1990 Vol. 14, No. 6
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The first measurement results of the characteristics of the synchrotron radiation spot from the photon beam line 4W1A,such as the size,intensity,energy,spectrum and position stability are reported in this paper.The results are quite consistent with the theoretical predictions.
The inelasticity of p-air and A-air interactions of superhigh energy cosmic rays is analysed and the influence of the nuclear collision geometry is investigated.
In this paper,we present the design and construction of the luminosity monitor,the main features of the detectors,and the functions of the functions of the read-out circuits and data acquisition system of the Beijing spectrometer (BES).In october of 1988,the luminosity monitor provided the first colliding luminosity of BEPC,and the initial luminosity was 5×1028/cm2.sec.During the later colliding experimental operation,the luminosity monitor also provided the colliding luminosities,which were in good agreement with those calculated by the operation parameters of the BEPC.
The canonical transformation in two dimensional Heisenberg antiferromagnetic system is given in this paper.It is found that under this transformation the 2D Heisenberg antiferromagnetic model is the nonlinear O(3) σ model with a topological term in the continnum limit.Since there exists a large uncertainty when one chooses the canonical variables,it is not completely concluded that whether the topological term really occurs in this system.Finally,the physical meaning of the canonical transformation is also investigated,and it is found that it corresponds to the collective excitations of system spins,i.e.,a kind of spin waves exists in this case.
In this paper we give the helicity formalism of the angular distribution for processes e+e－→J/ψ→V+X,V→P1P2 and e+e－→J/ψ→V+X,X→P4P5.It provides the theoretical formula for e+e－ experimental data analysis.
A Realistic Chiral Tripreon Model with SU(3)×SO(5) metacolor group is obtained This model has a low metacolor energy scale and three generations of composite fermions with the quantum numbers of quarks and leptons of the standard model.This model also satisfies complementarity.
According to the perturbative QCD method,we have calculated the P⊥ distributive cross sections,the Y distributive cross sections of the large P jets and the final state meson productivities in 800GeV/c Proton-Nucleus (Be,C,Al,Cu and Pb) collisions.The A dependence of the cross section at a given P⊥ was discussed by the EMC effect. The dσ/dP⊥ differential cross sections vs .P⊥ for various PA collisions are consistent with the new data.
The change of the internal energy of the α-particle is usually neglected in the previous calculations of the binding energy of 5He.The present work shows explicitly that the change of the internal energy of the α-particle can influence significantly the theoretical value of the binding energy of 5He.
In this paper,the nucleon is described by the MIT bag model,and the internal quark motion in the nucleon is modified by the scalar and vector meson fields.The Fermi motion of nucleon in nuclear matter is considered.The changes for intrinsic properties of nucleon in nuclear matter at different temperature are calculated as a function of the density.The binding energy per nucleon for different temperature is given.
Using the many-body field theory the problems of μ－ captures in nuclei are systematically studied.Without ajustable parameter,calculations are performed for the total nuclear capture rates of muon for nuclei ranging from light to heavy ones.It shows that the renormalization due to the spin-isospin-dependent strong interaction and the muon binding in the μ－ atom are essential for a thorough understanding of this type of weak interaction processes.
The inclusive neutron multiplicity distribution in the heavy-ion reactions measured by a 4π neutron detector is presented in this paper.Results for 40Ar+197Au and 40Ar+232Th at 27,35,44 and 77MeV/u are displayed.The distribution provides an overview on the reaction characteristics concerning the relative strength of contributions according to their degree of dissipation.
The cross sections of 59Co(n,p)59Fe,59Co(n,α)56Mn AND 59Co(n,2n)58Co reactions have been measured at neutron energy region of 12.8MeV—17.8MeV by activation method.The coveriance matrix of measured errors was calculated,and the comparison between the values of measured and calculated using theory model was made.The evaluated excitation functions for the three reactions are given.
Based on the finite temperature self-consistent semiclassical (FTSCSC) approach and the local density approximation (LDA),the imaginary part of the microscopic nucleon-nucleus optical potential is evaluated and discussed.This work indicates the necessity of using temperature dependent nucleon density in dealing with optical potentials at finite temperature.
The dependence of phase transition,associated with the disassembly of hot nuclei,on the mass number of hot nuclei is investigated.By studying six hot nuclei ranging from 56Ni* to 238U*,we find that in the curves of excitation energy of hot nuclei vs.Thermodynamic temperature T(E*) of 63Cu* and heavier ones there are always two temperature plateaus,but in T(E*) of 56Ni the first temperature plateau (at lower excitation energy) shrinks into a kink.
In the case of central collisions,the collision mechanism of complete,incomplete fusion,and fragmentation were systematically studied via the Boltzmann-Uehling-Uhlenbeck theory which included the nuclear mean field dynamics,two-body collisions,and Pauli blocking between 5 and 150MeV/u for 20Ne+20Ne collision system.How the mean field,Pauli blocking of the two-body collisions were affected by bombarding energy and their effect on the reaction mechanism was discussed.
The method of determination for average neutron energy from D-T reaction by using two silicon semiconductor detectors and the cross section ratios of 58Ni(n,p)58m+gCo and 58Ni(n,2n)57Ni reactions is described.The plot of the cross section ratio against the neutron energy has been obtained.The results have been compared with existing data.
According to a method of numerical solution of Hill-Wheeler equation proposed by us recently,the dynamic evolution of shapes in the Yrast band of 172Os was calculated.Results show better agreement with the recent lifetime measurement than the normal TRS calculation.This means the dynamic effect on the nuclear shape is not negligible at least for the transitional nuclei like 172Os.
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