2000 Vol. 24, No. 1
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The transverse distributions of energy in family events observed by emulsion chambers at Mt. Kanbala are showed in comparison with Monte Carlo simulations. Analysis indicates that a character of energy concentration exists in ultra high energy families.
A method for measuring the integrated luminosity of the e+ e－ colliding experiment by using the wide-angle Bhabha events at the center of mass energy of the ψ(2S) resonance is presented. The determination of the integrated luminosity for the ψ(2S) data collected by the BES detector at the BEPC collider shows the feasibility of the method.
The non-diagonal solutions to the reflection equation of 15 vertex model A2(1) model and supersymmetric t-J model were obtained. The results show that solutions of A2(1) model' have three forms and each form contains two solutions; the solution of supersymmetric t-J model' takes only one form in which there are two solutions; each one of all those nondiagonal solutions only have three arbitr ary parameters.
We present the constant solutions with all matric elements non-Vanishing to the reflection equation of 19 vertex model-A2(1) model. Some nondigonal solutions are also obtained.
The emission time of intermediate mass fragments (IMF) has been studied as a function of spatial evolution of the emission source for 40Ar+natAg reaction at 30MeV/u, and the spatial-time evolution of projectile-like fragments emission has also been discussed. The investigation for spatial-time evolution of the reaction system shows that the emission time of the IMF mainly depends on the correlation functions and the density of nuclear matter, and that it is not sensitive to the mass number of emitting sources. For high-energy fragments, a smaller nuclear density would lead to a smaller assignment for emission time τ; therefor the τ values extracted from the normal nuclear density could be taken as upper limits of real τ values. For the mid-velocity fragments, their emission times do not change with size of the source and these τ values could be taken as the real values directly.
The angular & Z distributions of foe fragments emitted in the forward and intermediary angles are measured at the reaction of 25 MeV/u 40Ar+115In,58Ni,27Al. Their characteristics are investigated based on the model of Modified Qantum Molecular Dynamics (MQMD). Generally, the theoretical calculations are in good agreement with the experiment data. But in the forward angles the yield of the fragments is underestimated by MQMD model while in the case of the intermediate angle region, the calculation is higher than the experiment data in some degree for the fragments whose charge numbers are in the vicinity of the proiectile. The angular & charge distributions of the fragments are also compared with the statistical model of GEMINI. The results turn out to be that a small proportion of the statistical evaporation component exists in the forward angles while in the intermediate angle region, this component increases to some extent. However, its ratio is still small. It is found that the equilibrium evaporation component decreases gradually when the Z of the fragments becomes smaller.
We have investigated the yield and the spectrum of the K－ mesons in the heavy-ion collisions with the relativistic RBUU approach. It's found that the ratio of the yield of K+ to K－ depends on the size of the nuclear systems. One main reason is caused by the absorption effect of the K－ mesons in the nuclear medium. We have found that the mean-absorption path of the K－ mesons are different for light nuclear system and for the middle or heavy nuclear systems. The extent of the absorption of K－ mesons is different for different elementary production channels. It's one important reason to make the channel Bπ→K－X play an important role in the K－production, especially for light and middle systems.
Microcanonical simultaneous multifragmentation statistical model was used to analyse the ALADIN caloric curue. It is indicated that each theoretical representative point located in the temperature plateau (temperature backhanding) of ALADIN caloric curve does not necessarily fall-down into the region of temperature plateau (temperature backhanding) of the caloric curve of corresponding projectile remnant (hot nucleus). Therefore, regarding the temperature Plateau in ALADIN caloric curve as an evidence of nuclear liquid-gas phase transition might be questionable.
The △I= 1 staggering is investigated for the superdeformed bands observed in the doubly odd nuclei 150,152Tb,144,148Eu and 130,132Pr. The spin values of these bands are assigned from the ab-and modified ah-fitting. The possible mechanism and the inherent physics of the △I=1 staggering are outlined in the case of doubly odd nuclei.
The spins of superdeformed bands in A≈150 region are assigned by the ah fitting provided the fluctuation are removed from the observed transition energies. Some typical superdeformed bands are discussed. For some superdeformed bands, the precision of spin assignments by the ah fitting could be improved.
The ratio between the coherent and incoherent densities of a coherent harmonic generation FEL is proportional to the square of the modulation rate of the spontaneous emission spectrum of its optical klystron. Therefore enhancing the modulation of the spontaneous emission spectrum of an optical klystron is important for coherent harmonic generation. A coherent harmonic generation experiment is under way on the 800MeV electron storage ring at University of Science and Technology of China. A modulation rate of 0.8 of the spontaneous emission spectrum of an optical klystron has been obtained. This paper reports the measurement and enhancement of the modulation rate.
Irradiation effecs, mainly including transformation from crystalline into amorphous state, of C60, films induced by 120keV H, Ar and Fe ions irradiation were analysed by means of Raman scattering technique. The results indicate that amorphization process in the cases of Ar and Fe ions irradiation is dominated by nuclear collision, but in the case of H ion irradiation, the process is dominated by electronic energy transfer. The annealing effect of electronic energy loss which induced the intermediate graphitization process before amorphization in lower irradiation dose ranging from 2×1014 ions/cm2 to 5×1016 ions/cm2 was found in the case of H ion irradiation for the first bine.
In the Paper we give some results about nuclear shadowing of real photon at LHC. We show that shadowing grows strong with the increasing of Photon energy Eγ. The CMS energy dependence of total cross sections of production of ρ,ω and φ in the process γ+A→V+A is also given. The results show that there is a critical energy point, above which the nuclear shadowing is strong enough to be observed.
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