2005 Vol. 29, No. 06
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Based on the nonlinear σ-ω-ρ mode in the relativistic mean fields approximation, we have obtained the relation between nuclear density r and the effective masses M*Θ+ of the pentaquark Θ+ by using the function of energy density. We investigated the parameter of the different models effects on the effective masses M*Θ+ of the pentaquark Θ+ in the nuclear density r. At the same time, we also try to study the couple coefficient ΓΘ/Baffect on the effective masses M*Θ+ in different parameters.
By solving the complex Schrodinger equation with the phenomenological Paris optical potential between nucleon (N) and antinucleon(N)，the near-threshold binding and resonant behaviors of the pp system are studied. As the result, a 13P0 resonance state of pp is obtained. It is found that the energy and width of the state are compatible with the BES data in which the observed enhancement in the J/ψ→γpp decay was fitted by a Breit-Wigner (B-W) formula either in the S-wave or in the P-wave. The indication of the results and the suggestion for the further theoretical investigation are discussed.
We have applied the χ2-minimization technique that takes backgrounds and systematic uncertainties into account to optimize the baseline of the reactor neutrino experiments designed for determining the mixing angle θ13 of neutrino. The effect of oscillation, systematic errors, statistic errors and backgrounds in the optimization are investigated. Although the experimental conditions may be very different, the optimal baseline is constrained in a narrow range.
The distortion of the secondary charged particle trajectories of EAS in the geomagnetic field distorts the lateral distribution of the secondaries. The variation of the geomagnetic effect with the azimuth angle in different zenith angle intervals for YBJ-ARGO experiment is studied using Monte Carle simulation. The geomagnetic field leads to a stretched lateral distribution of the secondaries, thus both the density of the secondaries near the shower axis and the trigger efficiency of the array decrease. This effect is larger for the showers coming from the north than that from the south, such that the trigger efficiency for the former is lower than that for the latter. The north-south asymmetry becomes more evident with larger zenith angles.
Relativistic effects in two-photon decay of quarkonium are investigated with a relativistic phenomenological approach.Compared with the NR approximation usually used, the relativistic phenomenological approach gives corrections coming from three sources: qq relative momentum distribution,qq relative energy distribution and description of quark spinors in the meson. These relativistic effects are studied in detail for cc and ss systems.
Cross-sections for (n,2n) and (n,p) reactions have been measured on platinum isotopes at the neutron energies of 13.5 to 14.6 MeV using the activation technique. Data were reported for the following reactions: Pt(n,2n)197m+gPt,198Pt(n,2n)197mPt,192Pt(n,2n)191Pt, 194Pt(n,p)194Ir, 195Pt(n, p)195mIr, and 196Pt(n,p)196mIr. At the neutron energies of 13.5, 14.1 and 14.6 MeV, the cross sections in mb are 2038±159, 1919±73 and 1836±68 for 198Pt(n,2n)197m+gPt reaction; 974±37, 1055±39 and 1042±39 for 198Pt(n, 2n)197mPt reaction, respectively. The cross sections are 1680±103, 1810±67 and 2047±97 for 192Pt(n,2n)191Pt reaction, and 1.0±0.2, 1.6±0.2 and 1.8±0.2 for 195Pt(n, p)195mIr reaction, respectively, at energies of 14.1, 14.4 and 14.6MeV. At 14.1 and 14.4 MeV neutron energies, the cross sections are 3.8±0.4 and 5.4±0.5 for 194Pt(n,p)194Ir reaction. While, the data are (1.13±0.07) and (1.18±0.06) mb at energies of 13.5 and 14.4 MeV, respectively, for 196Pt(n,p)196mIr reaction.The neutron fluences were determined using the monitor reaction 93Nb(n, 2n)92mNb or 27Al(n, a)24Na. A comparison was made between the present cross sections and the collected data for the measured reactions.
Using the RMF theory to describe the neutron liquid region in the neutron star and the Fermi gas model or FMT, BPS,and BBP model to describe the crust of the neutron star (referred as Fermi gas+RMF and RMF* respectively),the properties of the neutron star are calculated and compared with those from the RMF theory. Although the EOS at low density has negligible influence on the maximum mass of the neutron star, and its corresponding central density, energy density, and pressure, it changes the mass-radius relationship of neutron stars considerably. The differences of the neutron star radius corresponding to maximum mass between the RMF theory and RMF* calculations are 0.23-0.33 km.
It is one of the most important contents to analyze the energy level structure in the nuclear physics. At present the high-spin state of the odd-A nuclear 143Pm have been investigated by using heavy-ion beam reaction the excitation energy level 8.4MeV and spin (47/2) (h=1) has been obtained. In this paper, according to the principle of the nuclear shell model and experiment information ,the 143Pm nuclear structure has been analyzed with 2 interaction potentials and to the weak-coupling model(WCM) result,especially explore the sequences of γ-ray transitions,which depend to the corresponding dominant configuration. The program OXBASH code is adopted.
Isospin effect of multifragmentation for the finite nuclei 112Sn and 132Sn is studied by using a phenomenological asymmetric nuclear equation of state and an isospin dependent quantum molecular dynamics (IQMD) model. It is found that the isospin effect vanishes gradually with increasing temperature, Production mechanism of intermediate mass fragments is also analysed for different density distribution in coordinate space at a given temperature.Critical phenomena are investigated preliminarily by using correlation analysis of fragments.
