text: Perturbative expansions over one variant of this theory can have coupling-constant related artifacts removed by the "tadpole improvement" method.
full_question: Perturbative expansions over one variant of this theory can have coupling-constant related artifacts removed by the "tadpole improvement" method. This theory predicts that the propagator factor for spacelike branching exhibits both a soft and a collinear singularity. The one-loop beta function in this theory is negative. At low energies, the coupling constant in this theory is so large that perturbation theory is ineffective, and that coupling constant decreases as 1 over the natural log of energy with increasing energy. The symmetry group which underlies this theory has eight generators known as the Gell-Mann matrices. This theory describes a force whose underlying potential has a term proportional to distance, meaning separating two particles to infinity requires infinite energy. This gauge theory with SU(3) symmetry exhibits the properties of asymptotic freedom and confinement. For 10 points, name this theory that explains the strong force using the concept of color charge.
first_sentence: Perturbative expansions over one variant of this theory can have coupling-constant related artifacts removed by the "tadpole improvement" method.
raw_answer: quantum chromodynamics [or QCD; or lattice QCD]