Rare Decays of D Mesons into Vector Light Mesons

Rare decays of the D mesons into vector light mesons are studied in detail within the framework of the relativistic quark model based on the quasipotential approach and quantum chromodynamics. The hadronic matrix elements of the weak current between meson states are calculated with the consistent account of relativistic effects. The invariant form factors that parameterize these matrix elements are obtained as the overlap integrals of the initial and final meson wave functions. Their dependence on the square of the transferred momentum q² is explicitly determined within the whole accessible kinematic range. A convenient analytical approximation for numerical values of form factors is given. Effects of electroweak physics at short distances and contributions of the intermediate resonances at long distances are taken into account using effective Wilson coefficients. Helicity formalism is employed for the calculation of the differential decay rates and branching fractions of the charm meson into vector light mesons. Reasonable agreement with experimental upper bounds on the rare decay branching fractions is obtained.