Analysis of $D^+ o\bar K^0e^+ u_e$ and $D^+ o\pi^0e^+ u_e$ Semileptonic Decays

摘要

Using 2.93~fb$^{-1}$ of data taken at 3.773 GeV with the BESIII detectoroperated at the BEPCII collider, we study the semileptonic decays $D^+ \to \barK^0e^+\nu_e$ and $D^+ \to \pi^0 e^+\nu_e$. We measure the absolute decaybranching fractions $\mathcal B(D^+ \to \bar K^0e^+\nu_e)=(8.60\pm0.06\pm0.15)\times10^{-2}$ and $\mathcal B(D^+ \to\pi^0e^+\nu_e)=(3.63\pm0.08\pm0.05)\times10^{-3}$, where the firstuncertainties are statistical and the second systematic. We also measure thedifferential decay rates and study the form factors of these two decays. Withthe values of $|V_{cs}|$ and $|V_{cd}|$ from Particle Data Group fits assumingCKM unitarity, we obtain the values of the form factors at $q^2=0$, $f^K_+(0) =0.725\pm0.004\pm 0.012$ and $f^{\pi}_+(0) = 0.622\pm0.012\pm 0.003$. Takinginput from recent lattice QCD calculations of these form factors, we determinevalues of the CKM matrix elements $|V_{cs}|=0.944 \pm 0.005 \pm 0.015 \pm0.024$ and $|V_{cd}|=0.210 \pm 0.004 \pm 0.001 \pm 0.009$, where the thirduncertainties are theoretical.