1991 Vol. 15, No. S3
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The method of determining the bunch length of collider by the vertex of charged particles which come from J/ψ decay is discussed. The bunch length of Beijing electron positron collider (BEPC) at the colliding region is presented.
The γ ray energy from the parapositronium 2γ annihilation is measured as 510998.7(2.5) eV by using a silica aerogel sample with oxygen gas filled as the positronium source and by comparing with the known γ energy 511856.2(2.3) eV of the 106Ru γ ray. The result, after correction of the binding energy of Ps,is compared with the adjusted value of the electron rest mass.
Based on a large amount of experiment information, it is assumed that SQS avalanche is developed when the electric field around the anode wire is heavily distorted by the space charge accumulated in the primary avalanche. Following this assumption calculations are performed. The dependence of charge output on the high voltage of the counter is presented. Some key quantities, such as SQS transition voltage Vtr and charge output Qpt and Qst are calculated. Their dependence on gas composition is also presented.
A detailed study of the basic characteristics of the proportional inclined chamber is conducted by analyzing the data from both beam test and theoretical simulation of the chamber. It shows that the position accuracy in the wire plane along the direction perpendicular to anode wires is better than 200 μm and the theoretical simulation can explain the experimental results very well.
The main characteristics, the performance improvement,the current status,and the applications of Beijing Proton Linac (BPL) are described in this paper.
We suggest that the heavy neutral leptons in a specific version of SU(3)L×U(1) model not only act as dark matter particles but also provide a source of anomalous hard positrons in the cosmic rays above 10 GeV.
In the framework of the potential model, the mass, width and branching ratios of η'c are estimated. It is shown that it is possible for the width of the forbidden Ml transition η'c → γJ/ψ to raise one order of magnitude after considering relativistic corrections in comparison with the non-relativistic result. The possibilities to measure the cascade electromagnetic radiation processes ψ'/(3686) → γη'c→ γγ1P1,γγJ/ψ,3γ at the Beijing Electron-Positron Collider (BEPC) are discussed.
Boudjema et al. have found a very good method to identify the theoretical origin of various extra z0 bosons. This method can distinguish the different models very well. We calculate the z20 decay width from another model by using their method and compare it with the E6 and other models.
In this paper we give some relations for discriminating -+ exotic states and 1++ ordinary mesons in J/ψ hadronic decays by using the generalized moment analysis.
Using the Plana summation formula in the complex variable function theory, we calculate the Casimir energy related to the zero point fluctuations of an electromagnetic field in the three-dimensional vacuum space without introducing any cutofTparameter or function. The finite analytic expression derived by us coincides with the known experimental and theoretical results. The Casimir effect in the high dimensional space and that induced by a massive scalar field are also discussed.
The Bjorken formula about maximum energy density in heavy ion collisions is improved. An effective way to increase the energy density is analyzed. Hydrodynamical equations and the equations of state in the central and fragmental regions are discussed. It is pointed out that because of the energy diffusion caused by the expansion of the system, it is difficult to produce quark matter in the fragmentation region. For the Au-Au collisions at RHIC to be built in BNL, the space-time region for the formation of quark matter and the corresponding range of the impact parameter are predicted.
The relativistic hydrodynamic equations derived from the conservation of energy-momentum are generalized by including the equation of the particle number conservation. The influence of the latent heat and particle distribution on the spectrum is studied on the basis of the new description. It is shown that in order to make a reasonable prediction for the formation of quark matter, these effects should be included.
The N* (1535) model is proposed for pionic η-production reactions. The πN → ηN reaction cross-sections near the threshold and the S-wave η-N scattering length are calculated and compared with the experimental data and other theoretical calculations.
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