Recent BES results and the BESIII upgrade

• Published in: arXiv.org 2007-12
• Main Authors: Harris, Frederick A, the BES Collaboration
• Format: Article
• Language: English
• Subjects: Center of mass; Luminosity; Particle accelerators; Sensors
• ISSN: 2331-8422

Using 58 million \(J/\psi\) and 14 million \(\psi(2S)\) events collected by the BESII detector at the BEPC, branching fractions or upper limits for the decays \(J/\psi\) and \(\psi(2S) \to \Lambda \bar{\Lambda} \pi^0\) and \(\Lambda \bar{\Lambda} \eta\) are measured, and the decays of \(J/\psi\) and \(\psi(2S)\) to \(n K^0_S \bar{\Lambda}+c.c.\) are observed and measured for the first time. Finally, \(R\) measurement data taken with the BESII detector at center-of-mass energies between 3.7 and 5.0 GeV are fitted to determine resonance parameters of the high mass charmonium states, \(\psi(3770)\), \(\psi(4040)\), \(\psi(4160)\), and \(\psi(4415)\). The Beijing Electron Collider is being upgraded to a two-ring collider (BEPCII) with a design luminosity of \(1 \times 10^{33}\)cm\(^{-2}\) s\(^{-1}\) at 3.89 GeV and will operate between 2 and 4.2 GeV in the center of mass. With this luminosity, the new BESIII detector will beable to collect, for example, 10 billion \(J/\psi\) events in one year of running. BEPCII and BESIII are currently nearing completion, and commissioning of both is expected to begin in mid-2008.