Lepton spectrum in the semileptonic weak decays of charmed mesons

Abstract

If we assume that the semileptonic decays of the charmed $D$ mesons are dominated by the two channels $D\to \mathrm{Kl}\nu$ and $D\to K^{*}l\nu$, then, by measuring the average energy of the decay lepton, we can put an upper bound on the ratio $R=\frac{\Gamma (D\to \mathrm{Kl}\nu )}{\Gamma (D\to K^{*}l\nu )}$. Using a limited quantity of data from DESY, we find $R\lesssim 0.7$.