Light scalar mesons in QCD

I present a mini-review of the masses and couplings of the bare (unmixed) light scalar mesons: , , , gg from QCD spectral sum rules (QSSR) and low-energy theorems (LET) which we compare with recent lattice calculations when available. Some unbiased comments on the different scenarios are given. The possiblity for the σ(0.6) to be mostly a gluonium/glueball with a huge violation of the OZI rule in its decay is discussed. This review complements and updates the ones presented earlier [For reviews, see e.g., S. Narison, Phys. Rev. D 73 (2006) 114024 [hep-ph/0512256]; S. Narison, Nucl. Phys. Proc. Suppl. 121 (2003) 131; Nucl. Phys. Proc. Suppl. 96 (2001) 244; S. Narison, Nucl. Phys. Proc. Suppl. 23 B (1991) 280; Nucl. Phys. A 675 (2000) 54c; S. Narison, hep-ph/0009108]. Despite some progresses, the internal structure of the light scalar mesons remain puzzling, and some further efforts are required. It will be more fun at LHC if the Higgs of the Standard Model is a σ-like resonance.