分类: 物理学 >> 核物理学 提交时间: 2016-08-25
摘要: The branching fractions of the Υ(1S) inclusive decays into final states with a J/ψ or a ψ(2S) are measured with improved precision to be $\BR(\Upsilon(1S)\to J/\psi + {\rm anything})=(5.25\pm 0.13(\mathrm{stat.})\pm 0.25(\mathrm{syst.}))\times 10^{-4}$ and $\BR(\Upsilon(1S)\to \psi(2S) + {\rm anything})=(1.23\pm 0.17(\mathrm{stat.})\pm 0.11(\mathrm{syst.}))\times 10^{-4}$. The first search for Υ(1S) decays into XYZ states that decay into a J/ψ or a ψ(2S) plus one or two charged tracks yields no significant signals for XYZ states in any of the examined decay modes, and upper limits on their production rates in Υ(1S) inclusive decays are determined.
分类: 物理学 >> 核物理学 提交时间: 2016-08-24
摘要: The process γγ→pp¯K+K− and its intermediate processes are measured for the first time using a 980~fb−1 data sample collected with the Belle detector at the KEKB asymmetric-energy e+e− collider. The production of pp¯K+K− and a Λ(1520)0 (Λ¯(1520)0) signal in the pK−~(p¯K+) invariant mass spectrum are clearly observed. However, no evidence for an exotic baryon near 1540~MeV/c2, denoted as Θ(1540)0~(Θ¯ (1540)0) or Θ(1540)++~(Θ(1540)−−), is seen in the pK−~(p¯K+) or pK+~(p¯K−) invariant mass spectra. Cross sections for γγ→pp¯K+K−, Λ(1520)0p¯K++c.c. and the products $\sigma(\gamma \gamma \to \Theta(1540)^0 \bar{p} K^+ +c.c.)\BR(\Theta(1540)^0 \to p K^{-})$ and$\sigma(\gamma \gamma \to \Theta(1540)^{++} \bar{p} K^- +c.c.)\BR(\Theta(1540)^{++}\to p K^{+})$ are measured. We also determine upper limits on the products of the χc0 and χc2 two-photon decay widths and their branching fractions to pp¯K+K− at the 90\% credibility level.