Puzzle in the charmed Ds meson decays into pions: Could the light quarks be not so light?

The inclusive decay rate into pions of the charmed Ds meson is surprisingly larger than estimates expected from the W annihilation, adopting commonly used values of current-algebra up and down quark masses. We go beyond this tree diagram and consider possible QCD effects that might cause such a large rate. There are two: the first one is related to the spectator decay cs → ss + ud followed by ss → dd,uu via two-gluon exchange box diagram. The second one is a gluon emission in weak annihilation for which the usual helicity suppression is vitiated: Ds → W + g followed by W → ud, g → dd,uu. These two contributions, however, turn out to be insufficient to explain the data, implying that the puzzle could be understood if the up, down quarks have higher mass values. Furthermore, on the basis of experimental information on the spectral function ϱ3π(Q2) deduced from the exclusive Ds → 3π mode, the QCD sum rules also point to a higher mass for light quarks.