Spin- and flavor-symmetry-breaking corrections to decay constants of heavy mesons are analyzed in next-to-leading order in the $\frac{1}{m_Q}$ expansion. The general structure of these corrections is derived in an effective-field-theory approach. The subleading universal form factors, which parametrize the matrix elements of higher-dimensional operators in the effective theory, are estimated using QCD sum rules. The renormalization-group improvement of these low-energy parameters is discussed in detail. As an application, the spin-symmetry-violating effects responsible for the vector-pseudoscalar mass difference and for the ratio of the corresponding decay constants, $\frac{f_V}{f_P}$, are calculated.

• Received 2 April 1992

DOI:https://doi.org/10.1103/PhysRevD.46.1076