1993 Vol. 17, No. 10

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Application of dE/dx Method for e/π Identification to the Measurement of the Mass of τ Heavy Lepton by BES
RONG Gang, CA Ji-Mao, MAO Hu-Shun, WANG Tai-Jie, BAI Jing-Zhi, LI Wei-Guo
1993, 17(10): 865-872.
The application of dE/dx method for e/π identification to the measurement of the mass of τ heavy lepton by Beijing Spectrometer(BES) operated at Beijing Electron Positron Collider (BEPC) is described.With this method,the efficiency of selecting the eμ events from decaying from τ+τ is increased by a factor of more than 3 compared with using traditional e/π identification by electromagnetic shower measurement.It results in not only that the loss of the eμ events in off-line selection is reduced,but also that the amount of the time needed to run the BES/BEPC for data collection and computer CPU time for data off-line processing is reduced by ~75% for selecting the same number of τ+τ events.
Measurment of the Iodine Isotopic Yields from the Interaction of 47MeV/u 12C with 133Cs
YANG Wei-Fan, ZHAO Zhi-Zheng, LI Zong-Wei, SUN Xiu-Rong, XIE Xiu-Jun, MU Wan-Tong, QIN Zhi, ZHANG Li, YANG Yong-Feng, SUN Ru-Lin
1993, 17(10): 873-877.
The formation cross sections of iodine isotopes from the intereamtion of 47MeV/u 12C with 133Cs have been measured radio-chemically.The isotopic yield distribution curve has been costructed.It is found that the peak of the curve is in the vicinity of 124I and the curve has a FWHM of 6.5 mass units.The mass loss of the most probable product is 9.2 mass units.The cross section of 131I which is produced by striping of two protons from the target nuclei is 0.47—0.87mb.The activities of 132I was not observed.
Transformation Groups in Beam Optics (Ⅰ) General Theory
YU Qing-Chang
1993, 17(10): 878-884.
The motion of charged particle beams in a beam optical system can be described by means of the transformations of the phase space contours and particle distribution functions.These transformations compose several groups—the beam transport group (BT group),contour preserving group (CP group),distribution preserving group (DP group) and so on.The principal problems of beam optics can be reduced to two:the determination of the eigen phase space contour of a transformation and the determination of the transformation can preserve the shape of a phase space contour.
Gluon Fragmentation in Υ Decay
TIAN Li-Li, XIE Qu-Bing
1993, 17(10): 885-891.
Up to now,no model can reproduce the baryon rates measured by ARGUS collaboration in direct Υ decays,except a qualitative explanation given by Lund model.Instead of the string fragmentation model in Lund picture,we apply the quark production rule and combination rule for qq fragmentation to the colour string for Υ→3g.The results agree well with ARGUS data without extra parameter.
Moment Analysis and ξ(2220)
YU Hong, SHEN Qi-Xing
1993, 17(10): 892-897.
In order to reduce the influence of the geometrical acceptance and improve the precision we introduce the pseudoscalar meson angular distribution of the moment HJ(jm,θ).It is more sensitive than the usual projective pseudoscalar meson angular distribution WJ(θ) for determining that the spin of the ξ(2220) is 2 or 4.We also give some moments which are needed for the moment analysis and some relations of moments to represent the helicity amplitude ratios xJ and yJ directly.
General Forms of the Polarization Tensors of Z→3γ and γγ→γγ
JIANG Xiang-Dong, ZHOU Xian-Jian
1993, 17(10): 898-906.
In this paper the general forms of the polarization tensors of Z→3γ decay and γ→γ scattering at one-loop level are discussed.The constrained equations for the tensors are deduced from the S3 symmetry and gauge invariance.We give the procedures of our method and compare the results of W-boson-loop with those of fermion-loop.
A Non-Hermitian Approach of Dyson Boson Expansion to Interacting Boson Model
DENG Wei-Zhen, YANG Ze-Sen, WANG Yu-Cheng
1993, 17(10): 907-911.
Through boson expansion and the modified Jancovici-Schiff substitution a 1-to-1 corre-spondence between fermion collective pair space and the interacting boson space is obtained.The boson mappings of fermion operators are uniquely determined and the IBM Hamiltonian takes a non-Hermitian form.The calculation of fermion matrix elements and spurious problem are also discussed.
n-Particle Transverse Correlation and Collectivity for Collisions 1.2A GeV Ar+KC1
LIU Qing-Jun, JIANG Yu-Zhen, WANG Shan, LIU Yi-Ming
1993, 17(10): 912-917.
