Vacuum Structure and Chiral Symmetry Breaking

We relate here the vacuum structure of chiral symmetry breaking to a wide class of low energy hadronic properties to examine consistency with experimental results. Phase transition of chiral symmetry breaking is described through explicit vacuum realignment. We find that for the present ansatz, vacuum structure of the light quark sector can be determined from $f_\pi=92$ MeV, which then yields that $\Gamma(\pi^0\rightarrow 2 \gamma)=8.3$ eV and, $R_{ch}=0.67$ fms, in agreement with experiments. This amounts to three independent `observations' of the vacuum structure of the light quark sector. For the calculation of $\Gamma(\pi^0\rightarrow 2\gamma)$, we do not use the anomaly equation - local gauge invariance for vacuum realignment becomes adequate. The above width is sensitive to the vacuum structure, and can give evidence regarding progress towards chiral symmetry restoration in QGP. The corresponding results for $s$ quark sector are moderately good. We also exploit similar ideas for heavy quarks, but here the experimental data are rare, and the theoretical techniques are likely to need refinements.