1987 Vol. 11, No. 4
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Measurements of secondary neutron yields and angular distribution released by 80MeV electron incident on Pb thick target with moderated Indium foils are described. The angular distribution of neutron is isotropic and the yield is (2.20±0.13)×1012n/s. kW, these results agree with that of the theoretical calculation.
The possibility of using moderated Indium foil to measure the neutron field around the electron linear accelerator with energy less than 100MeV is also discussed, and the answer is positive.
In order to provide a large scale proportional counter array with gas, we have measured and discussed the influence of gas pressure, temperature, oxygen contamination and variation of composition on signal amplitude of proportional prototype counters. The result provides experimental data, such as arrangement of counter tubes, gas line connection, leakage rate, allowance variation of composition, allowance of oxygen impurity and flow selection, for gas system design.
The prototype with cell and layer design of BES main drift chamber has been built and tests of the prototype on K2 Test Beam of KEK Proton Synchrotron have been made with 0.5～1.5GeV/c e+,π+, and p beams. The spatial resolution for single wire of σx=170～210μm has been obtained within cell half width of 3.1cm. The energy resolution σE/E corresponding to 40dE/dx samplings of 1 cm is about 15%.
Starting from QCD lagrangian with massless fermions and using the bilinear external sources, we derive the effective potential as a functional of composite operators, i.e.,functional of fermion propagator and gluon propagator, and then derive the Dyson--Schwinger equation for the propagators. There exist two sets of solution, the chiral-symmetry solution and chiralbreaking solution. By studying the asympotic solution of equation, we find that for the coupling constant beyond a critical value (α=1/4), a chiral-breaking solution is found, while for α<1/4 the chiral-symmetry consetrves. Using the asympotic behavior of the quark self-energy and the experimantal value for π ion decay constant fπ, we estimate the dynamical generated quark mass value, which is in agreement with the values obtained from other theoretical and experimental methods. Significance of the results are discussed.
We perform Monte Carlo simulation for the SU(2)-Y(120) group space decimation approximate effective action in 44 periodic lattice, find that the effective action system does not have freezing point at β≤9, but the internal energy curve of the system is different from that of SU(2) group with Wilson action. This indicates that although group space decimation method in principle can make discrete subgroup substitute for continuous group available in Monte Carlo simulation, it is not an effective method as to save MC computer time.
We generalize the Skyrme model to SU(4)×SU(4) chiral invariant case. With the flavor symmetry brea king terms of PCAC formula of pseudo scalar meson, we evaluate the mass splitting of the baryons in the representation 20M of the flavor symmetry group SU(4). The theoretical results agree with the experimental values to a certain extent. We also discuss the results obtained.
Using the earlier proposed picture of combining the "three fire-ball model" of non-diffractive hadronic reaction and "quark combination", yields of final hadrons are calculated further with different relative weights of 0－ to 1－ meson. The result of long-life particles is in consistent with the data and is nonsensitive to the 0－ to 1－ meson ratio.
In this paper, an exact boson representation of the antisymmetrizer has been derived. The effect of the antisymmetrization is expressed by different kinds of many-body forces in boson space. An estimation to the importance of many-boson forces has made. With the inclusion of the three-boson force, a calculation of the spectrum of a six fermions system in j=13/2 shell has been carried out in boson space and exact coincidence with the exact spectrum is recovered. We found that the 3-boson force is indispensable when the fermion space is crowded.
Branching ratios of cross section for pp annihilation into two various meson processes are calculated by using the one-gluon-exchange quark-antiquark annihilation potential model. The results are compared with the experimental data and other theoretical values. For the processe pp→π+π－, the cross section as a function of incident momentum of p is also studied and it is in agreement with the measured result.
The projectile-like fragments of 14N+27Al reaction (ELab=93 and 77MeV) were measured by using the large area position sensitive ionization chamber. The contour plots of d3σ/dΩdEdZ in TKE-θ plane, angle distributions integrating over different TKEL window, the Z-distribution and angle distributions of different fragments from Li to Na were obtained. Variations of σ2, τ with TKEL were deduced. A brief discussion of the experimental results was given also.
The boson representation of k-level Lipkin model for a fermion system was given by using the theory of coherent states. The method discussed in this paper can be used not only for the k-level Lipkin model corresponding to Sp (2k) group, but also for other solvable model corresponding to other semisimple Lie groups. It was pointed out that the norm operator is a function of the Casimir operators of dynamical group and its maximum stationary subgroup.
Large deformation of fission process may be described by Cassinian ovaloid with two variables, symmetry ε and mass asymmetry p. It is a simple and intuitive method. Based on the standard liquid drop model and the ovaloid, One can reproduce some fission data, such as effective moment of inertia, fission threshold energy at saddle point and also TKE at scission point without any adjustable parameters. The paper presents some simple expressions for Coulomb energy and surface energy as function of ε and p, and also analytical expression for moment of inertia.
Forming the collective p-h pair of quadrupole type, Generator Coordinate Method (GCM) is used to derive microscopically the TQPM-hamiltonian and E2 transition operator from an original hamiltonian containing monopole pairing and quadrupole interaction. Further connection with IBM1 is investigated by numerical testing the availability of the microscopically calculated quantities, which are the input parameters for IBM1 calculation.
The experimental (n, 2n) cross sections around 14MeV have been collected, analyzed, and evaluated Data were taken from 124 nuclei for A=19—209 up to the end of 1984. Relation between σn, 2n and (N—Z)/A has been studied. No neutron shell effect is found. The cross sections for some nuclei have been calculated by using a statistical theory. The good agreement with the experimental σn, 2n at 14MeV has been obtained in terms of a single set of fitting parameters.
We introduce a normal fuzzy lattice fermionic action. If the parameter b introduced in the theory is not of the same order as the spacing a, or even smaller, it will break the karsten and Smit's no-go theorem, which says it is impossible to introduce a lattice fermionic chiral action with correct space-time limit to continuum and without unnecessary fermion modes.
The nuclear structure part of the 2v mode ββ decay of 82Se and 130Te are calculated by quasiparticle Tamm-Dancoff Approximation treating the Gamow-Teller transitions to the intermediate odd-odd nucleus and the single particle configurations generated from Skyrme force(Ⅲ) Hartree-Fock procedure. With the relevant paring effect and correct dealing with both initial and final state, the nuclear matrix element observed experimentally can be reproduced satisfactorily.
The experimental data on multiplicity moments for 12 energies in the range of √s from 11.5 to 900GeV are analysed. It turns out that the results calculated by the three fire ball model fit the data very well. It is found that the average size of the side-fire balls displays two plateaus as the energy changes.
Employing the analytic expression (to the next leading order) for non-singlet component of structure function which we got from QCD theory and putting recent experiment result of neutral current structure function at Q2=11(GeV/c)2 as input, we give the QCD prediction for neutral current structure function of their scaling violation behaviours.
A usual majority rule and a new block method are applied to Ising model on two-dimensional random triangle lattice. Either of them has got a good critical exponent. The new block method has an advantage of easily extending to higher dimensional random lattice.
We apply the background field method to calculate the operator expansion of the two-piont correlation function related to the moments of meson distribution amplitude. It is shown that the non-pertur bative effects depend in detail on the meson helicity and quark mass.
The physical design and beam test for the BPL 35.5MeV beam transport system are described. This system was constructed and put into operation into operation in December 1986. After preliminary adjustment, the beam transfer efficiency of the two beam lines of this system reached 88% and 93% respectively.
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