Pion decay widths of D mesons

The pionic decay rates of the excited L = 0, 1 D mesons are calculated with a Hamiltonian model within the Framework of the covariant Blankenbecler-Su gar equation. The interaction between the light quark and charm antiquark i s described by a linear scalar confining and a screened one-gluon exchange interaction. The decay widths of the D* mesons obtain a contribution from t he exchange current that is associated with the linear scalar confining int eraction. If this contribution is taken into account along with the single- quark approximation, the calculated decay rates of the charged D* mesons ar e readily below the current empirical upper limits if the axial coupling co nstant of the light constituent quarks is taken to be g(A)(q) = 0.87, but r each the empirical upper limits if g(A)(q) = 1. With the conventional value s for g(A)(q), the calculated widths of the D-1 and D-2* mesons fall somewh at below the experimental lower limits, leaving room for other decay modes as well, such as pi pi decay. The unrealistically large contribution from t he axial charge operator to the calculated pion decay width of the D-1 meso n is suppressed by taking into account the exchange charge effects that are associated with the scalar linear confining and vector one-gluon exchange interactions. The predicted values for the pionic widths uf the hitherto un discovered L = 1 D-1* and D-0* mesons are found to be smaller than previous estimates. (C) 2001 Elsevier Science B.V. All rights reserved.