233 research outputs found

    Existence of Kähler–Einstein metrics and multiplier ideal sheaves on del Pezzo surfaces

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    We apply Nadel’s method of multiplier ideal sheaves to show that every complex del Pezzo surface of degree at most six whose automorphism group acts without fixed points has a Kähler–Einstein metric. In particular, all del Pezzo surfaces of degree 4, 5, or 6 and certain special del Pezzo surfaces of lower degree are shown to have a Kähler–Einstein metric. These existence statements are not new, but the proofs given in the present paper are less involved than earlier ones by Siu, Tian and Tian–Yau

    Measurements of the observed cross sections for e+e−→e^+e^-\to exclusive light hadrons containing π0π0\pi^0\pi^0 at s=3.773\sqrt s= 3.773, 3.650 and 3.6648 GeV

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    By analyzing the data sets of 17.3, 6.5 and 1.0 pb−1^{-1} taken, respectively, at s=3.773\sqrt s= 3.773, 3.650 and 3.6648 GeV with the BES-II detector at the BEPC collider, we measure the observed cross sections for e+e−→π+π−π0π0e^+e^-\to \pi^+\pi^-\pi^0\pi^0, K+K−π0π0K^+K^-\pi^0\pi^0, 2(π+π−π0)2(\pi^+\pi^-\pi^0), K+K−π+π−π0π0K^+K^-\pi^+\pi^-\pi^0\pi^0 and 3(π+π−)π0π03(\pi^+\pi^-)\pi^0\pi^0 at the three energy points. Based on these cross sections we set the upper limits on the observed cross sections and the branching fractions for ψ(3770)\psi(3770) decay into these final states at 90% C.L..Comment: 7 pages, 2 figure

    Partial wave analysis of J/\psi \to \gamma \phi \phi

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    Using 5.8×107J/ψ5.8 \times 10^7 J/\psi events collected in the BESII detector, the radiative decay J/ψ→γϕϕ→γK+K−KS0KL0J/\psi \to \gamma \phi \phi \to \gamma K^+ K^- K^0_S K^0_L is studied. The ϕϕ\phi\phi invariant mass distribution exhibits a near-threshold enhancement that peaks around 2.24 GeV/c2c^{2}. A partial wave analysis shows that the structure is dominated by a 0−+0^{-+} state (η(2225)\eta(2225)) with a mass of 2.24−0.02+0.03−0.02+0.032.24^{+0.03}_{-0.02}{}^{+0.03}_{-0.02} GeV/c2c^{2} and a width of 0.19±0.03−0.04+0.060.19 \pm 0.03^{+0.06}_{-0.04} GeV/c2c^{2}. The product branching fraction is: Br(J/ψ→γη(2225))⋅Br(η(2225)→ϕϕ)=(4.4±0.4±0.8)×10−4Br(J/\psi \to \gamma \eta(2225))\cdot Br(\eta(2225)\to \phi\phi) = (4.4 \pm 0.4 \pm 0.8)\times 10^{-4}.Comment: 11 pages, 4 figures. corrected proof for journa

    Direct Measurements of Absolute Branching Fractions for D0 and D+ Inclusive Semimuonic Decays

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    By analyzing about 33 pb−1\rm pb^{-1} data sample collected at and around 3.773 GeV with the BES-II detector at the BEPC collider, we directly measure the branching fractions for the neutral and charged DD inclusive semimuonic decays to be BF(D0→μ+X)=(6.8±1.5±0.7)BF(D^0 \to \mu^+ X) =(6.8\pm 1.5\pm 0.7)% and BF(D+→μ+X)=(17.6±2.7±1.8)BF(D^+ \to \mu^+ X) =(17.6 \pm 2.7 \pm 1.8)%, and determine the ratio of the two branching fractions to be BF(D+→μ+X)BF(D0→μ+X)=2.59±0.70±0.25\frac{BF(D^+ \to \mu^+ X)}{BF(D^0 \to \mu^+ X)}=2.59\pm 0.70 \pm 0.25

