1999 Vol. 23, No. 3
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Considering the absorption of extragalactic high energy gamma rays by cosmic background photons, the possibility of measuring Hubble Constant and background infrared radiation with Yangbajing RPC carpet experiment is presented.The conclusion is that in one to three years experiment the Hubble Consent and background infrared radiation density can be determined with good precision.
The temperature of hot nuclei was simultaneously deduced with double isotope ratios and with slope method at angle of 110°in 40Ar+159Tb and natAg reactions at 30 MeV/u. The values of isotopic temperature for different ratios, such as 1,2H/3,4He,2.3H/3,4He and 6,7Li/3,4He were all the same, i.e. 4.6 MeV. The slope temperature values were different for various particles or complex fragmenL The slope temperature for α-particle or panicles with mass number less than 4 was normal,however, for the heavier fragments the slope temperatures were higher than limiting temperature Tlim.It may be expected because the heavier fragments were emitted at the early stage of the formation of compound nuclei or because of Coulomb instability.For larger slope temperature than Tlim its angular dependence was tested too.
In this paper we present a timing pickup detector used at Radioactive Ion Beam Line in Lanzhou (RIBLL). It has low detection threshold and is radiation-resistant. The photons induced by radioactive beam ions passing through a thin plastic-scintillator foil, east from the foil center corresponding to one focus point of a aluminum ellipsoidal mirror and are reflected to another focus point at which the cathode of a photomultiplier tube locates. The readout pulse signals were sent into a CAMAC's TDC module. A time resolution of about 140ps is achieved and the counting face up to 108pps is allowed.
The design, structure and performances of RIB diagnostic devices for Radioactive Ion Beam Line in Lanzhou (RIBLL) are described. Several RIB diagnostic devices based on fiber are shown in greater detail. The devices have high detection efficiency, faster bine response, stable function and easy operation. The RIB 17N intensity contours are given, which illustrates the functions of the diagnostic devices in tuning RIBLL parameters.
A He-jet laser bine-of-flight (TOF) mass spectrometer system is built. The sample atoms evaporated in the atomization chamber are used to simulate the reaction products. The sample atoms are transferred by helitim gas trough a thin capillary.After passing through a skimmer, the sample atoms are formed into a neutral atom stream.A two-or three-color laser beams perpendicular to the atom jet is used to excite and ionize the atomes multi-steply. Then a pulsed electrical field pulls the ionized atoms to the TOF mass spectrometer. By this processing, the (Z, A) values of the sample atoms can be determined precisely. The efficiency of the spectrometer is studied by measuring the radioactivity of 24Na atoms. The transmission efficiency consists of two parts, the transportation efficiency and the efficiency of laser resonance ionization. The transportation efficiency is determined to be about 17%.
The decays t→cV(V= Z,γ, g) induced through loop processes are calculated in Topcolor-Assisted Multiscale Technicolor model. We find that the extended technicolor interactions provide the main contribution to these decays, and the total contribution can enhance the Standard Model branching ratios by as much as 5 to 6orders of magnitude, i.e., B(t→cZ)～10－6,B(t→cβγ)～10－7,B(t→cg)～10－5,for the favorable parameter values.
The infrared divergences in vacuum graghs of quark (ignored mass) field at high tempethere are calculated in detial by real-time formulation of Green function, a kind of infrared divergent integral related to F-D statistical factor is pointed out and its regularization is discussed. All of the infrared divergences in three-loop vacuum graghs of quark field are isolated.
J/ψ and ψ′production cross sections in fixed-target experiment is calculated, considering the contributions from both color-singlet and color- octet mechanisms. The resultS are applied to the investigations of the J/ψ suppression and the ψ′/ψ ratio problems in p-A collisions. The results agree with the experimental data as the (cc)-nucleon absorption cross sections σabs8≈10mb for (cc)8 and σabs1≈0mb for (cc) .The model is further used to investigate A-A collisions when comover absorption mechanism is also considered. It is found that the observed experiment data of J/ψ and ψ′/ψ ratio in S-U collisions and Pb-Pb collisions can not be explained consistently within this model. The possibility of QGP formation in S-U and Pb-Pbcollisions is also discussed.
A new method used to select identical bands is given from the energies.More than one hundred superdeformed bands were analysed by this method, and many identical bands were found. A concept of quantized region is used to analyse the quantization of incremental alignments. It is pointed out that the quantization of incremental alignments strongly depends on the criterion of selecting identical bands.The relation between particle-rotor model and the selection method is also revealed.
Using the Hamiltonian and the natural operators, we obtain a nonlinear spectrum-generating algebra for the symmetrical Pöschl-Teller Potential. This algebra gives a new method with obvious physical meaning to describe and solve the quantum motion in the Potential, and can be regarded as a new deformation of the oscillator algebra.
This paper describes the working principle and structure of the control system of the Radioactive Ion Beam Line in Lanzhou (RIBLL).
In this paper the equations of motion for charged particles in radio-frequency quadrupole lenses are studied, the transfer matrix elements are derived and the relations between the focusing properties of the lenses and the lens parameters are discussed.
The principle of beam energy measurement and its correction in synchrotrons are described. The formulas of beam energy correction for closed orbit distortion and dipole correctors are derived. The application of these formulas in the Beijing Electron-Positron Collider (BEPC) is introduced and the results are discussed.
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