X-ray absorption and optical spectroscopy studies of (Mg1−x_{1-x}Alx_x)B2_2

X-ray absorption spectroscopy and optical reflectance measurements have been carried out to elucidate the evolution of the electronic structure in (Mg$_{1-x}$Al$_{x}$)B$_{2}$ for \emph{x} = 0.0,0.1, 0.2, 0.3, and 0.4. The important role of B 2\emph{p} $\sigma$ hole states to superconductivity has been identified, and the decrease in the hole carrier number is \emph{quantitatively} determined. The rate of the decrease in the hole concentration agree well with the theoretical calculations. On the other hand,while the evolution of the electronic structure is gradual through the doping range, $T_c$ suppression is most significant at \emph{x} = 0.4. These results suggest that the superstructure in (Mg$_{1-x}$Al$_{x}$)B$_{2}$, in addition to the $\sigma$ holes, can affect the lattice dynamics and contributes to the $T_c$ suppression effect. Other possible explanations like the topological change of the $\sigma$ band Fermi surface are also discussed.Comment: 17 pages, 5 figures. Phys. Rev. B, in pres

Search for D to phi l nu and measurement of the branching fraction for D to phi pi

Using a data sample of integrated luminosity of about 33 pb$^{-1}$ collected around 3.773 GeV with the BESII detector at the BEPC collider, the semileptonic decays $D^+ \to \phi e ^+\nu_e$, $D^+ \to \phi \mu^+\nu_\mu$ and the hadronic decay $D^+ \to \phi \pi^+$ are studied. The upper limits of the branching fractions are set to be $BF(D^+ \to \phi e ^+\nu_e) <$ 2.01% and $BF(D^+ \to \phi \mu^+ \nu_\mu) <$ 2.04% at the 90% confidence level. The ratio of the branching fractions for $D^+ \to \phi \pi^+$ relative to $D^+ \to K^-\pi^+\pi^+$ is measured to be $0.057 \pm 0.011 \pm 0.003$. In addition, the branching fraction for $D^+ \to \phi \pi^+$ is obtained to be $(5.2 \pm 1.0 \pm 0.4) \times 10^{-3}$.Comment: 6 pages, 5 figures, to be published in Eur.Phys.J.

Measurements of branching fractions for inclusive K0~/K0 and K*(892)+- decays of neutral and charged D mesons

Using the data sample of about 33 pb-1 collected at and around 3.773 GeV with the BES-II detector at the BEPC collider, we have studied inclusive K0~/K0 and K*(892)+- decays of D0 and D+ mesons. The branching fractions for the inclusive K0~/K0 and K*(892)- decays are measured to be BF(D0 to K0~/K0 X)=(47.6+-4.8+-3.0)%, BF(D+ to K0~/K0 X)=(60.5+-5.5+-3.3)%, BF(D0 to K*- X)=(15.3+- 8.3+- 1.9)% and BF(D+ to K*- X)=(5.7+- 5.2+- 0.7)%. The upper limits of the branching fractions for the inclusive K*(892)+ decays are set to be BF(D0 to K*+ X)<3.6% and BF(D+ to K*+ X) <20.3% at 90% confidence level

Direct Measurements of the Branching Fractions for Inclusive K±K^\pm and Inclusive Semileptonic Decays of D+D^+ and D0D^0 Mesons

With singly-tagged $\bar D$ samples selected from the data collected at and around 3.773 GeV with the BESII detector at the BEPC collider, we have measured the branching fractions for the inclusive $K^\pm$ decays of $D^+$ and $D^0$ mesons, which are $BF(D^+\to K^-X) = (24.7 \pm 1.3 \pm 1.2)$, $BF(D^+\to K^+X) = (6.1 \pm 0.9 \pm 0.4)$, $BF(D^0\to K^-X) = (57.8 \pm 1.6 \pm 3.2)$ and $BF(D^0\to K^+X) = (3.5 \pm 0.7 \pm 0.3)$, respectively. We have also measured the branching fractions for the inclusive semileptonic decays of $D^+$ and $D^0$ mesons to be $BF(D^+ \to e^+ X)=(15.2 \pm 0.9 \pm 0.8)$ and $BF(D^0 \to e^+ X) =(6.3 \pm 0.7 \pm 0.4)$. These yield the ratio of their partial widths to be $\Gamma(D^+ \to e^+X)/\Gamma(D^0 \to e^+X)=0.95 \pm 0.12 \pm 0.07$.Comment: 6 pages, 5 figure

Measurement of the branching fractions of psi(2S) -> 3(pi+pi-) and J/psi -> 2(pi+pi-)

Using data samples collected at sqrt(s) = 3.686GeV and 3.650GeV by the BESII detector at the BEPC, the branching fraction of psi(2S) -> 3(pi+pi-) is measured to be [4.83 +- 0.38(stat) +- 0.69(syst)] x 10^-4, and the relative branching fraction of J/psi -> 2(pi+pi-) to that of J/psi -> mu+mu- is measured to be [5.86 +- 0.19(stat) +- 0.39(syst)]% via psi(2S) -> (pi+pi-)J/psi, J/psi -> 2(pi+pi-). The electromagnetic form factor of 3(pi+pi-) is determined to be 0.21 +- 0.02 and 0.20 +- 0.01 at sqrt(s) = 3.686GeV and 3.650GeV, respectively.Comment: 17pages, 7 figures, submitted to Phys. Rev.

Physics at BES-III

This physics book provides detailed discussions on important topics in $\tau$-charm physics that will be explored during the next few years at \bes3 . Both theoretical and experimental issues are covered, including extensive reviews of recent theoretical developments and experimental techniques. Among the subjects covered are: innovations in Partial Wave Analysis (PWA), theoretical and experimental techniques for Dalitz-plot analyses, analysis tools to extract absolute branching fractions and measurements of decay constants, form factors, and CP-violation and \DzDzb-oscillation parameters. Programs of QCD studies and near-threshold tau-lepton physics measurements are also discussed.Comment: Edited by Kuang-Ta Chao and Yi-Fang Wan