1997 Vol. 21, No. 8
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A search for gamma-ray bursts at 1OTeV energy region was made using data of Yangbajing air shower experiment in Tibet.About 4×108 events were analysed to search for shower clusters appearing in a given time interval and a given small sky bin. An equal-zenith angle method is adopted to estimate the background. Some clusters show excesses over the background but with less significance as the evidence of gamma-ray bursts.The much higher sensitivity of the Yangbajing second phase array to the detection of 1OTeV gamma-ray bursts is discussed.
Coincidence measurements of fission fragment and light charged particle have been perfotrmed for the reactions of 40Ar+natAg,209Bi at E/A=25MeV using 4 PPAC and 11 sets of ΔE-E telescopes.Angular correlations of fission fragment were ploted as a function of the folding angle between the two detected fission fragments.The linear momentum transfer distributions were derived by measuring angular correlations.The backward spectra of light particles detected in coincidence with fission fragments having different average〈LMT〉are analyzed with Maxwell distribution.After some corrections the initial temperatures of the hot nuclei are determined from the energy spectra.The excitation energies corresponding to the different average〈LMT〉are obtained considering the reaction Q values and pre-equilibrum emission.In the central collision of the 40Ar+natAg,209Bi reactions,excitation energies are measured to be about 4.2MeV/u,2.4MeV/u and temperatures about 6.1MeV,5.5MeV,respecdvely.In semi-central collision,excitaionen energies are measured to be about 3.5MeV/u,1.9MeV/u and temperatures about 5.8MeV,4.8MeV respectively.
Based on the existing concept design and the expected performance of the detector at the future τ-charm factory,a fast Monte Carlo simulation program package using the BES software frame and data structure has been devcloped.Vadous important and/or interesting physics issues have been simulated by using this method,and a series of important physics results have been got.The design idea,the program frame,and the advantages of this method have been described.One can conclude that this Monte Carlo simulation method can greatly save CPU and disk space,and is specially suitable for BES users.The physics results obtained from the simulation demonstrate that it is essential to build the BTCF.
The h-analogue of the Sugawara operater is constructed for the Yangian double with central extension in the sl2 case.Using the free fields realization of the quantum currents,the h-analogue Miura transformation is obtained.
From the bosonization of vertex operators for A(1)n－1 face model given by Asai,Jimbo,Miwa and Pugai,using vertex-face correspondence,we obtain bosonized vertex operators for Zn symmetric Belavin R matrix,which realize the Zamolodchikov-Fadeev algebra for that R matrix.
We suggest a new method,named knitting ansatz,to generate solutions to Yang-Baxter equation with lower dimensional representations of braid group.To support our ansatz,we work out an example of a new 16×16 R-matrix constructed along this idea,with two 4×4 braid group representations of familiar 6-vertex type with different q-parameters.
We have used the event generator LUCIAE to analyse the data of singly strange particle production in pp,pS,and SS reactions at 200AGeV.The results seem to indicate that in comparing with the pp and the pS minimum bias event,the SS center collision seems having stronger final state interaction,shorter fomation time of strange particles,and larger s quark pair suppression factor.The strangeness enhancement evidence from pp to pS and to SS could be explained without the introduction of quark-gluon plasma formation.
Using QMD model the time evolution of Au+Au system at 100MeV/u is studied.For very central collisions the conditions for freeze-out and how the different physical quantities approaching equlibrium are investigated.The calculated results show that for 100MeV/u Au+Au at b=0fm,the maximum density can reach 1.6ρ0 and after that the system expands to a low density region.A position correlated central flow is developed during the expansion stage.By studying the two pamicle reladve momentum spectrum it is able to separate central flow from random thenmal motion.The dependence of this central flow on E.O.S.is also discussed.
The energy spectra and wavefunctions of 207—210T1 and 207,208Hg are calculated in terms of shell model.The calculated results using different effective interactions are similar and agree well with experimental data,which shows that those effective intemcdons widly used in lead region are still valid to describe the energy levels for nuclei such as 208T1 etc.
The optical model of 16O is studied based on the dispetsion relation theory at neutron energy up to 20MeV.The total cross section anomaly is removed essendally at low energies for 16O.
Udlizing the consistent Q framework via an additional three-body potendal of L=3 in the interacting boson model,ananalytical descdption for the triaxial deformation in the O(6)-like nuclei is given on the basis of the intrinsic frame.The deformation parameters β and γof the even-even Xe,Ba and Ce isotopes are calculated.The calculated results are in good agree nont with the results of the rigid triaxial rotor model.
Based on the potential resonance in heavy-ion collisions and on the optical model,the gross resonant structure appeared in the complete fusion excitation function and the phenomenon of the backward-angle oscillatory rise in the elastic scattering angular distribution for 16O+24Mg system are studied by using a deep opdcal potendal.The calculated results of the opdcal model are compared with those of the nuclear molecular orbital model.The origin of the gross resonant structure is discussed.
We use the method of point canonical transformation and the Feynman path integral method to find energy spectra and wavefunction of the effective screcned potential (ESP).We show that ESP has shape invariance.In the some way,we obtain energy levels of ESP.
This article presents the BSRF white beam topography expeimental system,including a white radiation topography camera,a versatile environmental chamber,an X-ray video imaging system and an image processing facility.The specification of the experimental system and some physical results have heendiscussed.
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