A STUDY OF EXCLUSIVE SEMILEPTONIC D DECAYS TO PSEUDOSCALAR PION AND KAON FINAL STATES WITH THE CLEO-C DETECTOR.

摘要

Using a sample of 1.85 million $Dar{D}$ mesons collected at the $Psi(3770)$ withthe CLEO-c detector, and a reconstruction method based on the full eventhermeticity, we measure branching fractionsand branching fraction ratios for the four exclusive semileptonic decaymodes $D^0 o pi^- e^+ u$, $D^0 o K^- e^+ u$, $D^{+} o pi^0e^+ u$ and, $D^{+} o ar{K}^0 e^+ u$. For the branching fractions we find ${cal B}(D^0 o pi^- e^+ u) = 0.299 pm 0.011 pm 0.008 ;%$, ${cal B}(D^0 o K^- e^+ u) = 3.55 pm 0.03 pm 0.08 ;%$, ${cal B}(D^+ o pi^0 e^+ u) = 0.371 pm 0.022 pm 0.013 ;%$ and ${cal B}(D^+ o ar{K}^0 e^+ u) = 8.53 pm 0.13 pm 0.22 ;%$. The ratiosare found to be ${cal B}(D^0 o pi^- e^+ u) slash {cal B}(D^0 oK^- e^+ u) = 0.084 pm 0.003 pm 0.001$, ${cal B}(D^+ o pi^0 e^+u) slash {cal B}(D^+ o ar{K}^0 e^+ u) = 0.044 pm 0.003 pm 0.001$,$Gamma(D^0 o pi^- e^+ u) slash Gamma(D^+ o pi^0 e^+ u) =2.04 pm 0.14 pm 0.08$ and $Gamma(D^0 o K^- e^+ u) slashGamma(D^+ o ar{K}^0 e^+ u) = 1.06 pm 0.02 pm 0.03$.In addition, form factors are studied through fits to the partial branching fractions obtained in five $q^2$ ranges. Combining our resultswith recent unquenched lattice calculations we extract the CKM matrix elements $|V_{cs}|$ and $|V_{cd}|$. Averaging over isospin conjugatemodes, we find$|V_{cs}| = 1.01 pm 0.01 pm 0.01 pm 0.11$ and $|V_{cd}| =0.217 pm 0.010 pm 0.004 pm 0.023$.