2000 Vol. 24, No. 4
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The differences of space distributions and time profiles between the γ-ray and proton induced shower particles are studied using Monte Carlo simulation data. The multifractal analysis is performed with the G-moment method for the distribution fluctuation of secondary particles near the core of showers induced by γ-rays and protons. From the spectrum functions of γ and proton events, it is seen that this method can be adopted as a basis for the γ/proton separation. It is shown that the separation of γ and proton can be achieved with a good efficiency in the energy region of 1—10TeV.
The erraticity analysis was performed for the experimental data of multiparticle production in pp collisions at 400GeV/c. New parameters of erraticity are calculated. Com-paring this with the results obtained by Cao Zhen and Rudolph C.Hwa, they have used a soft-interaction model ECOMB to simulate the experiment of hadron-hadron collisions at NA22 energy region, a similarity is seen clearly. This means that the model ECOMB is a soft-interaction multiparticle production model which can reproduce the fluctuations of the event structure of the final states of high energy hadronic collisions.
Traditionally, research on the phenomenological theory for neutral kaon system use the effective Htmiltonian theory based on the Wigner-Wesskopf approximation. For describing this system precisely,we use the state evolution matrix without using the Wigner-Weisskopf spproximation and get four complex parameters to describe the CP and CPT voila-tion properties of nuetral kaon system. Also we have estimated that when the order of experi-mental resolution reaches to 10－14,we will have to use state evolution matrix to describe the neutral kaon system and can not use the effective Hamiltonian theory.
We gave a new Lax representation of rational Ruijsenaars-Schneider models(n=2) which is governed by the same r-matrix as in Calogero-Moser model,and found that the corresponding r-matrix is non-dynamical.
The decay of 101Mo to levels in 101Tc has been studied using the three-parameter (γ-γ-t) coincidence system of HpGe-HpGe detectors. From the coincidence data, the new decay scheme was constructed. The previously reported 104. 70, 105. 95 and 774. 15 keV γ rays were Observed, and have been assigned to the decay scheme for the first time. A newly observed 1508. 01 keV γ ray has also been assigned to the scheme for the first time. The-tensities of β and the values of log ft to most levels were calculated.
The q-deformed moment of inertia, formulated by was first introduced as the mechanical moment of inertia of superdeformed (SD) nuclei. The E2 transition γ-ray energies and the dynamical moment of inertia of the lowest-formed bands in Hg, Ph, and TI isotopes are calculated. The calculated results indicate that the SD bands may be described by the ided-rotor with the q-deformed mpment of inertia.
Within the framework of an IQMD model, the stopping rate Erat, linear momen-tum transfer LMT, charged-particle multiplicities N., light charged-particle multiplicities N1c, neutron multiplicities N., and Zbound are investigated as a function of the impact param- eter b in reactions of 112Sn+112Sn and 124Sn +124Sn at 40 and 100 MeV/u. The results indi-cate that Nn is isopsin-dependent as a function of b at both 40 and 100 MeV/u, and Zbound is also isopsin-dependent at 40 MeV/u but not at 100 MeV/u. Meanwhile, we also discuss how to determine impact parameter of an event at lower and higher incident energies.
Based on the light charged particles and fragments emitted towards forward angles by using the heavy projectile on the light target, we have made use of isospin-dependent quantum molecular dynamics to investigate a sensitive probe on the isospin effects in the process of intermediate energy heavy ion collision. The calculation results show that the correlation between the multiplicity of intermediate mass fragments and the total number of charged par- ticles in the energy region above 80MeV/u is a sensitive probe on the isospin-dependent nucleon-nucleon cross section in medium in intermediate energy heavy ion collision, meanwhile the isospin effects of symmetric energy is not obvious in the same energy region.
Coherent states of two dimensional asymmetrical harmonic oscillator, which prop- agate in additional octupole deformation potentials, are used to investigate the characteristics of expectation values and uncertainty measures of canonical variables in space-temporal varia- tions.The quantum chaotic system shows varying behaviors as the corresponding classical chaotic system does. Thus the characteristics of quantum chaos are associated with the geom- atric symmetry of the potential surface, specifically, the existence of the negative curvature and the magnitude of the curvature in the potential surface.
