2003 Vol. 27, No. 9
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The properties of four factorized chi-square forms, which are used in minimization of correlated data, are studied, including their biasness and unbiasedness. The simplified R-value measurement are quoted to test the conclusion quantitatively.
Using the hypothesis of maximum non-perturbative strong interaction reaction and basing on the character of none unitarity corrections in the amplitude for exchanging the non-perturbative color octet gluer, constituent of Pomeron, in strong-soft interaction processes, we proposed an alternative approach to discuss the electromagnetic decay of ηc into two photons.
The two-body nonleptonic charmed meson decays into two pseudoscalar mesons are studied using one-particle-exchange method. The effects of the final state interactions are analyzed through the strong phases extracted from the experimental data.
A periodic solution in two-dimensional dilaton gravity model is obtained in this paper, the equivalence of periodic solution with electric sine-Gordon soliton solution is proved through coordinate transformation.
Supersymmetry and Shape invariance of Double ring-shaped oscillator (DRSO) is studied. The energy eigenvalues and eigenfunctions of DRSO are obtained.
In this paper, we make use of the Burgan et al's method to derive the solution of the time dependent coulomb potential and linear potential with a special form, V(r,t)=-a0ξ 12r+a 1rξ32, (where ξ=at 2+bt+c, a 0, a 1, a,b,c are parameters with certain relations) and furthermore we discussed the wave function for V(r,t)=-a 0ξ 12r+nk=1 a kr kξ k2+1 (where a 0, a 1, ..., a n are constants), Meanwhile we analyzed the physical meaning of this special potential and the importance of the linear scaling factors C(t) in the study of repeated elastic reflections of a particle in an expanding spherical cavity.
Some results have been introduced on China-Italy DAMA cooperation--100kg NaI(Tl) crystal set-up experiments. There are lots of background problems need to be studied carefully, which would affect the results of DAMA experiments. Here, the radiation backgrounds in 100kg NaI(Tl) set-up have been studied by Beijing Group, and the Monte-Carlo simulation results are in good coincidence with the measurement of DAMA experiments. In addition, the contribution coming from fast neutrons' or solar neutrinos' interactions have been obtained through the simulation, which made very small effects on the experiments.
High spin states of 80Rb have been studied by using fusion evaporation reactions,65Cu+19F,66Zn+18O and 68Zn+16O with beam energies of 75MeV, 76MeV and 80MeV, respectively, at HI-13 Tandem accelerator Beijing and JAERI Japan. γ-γ coincidence and DCO ratios were measured by the HPGe detector systems. About twenty new γ transitions are added to the previously proposed level schema from the present experiments. The second negative band is pushed up from 12－ to 22－. Abackbending at frequency of 0.49MeV is observed. Evidence has also been found for two hitherto unknown sidebands built on the negative yrast band. Signature splitting in both negative bands is observed. Signature inversion occurs only in the yrast negative band at spin of 15 and it is close to that of 82Y. The plots of [E(I)-E(I-1)]/(2I) vs I are given and compared with its isotones 78Br and 82Y as well as its isotopes 76Rb and 78Rb.
In this paper, we calculate the properties of the spin polarized isospin asymmetric nuclear matter by employing the Skyrme effective interaction with two sets of parameters SKM * and SⅢ, giving the equation of the state and the radio det(1/χ)det(1/χF) which is shown as a function of the density for several values of the asymmetry parameter β. It is shown within the Skyrme-Hartree-Fock framework that there is the ferromagnetic phase transition in the isospin asymmetric nuclear matter at some density, above which the nuclear matter becomes stable against spin fluctuation, and the critical density for the ferromagnetic transition decreases with increasing the asymmetry parameter. In addition, we also compare the phenomenological Skyrme model with microcosmic BHF (Brueckner-Hartree-Fock) theory with respect to the phase transition.
The shell closure and shell anomalies of Mg, Si and S isotopes are investigated in the framework of relativistic mean-field theory. From two-proton and two-neutron separation gaps, we find that (1) there exist obvious shell effects at N=12, 16 in Mg isotopes, at N=14 in Si isotopes, and at N=16 in S isotopes, (2) the shell structure of Si isotopes at N=28 does not disappear, (3) the shell effects of Mg, Si and S isotopes at 20 are not very obvious.
