Abstract
We extract the K+K- couplings of the isoscalar scalar mesons sigma/f_0(600)and f_0(980) from pi pi to pi pi / K K scatterings and found: |g_{sigma K+K-}|/|g_{sigma pi+pi-}|= 0.8 and |g_{f_0 K+K-}|/ |g_{f_0 pi+pi-}|= 1.7. Theseresults, together with the tiny "direct" gamma gamma width of the sigma and itslarge hadronic width, are a strong indication for the gluonium/glueball natureof the sigma-meson, as predicted by QCD spectral sum rules (QSSR) + somelow-energy theorems (LET), while some other assignements (pi pi molecule,tetraquark state and ordinary qq meson) do not satisfy simultaneously theserequirements from the data. These properties suggest that the sigma can be ascalar meson associated to the U(1)V conformal anomaly like is the eta'-mesonfor the U(1)A anomaly.