Beauty-charm tetraquarks predicted at the edge of stability
A computation in lattice quantum chromodynamics (QCD) performed by Prof. Stefan Meinel and collaborators predicts the existence of exotic bound states composed of heavy beauty and charm antiquarks together with light up and down quarks (as well as the partners composed of beauty and charm quarks together with up and down antiquarks). These tetraquarks are similar to the doubly-charm tetraquark Tcc discovered at the Large Hadron Collider in 2021. There is a consensus among theorists that replacing the two charm quarks in the Tcc by two heavier beauty quarks would yield a more stable bound state, but the mixed charm-beauty case has remained puzzling, with previous calculations yielding unclear or even contradictory results. In this work, Meinel and collaborators computed the momentum dependence of the strong-interaction scattering amplitude between charm and beauty mesons for the first time using lattice QCD and found that these mesons form tetraquark bound states very close to the edge of stability under the strong interactions. The calculation also predicts signatures of these beauty-charm tetraquarks that may be discovered with more data from the Large Hadron Collider in the future. The work was published in Physical Review Letters this week.