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 $D\ensuremath{\rightarrow}\mathrm{Kl}\ensuremath{\nu}$ and $D\ensuremath{\rightarrow}{K}^{*}l\ensuremath{\nu}$, then, by measuring the average energy of the decay lepton, we can put an upper bound on the ratio $R=\frac{\ensuremath{\Gamma}(D\ensuremath{\rightarrow}\mathrm{Kl}\ensuremath{\nu})}{\ensuremath{\Gamma}(D\ensuremath{\rightarrow}{K}^{*}l\ensuremath{\nu})}$. Using a limited quantity of data from DESY, we find $R\ensuremath{\lesssim}0.7$.