1992 Vol. 16, No. S4
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The τ lepton mass was measured with the data taken by the Beijing spectrometer (BES) at the BEPC at the Institute of High Energy Physics in Beijing. Approximately 5000 nb-1 integrated luminosity was accumulated. Pairs of τ lepton produced near the threshold have been studied in eμ final states. The maximum likelihood method was used for both of predicting a sequence of experimental energies to approach the threshold and data fitting. The measurement yields the τ mass of 1776.9-0.5+0.4 ±02 MeV.
This paper reports the design and construction of the primary beam of the test beam on the BEPC, as well as the acquisition of the positive-charged secondary beam. The various particles, e+,π+,μ+, p, in the secondary beam have been measured with TOF method and threshold Cherenkov counter. The radiation damage studies of SDC (Solenoidal Detector Collaboration) calorimeter modules using the test beam have also been briefly described.
The pseudorapidity distributions of charged particles produced in pp collisions at 400 GeV/c have been measured using LEBC films. The multiplicity distributions in forward hemisphere at fixed total multiplicities are obtained. The forward-backward multiplicity correlation strength in full-phase space, central region, and off-central region of the pseudorapidity distribution are calculated. The correlation strength versus pseudorapidity windows are obtained. The experimental data of the forward-backward correlation have been analyzed with cluster model. The results show that the average cluster size is dependent on whether the leading-particle effect is taken into account.
The measurements of radiation damage of a tile/fiber scintillator modules to be used for the SDC calorimeter are described. Four tile scintillator modules were irradiated up to 6 Mrad with the BEPC 1.1 GeV electron beam. We have studied the light output at different depths in the modules and for different integrated doses. The recovery process and the dependence of radiation damage on the ambient atmosphere are also investigated.
Based on the 2.5 million J/ψ's collected by the Beijing spectrometer at the Beijing electron positron collider, through the hadronic decay J/ψ → ωf2 (1270),f2(1270) → π+π-, ω→π+π-π0, we studied the properties of the resonance f2(1270):the mass,width, and branching ratio. The angular distribution is Otted with the maximum likelihood method, determining its spin-parity JPC=2++, and giving for the first time the helicity amplitude ratios of this process as:x=0.99 ±0.29, y=-0.24 ±017, z1=0.90 ±0,57, z2=0.56 ±022.
Using the precise expression of electron, positron distribution functions we obtained previously, we get the rigorous analytical expression of the radiator in e+e- collision processes. This series expression converges rapidly to the precise result required. The comparison with existing approximate expression is also given. Our result benefits the precise calculation for the radiative corrections in e+e- collision processes.
The hadronic decay processes J/ψ→V1+X、X→ V2 + V3,V2,V3→2P (or 3P) (where Vi and P stand for the vector arid pseudoscalar meson, respectively) are discussed in this paper. For the intermediate state X with various spin-parity JP, the corresponding helicity formalism of the angular distributions are presented. They are helpful for determining the spin-parity of the intermediate state in the above processes by using the J/ψ events
We constructed the factorizable S-matrix and obtained the symmetry operator which commutes with the 5-matrix and has a new form of "coproduct," the elements of which depend on the parameters defining the toroidal rapidity surface. By defining a new operator which commutes with the symmetry operator the Yang-Baxter equation can be obtained. Finally, the relation between the hroken ZN-symmetric model and the chiral Potts model was expressed explicitly in the seif-dual genus zero limit.
This paper studies the influence on the baryon and its resonances from a new additional mass term which is derived by the Skyrme Lagrangian after quantum mechanical treatment.
The structure and Verma module of the matrix element algebra A(3)q of the quantum group GL(3)q are studied using a similar method for studying the structure and Verma module of semisimple Lie algebras. The q-boson realization of A(2)q is constructed from its Verma representation and the cyclic representation of A(3)q is obtained in terms of the q-boson realization.
The influence ofmulti-pion correlations on two-pion interferometry analyses in multi-pion events can be expressed as the ratio of a multi-pion correlation factor for the sample of like-pion pairs to a residual correlation factor for the reference sample. Although these two correlation factors can partially cancel each other in data analyses, the difference between the two factors in the low relative momentum region is so large that the distortion from multi-pion interference becomes a serious problem when the pion source has a small radius and the pion multiplicity is high. The distributions of the multi-pion correlation factor Cn-2(q) offers a good sensitivity to multi-pion correlation effects. Analyses of the multi-pion correlation factor for two Bevalac streamer chamber data samples of 2.1 A GeV Ne + Pb and 1.8 A GeV Ar + Pb collisions show that the multi-pion correlation effect in the former sample is greater than that in the latter.
By means of the quark-antiquark pair creation model via one-gluon exchange, the effective ion among quarks,which is equivalent to the meson exchange intervening between two hadrons, is discussed. It is shown that this process includes interactions not only between two quarks, but also among three quarks. Obviously, such effective interaction is more general than one gluon exchange potential (OGEP).
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