The unexpected discovery of the double-charm tetraquark highlights an uncomfortable truth. While physicists know the exact equation that defines the strong force — the fundamental force that binds quarks together to make the protons and neutrons in the hearts of atoms, as well as other composite particles like tetraquarks — they can rarely solve this strange, endlessly iterative equation, so they struggle to predict the strong force’s effects.
The tetraquark now presents theorists with a solid target against which to test their mathematical machinery for approximating the strong force. Honing their approximations represents physicists’ main hope for understanding how quarks behave inside and outside atoms — and for teasing apart the effects of quarks from subtle signs of new fundamental particles that physicists are pursuing.
Charlie Wood, “‘Impossible’ Particle Discovery Adds Key Piece to the Strong Force Puzzle” at Quanta