Influence of the shell effect on the emission of light particles prior to scission is explored in the framework of the Smoluchowski equation. Doubly magic nuclei 208Pb and 132Sn are chosen as examples to demonstrate this shell effect. Results show that shell has an effect on light particle emissions. For neutrons, the shell effect is significant. Moreover, it is found that this shell effect on neutron emission gradually fades out with increasing the excitation energy.
The dependence of entropy index μ 2 on the width and shape of multiplicity distributions are studied in detail by using Monte Carlo method and comparing with the results from NA22 experiment.It is found that the entropy index is insensitive to the shape of multiplicity distribution but decreases with the increase of the distribution width.The latter observation contradicts the usually expected role of the index,indicating that μq is not an appropriate parameter for measuring event-by-event fluctuation.
The software of track reconstruction of the vertex chamber of BESⅡ-VCJULI was studied when it was transplanted from the HP-Unix platform to PC-Linux. The problems of distinct dictionary storage and precision treatment in these two different platforms were found and settled in the modified software. Then the obvious differences of the candidate track number in an event and some track parameters caused by them were reduced from 74% to 0.02% and from 5% to 0.5%, respectively. As a result, the quality of the track finding was greatly improved and the CPU time saved.
Kinematic Fitting is one useful method for physics analysis in order to improve the precision of the parameters to be fitted. Based on the Telesis package written with Fortran which is the code for kinematic fitting, we design a new package called Telesis++ with most popular Object-Oriented C++ language. The packages written with C++ have many characteristics such as flexibility, compatibility and expansibility. The result shows that Telesis++ has the same result with the Telesis. Telesis++ can be one of physics analysis tools for BESⅢ in the future.
In designing the 3rd generation synchrotron radiation light source, many long, and dispersion free straight sections are left for installing undulators to produce coherent radiation. For the damping ring used as pre-injector of next generation linear collider, many wigglers are used to increase radiation damping rate. So it is important to understand those Insertion devices'(ID) influence on beam dynamics in design and optimization stage. This paper introduces the study of insertion device's influence on beam dynamics in electron storage ring using the symplectic Lie mapping. Firstly the Hamiltonian of charged particle's motion along ID axis is given, then two methods are adopted to analyse ID's influence on beam dynamics. One method is expanding Hamiltonian to 4th order Taylor series, then all kinds of multipole components (till to octupole) can be obtained; another is constructing a second order symmetrical, symplectic integrator using Lie map product by similar transformation directly. The simulation results show those two methods are consistent. The primary results of influence on beam dynamics of UD-1, a new undulator which will be installed in Hefei Light Source storage ring soon, are also given. The tune-shift and decrease of dynamic aperture caused by UD-1 can be found in simulation results.
With the help of electron cooling code, the cooling time of 16O8+ ion beam are simulated in various parameters of the ion beam in the HIRFL-CSR electron cooling storage main ring, such as ion beam energy, initial transverse emittance, and momentum spread. The influence of the machine optical parameters-betatron function, and dispersion function on the cooling time are investigated in this paper.
Particle simulation results of coherent stimulated radiation from subnanosecond electron bunches moving through a periodic waveguide and interacting with a backward propagating TM01 wave are presented. The longitudinal guiding magnetic field is 1.8T, the peak power as high as 100 MW for the 300ps pulses at 38GHz. The mechanism of microwave pulse generation was associated with the mutual influence of different parts of the electron pulse due to slippage of the wave with respect to the electrons; The dependence of peak power on the square of the total charge is almost linear, it means that all electrons of e-bunch radiate coherently. This can be interpreted as superradiance.
Measurement of electron bunch length through its generated CTR is a new frequency domain technique developed in the accelerator and FEL fields recently. In this paper we analyze theoretically and calculate numerically CTR produced by a train of RF-linac electron bunches of a few picoseconds at BFEL. For the CTR emitted at wavelengths longer than the bunch length (λ≥2πσz),the intensity is enhanced by a factor of 108which is the number of electrons in the bunch; CTR energy is mainly concentrated near the beam axis and can be up to several millijoules for Gaussian and rectangular bunches. A polarized-type Michelson interferometer was designed to measure autocorrelation interferograph of CTR, from which one can diagnose longitudinal length of this bunches and derive its electron density distribution.
Standard radiative source are monitored by a system containing several detectors. When a source moved out from the monitored area, the counting rates of the system will be changed, and the position and radiation intensity of the source can be estimated by the counting rates variations.
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