2000 Vol. 24, No. 9
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The investigation of the multiparticle production mechanism in high energy collisions by fractal is a new crossing science. It is very important to get the multiparticle multifractal spectrum to understand the collision mechanism. An improved factorial moments of continuous order method has been applied in selfaffine analysis of multiplicity production in 400GeV/c pp collisions. A self-affine multifractal spectrum has been obtained for the first time.
It is important to give a set of wave functions of arbitrary spin particles for the analysis of amplitudes in high energy processes. We enhanced the method of Bargmann Wigner about high spin states and created a new method. In this way, we wrote the covariant states of any integral spin, including canonical states and helicity states.
The coupled cluster method is improved to calculate 0++glueball mass m/e2 in 2+1-D SU(3) lattice gauge theory. In this method, we take the linear combination of connected hollow graphs as trial wavefunction and introduce the average for small wilson loop. The second order and the third order 0++ glueball masses (m/e2) as the function of the coupling constant β=6/g2 show good scaling behavior and good convergent behavior. The vacuum energy W0obtained by this method is lower than that by common method.
We calculated the Pseudo Goldstone boson correction to e+e－→tc process at the energy √<span style="border-top: 1px solid; padding-top: 0px;">s</span>=500GeV in topcolor-assisted technicolor model. We find that the total contribution is larger than the standard model results by as much as 1 to 2 orders,i.e.the production cross section σ(e+e－→tc) can be as large as 10－37cm2 within the considered parameter space. So It may be observable at future e+e－ collider.
Temperature of 5MeV was extracted from double isotope ratios Y6Li/Y7LiY3He/Y4He measured at backward angle in laboratory system in the reaction 30MeV/u 40Ar+nat Ag. It is observed that this temperature increases continuously from 5MeV to 6MeV with the increase of the energy threshold Ecut/A.A Monte Carlo simulation on particle emission process of hot nuclei shows that the average temperature of hot nuclei as emission sources goes up gradually with increasing energies of emitted particles. It is demonstrated that hot nuclei with higher temperature are more probable to emit higher energy particles.
The 208Hg has been produced in multi-nucleon transfer reactions induced by 18O ion beam on a thick,natural lead target.The irradiated lead pieces were put into agasthermochromatographic device, in which the Hg-element products were separated and collected.The 4πΔEβγ-γ and γ-X(γ) coincidence as well as time-succesive γ-ray single spectrum measurements were performed. A partial γ scheme following 208Hg β－ decay has been proposed for the first time, which has taken into account 21 γ-rays and two new energy levels at 1365 and 1727keV,respectively.
The superdeformed bands in the A～190 region are systemically analyzed by using Bohr-Mottelson's two, three and four-parameter I(I+1) expansions. All results show that three formulas are reasonable to the description of superdeformed bands and the agreement with the spin determination. The parameter-relation R1 for most of bands agrees with the theoretical expected value of ab formula and the parameter-relation R1 for a part of bands agrees with the theoretical expected value of Harris formula. The parameter relation R3 for half bands deviates from the theoretical expected value of Harris two-parameter ω2 expansion, but is closer to the theoretical expected value of ab formula, which may indicate that the ab formula is superior to the Harris two-parameter ω2 expansion.
Taking into account perturbative QCD αs order approximation, using double Q2 rescaling model, the cross section ratios of Drell Yan process in p-A collision to p-D collision are calculated. Comparing these results with the ratios without QCD corrections, it shows the neclear effect functions RQCD(xA,Q2) are suppressed by different extent for different nucleus, in different ranges of xA(T). Comparing with the E772 experiment data, RQCD(xA,Q2) are better fitted than R(xA, Q2). It is shown that the QCD corrections are interesting in studing the nuclear effect of D-Y process. After taking into account of αs order corrections, double Q2-rescaling model is still effective.
We have studied the fragment mass distribution of the spallation reaction induced by 322MeV, 660MeV and 800MeV protons bombarding 208 Pb by using quantum molecular dynamics model (QMD) plus empirical fission model. The details of the empirical fission model is described. The calculation results are in good agreement with the experimental measurements.
In the framework of the extended Ginzburg-Landau model,the dependence of the multiplicity difference correlators Fq on phase space intervals δ is different in first-and second-order QGP phase transitions.Once ln Fq are expressed as functions of δ1/3 and data-fitting by polynomials,one can determine the order of the phase transition by comparing the signs of the coefficients of the first power from fitting and from theoretical calculations. One virtue of this method is the independence of the unknown temperature parameter,and one can get the same information about the phase transition from one and higher dimensional analyses of the experimental data.
A longitudinal field twin-fold ionization chamber (607mm×490mm×144mm) with an active area 410mm×100mm for particle identification at the Radioactive Ion Beam Line in Lanzhou (RIBLL) was described. It has a configuration of one common cathode and double position sensitive anodes with grounding Frish-grids. The entrance and exit windows as well as cathode and anodes were all made of 4μm thick mylar foils. The cathode was coated with 1.5μm silver on both sides and the anodes were deposited with 13 and 3 silver strips (31.5mm width and 0.5mm interstrip gap) in vertical and horizontal directions respectively. The plateau curves of the pulse-height dependence on the cathode and anode voltages and the energy resolution ΔE/E for a working gas P10(10%CH4+90%Ar) were measured with an α source. In the case of gas pressure 250 mbar, cathode voltage-1600V and anode voltage 220V, an energy resolution of 4.7% was achieved.
This paper introduces the simulation results of ion-trapping instability and beam shaking mechanism using strong-weak model in an electron storage ring. These results can reasonably explain some phenomena observed in the HLS storage ring.
A proposal to produce monochromatic γ rays of high brightness and high polarization is presented by Compton backscattering in the collision between intense polarized laser and intense current electron beam of high brightness in BEPC. The features and applications of this new kind of γ-ray source are also described.
Position sensitive photomultiplier tube (PS-PMT) represents a technological improvement in the development of new concept gamma cameras based on the principle of a single tube. Very recently, a new compact PS-PMT, Hamamatsu R7600-C12, has been developed. The PS-PMT has 11 stages of metal channel dynodes and 6(x)+6(y) crossed plate anodes in a 25.7mm square ×20mm high metal can package, where the effective area is 22×22mm 2. Tests of spatial resolution, spatial linearity, gain uniformity and timing resolution were carried out by coupling the PS-PMT to the LSO an GSO scintillators in terms of applicability to Positron Emission Tomography (PET) system. High spatial resolution of about 1.4mm is obtained by using LSO crystals coupled to the PS-PMT, and the good spatial linearity, gain uniformity and timing resolution are also obtained.
We investigate the binding energy of six-quark systems with strangeness s=－3 under the constituent quark model in the framework of RGM. The single NΩ channel with spin S=2 and the single ΔΩ channel with spin S=3 are considered, respectively. The results show that both two systems can form loosely bound states: the binding energies are ranged from 3.5—12.7 MeV for NΩ and 4.4—14.2 MeV for ΔΩ system, respectively.
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