2004 Vol. 28, No. 1
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We report the results of an experimental study of the exclusive hadronic decays for D0→K0 sπ+π - and K 0 sK +K - and their resonant structures using BES-Ⅰ detector at the BEPC Collider. Using the data sample of 22.3 pb -1 collected at the center-of-mass energy s=4.03 GeV, we measured the branching fraction for D 0→K 0π +π - to be (5.32±0.53±0.40)%, the branching fractions for the decays D 0→ K *-π +, D 0→K 0ρ 0 and D 0→K 0(π +π -) non-resonant to be (6.05±0.32±0.49)%, (1.17±0.17±0.13)% and (1.35±0.22±0.17)%, respectively. We measured the branching fractions Br(D 0→f) to be (1.04±0.24± 0.16)% for f=K 0K +K -, (1.12±0.34±0.15)% for f=K0, and (0.27±0.13±0.03)% for f=K 0(K+K-)non-.
From calculation and analysis of the mean light flavor quark production probability in light quark jet events, e＋e－→q0q0→h′s, which involves electromagnetic interaction and hadronic interaction, we determine the dependence of the mean production rates of particles in light (uds) quark jets on the primary quark flavor and number of quark pairs N. Moreover, the relative production rates of leading hadrons are obtained, which shows a strong correlation with the quark pair number N. These results provide a basis for furture studies of particle production in light favor jet at low center-of-mass energy range.
According to the Dirac constraint theory and the extended gauge condition, the gauge generators and the BRST transformation of (1+1) dimension O(3) non-linear model under the new general condition have been deduced. A new general commutation relation of ghost field, the BRST charge from gauge generator is obtained and a kind of BRST quantization of the model is completed, on these bases, then the generating functionals of Green function, connecting Green function and proper vertex are also deduced and finally three kinds of Ward identities of this model are acquired.
The excited k-boson q-coherent state a+m qz,k,j〉 q is constructed. The m dependence of the antibunching effect is numerically studied. It is shown that the antibunching effect evidently depends on m: For big x(x=z 2), the excitation can change the region where the antibunching effect appears; For small x, when j=0, the excited states exhibit strong antibunching effect but the unexcited states exhibit strong bunching effect; For small x, when j≠0, both the excited states and the unexcited states exhibit strong antibunching effect.
A chiral hadronic model is extended to investigate the influences of trapped neutrinos on the equation of state of dense matter and structure of protoneutron stars. Our results show that trapped neutrinos lead to the increase of proton fraction and make the equation of state of dense matter soft. Furthermore, maximum masses and radii of protoneutron stars decrease when neutrinos are trapped.
By means of the component coefficient equation and the updated data of abundances of the solar system, we calculate the element abundances of 64 poor-metal stars. The result shows that the rapid neutron capture process (r-process) is the main source of neutron capture elements in poor-metal stars. Besides, the yields of heavy neutron capture elements in stars whose metallicity is less than -2.5 may come from pure r-process. The producer of the heavy neutron capture elements may differ from that of the light.
High spin states in neutron-rich 116,118,120Cd nuclei have been investigated by observing high-fold prompt γ-ray coincidence events from the spontaneous fission of 252Cf with the Gammasphere detector array. The yrast bands have been extended with spin up to 18h in118Cd and 16h in 116,120Cd respectively. The band structures are calculated using the cranked shell model and possible origination for the backbends in the yrast bands is discussed. Proposed 5－ and 7－ levels are observed in each of these cadmium isotopes, and possible explanation for the negative states is discussed based on systematic comparison. A quasi-rotational band based on 7－ level in 118Cd has been established.
This work is done for improving the current international standard cross section of nuclear reaction. The features of covariance propagation in R-matrix model fitting for 7Li,11B and 16O systems are researched systematically with Code RAC, and the results about propagation of non-diagonal elements of covariance matrix are presented. It is found that in R-matrix model fitting, short-energy-range parameters result in relatively smaller covariance propagation coefficient (CPC), medium and long-energy-range parameters produce relatively larger CPC. Especially the medium-energy-range component of systematic error plays very important role in propagation of covariance. In the evaluation procedure of nuclear data both long-energy-range component (LERC) and medium-energy-range component (MERC) of systematic error should be considered in experimental data-base file. Furthermore, these conclusions are suitable for the similar model fitting in other science fields.
Based on experimental data of total, nonelastic, elastic cross section and elastic scattering angular distributions for n+Pb reactions, a set of neutron optical model potential parameters is obtained in the region of incident neutron energy from 1—300 MeV. The cross sections, angular distributions and energy spectra are calculated and analyzed by optical model, distorted wave Born approximation theory, Hauser-Feshbach theory, exciton model and cascade mechanism inside nuclear. The results indicate that the cross sections can be given for n+ 208Pb reactions which are all in good agreement with experimental data.
Through the analysis of the 3He elastic scattering on the 12C nucleus, two different folded optical potentials, one is constructed based on the α-particle model of the 12C nucleus, another is constructed based on the nucleon component model of 12C, are compared. The comparison shows that the former optical potential has some advantages.
