2008 Vol. 32, No. 5
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The results of a study of event tagging strategies for elementary physics processes in the τ-charm region are presented. The algorithm for online event filtering is optimized by adopting the information provided by different sub-detectors according to their strengths and capacities. The algorithm is tested with various generated physics and background events. The results indicate that the algorithm satisfies the requirements of BESⅢ physics analysis and its
In this paper the laws of motion of classical particles have been investigated in a non-commutative phase space. The corresponding non-commutative relations contain not only spatial non-commutativity but also momentum non-commutativity. First, new Poisson brackets have been defined in non-commutative phase space. They contain corrections due to the non-commutativity of coordinates and momenta. On the basis of this new Poisson brackets, a new modified second law of Newton has been obtained. For two cases, the free particle and the harmonic oscillator, the equations of motion are derived on basis of the modified second law of Newton and the linear transformation (Phys. Rev. D, 2005, 72: 025010). The consistency between both methods is demonstrated. It is shown that a free particle in commutative space is not a free particle with zero-acceleration in the non-commutative phase space, but it remains a free particle with zero-acceleration in non-commutative space if only the coordinates are non-commutative.
In the strong uniform magnetic field, the noncommutative plane (NCP) caused by the lowest Landau level (LLL) effect, and QED with NCP (QED-NCP) are studied. Being similar to the condensed matter theory of quantum Hall effect, an effective filling factor f(B) is introduced to characterize the possibility that the electrons stay on the LLL. The analytic and numerical results of the differential cross section for the process of backward Compton scattering in accelerator with unpolarized or polarized initial photons are calculated. The existing data of BL38B2 in Spring-8 have been analyzed roughly and compared with the numerical predictions primitively. We propose a precise measurement of the differential cross sections of backward Compton scattering in a strong
perpendicular magnetic field, which may reveal the effects of NCP.
In this work, the neutron radiation field at Heavy Ion Research Facility in Lanzhou (HIRFL) was investigated. Total neutron yields, spectra and angular
distributions in the bombardment of various thick targets by 12C and 18O ions with energies up to 75 MeV/u were obtained using the activation method. The neutron dose equivalent rates of 60 MeV/u 18O on various thick targets at different angles were measured with a modified A-B remmeter. Our results are compared with those of other reports.
A study of intermittency of target associated fragments produced in the interactions of 16O-AgBr at 4.5 AGeV/c with nuclear emulsion using the method of factorial moments, Fq, has been performed. The dependence of the moments on the number of bins M is found to follow a power law behavior for the experimental data in terms of new scaled variable χ(z) suggested by Bialas and Gazdzicki. The anomalous dimensions, dq, increase linearly with the order of moments, q. This observation indicates the association of multifractility with production mechanism of target associated fragments.
We carry out a systematic study of the different contributions to the deviations of the elliptic flows from the quark number scaling in high energy heavy ion collision in a quark combination model. The effects that we considered are: the resonance decay, the flavor dependence of the quark elliptic flow and the combination of quarks/antiquarks with slightly different transverse momenta. Our results show that the deviations observed in experiments can be well reproduced within the combination framework if all the three effects are considered. We make a detailed analysis of the different contributions using a Monte-Carlo program and suggest measuring the quark number scaling in intermediate pT range more precisely.
The construction of the Bayesian credible (confidence) interval for a Poisson observable including both the signal and background with and without systematic uncertainties is presented. Introducing the conditional probability satisfying the requirement of the background not larger than the observed events to construct the Bayesian credible interval is also discussed. A Fortran routine, BPOCI, has been developed to implement the calculation.
The energy response calibration of the commonly used high pressure ionization chamber is very difficult to obtain when the gamma-ray energy is more than 3 MeV. In order to get the calibration of the higher part of the high pressure ionization chamber, we use the Fluka Monte Carlo program to perform the energy response in both the spherical and the cylindrical high pressure ionization chamber which are full of argon gas. The results compared with prior study when the gamma-ray energy is less than 1.25 MeV. Our result of Monte Carlo calculation shows agreement with those obtained by measurement within the uncertainty of the respective methods. The calculation of this study is significant for the high pressure ionization chamber to measure the high energy gamma-ray.