A method of n-particle transverse correlation function for the study of collective flow is proposed,which extends both the study of n-particle azimuthal correlations and the estimation of collectivity to the study including the magnitudes as well as the azimuthal angles for all the n-particle transverse momentum vectors.This method is more sensitive to the collectivity of collective flow than the method based on multi-particle azimuthal correlations.Using the new method,n-particle transverse correlations are analyzed for collisions of 1.2A GeV Ar+KC1 in the Bevalac streamer chamber,and the results have been compared with a Monte-Carlo simulation,which show that the collectivity for this experiment is between 85% and 95%.
Parameterized Full Amplitudes for Proton 4He Scattering in the Intermediate Energy Range
LI Qing-Run, ZHOU Jin-Li
1993, 17(10): 918-924.
The parmeterized full amplitudes for proton 4He scattering at energies 200,350,500,560,800,1030,1240,and 1730MeV are obtained.These amplitudes are useful as input for studing the α-particle structure of nuclei by means of intermediate energy proton.
High Energy α-Particle Scattering on 4He
HE Gan-Ming, LI Qing-Run
1993, 17(10): 925-928.
The high energy α-particle elastic scattering on 4He is studied applying the Glauber formalism.The results show that the theory provides a satisfactory description of the data in the middle momentum transfer range.
A Relativistic Approach for pp Annihilation Into Two Mesons
XU Xiao-Ming
1993, 17(10): 929-933.
In this work the cross sections and angular distributions for pp→π+π and K+K reactions are calculated on the basis of the 3S1 model by adopting relativistic transition potentials and quark (antiquark)spinor.
Energy Correlation of the Variation of Average Transverse Momentum with Respect to Multiplicity in Hadron-Hadron Collisions and the Three Fire Ball Model
LAN Qi-Kai, LIU Lian-Shou
1993, 17(10): 934-940.
The relation between average transverse momentum and multiplicity in hadron-hadron Collisions is calculated using the Three Fire Ball Model.Starting from the change of contribution from the two side-fireballs,the raising of slope of average transverse momentum versus multiplicity as the energy increases is successfully explained.
Effective Local N-Y Potentials with S=-1 in Quark Cluster Model
SHEN Peng-Nian, SHEN Xiao-Yan, ZHANG Zong-Ye, YU You-Wen
1993, 17(10): 941-948.
The dynamics of the N-Y system with S=-1 is re-solved,and the spurious resonances in the former calculation are removed.By using the double Fourier transformation,the GCM kernels are transformed into RGM kernels,and then,the effective local N-Y potentials with S=-1 is calculated.It is shown that these potentials are similar to that of Yamamoto's obtained by using the OBE model with phenomenological hard cores.With these potentials,the phase shifts and cross sections of the system can be re-produced.
Intermittency for Weighted Distribution
LU Zhong-Dao, SA Ben-Hao, ZHENG Yu-Ming, ZHANG Xiao-Ze
1993, 17(10): 949-954.
In order to take the influence of the average distribution of particles into account in the intermittent behavior,the weighted distribution is proposed.The weight factors are determined and calculated by the average distribution of particles.The calculations show that the lni>~lnM drawings of the weighted distribution has a double-slope behavior which is consistent with the experimental prediction and is important for correctly understanding the intermittent behavior in the multiparticle production in the relativistic reactions.
Calculation of Multipolarity Mixing Ratio and Internal Conversion Coefficients for γ Transition
ZHOU Chun-Mei
1993, 17(10): 955-958.
Briefly described are the calculation methods of the multipolarity mixing ratio δ,the internal conversion coefficients αKLM,and αN+O of K,L,M,N and O shell,and the total internal conversion coefficient α for a γ transition from measured internal conversion coefficient for one of shells.
The Synthesis and Identification of New Neutron-Rich Heavy Nuclide 237Th
YUAN Shuang-Gui, ZHANG Tian-Mei, XU Shu-Wei, LI Zong-Wei, PAN Qiang-Yan, ZHAO Zhi-Zheng, YANG Wei-Fan, ZHANG Xue-Qian, LI Wei-Sheng, YIN Xi-Jin, DU Yi-Fei, WANG Yi-Hao
1993, 17(10): 959-960.
New neutron-rich heavy isotope 237Th was produced in the 238U(n,2p)237Th reaction by 14MeV neutron irradiation of (NH4)2U2O7 powder and separated by radiochemical methods.The new activity was first identified by following the time sequence spectra of the γ-rays of its daughter 237pa.A radioactive series decay analyzing program was applied resulting in the halflife of 5.0±0.9min for 237Th.In addition,a new 35.1±0.3keV γ-ray with T1/2=5.0±1.1min was found and assigned to 237Th.