Pionic decays of hadrons and the coupling of pions to quarks

The pion decay rates of excited heavy-light flavor mesons states can provide direct information on the coupling of pions to light-flavor constituent quarks because pions only couple to their light flavor constituent. The chiral quark model describes the empirical widths of excited D-mesons fairly satisfactorily. In this model the pion coupling is determined by the axial coupling of the light flavor quarks. The reaction Ds* → DsπO provides information on the η-meson coupling to strange constituent quarks, as it is mediated by π0 - η mixing. The two pion decay rates of heavy quarkonia implies pion exchange between heavy quarks and antiquarks, which is phenomenologically significant. (author)