Weak decays of charm and quark masses

We calculate the effects of finite quark masses for the semileptonic and nonleptonic decays of charmed particles. The total lifetimes of charmed particles are not sensitive to the masses of the quarks in the final state. However the semileptonic branching ratios changes considerably. Using conventional constituent quark masses, one expect e.g. B_e(D⁺)≈ 21%. The brancing ratios and lifetimes of the charmed particles are estimated, taking into account the annihilation hypothesis.