracted using a large set of operators, containing two-particle operators corresponding to two pions or two vector mesons, and local tetraquark operators. Using Lüscher’s quantization condition, we constrain the infinite-volume scattering amplitudes and investigate subleading 𝑁c corrections to the large 𝑁c limit. For one of the channels, we find indications of a virtual bound state at 𝑁c = 3, which may be related to one of the aforementioned exotic states.
Baeza-Ballesteros et al. (Tue,) studied this question.