The installation of the BESⅢ RPC system has been completed. Cosmic ray test results show that they perform very well in streamer mode and meet the BESⅢ requirements. We have tested several RPCs in the avalanche mode with the addition of extra SF6 in the gas mixture. We find an efficiency plateau that reaches ～95%, and a time resolution of 1.8 ns. This demonstrates that the BESⅢ-type RPC can work in the avalanche mode as well.
The production and transportation of fluorescent light produced in wavelength-shifting fibers (WSFs) coupled to YAP scintillation crystal is simulated using the GEANT4 codes. An advantage of the wavelength-shifting fiber readout technique over a direct readout with a position-sensitive photo-sensor is the reduced requirement for position sensitive photomultiplier tube photocathode area. With this gamma-ray detector, the gamma camera is small and flexible and has larger effective field of view and low cost. Simulation results show that a) a mean 12 of photons per 59.5 keV gamma ray interaction is produced in the WSF located nearest to the incident gamma ray, and a spatial resolution of 3.6 mm FWHM is obtained, b) a mean 27 of photons per 140 keV gamma ray interaction is produced and a spatial resolution of 3.1 mm FWHM is obtained. Results demonstrate the feasibility of this concept of a compact gamma-ray detector based on wavelength-shifting fibers readout. However, since the very low photoelectron levels, it is very important to use a photon counting device with good single photo-electron response to readout the WSFs.
The optically stimulated luminescent (OSL) radiation dosimeter technically surveys a wide dynamic measurement range and a high sensitivity. Optical fiber dosimeters provide capability for remote monitoring of the radiation in the locations which are difficult-to-access and hazardous. In addition, optical fiber dosimeters are immune to electrical and radio-frequency interference. In this paper, a novel remote optical fiber radiation dosimeter is described. The optical fiber dosimeter takes advantage of the charge trapping materials CaS:Ce, Sm that exhibit OSL. The measuring range of the dosimeter is from 0.1 to 100 Gy.
The equipment is relatively simple and small in size, and has low power consumption. This device is suitable for measuring the space radiation dose and also can be used in high radiation dose condition and other dangerous radiation occasions.
RF cold test of a novel C-band cavity beam position monitor (PBM) to be used in the SDUV-FEL Test Facility is described. The test results are presented and some characteristics discussed. The main parameters obtained are in reasonable agreement with the analytical estimations. Effective suppression of the common mode has been demonstrated. The position sensitivity over the test region of ±0.5 mm is about －21.58 dB/10 μm for the TM110 mode and is linear in the central region of the BPM cavity.
In this work, highly charged ions have been extracted from the advanced Electron Beam Ion Source (EBIS-A) developed in a scientific cooperation between the Dresden University of Technology and the DREEBIT GmbH Dresden. The charge state distributions of ions extracted from the EBIS-A are measured in the pulse and leaky modes under different operation conditions. Ar16+ ions with current of 2 pA are produced and extracted in the leaky mode. 3×105 Ar18+ ions per pulse are extracted in the pulse mode. The ion charge state distribution is a
function of the ionization time.
A synchrotron is designed for tumour therapy with C6+ ions or proton. Its injector is a cyclotron, which delivers C5+ or H2+ ions to the synchrotron. After comparing the methods of the single-turn injection, the multi-turn injection and the stripping injection, this paper chooses the stripping injection method. In addition, the concept design of the injection system is presented, in which the
synchrotron lattice is optimized.
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 software—ANSYS®,2) are presented and discussed.
An overview of research status of soft physics in high energy heavy-ion collision experiments and recent experimental results are presented. The experimental status on fluctuations and correlations has been reviewed and the outlook for research status of soft physics in LHC/ALICE has been introduced in this paper.
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