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.
55451255
Determining Reactor Neutrino Flux
Abstract Flux is an important source of uncertainties for a reactor neutrino experiment. It is determined from thermal power measurements, reactor core simulation, and knowledge of neutrino spectra of fuel isotopes. Past reactor neutrino experiments have determined the flux to (2–3)% precision. Precision measurements of mixing angle θ 13 by reactor neutrino experiments in the coming years will use near-far detector configurations. Most uncertainties from reactor will be canceled out. Understanding of the correlation of uncertainties is required for θ 13 experiments. Precise determination of reactor neutrino flux will also improve the sensitivity of the non-proliferation monitoring and future reactor experiments. We will discuss the flux calculation and recent progresses.
125502899
Daya Bay reactor neutrino experiment
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.
121084890
Detection methods at reactor neutrino experiments
Abstract In 2011 and 2012, the smallest neutrino mixing angle θ 13 was determined to be unexpected large by reactor neutrino experiments Daya Bay, Double Chooz, and RENO, and accelerator experiments T2K and MINOS. The most precise measurement is sin 2 2 θ 13 = 0.089 ± 0.010 ( stat . ) ± 0.005 ( syst . ) , provided by Daya Bay. The measurement of θ 13 opened the gateway to the mass hierarchy and CP phase measurements. It also marked the beginning of precision measurements in neutrino studies. With near-far relative measurement and improvements in detector design, the relative precision of neutrino detectors reached 0.2%. Detection methods for reactor neutrinos are reviewed. The highlighted techniques include gadolinium-doped liquid scintillator, three-layer detectors, functionally identical detectors, reflective panel, background shielding, etc. The next generation reactor neutrino experiment Daya Bay II and its technical challenges are briefly described.
15989714
Deuteron electromagnetic form factors in the intermediate energy region.
Based on a perturbative QCD analysis of the deuteron form factor, a model for the reduced form factor is suggested. The numerical result is consistent with the data in the intermediate energy region. {copyright} {ital 1996 The American Physical Society.}
54740568
A PRELIMINARY EXPERIMENT FOR THE BEAM BASED CALIBRATION OF BEAM POSITION MONITORS AT BEPC
By varying an individual quadrupole magnet and observing the effect on the orbit, the offset of the adjacent beam position monitor (BPM) with respect to the magnetic center of that quadrupole magnet can be determined. At BEPC, 4 BPM offsets in the vertical plane were measured by using this beam-based method. The measurement results will be shown in this paper. 1 GENERAL DESCRIPTION The properties of an electron positron collider are mainly determined by the quadrupole magnets. The highest luminosity and best performances are obtained when the beam is well centered in the quadrupole magnets. The quadrupole magnets of the Beijing Electron-Positron Collider (BEPC) are aligned with an accuracy of better than 0.2 mm rms to form the absolute closed orbit reference. Thirty-two button-type beam position monitors (BPMs) are installed in the BEPC storage ring close to the quadrupole magnets. In order to measure and correct the beam orbit to the reference orbit, it is necessary to know the relative offset between the beam position monitor’s electric center and the adjacent quadrupole’s magnetic center. Despite careful alignment and electric calibration of the beam position monitors, there can still be residual offsets. These residual offsets can be measured by a beam-based alignment technique. Figure 1 shows the principle of the beam-based calibration. When the integrated strength of a quadrupole magnet at the location s 0 of the storage ring is changed by ∆ kl, the beam obtains a local angular kick ∆ y’(s0) = ∆ kly(s 0 ), where y(s 0 ) is the transverse beam position displacement or offset in the quadrupole magnet. This angu) ( ’ ] ) ( ) ( ) ) ( ) ( ) (
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.
110785343
BEPC STORAGE RING BEAM LOSS MONITOR SYSTEM DESIGN
The Beijing Electron Positron Collider (BEPC) is a large experimental equipment for high energy physics as well as synchrotron radiation research in parasitic or dedicated mode. The beam loss phenomenon is frequently observed in the BEPC storage ring, especially when BEPC operates in the dedicated synchrotron radiation mode. Although the accelerator physics group has carried out some studies on this phenomenon, but so far this phenomenon has not well explained. The beam loss monitors (BLMs) have been developed for detecting and locating any possible excessive beam loss with the injection process, beam instabilities, bad vacuum, ion trapping, etc. This paper will discuss the system design considerations such as the detector-type selection, the BLM location in the ring and related experiment results, and so on.
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.
22957262
DAQ System of BPM and BCT for the BEPCII Linac
Following the BEPCII upgrade, total about 19 BPMs and 12 BCTs have been newly installed in the BEPCII Linac. Also, a set of distributed control system based on EPICS architecture has been built, and the BPM and BCT system are merged into the new control system for the data acquisition. In order to reduce the effects of RF noise, a special gated integrator was used for the BCT system. In this paper we will describe the DAQ system of BPM and BCT including calibrations in detail.