1997 Vol. 21, No. 05
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Decays of the J/ψ resonance into the final states with three photons are investigated.Branching ratios for the decays of J/ψ→γπ0 and J/ψ→γη'are determined to be Br (J/ψ→γπ0)=(4.6±1.1)×10－5 and. Br(J/ψ→γη')＝(4.12±0.82)×10－3. The ratio of the two decay rates,(J/ψ→γη')/(J/ψ→γη),is 4.79±0.85. Within experimental errors, this value agrees well with the predictions of two theoretical models'.
High-spin states in 162Lu have been roduced and studied via 147Sm (19F, 4nγ) 162Lu reaction. lh-beam γ-rays were measured by using 1 planar detector and 7 high purity Ge detectors with BGO anti-Compton Shield. The level scheme of the yrast band in 162Lu was established for the first time and the signature inversion in energy was discovered for The yrast bands of doubly odd nuclei around A=160 mass region have been reinvestegated and the systematics of signature inversinon was discussed briefly.
Yields of lr isotopes from 12C (47MeV/u)＋197Au have been measured by using chemical separation and γ spectroscopy method. The lr isotope distribution was ob tained after correction for decay during the irradiation period by using the accutnulation yields of Pt. The cross sections of A>170 neutron-rich isotopes , the Qgg systematics of cross sections and the residual excitation energy of target - like frafpnents are discussed.
The density matrices of J/ψ produced in the non-polarized e+－e－ collisions in both experimental laboratory and helicity frame are discussed. The results show that rthe conclkusion for only J/ψ with the helicity ±1 having contributions to the procss is correct only in the experimental laboratory frame under some conditions. The number of the moments is the same and there is a simple relation between the moments in the two frames.
We calulate the psedo-Goldstone-bosons (PGB) contributions to the decay Bc→Ds γ in one generation technicolor model (TCI) and the technicolor model with massless doublet (TCⅡ),and compare with the contributions estimated in the standard model. We find that the contributions of PGBs in the TCI to the electri-magnetic penguin dirgram are large, whereas those of the TCⅡ are small. However, the contributions to the weak annihilation diagrams can be neglected. It is expected that the difference of the branching ratio Br (Bc→Dsγ)in various models can be studied at LHC in near future, and will be an important test to different models.
The infrared divergences of three-loop vacuum graphs of massless scalar and gluonfields and their regularization are discussed. The expression for analytical continuation is given. How to seperate the infrared and collinear divergences from overlap ones is also discussed.
Using the extended x-rescaling model and taking account of the nuclear shadowingeffect by the spatial overlap of sea quarks and gluons from neighbouring nucleons in the nucleus in small x region, we calculate the ratios Gsn(x)/Gc(x). The calculated results arein good agreement with recent NMC experimental data.
Within the framework of the nuclear pair shell model, numerical calculation is performed in the truncated SD subspace. In this calculation, the S pair is taken as that from the BCS calculation, the D pair is obtained through D＝for the even-even nuclei with cases in the region. The contributions from the single particle energy term H and from the abnormal parity level are discussed.
A Simulation is carried out for five different phases of nuclear equation of state. thegas, the liquid, the super heated liquid, the super cooled gas and the mechanical instability of spinodal phases, which are obtained from a deasity, tempemperature, and momentum depen dent mean field for 197Au at finite temperature T=6MeV in real space and in momenturn space The nuclear cluster is sorted a coalescence model. lt is demonstrated that the intermittent pattern comes from the mechanical ionstability of spaiodal phase and the criti cal behaviour comes mainly from the mechanical instability of spinodal phase while there is also a small contribution from the super heated liquid phases from the analyses of the conditional moments and the scaled factorial moments.
Monte Carlo Calculations of the isomeric cross section ratio for (n,2n)reaction based on the compound nuclear reaction theories and exciton-model are presented. Thecalculations are compared with experimental measurements for 59Co (n,2n)58Co, 93Nb(n,2n)92Nb and 181Ta(n,2n) 180Ta reactions in the energy region from threshold to 20MeV. The agreemeat between calculation and experiment indicates that the present method is suitable to calculate the isomeric cross section ratio for (n,2n)reactions.
The relationship between Bose-Einstein coheremt radius and source radius (orroot-mean-square radius),and their dependence on the experimental windows of rapidity and transverse momentum are studied for pion source in 160A GeV/c Pb+Pb collisions,The model pion source is Produced by generator URASiMA. The results show that the coherent radius and source radius at freeze-out not only have difference in magnitude but also in behavior.
The different modes are to Study the effect of the compet ition between the energy internalvibration and thecollective rotational energy. It is found that thie competition will affect the geometricstu cture and the space orientation. of the states of 3-Particle systems.
A novel multi-cavity RF thermionic gun with much less back bombardment effect has beea designed, built, tested and experiraeated. ln this paper we mainly discuss the expermental results of this RF gun From the pulse shapea of BCT at the gun exit and energy spectra at different. positions of the pulse, we have seen that the back bombardment power is much less than the single cavity RF gun. The current after the a-magnet is 200mA, and electron energy is about 1.8MeV. The geometric RMS emitttance is less than 28π nm . mradia x-direction, and lessthan 22π·mm·mrad in y-direction at the linac entrance.
The synchrotron radiation (SR)microprobe XRF experimental station of Beijing Synchrotron Radiation Facility (BSRF)is located at the end of the 4W1A white SR beam line.The major instruments of the station are: ion chamber system for beam intensity monitor; slits and laser collimation system;multidimensional sample stage andits stepping motor driviing system; tele-microscope and video viewing system; Si(Li)energy dispersive spectrometer.The equipment has very high sensitivity (absoluteMDL, 10－10—10－13g,relative MDL:N×μg/g-N×0.1μg/g,and relative MDL fortotal reflection XRF is 1－5ng/g),good spatial resolution (50μm for thick sample,200μm for Bio-tissue). A lot of researches were performed on Geo-Science,Bio-Science,Material Science and so on.
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