1997 Vol. 21, No. 7
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A 36-unit scintillant multidetector system was built for measurement of charged particles at forward direction (5°≤θ≤20°)in heavy ion reactions of intermediate energy (10-100MeV).Each phoswich is composed of 1mm thick scintillator NE102A and 100mm thick slow scintillator NE115.A good particle identification was achieved from atomic number Z=1 up to Z=20 using QDC method.The resolution power Z/△Z reaches to ～45.
Two tracking atmospheric Cherenkov telescopes have been operated at Xing Long Station,Beijing Astronomical Observatory,on the basis of atmospheric Cherenkov radiation produced by extensive air shower.They are used to search for point sources of very high energy gamma ray and to study their emission characteristics as well as to detect the spatial distribution of very high energy gamma ray intensity.The construction and the performance of the telescopes as well as the testing results under observation conditions are presented in this paper.
We calculate the Pseucdo-Godstone-Bosons(PGBs) corrections of order αm2t to qq→tt at the Tevatron in the framewords of the one generation technicolor model(OGTC) and a minimal technicolor model(MTC) with a massless weak doublet recently presented by C.D. Carone and H.Georgi.The PGBs correction can decrease the total tt production cross section by as much as-38% for top mass of 176GeV and color octet PGBs mass of 150GeV in the OGTC model,which is potentially observable at the Tevatron.However,the results show that the corrections to the pprocess are unmeasurablly small in the MTC model.
In this paper,the classical transport equation of gluons in QGP is set up and the relations between it and the quantum transport equation of gluons as well as the classical transport equation of quarks are discussed.
The experments about anomalous scaling of the factorial moments in nuclear-nuclear collisions show that in the final state higher-dimensional phase space,the log-log plot of the factorial moments versus partition number seem to show a stmngly upward bending.Taking into account that the nuclear-nuclear collision is mixture of many elementary collisions,we give an explanation for the above phenomenon.A random cascading model is set up based on the above view point,and the Monte Carlo simulation fits the expedmental phenomenon qualitadvely.The possible application of this effect is discussed.
After carefully analysing the scatter plot of pt vs.N of hadron-hadron collisions at s=540GeV,we point out that the appearence of large average transverse momentum per event pt and large multiplicity N is a new experimental evidence of existing hard component at the collision.The Monte Carlo simulation for one(soft) and two(both hard and soft) component model demonstrates qualitatively correct ness of this arguement.
The single particle level densities,calculated with the local density approximation and Fermi gas model respectively,are used to obtain the partition functions.The internal excitation of the IMF emitted from the decay of hot nucleus has an effect upon the isotope nuclear temperature.
The △I=1 staggering in superdeformed nuclei in A～190 region is systematically investigated.Large staggerings are seen for most of the signature partners in odd superdeformed nuclei of this region.The behavior is analyzed in the convendonal collective model.
Influence of the central collective flow on two-pardcle correlation function is discussed.The Monte-Carlo calculation is used to describe how the single particle and two-particle spectrum from a hot emission source are effected by the central collective flow.The two-proton correlation function for Ni+Ni system.with b=0fm at 100MeV/u is calculated by using QMD model.The particle interchange model is developed and used to prove the existence of a central collective flow in central sions of 100MeV/u Ni+Ni system.The results show that the two-particle correlation functions are indeed sensitive to the central collective flow.This might provide a method for studying the central collective flow formed in central collisions for medium heavy system at energies above 100MeV/u.
The spurious components due to the seniority mixing in the collective states composed of the S and D nucleon pairs are expressed and evaluated.
A method is presented to get nuclear effect functions RAv(xt)and RAs(xt)on valence quark distributions and sea quark distributions from the data of 1-A DIS process and nuclear Drell-Yan process.Both the functions may be used to test the theoretical models explaining the nuclear effects.As aexample,we obtain RFev(xt)and RFes(xt)of the iron nucleus by this method.
A folding model for the 16O+16O system is established. The model can well reproduce the experimental angular distribution for the 16O+16O elastic scattering at 124MeV.
Using the three schemes for the spin assignment of rotational bands,the superdeformed bands of even-even nuclei observed in the A～190 region were analyzed.For the yrast SD bands 194Hg(1)and 194Pb(1),the spin assignment are consistent with the experimental results.The spin assignment for the other SD bands in even-even nuclei(A～190)are also believed to be reliable.Otherwise,the validity of the available theory should be re-examined when applied to the superdeformed nuclei.
In this paper,using a cylinder model of space charge,the formulae of self-energy and emittance growth for a bunched beam with Gaussian type density distribution in both longitudinal and transverse directions in linac are derived.And the scaling law relating the beam parameters with the machine parameters are discussed by means of the numerical simulation results.
There are a lot of crucial problems for beam lines design in the third generation of the synchrotron radiation source.One of the problems is high heat load.The principle,device and test results for liquid nitrogen cooling of silicon crystal monochromator are described.
New β-delayed proton precursor 121Ce has been produced by the reaction 92Mo(32S,3n) and studied by using γ(X)-p coincidence with a He-jet recoil fast tape transport system.The half-life of 121Ce was determined to be(1.1±0.1)s.Its β-delayed proton spectrum has been observed and the β-delayed proton branching ratio for 121Ce was estimated to be(1.0±0.5)%.
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