1992 Vol. 16, No. 10
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The τ lepton mass was measured with data taken by the BES detector at BEPC collider at Institute of High Energy Physics in Beijing.Approximately 5000nb－1 luminosity was accumulated.Pairs of τ lepton produced near the threshold have been studied in eμ final states.The likelihood method was used for both of predicting a series of experimental energy and data fitting.The measurement yields the τ mass to be 1776.9±0.4±0.2MeV.
The measurement of radiation damage of 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 1.1GeV electron beam.We have studied the light output at different depths in the modules and defferent integrated doses,the recovery process and the dependence on the ambient atmosphere.
Using a part of China-Japan Pb emulsion chambers (K6 K7,thick 30 c.u.)exposed at Mt.kanbala (5500m,atmospheric depth 520g/cm2),the high energy gamms rays and hadrons are studied.The vertical intensities,energy spectra,zenith angie distributions and attenuation length of gamma rays and hadrons in air are presented.The results are compared with previous data.It is shown that the vertical intensity of gamma rays given by the previous work is lower than the present result and other characteristics are consistent with each other.
In this paper we have investigated the infrared divergence in QFT from the point of view of unitarities and analyticities.We have shown that in QED,the infrared divergence for the imaginary part of a bubble diagram at any order of a would be canceled each other between the set of cutting-bubble diagrams got from cutting rules of Landau Cutkosky.From the concept of generalized optical theorem and the hypothesis of analyticities of the scattering amplitude,we have drawn the physical connotation from the general formula of unitarity.for "forward scattering processes",and thus getting a criterion in QED for whether in a process there exist infrared divergence or not.Also from the variation of thresholds of a bubble diagram of π(q2)in the -q2 plane as the photon mass λ approaches to zero,we have shown diagrammatically how the infrared divergence in the corresponding cutting-bubble diagrams be canceled between them.At last we give a short discussion about difficulties and problems for treating infrared divergence in QCD.
After a summary of the predictions for th neutron electric dipole moment in a number of models of CP violation,we review mainly the recent developments associated with Weinberg's purely gluonic CP violation operator.Its implications on the neutron electric dipole moment in various models of CP violation are discussed.Inspired by Weinberg's work several new mechanisms of generating large electric dipole moments of charged leptons and large electric and chromo-electric dipole moments of light quarks are recently proposed.Brief discussions on these new developments are also given.
The structure and Verma module of matrix element algebra A(3)q of 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(3)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 hadronic decay process J/ψ→V1+X,X→V2+V3,V2,V3→2P(or 3P)(here Vi and P stand for vector and pseudoscalar meson,respectively) has been discussed in this paper.For the intermediate state X with various spin-parity JP,the corresponding helicity formalism of angular distribution formulas have been presented.They are helpful for determining the spin-parity of the intermediate state in above process by using the J/ψ events obtained from BEPC.
The production process of grey particles in high energy nucleus-nucleus collisions is in-vestigated in this paper.The comparison of the experimental mulitiplicity distributions with the calculations reveals that the statistical model well describes the production of grey particles.The correlation between the number of participating target N,the impact parameter b and the multiplicity of grey particles ng is studied.
A high mass resolution telescope was built for heavy-ion reaction mechanism research at intermediate energies (20—100MeV/u) This telescope consists of three silicon ΔE detectors (130μm+1580μm+5000μm) and a CsI(Tl) scintillator with photodiode readout E detector It can be used for particle identification with its high mass resolution (typical for 12C ΔA/A=25% FWHM) and for energy measurment in the broad range (typical 16—350MeV for α particle)with its high energy resolution.
The high spin states of 121Cs have been populated via the 112Sn (12C,p2n) reaction and measured by in beam γ technique.Two new levels in each of the πh11/2,ΔJ=2 and πg9/2,ΔJ=1 bands were observed.
There exist a lot of parameters of optical-model from elastic scattering and the cross sections of nuclear reaction.The effective distance and its nuclear potential have been analysed.Comparing with other phenomenological potentials,The systematic differences for light projectile system have been found and fitted using a new set of poximity nuclear potential parameters.
Effective boson numbers in IBM-Ⅱ are tackled with a simple semi-empirical method,the saturation of proton boson numbers and neutron boson numbers is suggested.It explains the strong correlation and saturation effect of E2 and M1 transition strengrths in even-even rare-earth nuclei.Finally.the results here are compared with effective boson numbers calculated microscopically,the agreement is good.
In this paper,considering the three-body interaction between the d bosons,a simple effective three-body potential is introduced into the IBM Hamiltonian,and its influence on the breaking of the O(6) symmetry is inve stigated.Also the energy spectra of even-even nuclei 196Pt、134Ba、192Os、72—76Ge and 124—130Xe are calculated.The good fits with the experimental data are obtained.
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