Studies of the Cabbibo-Suppressed Decays $D^+ \to π^0 \ell^+ ν$ and $D^+ \to ηe^+ ν_e$

Abstract

Using 4.8 fb$^{-1}$ of data taken with the CLEO II detector, the branching fraction for the Cabibbo-suppressed decay $D^+\toπ^0\ell^+ν$ measured relative to the Cabibbo favored decay $D^+\to\bar{K^0}\ell^+ν$ is found to be $0.046\pm 0.014\pm 0.017$. Using $V_{cs}$ and $V_{cd}$ from unitarity constraints, we determine $| f_+^π(0)/f_+^K(0)|^2=0.9\pm 0.3\pm 0.3$ We also present a 90% confidence level upper limit for the branching ratio of the decay $D^+ \to ηe^+ν_e$ relative to that for $D^+ \to π^0 e^+ν_e$ of 1.5.