2003 Vol. 27, No. 5
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The equivalence of two χ2 forms is proved by matrix calculation. The bias of minimization estimate is also discussed. The simplified R-value measurements are quoted to test the conclusion quantitatively.
Using double gluon exchange model and the heavy quarkonuim color octet production mechanism, the diffractive cross sections of ψ in the π a p collision process are calculated and discussed. The results show that the diffractive total cross section of ψ increases with the increasing center of mass energy. Furthermore, the discrepancy of the total cross section calculated with different gluon distribution functions also increases with the increasing center of mass energy. Comparing the calculated results with the future experiment data, the gluon distribution function of π and double gluon exchange model could be examined.
A method to calculate infrared divergence of loop function is introduced. Using this method, we analysis the divergence property of three point loop function and get the criterion to judge whether there exists infrared divergence for three point functions. The explict forms of infrared divergence in some cases are obtained with mass regulation or dimension regulation. Such method can also be applied to four point loop functions.
We consider N=2 superconformal field theories on a two dimensional torus with central charge c=3. In particular, we present the partition function for this theory. Furthermore, to generate new theories, we recall general orbifold prescription. At last, we construct the modular invariant Z2 orbifold prime model.
This paper studies quantum correlations of quantum systems and the basic dynamics process, which initiates the forming of quantum correlations. It discusses the mutual contact between the emergence of the condensate and the formation of off-diagonal long-range order. It discusses the one-particle density matrix as a primary object displaying such an order. And it derives an expression for the cross section of the direct and the reversed processes in the lowest order. Accordingly, important information about quantum correlations can be deduced directly from the differential scattering cross section of these processes.
The μ pair decayed from Z0 is a good means to check the quality of reconstruction program in L3 Cosmic experiment. This paper describes the method of selecting Z0→μ+μ－events from data sample recorded during April,May,August and September,2000 when the LEP was running at Z0 energy.The momentum resolution of (5.47±0.25)% for 45 GeV muon is obtained.
Near barrier fusion excitation function of 6Li+208Pb system has been measured. The CCFUS calculations with and without the coupled elastic channels taken into account were performed.By comparing the theoretical and experimental results, we can conclude that at the above barrier energies,the fusion cross sections have decreased due to the break up effects,but in the sub barrier energy region,the influence of the break up on the fusion cross section is modest.
High spin states of 207Rn have been investigated via the 196Pt(16O,5n)207Rn reaction at 16O energies from 85 to 95 MeV using techniques of in beam γ-ray spectroscopy. The measurements of γ-ray excitation fuction,γ-ray spectra,γ-γ-t coincidences and decay γ ray spectra were performed with 10 BGO(AC)HPGe detectors.Based on these measurements,a level scheme of 207Rn with 17 γ rays is established. The spins for most of the levels in the scheme are proposed according to the results of measured γ-ray DCO ratios. Comparing the structure between 208Rn and 207 Rn, the low lying levels in 207Rn are interpreted by coupling a valence neutron hole (f 5/2) to the excited states in 208Rn core.
High-spin states in 141Nd have been studied using in beam γ-ray spectroscopic techniques with the heavy ion induced 130Te(16O,5nγ)141Nd reaction at 85 MeV beam energy. Nine anti Compton HPGe detectors were employed for the measurements of γ-ray singles and γ-γ coincidences. The previously reported 141Nd level scheme is significantly revised and extended up to much higher excitation energy. Spins for many excited states in 141Nd are tentatively assigned according to the measured γ-ray anisotropies. The level structure of 141Nd is interpreted by coupling a h11/2 neutron-hole with the respective excited states in the 142Nd core.
Ground state systemic properties of single-Λ and double-Λ hypernuclei for even N Ca isotopes ranging from the proton drip line to the neutron drip line are studied by using the relativistic continuum Hartree Bogoliubov theory with a density dependent δ pairing interaction. Compared with the ordinary nuclei, the predicted neutron drip line nuclei are 77Λ Ca and 78 ΛΛ Ca respectively, i.e., the last bound hypernuclei has two more neutrons than that of ordinary nuclei. Based on the analysis of two neutron separation energies, neutron single particle energy levels, the contribution of continuum and nucleon density distribution, giant halo phenomena due to pairing correlation and the contribution from the continuum are suggested to exist in Ca hypernuclei.
Within the isospin dependent Extended Brueckner-Hartree-Fock framework,the single particle potentials and effective masses of a neutron and a proton in isospin asymmetric nuclear matter as well as their isospin denpendence have been investigated. The effects of ground state correlations are also studied and discussed.It is found that the meutron mean field becomes more repulsive while the proton one becomes more attractive as increasing asymmetry parameter β,and both display a linear dependence on β at the lowest order approximation. The ground state correlations lead to a repulsive and nonlinear β-dependent contribution to both the neutron and proton single particle potentials.
