Comparing the broken U3 x U3 linear sigma model with experiment

The linear σ model with broken U3 x U3 is compared with data of the lightest scalar and pseudoscalar mesons. When 5 of the 6 parameters are fixed by the pseudoscalar masses and decay constants, one finds that, already at the tree level, one has a reasonable description for the 4 scalar masses, describing mixing and up to 8 trilinear couplings of lightest scalars, taken as a0(980), f0(980), σ(∼500) and K*0(1430). This clearly indicates that these scalars are the chiral partners of the π, η, η', K, and this strongly suggests that they, like the latter, are (unitarized) q anti q states. (orig.)