201926003
THE BEPCII DCCT SYSTEM
A DC Current Transformer (DCCT) as a standard diagnostic system for beam current plays an important role in BEPCII, the upgrade project of the Beijing Electron Positron Collider. Two DCCTs are operating now, separately in the electron and positron rings, to monitor the beam current, the beam injection rate, the beam loss rate and the beam lifetime. In this paper, the mechanical structure design, readout system and data processing are presented. The progress of DCCTs on each step of BEPCII commissioning, such as improving the beam lifetime and reducing the background noise, are also included.
173169030
WIRE SCANNER FOR TRANSVERSE BEAM PARAMETER MEASURE- MENT IN BEPCII
BEPCII, the upgrade project of Beijing Electron Positron Collider (BEPC), is an accelerator with large beam current and high luminosity, so an efficient and stable injector is required. Several beam diagnostic and monitoring instruments are used. A new diagnostic instrument wire scanner, has been designed and will be used to measure the profile of the linac beam of BEPCII. This paper describes the prototype of this system and the cause of heat generating of the wire. Some simulation results of the heat and force by using finite element method softwareANSYS, are presented and discussed.
125502899
Daya Bay reactor neutrino experiment
119235151
Higgs decay to dark matter in low energy SUSY: is it detectable at the LHC?
A bstractDue to the limited statistics so far accumulated in the Higgs boson search at the LHC, the Higgs boson property has not yet been tightly constrained and it is still allowed for the Higgs boson to decay invisibly to dark matter with a sizable branching ratio. In this work, we perform a comparative study for the Higgs decay to neutralino dark matter by considering three different low energy SUSY models: the minimal supersymmetric standard model (MSSM), the next-to-minimal supersymmetric standard models (NMSSM) and the nearly minimal supersymmetric standard model (nMSSM). Under current experimental constraints at 2σ level (including the muon g − 2 and the dark matter relic density), we scan over the parameter space of each model. Then in the allowed parameter space we calculate the branching ratio of the SM-like Higgs decay to neutralino dark matter and examine its observability at the LHC by considering three production channels: the weak boson fusion VV → h, the associated production with a Z-boson pp → hZ + X or a pair of top quarks $pp \to ht\overline t + X$. We find that in the MSSM such a decay is far below the detectable level; while in both the NMSSM and nMSSM the decay branching ratio can be large enough to be observable at the LHC. We conclude that at the LHC the interplay of detecting such an invisible decay and the visible di-photon decay may allow for a discrimination of different SUSY models.
123938232
A QCD-INSPIRED MODEL FOR THE DEUTERON FORM FACTORS IN THE INTERMEDIATE-Q2 REGION
Based on a perturbative QCD analysis of the deuteron form factors a QCD-inspired model is suggested. The contributions of helicity-flip matrix elements to the deuteron form factors are discussed. Our numerical results are consistent with the data in the intermediate-Q(2) region.
55221705
Measurement of decay time of liquid scintillator
In this paper we describe a single photon method to measure the decay time of two kinds of homemade liquid scintillator. We find that the fast and slow decay time constants of these two samples, with 5cm diameter and 4cm height, are about similar to 4ns and similar to 17ns, respectively. These results are checked through a reference measurement by recording the scintillation pulse shapes at the output of a fast response PMT directly by a digital oscilloscope. The time responses of these two samples are as good as those of commercial liquid scintillator. (C) 2008 Elsevier B.V. All rights reserved.