Tetraquarks at large N and large M

Tuesday, 05 November 2024 at 11:15

I will discuss  tetraquarks in large N QCD with heavy quarks, in the domain where non-relativistic quantum mechanics offers an adequate approximation. I will show how within the regime of validity of the Born-Oppenheimer approximation, we can systematically study and explicitly construct tetraquark states. At leading order in the 1/N expansion, the bound spectrum consists of free mesons, while the 1/N corrections give rise to a Born-Oppenheimer potential that can bind the mesons into tetraquarks. We find two different types of tetraquarks, each endowed with distinct color-spatial wavefunctions. These states arise in the presence of an O(N ) mass hierarchy between the quarks and the antiquarks. I will then provide a quantitative argument indicating that only for such a hierarchy is the ground state of the system a tetraquark. Finally, I will discuss what the extrapolation of our results to realistic values of the parameters  implies for the QCD tetraquark states.