Remarks on the Differing Lifetimes of Charmed Mesons

Abstract

Differences in the $D^{+}$ and $D^0$ lifetimes may arise either from 6 dominance in the effective nonleptonic Hamiltonian, or from the dominance of a particular $W^{+}$-exchange diagram which behaves like a $D^0-{{\overline{K}}^0}^{*}$ pole. If 6 dominance holds, then the $F^{+}$ will have a relatively short lifetime and a small semileptonic branching ratio, just like the $D^0$; but if $W^{+}$ exchange is dominant, the $F^{+}$ will have a long lifetime and large semileptonic branching ratio, like the $D^{+}$.