Coherent states of two dimensional asymmetrical harmonic oscillator,which prop-agate in additional octupole deformation potentials, are used to investigate the complexity of the density matrix and the sensitivity against the strength of disturbance. It was found that according to the regular, partly chaotic and overall chaotic characteristics of the phase space of the classical system,its quantum analogy bears out corresponding characters, which were associated with the existence of the negative curvature at the potential surface and the magni-tude of the negative curvature.
Using Particle-Rotor Model, the energy spectra and electromagnetic transitions of the negative-parity yrast states, before and after the band-crossing in odd-A Lu isotopes, are investigated and compared with the experimental data. It is noted that before and after the band-crossing the moment of inertia of the core is a smooth function of the total angular mo-mentum I and can be described by the ah formula; The triaxial deformation before and after the band-crossing determined from the calculations is appreciably different for 161,163,165Lu, while it is more or less similar for 167Lu.
Experimental studies on simultaneous acceleration of O+ and O－ beams have been carried out in a 26MHz integrated SPlit Ring (ISR) RFQ at Peking University. Both O+ and O－ beams can be accelerated to more than 300keV. Output macro-pulse of O+ and O－ was gotten simultaneously at the exit of RFQ when O+ and O－ beams were inputted into the RFQ cavity at the same time. The output micro-pulse beams Of O+ and O－ were measured with a fast target after O+ and O－ beams were accelerated simultaneously in the RFQ. The frequency of micro-pulse is as same as the RF frequency applied to RFQ. The phase difference of O+ and O－ micro-pulse is n that coincides with the anticipated results. The beam current gotten from simultaneous acceleration of O+ and O－ beams are much stronger than that gotten from acceleration of O+ or O－ only.
Semicrystalline polyethylene terephthalate foil stacks were irradiated with 35MeV/u Ar ions at room temperature. The induced bond breaking was studied by means of Fourier-transform infrared spectroscopy as functions of ion fluence, the mean electronic energy loss and the absorbed dose. Bond breaking processes mainly take place in the ethylene glycol residue of the trans configuration and in the para position of benzene rings. The change of benzene ring structures is very small under irradiation. The hand breaking processes strongly depend on both ion fluence and the mean electronic energy loss in PET films. Significant bond breaking is only found at the absorbed dose higher than 4.0 MGy.
The high-spin states of 206At have been studied in the 197An (12C, 3n)206At reaction at 12C energies from 60 to 80 MeV using technique of in-beam γ-ray spectroscopy. Measurements of Tray excitation functions, γ-γ-t coincidences, and y-ray angular distributions were performed. A level scheme for 206At, including a 10－ isomer with a measured half-life of 908±400 ns, was established for the first the. The characteristics of the 10－ isomers in doubly edd 206At nuclei were stressed.
The deformation and shape coexistence in 188Pb have been investigated in terms of the Projected Shell Model. Comparing the experimental data with the calculated results, it is shown that three shape configurations of sphere (Z=82 shell closure), oblate (two particle-two hole in proton h9/2 orbital) and prolate (multi-particle-hole)coexist each other in the low-lying excited states and the prolate band exhibits a mixture between two kinds of multi-particle-hole configurations, which means that the neutron i13/2 alignment happens gradually in this case. The mixing is discussed and the mixing coefficients are given. The oblate band structure is predicted and the 2+ prolate state is estimated to be in the energy range of 804—80keV.
High spin states in 174Re have been studied via the 159Tb (20Ne, 5nγ) 174Re reaction through excitation function, X-γ and γ-γ coincidence measurements. A stretched E2 cascade has been identified and assigned to be the doubly decoupled band band on the л1/2－⊙v1/2－ configuration. Other two bands with semidecoupled and strongly coupled characters have been found and their quasiparticle configurations are qualitatively discussed.
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