The microscopic mechanism of the variation with rotational frequency of moments of inertia and their odd-even differences for well-deformed actinide nuclei are analyzed by using the particle-number conserving (PNC) method for treating nuclear pairing interaction. The moments of inertia for bands building on high j intruder orbitals in odd-A nuclei, e.g., the 235U (ν7/2) band, are found to be much larger than those of ground-state bands in neighboring even-even nuclei. Moreover, there exist large odd-even differences in the ω variation of moments of inertia. All these experimental odd-even differences are reproduced quite well in the PNC calculation, in which the effective monopole and quadrupole pairing interaction strengths are determined by the experimental odd-even differences in binding energies and bandhead moments of inertia, and no free parameter is involved in the PNC calculation.
Based on the constrained relativistic mean field (RMF) theory,the potential surfaces of superheavy nuclei from Z=102 to Z=118 are calculated, and the properties of these nuclei are extracted, including binding energy and quadruple deformation of the equilibrium and saddle point, neutron separation energy and the height of the static fission barrier, etc. With the single particle levels obtained from the constrained RMF theory, the shell correction energy, the pairing correction energy and the microscopic energy are obtained by means of Strutinsky shell correction and BCS pairing correction approaches. Production cross sections of superheavy nuclei in cold fusion reactions are estimated by a simple phenomenological model with the above structure information. Using the properties of the compound nucleus and evaporation residue provided by the constrained RMF with TM1 parameters, satisfactory agreement has been obtained with the avaliable experimental production cross sections in cold fusion reactions. The prediction for the production cross section of the nucleus 293118 is two order smaller than the earlier prediction and much more close to the experimental observation. Similar conclusion can also be drawn for 293116.
The inelastic scattering of antiproton (plab=600MeV/c) by 12C leading to the excitation of the three normal parity T=0 levels is studied in the framework of Glauber model. The transition densities obtained from fitting to the electron scattering data and the three annihilation potentials derived from analysis of pp scattering data are used in the calculation. The inelastic angular distribution for exciting the three lowest normal parity T=0 states in 12C at 4.44MeV(Jπ=2+), 7.66MeV(Jπ=0+), and 9.63MeV(Jπ=3-) by 600MeV/c antiproton are calculated by selecting potential parameter suitably. The results are seen to be in fairly good agreement with the available experimental data. The results are given by using the elementary two-body amplitudes comparatively.
The isospin effect of particle emission for fissioning isobaric sources 110Tc,110Pd,110In and for isotopic sources of 110,117,124In were investigated within the framework of the Smoluchowski equation. Calculations show that the emission of prescission particles depends strongly on the isospin of the fission sources; With increasing isospin, neutron emission increases, but proton and α particle emission decrease; When a fissioning source has a larger isospin, light-charged particle emission is insensitive to the dissipation strength, indicating that for a light compound system with a high isospin, the multiplicity of proton and α particle is not a useful observable of extracting the magnitude of dissipation; The trend of various light particle emission with the isospin of fissioning systems is unrelated to the dissipation strength.
A RPC (resistive plate chamber) prototype made with domestic glass is tested, which is suitable for large area particle detection. The constituent elements are two parallel glass plates with 2mm gas gap. A gas mixture of Argon, Iso-butane and F134A is utilized. Test results show that the chamber efficiency is 97% and time resolution is 1.8ns at an operating voltage 9600V, it has a relatively lower single rates than a normal bakelite chamber. Except for the dead regions caused by the spacers and frame, the efficiencies from different strips in the same readout plate show good consistency. The technological design for mass production for this glass RPC is under investigation.
The determination of dynamic aperture is a critical issue in circular accelerator. In this paper, we solved the equation of motion including non-linear forces by using successive linearization method and got a criterion for the determining of the dynamic aperture of the machine. Applying this criterion, a storage ring with FODO lattice has been studied. The results are agree well with the tracking results in a large range of linear turn(Q). The purpose is to improve our understanding of the mechanisms driving the particle motion in the presence of non-linear forces and got another mechanism driving instability of particle in storage ring-parametric resonance caused by “fluctuating transfer matrices” at small amplification.
The low level RF control system is an essential part of the RF system for Shanghai Synchrotron Radiation Facility (SSRF). In the R&D of the SSRF, one set of low level control system was developed. It consists of a 500MHz signal generator, three feedback loops, an interlock and a protection system. This paper addresses the design of this system and mainly introduces the three feedback loops.
The adiabatic capture and acceleration for the heavy ion beam in CSRm are simulated based on the study of beam longitudinal phase oscillation. The distribution of particles at different time in longitudinal phase space is shown. The RF parameters according to the character of the machine are also obtained, and the variation of the parameter during the adiabatic capture process is presented.
In the paper an average field idea and a single particle model have been introduced, and the motion behaviours in small-scale of particles have been disscussed for 2 Dimension crystallization beams in storage rings. It is shown that a particle orbit is the spiral line moved along z axis and wended around z axis, the discountinuity in the azimuthal distribution and the structure phase transition of crystallization beams have been derived by the minimun-energy principle.
Chromium valence states in yeast biomass are investigated by X-ray absorption near-edge structure spectroscopy (XANES) using an upgraded experimental method. The main advantage of this new XANES method is to record the transmission and fluorescence experimental data simultaneously in a same ion chamber. Such method is very convenient to analyze a series of unknown chromium valence state samples (e.g.relatively low Cr concentration with fluorescence mode) comparing with a standard sample (Cr2O3) using transmission mode, in order to avoid systematic error associated to the uncertainty of the edge energy induced by the different experimental operating condition. The experimental results show that in yeast biomass almost all Cr(Ⅵ) is reduced to Cr(Ⅲ) addressing the potential use of biomass for chromium reduction.
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