Measurements of the absolute branching fractions for D->Kbar pi e+ nu_e, D-> K*bar e+nu_e and determination of Gamma(D+ -> K*0bar e+ nu_e)/Gamma(D+ -> K0bar e+nu_e)

Abstract

Using the data of about 33 pb${}^{-1}$ collected at and around 3.773 GeV with the BES-II detector at the BEPC collider, we have studied the exclusive semileptonic decays $D^{+}\to K^{-}\ddot{I}{€}^{+}{e}^{+}\hat{I}{½}_e$, $D^0\to {\bar{K}}^0\ddot{I}{€}^{-}{e}^{+}\hat{I}{½}_e$, $D^{+}\to {\bar{K}}^{\ast 0}{e}^{+}\hat{I}{½}_e$ and $D^0\to K^{\ast -}{e}^{+}\hat{I}{½}_e$. The absolute branching fractions for the decays are measured to be $BF(D^{+}\to K^{-}\ddot{I}{€}^{+}{e}^{+}\hat{I}{½}_e)=(3.50\pm 0.75\pm 0.27)$, $BF(D^0\to {\bar{K}}^0\ddot{I}{€}^{-}{e}^{+}\hat{I}{½}_e)=(2.61\pm 1.04\pm 0.28)$, $BF(D^{+}\to {\bar{K}}^{\ast 0}{e}^{+}\hat{I}{½}_e)=(5.06\pm 1.21\pm 0.40)$ and $BF(D^0\to K^{\ast -}{e}^{+}\hat{I}{½}_e)=(2.87\pm 1.48\pm 0.39)$. The ratio of the vector to pseudoscalar semileptonic decay rates $\hat{I}“(D^{+}\to {\bar{K}}^{\ast 0}{e}^{+}\hat{I}{½}_e)/\hat{I}“(D^{+}\to {\bar{K}}^0{e}^{+}\hat{I}{½}_e)$ is determined to be $0.57\pm 0.17\pm 0.02$.