The relation between event rapidity gap fluctuation and rapidity correlations is derived. It is shown that the new and interesting parts included in rapidity gap analysis are the generalized two-particle rapidity-correlation moments. The physical meanings of these moments for specific two particles and moment orders are clarified.
The End-Cap TOF (ETOF) of Beijing Spectrometer (BESⅢ) consists of 2×48 pieces of trapezoidal scintillator (BC408). Its main physics goal is to realize the 2σ π/k separation at momentum up to 1GeV/c, and to obtain TOF intrinsic time resolution of 80ps.In order to study the effects of several factors on the intrinsic time resolution of ETOF, the Monte Carlo simulation of the detector is carried out by using Geant4 software package. The performance of ETOF at different conditions, such as scintillator covered materials, shapes, and particle hit positions, is simulated and discussed in discussed in detail. The result can provide a reference for the design of ETOF detecor in BESⅢ.
The spatial resolution, dE/dx resolution and cell efficiency of two prototype of mall-cell drift chambers filled with He/C3H8(60/40) with cell sizes of 14.0mm and 16.4mm were measured using cosmic rays respectively. The results show that the performances of the two drift chambers are almost equivalent.
In order to measure the radiation dosimetry by heavy ions which entered the Shen-Zhou (SZ) shuttles, a solid state nuclear track detector CR-39 was installed in the inner wall of SZ recoverers. Using a CR-39 detector the energy transfer from heavy ions was measured when the shuttle was travelling in space. This work described a calibration of the response of CR-39 detector to the energy deposition using 9 ion accelerator beams from C to Kr. The calibration points cover the whole sensitive region of the CR-39 detector. For the linear energy transfer (LET ) is larger than 12.6 keV/μm-H2O, the total absorbed dose of SZ-3 and SZ-4 are obtained to be (23.50±0.46) μGy and (35.34±1.57)μGy , respectively, the corresponding total dose equivalent are obtained to be (355.6±9.7) μSv and (574.4±15.6)μSv，respectively.
Taking L3 Cosmics experiment (L3+C) as an example, we discussed a new Cellmap to reconstruct the hit in drift chamber of magnetic spectrometer for the very inclined comic-ray tracks, and compared the reconstruction results with the standard Cellmap of L3+C. It shows that, for the very inclined cosmic-ray tracks, the new Cellmap can reconstruct more hits than the standard Cellmap, and the distribution of χ2 of track reconstruction is also improved.
Dragon-Ⅰ is a linear induction electron accelerator. This facility consists in a 3.6MeV injector, 38 meter beam transport line and 16MeV induction accelerator powered by high voltage generators, including 8 Marx generators and 48 Blumlein lines. This paper describes the physics design, development and experimental results of Dragon- Ⅰ. The key technology is analyzed in the accelerator development, and the design requirements and operation of the major subsystems are presented. The experimental results show Dragon-Ⅰ generates an 18—20MeV, 2.5kA, 70ns electron beam. The X-ray spot size is about 1.2mm and dose level about 0.103 C/kg at 1 meter.
DAI Guang-Sen, ZHANG Lin-Wen, LIU Cheng-Jun,
ZHANG Wen-Wei, ZHANG Kai-Zhi, DAI Zhi-Yong, LAI Qing-Gui,
LI Hong, WEN Long, LIU Xiao-Ping, LI Wei-Feng, XIE Yu-Tong,
CHEN Si-Fu, YANG Guo-Jun, LI Xin, YANG An-Ming, WANG Min-Hong,
YANG Xing-Lin, PAN, Dragon-I Linear Induction Electron Accelerator[J]. Chinese Physics C, 2005, 29(06): 604-610.
For the severe requirements of BEPCⅡ injecting kicker magnets, the two schemes of low impedance kicker magnets used in other accelerator labs in the world are not adaptive to the BEPCII storage ring. A new scheme of kicker magnets proposed in this article solves the difficult problem of BEPCII kicker magnet design. And the successful construction of a prototype has demonstrated that the new scheme of kicker magnets is viable and the design of the kicker magnet structure is reasonable.
A new method for the measurement of the thermal emittance in the RF photoinjector is introduced in the paper. The measurements are affected mainly by three factors which are the RF effect, the space charge affect and the error of measurements. According to the theory of emittance growth in the RF photoinjector and the simulation, a new method to eliminate the RF effect is proposed for the thermal emittance measurements in RF photoinjector. Error of measurements is not included , and the space charge effect is also ignored on the condition of the low charge operation mode.
Coherent X-ray scattering spectra of some explosives (black powder, TNT, etc.) and some non-explosives (sugar, milk powder, coffee, paper, etc.) have been measured using polychromatic X-rays (1.2—38.2KeV) on Beijing Synchrotron Radiation Facility of IHEP Beijing. The measured peak positions of X-ray diffraction spectra can be regarded as a 'fingerprint' of the explosives. Principally, peak positions and identification techniques of diffraction spectra can be used for the identification of explosives.
Using the properties of the q-deformed boson creation and annihilation operators and their inversed operators, two kind of q-deformed pair coherent states are introduced. Antibunching effects and correlation properties between two modes in the states are investigated. It is shown that q-deformed pair coherent states exhibit antibunching effects and the photons of the two modes are correlated. These nonclassical effects are influenced by the parameter q. These effects increase when |lnq| increases.
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