    A study of charged kappa in J/ψ→K±Ksπ∓π0J/\psi \to K^{\pm} K_s \pi^{\mp} \pi^0

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    Based on 58×10658 \times 10^6 J/ψJ/\psi events collected by BESII, the decay J/ψ→K±Ksπ∓π0J/\psi \to K^{\pm} K_s \pi^{\mp} \pi^0 is studied. In the invariant mass spectrum recoiling against the charged K∗(892)±K^*(892)^{\pm}, the charged κ\kappa particle is found as a low mass enhancement. If a Breit-Wigner function of constant width is used to parameterize the kappa, its pole locates at (849±77−14+18)−i(256±40−22+46)(849 \pm 77 ^{+18}_{-14}) -i (256 \pm 40 ^{+46}_{-22}) MeV/c2c^2. Also in this channel, the decay J/ψ→K∗(892)+K∗(892)−J/\psi \to K^*(892)^+ K^*(892)^- is observed for the first time. Its branching ratio is (1.00±0.19−0.32+0.11)×10−3(1.00 \pm 0.19 ^{+0.11}_{-0.32}) \times 10^{-3}.Comment: 14 pages, 4 figure

    Study of J/psi decays to Lambda Lambdabar and Sigma0 Sigma0bar

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    The branching ratios and Angular distributions for J/psi decays to Lambda Lambdabar and Sigma0 Sigma0bar are measured using BESII 58 million J/psi.Comment: 11 pages, 5 figure

    Prunella vulgaris: A comprehensive review of chemical constituents, pharmacological effects and clinical applications.

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    Prunella vulgaris (PV) is a perennial herb belonging to the Labiate family and is widely distributed in northeastern Asian countries such as Korea, Japan, and China. It is reported to display diverse biological activities including anti-microbial, anti-cancer, and anti-inflammation as determined by in vitro or in vivo studies. So far, about 200 compounds have been isolated from PV plant and majority of these have been characterized mainly as triterpenoids, sterols and flavonoids, followed by coumarins, phenylpropanoids, polysaccharides and volatile oils. This review summarizes and analyzes the current knowledge on the chemical constituents, pharmacological activities, mechanisms of action and clinical applications of the PV plant including its potential as a future medicinal plant. Although some of the chemical constituents of the PV plant and their mechanism of action have been investigated the biological activities of many of these remain unknown and further clinical trials are required to further enhance its reputation as a medicinal plant

    Study of J/Psi decays into eta Kstar Kstar-bar

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    We report the first observation of \mPJpsi \to \mPeta\mPKst\mAPKst decay in a \mPJpsi sample of 58 million events collected with the BESII detector. The branching fraction is determined to be (1.15±0.13±0.22)×10−3(1.15 \pm 0.13 \pm 0.22)\times 10^{-3}. The selected signal event sample is further used to search for the \mPY resonance through \mPJpsi \to \mPeta \mPY, \mPY\to\mPKst\mAPKst. No evidence of a signal is seen. An upper limit of \mathrm{Br}(\mPJpsi \to \mPeta \mPY)\cdot\mathrm{Br}(\mPY\to\mPKst\mAPKst) < 2.52\times 10^{-4} is set at the 90% confidence level.Comment: 11 pages, 4 figure

    Measurements of the observed cross sections for e+e -> exclusive light hadrons containing K^S_0 meson at \sqrt{s} = 3.773 and 3.650 GeV

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    By analyzing the data sets of 17.3 pb−1^{-1} taken at s=3.773\sqrt s= 3.773 GeV and of 6.5 pb−1^{-1} taken at s=3.650\sqrt s= 3.650 GeV with the BES-II detector at the BEPC collider, we measure the observed cross sections for the exclusive light hadron final states of KS0K−π+K_S^0K^-\pi^+, KS0K−π+π0K_S^0K^-\pi^+\pi^0, KS0K−π+π+π−K_S^0K^-\pi^+\pi^+\pi^-, KS0K−π+π+π−π0K_S^0K^-\pi^+\pi^+\pi^-\pi^0, KS0K−π+π+π+π−π−K_S^0K^-\pi^+\pi^+\pi^+\pi^-\pi^- and KS0K−π+π0π0K_S^0K^-\pi^+\pi^0\pi^0 produced in e+e−e^+ e^- annihilation at the two energy points. We set the upper limits on the observed cross sections and the branching fractions for ψ(3770)\psi(3770) decay to these final states at 90% C.L..Comment: 6 pages, 1 figur
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