PUZZLE IN THE CHARMED D-S MESON DECAYS INTO PIONS - COULD THE LIGHT QUARKS BE NOT SO LIGHT

The inclusive decay rate into pions of the charmed D-s meson is surpri singly larger than estimates expected from the W annihilation, adoptin g commonly used values of current-algebra up and down quark masses. We go beyond this tree diagram and consider possible QCD effects that mi ght cause such a large rate. There are two: the first one is related t o the spectator decay <c(s)over bar --> <s(s)over bar> + <u(d)over bar > followed by <s(s)over bar> --> <d(d)over bar>, <u(u)over bar> via tw o-gluon exchange box diagram. The second one is a gluon emission in we ak annihilation for which the usual helicity suppression is vitiated: D-s --> W + g followed by W --> <u(d)over bar>, g --> <d(d)over bar>,< u(u)over bar>. These two contributions, however, turn out to be insuff icient to explain the data, implying that the puzzle could be understo od if the up, down quarks have higher mass values. Furthermore, on the basis of experimental information on the spectral function rho(3 pi)( Q(2)) deduced from the exclusive D-s --> 3 pi mode, the QCD sum rules also point to a higher mass for light quarks.