2001 Vol. 25, No. 1
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A simulation program of BES trigger is described and a comparison of its results with experimental data is presented. With this program, the efficiencies of BES trigger system for different kinds of events generated by Monte-Carlo simulation are given for the first time and they are consistent with those measured by the experimental method. It proves that this trigger simulation code is suitable for studying the performance of BES trigger system and is a Complement of BES Monte-Carlo simulation code library.
A model,which treats three initial parlous as two color singlets and then both of them fragment independently into hadrons, is employed to study the angular dependence of charged multiplicity distribution in e+ e- annihilation into three-jet events at LEP energy region. The calculated results show a distinguished dependence of charged multiplicity to topology structure of events, and also agree well with experiment data from ALEPH collaboration.
The completeness and higher-order squeezing properties of generalized odd and even coherent states of a Q-deformed non-harmonic oscillator are investigated. The results show that they may form a complete Hilbert space, and the odd-order squeezing effects exist in all of the states.
The large angle correlations for in-plane and out-of-plane have been measured for the pairs of the fragments and light charged particles (LCPs) in the reaction of 25MeV/u 40Ar+115In. The azimuthal correlation functions and the azimuthal asymmetry factors were obtained. The azimuthal correlation functions of all pairs between fragments and a particles are of minimum value in φ=90°plane. It indicates that the LCPs and fragments formed in the reaction exhibit an enhanced emission in the reaction plane due to collective rotation-like effect induced by attractive mean field. The more heavier the masses of the coincident LCPs and fragments are, the more stronger the left-right asymmetries of the coincident particles with respect to the beam direction in the reaction plane are, the more preferential the particle emission to the direction opposite to the coincident reaction products is. Along with the increase of the mass of the coincident LCPs and fragments, the influences of the sequential decay and particle final state interactions on the azimuthal correlation functions of the correlated pairs in the φ=0° plane decrease and vanish at last, the collective rotation-like effect is enhanced, and the azimuthal asymmetries increase.
In the relativistic σ-ωmodel, the influence of the parameters in self-interaction of a meson to the equation of state of normal nuclear matter, especially, to incompressibility, effective mass, and coupling constants, is studied in detail. We find that these parameters have an intense relationship to the property of nuclear matter. At the same time , we study the relation between the binding energy and pressure of relativestic △-resonance nuclear matter and temperature using using above results in the relativistic σ-ω-π model,and it is interesting to compare it to our prior work. In all these studies, the vacuum fluctuation on nucleon, △-isobar, and σmeson is considered.
Relativistic quark model is employed to study the helicity amplitudes and the electroproduction amplitudes of the Δ(1232) and N* (1440). The meson cloud effect is considered. The calculations show the improved results for those spin observebles. A good description for the Roper resonance is achived.
The variations of moments of inertia of superdeformed (SD) bands 194Hg(1)and 192Hg(1) with angular momentum (rotational frequency) are investigated using the particlenumber conserving (PNC) method for treating the cranked shell model. Calculations show that if both the monopole and Y20 quadrupole pairing forces are taken into account, the observed co variation of the moments of inertia of 194Hg(1) and 192Hg(1) can be reproduced very well both in the low-and high- ranges, in particular the J(2) downturn of 194Hg(1) and the flattening in J(2) of 192Hg(1) at>0.40MeV. On the contrast, the calculated J(2)'s with the Y2±1 or Y2±2 quadrupole pairing forces are in disagreement with the experiments. The microscopic mechanism of the co variation of J(2) is clearly exhibited in the PNC calculation (the contributions to J(2) from various major Shells and individual cranked Nilsson orbitals, the occupancy of each cranked Nilsson Orbital etc). The variation of moment of inertia is the result of the competition among the shell effect (single particle motion in a deformed potential), pairing correlation, Pauli blocking effect and Coriolis (anti-pairing) interaction.
Comparison of the difference between the neutron and proton RMS radii, RMS, calculated from the neutron skin thickness of the droplet model was made with the data obtained from the experimental total nuclear reaction cross section. It was found that the droplet model reproduced the RMS of normal nuclei well, but it underestimates the RMS for neutron skin and neutron halo nuclei. Since the small separation energy of last one or two neutron is one of the most important causes of the appearance of anomalous nuclear structure, an effective neutron skin thickness was used to distinguish nuclei with anomalous neutron distribution from normal nuclei, which succeeds to reproduce the abnormal increase of the neutron skin thickness for the light nuclei with neutron skin or neutron halo.
In electromagnetic calorimeter, Longitudinal light collection uniformity of crystal scintillator has sizeable influence on the energy resolution. Monte Carlo (MC) method is used to simulate the process of light transmission and collection in long lead tungstate (PbWO4 or PWO) crystal. Discussion focused on the role of factors such as attenuation length and refractive index to light collection is presented.
Because of the large emittance and momentum spread of injection beam, the edge field of magnets will affect beam optic property during injection into the experimental ring of HIRFL-CSR (Heavy ion Research Facility in Lanzhou-Cooling Storage Ring). The influence of edge field is probed in this paper by numeric tracking of particles through it. The influence is reduced to tolerable range by modifying injection central orbit and field distribution of the magnet.
This paper deduces the equation of coupler frequency deviation Δf and coupling coefficient β instead of only giving the adjusting direction in the process of matching coupler, on the basis of coupling-cavity chain equivalent circuits model. According to this equation, automatic measurement and quantitative display are realized on a measuring system. It contributes to industrialization of traveling-wave accelerators for large container inspection systems.
A new form solid Carbon has been synthesized consisting of a hexagonal close packing of a26 molecules under energetic C26 ion 2.4 MeV bombardment of ultra high molecular weight polyethylene. The beam current was about 150 mA and the total dose was 1×1016 ions cm－2. The residual gas pressure in the irradiation chamber was 1.3×10－4Pa during bombardment High-resolu-tion transmission electron microscopy, electron diffraction, and time-of-flight mass spectroscopy studies of the molecular packing confirm that the C26 molecules have the Caged fullerene structure.
Stacked polystyrene films of about 53μm in thickness were irradiated with 1.4GeV argon ions at room temperature and in vacuum. The radiation induced Chemical changes of each film were studied by the Fourier-transform infrared (FT-IR) and ultraviolet/visible (UV/VIS) spectroscopies. It is found that the material is seriously degraded after irradiation and the chemical modifications depend strongly on electronic energy loss. Significant degradation of the material occurs above about 0.77keV/nm at the dose of 5.5×1012 ions/cm2 corresponding to an energy deposition of 6. 4MGy. The main chains of PS as well as the phenyl ring are destroyed in the track core simultaneously. Damage cross sections Of alert 29urn2 are found for phenyl ring and the -CH2- group. Aldynes are produced above an energy loss of 0.77keV/nm .
The characteristics of a 50m2 RPC carpet(prototype of YBJ-ARGO experiment)was analyzed using its test run data. A correction method of the systematic time error is suggeSted, and nonunform azimuthal angle distribution possibly due to direction reconstruction error on an asymmetric carpet is reported
To describe the random motion in the symmetric space, the diffusion equations in a group manifold have been developed. A concrete formula of the diffusion equation on the compact Riemannian space was presented. Furthermore, the corresponding quantum diffusion motion in the space was also discussed.
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