Rare decays of $D_s$ mesons into light pseudoscalar mesons

Rare decays of $D_s$ mesons into pseudoscalar mesons are studied in detail within the framework of the relativistic quark model based on the quasipotential approach and quantum chromodynamics. The form factors that parameterize the matrix elements of the weak current between meson states are calculated with consistent account of relativistic effects. Their dependence on the square of the transferred momentum is explicitly defined in the whole accessible kinematic region. The effects of electroweak physics at short distances and the contributions of intermediate resonances at large distances are taken into account using effective Wilson coefficients,. In the framework of the helicity formalism, differential decay rates and branching fraction are calculated. The obtained results are consistent with the existing upper experimental limits.