The influence of medium correction of isospin dependent nucleon nucleon (NN) cross section on fragmentation in heavy ion collisions at intermediate energies is studied by using the isospin dependent quantum molecular dynamical model. The results show that the medium correction of isospin dependent nucleon nucleon cross section enhances the sensitivity of the free nucleons emission and multiplicity of intermediate mass fragments on the isospin effects of NN cross section. The character of nuclear stopping that depends strongly on the isospin effect of NN cross section and weakly on the different forms of symmetry potential is not affected by the medium correction of NN cross section.And hence this charater of nuclear stopping stems mainly from the isospin effects of free nucleon nucleon cross section.
Based on the quantum molecular dynamics(QMD),statistical decay model(SDM)and the semi-empirical multi-mode fission model,the mass yield distributions of proton-induced fission near 200MeV were calculated. By the experimental results of the 190MeV p+208Pb and 170MeV p+238U,the fitted parameters,which were used in the semi-empirical multi-mode fission model,can be gotten.Using these parameters in some other calculations one found that the results were in accordance with the experimental data.These methods and the fitted parameters were available.
The subjects related to the giant dipole resonance model for the γ production mechanisms induced by fast neutrons have been studied in the nuclear mass region 180≤A≤210.It contains the difference between the γ-ray strength functions of the cascad γ deexcitation processes in the (n,γ)and (n,n′γ)reactions as well as the variation tendency of the reaction cross section ratios between the direct-semidirect radiative captures and the compound nucleus statistical processes with the incident energies, nuclear mass numbers and the nuclear shells. The numerical calculations and the comparisons with the experimental values for 181Ta,
Based on experimental data of total,nonelastic, elastic cross section and elastic scattering angular distributions for n+Sn reactions, a set of neutron optical model potential parameters is obtained. The inelastic scattering cross sections and angular distributions of discrete levels are calculated and analyzed by the distorted wave Born approximation theory based on the unified Hauser Feshbach theory and the exciton model.With the fitting procedure the neutron optical model potential parameters are obtained.The results indicate that the systematicness of the inelastic scattering cross sections can be given for n+116,118,120,122,124Sn which are all in good agreement with experimental data.
A new approach of the kinematic fit in event reconstruction is introduced.In the new approach, the method of regula falsi is used to solve the constraint equations, instead of the conventional linear approximation. Applying this algorithm to E705/E771 Monte Carlo data of J/ψ→μ++μ－,the momentum resolution of J/ψ is significantly improved.
Based on the linear difference resonance coupling perturbation theory, studies on the coupling in Beijing Electron Positron Collider (BEPC) synchrotron radiation mode are carried out. The coupling coefficients are measured and the sources of coupling are analytically calculated and simulated. After introducing skew quadrupoles, the residual coupling is successfully compensated.
The effects of the parameters of RF system to electron beam intensity in Hefei storage ring are discussed in this paper. There appeared significant deviation respect to bean ideal orbit in the closed orbit distortion correction experiment, and therefore, necessary adjustments have been carried out for RF system parameters, such as frequency, cavity temperature, etc., to meet the requirement of intense beam injection. And the work have guidance effect to reconstruction of RF system in Phase Ⅱ project of Hefei storage ring.
The soft X-ray streak camera is very important detection tool for studying soft X-ray time characteristics. We have calibrated its absolute energy response in terms of X rays provided by synchrotron Radiation Source on the BSRF. The combined uncertainty of quantum efficiency of the streak camera in 100-1000 eV photon energy reagion is 23%.
This paper proposes a new method to measure the 2-D beam transverse phase space with computerized tomography (CT) technique and Cerenkov radiation "double imaging method". The usual method with CT technique entirely depends on the quadrupole-scanning and can not get a full π Radon rotation angle, which is essential to the Radon transform, the mathematic fundamental of CT technique. Therefore, it has to prior assume a certain kind of phase space distribution to extrapolate the vacancy of Radon rotation angle, which makes the reconstructed image imperfect and yields errors especially when the phase space distributions practically are not ideal. In this paper, by means of Cerenkov radiation double image method and mathematical analysis, we obtain a full rotation angle of the beam phase space precisely from 0 to π. Hence we can measure the actual 2-D transverse-phase-space density without making any prior assumptions about phase space distributions. The simulation results show that this new method is feasible and with much higher precision.
Fe+ ions with the energy of 110 keV were implanted into films of L(+)-cysteine. FTIR, UV VIS spectrometry and 1H- NMR analysis of the irradiated samples prove that some of the original bio-molecules were seriously damaged and significant modifications were induced. ESR analysis shows that a kind of long life radical was formed in the irradiated samples. The results of ESI-FTMS analysis further supports the molecular modification induced by low-energy ion beam irradiation. The radiation effects are closely connected with the energy deposition in solid L(+)-cysteine samples.
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