low energy physics Because Standard Model glueballs are so ephemeral (decaying almost immediately into more stable decay products) and are only generated in high energy physics, glueballs only arise synthetically in the natural conditions found on Earth that humans can easily observe. They are scientifically notable mostly because they are a testable prediction of the Standard Model, and not because of phenomenological impact on macroscopic processes, or their engineering applications. Lattice QCD simulations Lattice QCD provides a way to study the glueball spectrum theoretically and from first principles. Some of the first quantities calculated using lattice QCD methods (in 1980) were glueball mass estimates. Morningstar and Peardon computed in 1999 the masses of the lightest glueballs in QCD without dynamical quarks. The three lowest states are tabulated below. The presence of dynamical quarks would slightly alter these data, but also makes the computations more difficult. Since that time calculations within QCD (lattice and sum rules) find the lightest glueball to be a scalar with mass in the range of about . Lattice predictions for scalar and pseudoscalar glueballs, including their excitations, were confirmed by Dyson–Schwinger/Bethe–Salpeter equations in Yang–Mills theory. Experimental candidates Particle accelerator experiments are often able to identify unstable composite particles and assign masses to those particles to a precision of approximately , without being able to immediately assign to the particle resonance that is observed all of the properties of that particle. Scores of such particles have been detected, although particles detected in some experiments but not others can be viewed as doubtful. Some of the candidate particle resonances that could be glueballs, although the evidence is not definitive, include the following: Vector, pseudo-vector, or tensor glueball candidates X(3020) observed by the BaBar collaboration is a candidate for an excited state of the = 2, 1 or 1 glueball states with a mass of about . Scalar glueball candidates f0(500) also known as σ – the properties of this particle are possibly consistent with a glueball of mass or . f0(980) – the structure of this composite particle is consistent with the existence of a light glueball. f0(1370) – existence of this resonance is disputed but is a candidate for a glueball–meson mixing state f0(1500) – existence of this resonance is undisputed but its status as a glueball–meson mixing state or pure glueball is not well established. f0(1710) – existence of this resonance is undisputed but its status