On two-body decays of a scalar glueball

We study two-body decays of a scalar glueball. We show that in QCD a spin-0 pure glueball (a state with only gluons) cannot decay into a pair of light quarks if chiral symmetry holds exactly, i.e., the decay amplitude is chirally suppressed. However, this chiral suppression does not materialize itself at the hadron level such as in decays into π+π- and K+K-. We show this explicitly in the two cases with the glueball much lighter and much heavier than the QCD scale using low-energy theorems and perturbative QCD. For a heavy glueball, using QCD factorization based on an effective Lagrangian, we find that the hadronization into ππ and KK leads to a large difference between Br(π+π-) and Br(K+K-); even the decay amplitude is not chirally suppressed. Our results can provide some understanding of the partonic contents if Br(ππ) or Br(KK̄) is measured reliably.