1995 Vol. 19, No. 11
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High-spin states in 197Bi were populated by bombarding natural Re target and isotope 187Re target with 16O beam of 100 MeV. Using comprehensive γ-γ-t coincidence measurements,three new isomers in 197Bi were established and eleven new y-transitions were identified,while errors in the existing level scheme were corrected.From the level structure systematics of the odd-mass Bi isotopes, the configuration and decay properties of a new isomer with t1/2n=19.3±4.9ns in 197Bi were discussed.The y-ray angular distributions were also measured.A new level scheme of 197Bi was proposed.
The fractal behaviour of multiplicity production in 400 GeV/c pp collisions is analyzed using the modified multifractal moments.The generalized dimensions Dq,q=2—5,are calculated.A comparison with the results obtained by the method of scaled factorial moments has been made. The results show that the multifractal character is observed.The fractal analysis method proposed by Fujio Takagi has been tested.
The gamma-ray emissivity q/4π of galactic cosmic rays interacting with inter-staller gases at medium-latitude(|b|=10°—20°)is determined by using recent EGRET data. Meanwhile the method to obtain the emissivity by gamma-ray data themselve is adopted,and then the inverse compton (IC ) integral intensities as a function of galactic longitude are obtained. The differential IC intensities averaged over all galactic longitudes can be expressed by IIc(E)=1.58×10－6E－2.08±0.06cm－2·s－1·sr－1GeV－1,b=10°—20°and IIc(E)=2.08×10－6E－2.03±0.06cm－2·s－1·sr－1GeV－1,b=－20°—－10° for b=－20°—－10°,where the energy range is from 30 MeV to 4 GeV.
A systematic study about the production of secondary beams in 95MeV/u 12C+Be,Cu and An targets was performed by using the GANIL doubly achromatic spectrometer LISE.The maximum values of the secondary beam production calculated by programs LISE and INTENSITY are in agreement with the experimental results for the secondary beams near the β stability line.However,the calculations are larger than the experimental results for the secondary beams far from the β stability line.The optimum target thickness for the production of secondary beams corresponds to about 30% beam energy loss in the target.Beryllium target was found to offer higher production for all the secondary beams than copper and gold targets.
Using a silica aerogel sample with oxygen gas filled as the positronium(Ps)source and a time selecting energy spectrometer,the measurement of the y-energy of parapositronium(p-Ps)2y-decay is further improved and the result of hv=510995. 34±0.69eV is obtained by a slithering comparison with the precisely known y-energies of 192Ir.The rest mass of a pair of positron and electron is determined by the correction with the binding energy of Ps,which shows a mass equality within 1.4ppm between positron and electron by the comparison with the rest mass of electron.
Cross Sections and average forward recoil range FW were measured for target residues from the interaction of Cu with 40MeV/u 40Ar ions using off-line y-ray spectroscopy.The mass yield distribution was obtained with assumption of charge distribution.The linear momentum transfer was calculated from FW values.A comparison with similar results of 12C+Cu and 20Ne+Cu reactions indicates that the fractional linear momentum transfer,corresponding to central collisions,decreases with increasing projectile mass at the same energy per nucleon. However,the excitation energy of the composite system created from the collisions of Cu with 40Ar ions reached the value of 5.3MeV /u and was higher than those from the collisions with 12C and 20Ne ions.
The dimensional regularization at finite temperature is applied to calculate accurately the thermodynamic potential of two-loop QED and the overlapping divergences at arbitrary gauge.It indicates that the overlapping divergences are cancelled with each other and the result is gauge-independent.
We give explicitly the 2-dimensional cyclic representations of quantum algebra Uq(sl2)with central extension.The intertwiner for tensor representations in different ordersis constructed with C-G coefficients.This intertwiner is shown to be the R -matrix for eight vertex Ising model.
Starting from phase-space generating functional for the system with regular and singular Lagrangian respectively,the canonical Ward identities under the global symmetry transformation in phase space are deduced.The corresponding local transiormation is studied,the conserved charge is obtained at quantum level and the canonical Noether theorem in quantum case is given.The preliminary application of the results to a system of interacting nucleons and pious is discussed.
The ratios of strange baryon to antibaryon produced in the reaction S+ Pb at 200 AGeV beam energy are computed using new version of Fritiof with collective string interaction and rescattering.Theoretical ratios of and are comparable with experimental data within the range of the deviation among the data of different collaborations.It seems to indicate that these data of the ratios of strange baryon to antibaryon might be explained in the hadronic scenario.
The bandcrossing in the K=1/2 bands of odd-A nuclei was discussed in the particle-rotor model.The decoupling term in the rotational energy expression has a remarkable effect on the backbending frequency,which,in the band built on the ↓orbital,leads to a bandcrossing delay comparable with the observa tions.
The average binding energy,the radius of proton distributions and the radius of neutron distributions for the nucleus 100Sn have been calculated by the relativistic mean-field theory and the nonrelativistic mean-field theory.The numerical results by two methods have been compared and discussed.This is the first microscopic calculation on 100Sn.
The Boltzmann approximation of the phase-space distribution functions of quarks and of pious, previously adopted by the authors,is generalized to a complete expression.After calculating the density of particles from the temperature of the central rapidity region,the dilepton production in Bjorken's(1+1)dimensional scaling expansion system is studied.We find that the generalized approximation distribution function significantly changes the characteristic dilepton distribution for the prediction of the quark matter formation.
The collision dynamics and yields of the multifragmentation in intermediate energy heavy ion collisions are simulated within the frame of the modified quantum molecular dynamics(MQMD ).With this new MQMD,it is found that the obvious improvements about the agreements between the experimental data and the simulating results for the fragment production by means of MDI and Pauli potential are achieved.Meanwhile the different influences of MDI and Pauli potential on the collision dynamics of intermediate energy heavy ion collisions are obtained.Finally the possible reasons for the discrepancies between the experimental data and the present simulating results and remedies of these deficiencies are discussed in detail.
Using the Fermion Dynamical Symmetry Model (FDSM ),we give the microscopic mechanism of the stretching effect of the y-soft nuclei. The results of numerical calculation show that the relative errors between the calculated results and data are not beyond two percent.
The effect of the beam measurement error on the damping system has been studied.This error will reduce the damping speed and induce a closed orbit distortion.
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