1995 Vol. 19, No. 10
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The updated structure and specifications of the high performance detector system of TR4 at HIRFL are described. The system consists of Si multi-unit telescopes, IC + PSD + SPD + CsI(T1) logarithmic density telescopes, projectile-like fragment TOF spectroscopes, 3×3 and 6×6 CsI(T1) scintillator arrays and Si + CsI(T1) light particle telescopes. The Z/△Z～50 and BE/E～0.3% for St telescopes, Z/△Z～44.5 and △x～1.7mm for logarithmic density telescope,A/△A～86, Z/△Z～48, △E/E～0.78 % and △t～286ps for projectile-like fragment TOF spectroscope focusing with elliptic surface mirror are obtained.
The 28Si(p, p)and (p, p') reactions were studied with a 22 MeV proton beam.The differential cross sections for elastic scattering and inelastic scattering from 21+(1.78 MeV) and 41+(4.62 MeV) excited states were measured and compared with the results based on momentum space DWBA theory.A complex density-dependent and energy-dependent effective interaction(CEG) and transition densities obtained from electron scattering were used in the calculations. The present parameter-free calculations provide a satisfactory description of the low-energy proton scattering data on 28Si.
The differential cross section of fast neutrons on 6Li and 7Li has been measured at 14.7MeV using associated particle time-of-flight technique.Scattered neutrons are detected at 9 angles from 35 to 115 deg in massively shielded ST451 liquid scintillator located 254cm from the scattering sample.The efficiency curve of neutron detector was determined by measuring the n-p scattering in polyethylence. The total error of the differential cross section is from 10% to 15% including the statistical error of 1.0-5.0%and the measurment error of efficiency curve of 6.0%7.5 %.
360 thousands of Monte-Carlo EAS events have been simulated by using the "GENAS" package as well as the geometry and instrument response of Huairou EAS array.They are used for the investigation of array perfromance and event selection criteria,and for the check of experimental data.It shows that there are fair coincidence between the experimental and the simulated results on the trigger rate, the zenith angle distribution, the Size response etc.The accuracies of core position and arrival direction are about 3m and 2.5°, respectively.The relative error of EAS Size determination is about 8% when the Size is about 106,the peak value of energy response of array is 5×1014ev and the best fit of the relation between EAS Size and primary energy is E≈10.64N0.84.
Under the Thermofield Dynamics, according to the cutting theorem at finite temperature a set of systematic explicit cutting rules to the Feynman diagrams and the relative Feynman rules are proposed, which can be used as an easy approach to calculate the imaginary parts of the thermal Green functions. We applied it to study the imaginary parts of two-point,three-point and four-point Green functions as examples.
Using the Kinetic equation and considering the effect of the average field,the transport coefficients of quarks in QGP under the relaxation time approximation are calculated,and the viscous effect and thermal conductive effect of QGP are discussed.
The angular infrared divergences of three-loop vacuum graph in the massless scalar field φ3 theory and the scheme of dimensional regularization for these divergences are discussed.Its analytical expression in D-dimensional space is given.
Assuming that the produced particles decay isotropically in the center of mass system,the transverse energy rapidity distribution in hadron-nucleus interactions is derived.The calculated results are in a good agreement with the experimental data given by HELIOS collaboration working at CERN/SPS.
In this paper,the nucleon-nucleon elastic cross section σnn(E,ρ) in medium has been calculated and discussed at nonrelativistic energy region by using Skyrme interaction. It is found that under Pauli correction σnn in medium is larger than free nucleon-nucleon cross section for lower densities,and σnn in medium above spacial energy is larger than free nucleon-nucleon cross section for higher densities.
One rotational band of 160Lu was identified through the 144Sm(19F,3n)160Lu fusion-evaporation reaction.The Jπ assignments of this band are discussed on the basis of additivity law.
The effects of quark-antiquark pairs of quark sea and hybrid states of gluonquark are considered in the proton wave function. The spin-dependent structures of the proton,such as magnetic moment, axial-vector coupling constant GA/GV, and integrated structure functions g1p or g1n are calculated with some improvements using the wave function.
Starting from the Bohr Hamiltonian, a new formula is obtained to describe the γ-soft nuclei in terms of introducing an effective potential. The formula is fitted to the data.of the yrast lines of standard γ-soft nuclei.The relative errors are not beyond five percent.
Based on the quantum molecular dynamics model, the time and energy evolutions of intermediate mass fragments (IMF)and its dynamical origin are systematically studied for 40Ca+40Ca central collision.The transition of reaction mechanism, the relation between the density fluctuation and IMF and the time scale of IMF emission are discussed in detail.The relative density fluctuation attains to maximum at energy region of 50-80MeV/u corresponding to an obvious increase of IMF. The possible occurrence of total disassembly at incident energy of about 65MeV/u for the studied reactions is predicted.Meanwhile, a saturation value (140fm/c) for time scale of multifragmentation is obtained.
The design principle and main parameters of the permanent magnet Mini-βscheme for the Beijing Electron Positron Collider (BEPC) are described.In the design,the BEPC storage ring will have a Mini-β insertion and a conventional insertion in the southern and northern interaction regions respectively.The arc and injection regions are kept unchanged. The Mini-β insertion quadrupoles are designed to be permanent magnets.A vertical focusing electromagnet is positioned near each of the two gates of BES so that the dynamics perturbation due to the constant field strength of the permanent magnet in the energy ramping can be compensated. The designed βx*=1.2m, βy* = 0.036m,and the length and strength of the permanent magnets are 0.5m and 8T/m respectively.Compared with running mode now,the designed luminosity is incresed by a factor of about 3.
New heavy neutron-rich isotope 175Er was synthesized for the first time in the 176Yb (n,2p) 175Er reaction by 14 MeV neutron irradiation of natural metal ytterbium.The activity of 175Er was observed using γ(X) spectroscopic method. The 8 new γ rays of 76.5,120.9,123.7,128.5,227.3,234.0,281.4,1167.5 keV with half-life of 1.2±0.3min was found and assigned to the 175Er decay. A partial decay scheme of 175Er was proposed.
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