Recent Bes Results on psi(3770) and D Meson Production and Decay

Abstract

Using a data sample of 17.7 $\mathrm{p}{\mathrm{b}}^{-1}$ collected at 3.773 GeV with the BES-II detector at the BEPC, the cross sections for $D^0{\bar{D}}^0$ and $D^{+}{D}^{-}$ productions at 3.773 GeV have been measured. From the data sample about 33 $\mathrm{p}{\mathrm{b}}^{-1}$ taken around 3.773 GeV, 3 purely leptonic decay events of $D^{+}\to {\mu }^{+}\nu$ are observed. The branching fraction and the decay constant are measured to be $BF(D^{+}\to {\mu }^{+}\nu )=(0.120_{-0.063-0.009}^{+0.092+0.010})$ and $f_D=(365_{-113-28}^{+121+32})$ MeV. The semileptonic decay branching fractions for $D^0\to K^{-}{e}^{+}\nu$, $D^0\to {\pi }^{-}{e}^{+}\nu$ and $D^{+}\to {\bar{K}}^0{e}^{+}\nu$ are measured to be $BF(D^0\to K^{-}{e}^{+}{\nu }_e)=(3.52\pm 0.36\pm 0.25)$, $BF(D^0\to {\pi }^{-}{e}^{+}{\nu }_e)=(0.36\pm 0.14\pm 0.03)$ and $BF(D^{+}\to {\bar{K}}^0{e}^{+}{\nu }_e)=(8.64\pm 1.51\pm 0.72)$. The vector form factors are determined to be $|f_{+}^K(0)|=0.75\pm 0.04\pm 0.03$ and $|f_{+}^{\pi }(0)|=0.76\pm 0.15\pm 0.06$. The ratio of the two form factors is extracted to be $|f_{+}^{\pi }(0)/f_{+}^K(0)|=1.01\pm 0.20\pm 0.08$. The ratio of the decay widths is measured to be $\Gamma (D^0\to K^{-}{e}^{+}\nu )/\Gamma (D^{+}\to {\bar{K}}^0{e}^{+}\nu )=1.04\pm 0.21\pm 0.08$. From the data sample of about 27 $\mathrm{p}{\mathrm{b}}^{-1}$, the evidence of $\psi (3770)\to J/\psi {\pi }^{+}{\pi }^{-}$ non-$D\bar{D}$ decay is observed. The branching fraction is determined to be $BF(\psi (3770)\to J/\psi {\pi }^{+}{\pi }^{-})=(0.34\pm 0.14\pm 0.08)$, corresponding to the partial width of $\Gamma (\psi (3770)\to J/\psi {\pi }^{+}{\pi }^{-})=(80\pm 32\pm 21)$ keV.

6 pages, 7 figures, To appear in the proceedings of 39th Recontres de Moriond on Electroweak Interactions and Unified Theories, LaThuile, Aosta Valley, Italy, 21-28 March, 2004