of mesons and baryons, glueballs would be QCD color charge neutral. The baryon number of a glueball is zero. Total angular momentum Double-gluon glueballs can have total angular momentum (which are either scalar or pseudo-scalar) or (tensor). Triple-gluon glueballs can have total angular momentum (vector boson) or 3 (third-order tensor boson). All glueballs have integer total angular momentum which implies that they are bosons rather than fermions. Glueballs are the only particles predicted by the Standard Model with total angular momentum ( ) (sometimes called "intrinsic spin") that could be either 2 or 3 in their ground states, although mesons made of two quarks with and with similar masses have been observed and excited states of other mesons can have these values of total angular momentum. Electric charge All glueballs would have an electric charge of zero, as gluons themselves do not have an electric charge. Mass and parity Glueballs are predicted by quantum chromodynamics to be massive, despite the fact that gluons themselves have zero rest mass in the Standard Model. Glueballs with all four possible combinations of quantum numbers (spatial parity) and (charge parity) for every possible total angular momentum have been considered, producing at least fifteen possible glueball states including excited glueball states that share the same quantum numbers but have differing masses with the lightest states having masses as low as (for a glueball with quantum numbers = 0, = +1, = +1, or equivalently = 0), and the heaviest states having masses as great as almost (for a glueball with quantum numbers = 0, = +1, = −1, or = 0). These masses are on the same order of magnitude as the masses of many experimentally observed mesons and baryons, as well as to the masses of the tau lepton, charm quark, bottom quark, some hydrogen isotopes, and some helium isotopes. Stability and decay channels Just as all Standard Model mesons and baryons, except the proton, are unstable in isolation, all glueballs are predicted by the Standard Model to be unstable in isolation, with various QCD calculations predicting the total decay width (which is functionally related to half-life) for various glueball states. QCD calculations also make predictions regarding the expected decay patterns of glueballs. For example, glueballs would not have radiative or two photon decays, but would have decays into pairs of pions, pairs of kaons, or pairs of eta mesons. Practical impact on macroscopic