Chiral Symmetry Aspects of the Scalars

Abstract

Electromagnetic decays of the scalar mesons are shown to be constrained by chiral symmetry as a consequence of the fact that, in the chiral limit, the two and three-point functions $<SS-PP>$ and $<VVS>$ satisfy super-convergent dispersion relations. The QCD asymptotic behavior of the latter is canonical and it can be saturated by a finite number of resonances. The corresponding chiral lagrangian for vector and scalar resonances is constructed. Matching to the correct asymptotic structure generates non-minimal terms which have so far been ignored. It is found that the width $a_0(980)\to 2\gamma$ can be naturally reproduced suggesting that the $a_0(980)$ is not an exotic particle.

arXiv comment10 pages(latex)+1 fig (postscript file appended), Talk given at workshop "Two-photon physics from Daphne to lep200 and beyond", IPNO/TH 94-26

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• The $B_K$ Kaon Parameter in the Chiral Limit
• Large N_c in Chiral Resonance Lagrangians