Bepcii and Besiii
The Beijing Electron Collider has been upgraded (BEPCII) to a two-ring collider with a design luminosity of $1 \times 10^{33}$cm$^{-2}$ s$^{-1}$ at a center-of-mass energy of 3.78 GeV. It will operate between 2 and 4.6 GeV in the center of mass. With this luminosity, the BESIII detector will be able to collect, for example, 10 billion $J/\psi$ events in one year of running. This will be a unique facility in the world opening many physics opportunities. BEPCII and BESIII are both currently being commissioned, first events have been obtained, and data taking will take place in fall 2008.
Measurement of cross sections of the interactions e+e− → ϕϕω and e+e− → ϕϕϕ at center-of-mass energies from 4.008 to 4.600 GeV
Abstract Using data samples collected with the BESIII detector at the BEPCII collider at six center-of-mass energies between 4.008 and 4.600 GeV, we observe the processes e + e − → ϕ ϕ ω and e + e − → ϕ ϕ ϕ . The Born cross sections are measured and the ratio of the cross sections σ ( e + e − → ϕ ϕ ω ) / σ ( e + e − → ϕ ϕ ϕ ) is estimated to be 1.75 ± 0.22 ± 0.19 averaged over six energy points, where the first uncertainty is statistical and the second is systematic. The results represent first measurements of these interactions.
The micro-mechanical behaviour of artificially cemented sand particles under compression and shear
The mechanical behaviour of cemented sands at macro-scale has been widely studied in the past, while there is still a lack of laboratory test data for the micro-mechanical response. Therefore, a series of uniaxial compression and tangential shear tests on artificially cemented sand particles have been conducted using a microscope to observe their behaviour. First, the consistency of cemented particles with different cementing agents is discussed. Three breakage modes are proposed according to the images taken using a microscope camera. A new parameter named ‘local roundness at contact’ is introduced to emphasise the effect of contact morphology on sample strength. Moreover, the effect of bond thickness on the mechanical response of cemented particles has been investigated. Finally, the shear strength parameters of artificially cemented sand samples have been determined for two different sample diameters.