1996 Vol. 20, No. 3
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Using the method of tabing a μ first, then checking the recoil side to see if it is a Ds meson, two Ds→μv and three Ds→τv→μvvv candidate events are found from a data sample corresponding to 22.3ph－1, which has been collected at BES at Ecm=4.03GeV.The absolute branching ratio of Ds leptonic decay are determined to be Br(Ds→μv)=(0.72+0.70－0.44)% and Br(Ds→τv)=(14+11－8)%. And the Ds decay constant which is independent of any model is given as fDs=(355+96+28－90－28)MeV.
A two-dimensional position sensitive multi-stage detection system with a wide dynamic range for heavy ion reaction has been developed. It consists of four parts: a gas filled axial ionization chamber(IC), a position sensitive silicon detector(PSSD)(45×45)mm, 400μm), a large area PIN silicon photodiode(SPD) ((48×48)mm, 300μm) and the 16 element CsI(Tl) scintillation detector. The energy resolutions for IC and PSSD tested with α-source of 241Am (5.486MeV) were 3% and 2.6% respectively. Fragments with Z values from Z=2 to Z=21 were identified in the reaction of 25MeV /u 40Ar+115In. The Z resolving power was Z/△Z≈44.5(FWHM) for Z=18. The position resolution of PSSD was (0.86± 0.03)mm (FWHM).And the energy dynamic range for a particles was about 2-130MeV.
In this note, using Feynman path integual method we calculate the Casimir effct of QCD with massive fermion loop contribution between two parallel perfectly conducting wires at zero temperture.
The boundary S matrix for the SU(2) Thicking model is derived and the boundary state is constructed with the bosonic field.
On the basis of the generalized invariant theory, the invariant-related unitary transfoumation method is developed and used to study the evolution of the third-quantized wave function of the universe. The expressions for the phases and the wave functions are obtained.Then, by means of the construction of the coherent state, the solutions of the Wheeler-DeWitt equation and the quantum fluctuations caused by the third quantization are found.
A geometrical model is proposed for the hansverse energy distributions in ultra-relativistic heavy ion collisions based on the Glauber theory. The calculable distributions dσ/dET for 60 and 200A GeV 16O+197Au are in agreement with the data of CERN NA35 Collaboration pretty well. The relation with other geometrical models is discussd briefly.
A shell model calculation is carried out for nuclei with 9≤A≤14 and 3≤Z≤5. In the calculation 8He is treated as a core. The data for 24 experimental energy spectra are selected to determine the parameters of the modified surface δinteraction (MSDI) and the single-particle energies. The RMS=0.72MeV. Then the binding energies, the low-lying excited energy spectra and the electromagnetic properties are calculated and the results are in good agreement with experiment in general. The micromechanism of the halo structure and the parity conversion of the 11Be are discussed in detail. This work is carried out with the OXBASH code.
Using the matrix elements of M-3Y force as the equivalent G-matrix elements, the spectra of 210Pb,206Pb, 206Pg and 210Po are calculated in the framework of the Folded Diagram Method. The results show that such equivalent matrix elements are suitable for microscopic calculations of the nuclear structure in heavy mass region.
The theoretical expressions of energy spectrum and E2 transition probability in the sdIBMl derived by the 1/N expansion technique with high order modified terms are applied to the nuclei in the uranium region. The agreement between theory and experiment is satisfactory. It is shown that the high order modified terms play an important role for improving theory.
Nounal bands of the Well deformed odd A nuclei are studied with the cranking Bohr-Mottelson Hamiltonian. The condition of validity of the model and comparison with the Harris expansion are discussed.
The flavor-changing raciative B decays and flavo-conserving radiative decays of groundstate mesons are studied with another screened potential model. The results are compared with the counterparts of the comell potential and El hassan's work.
The energy and isospin dependent nucleon-nucleon cross section is incorporated in the QMD model. The numerical stable 11Li nucleus is sampled by using the harmonic oscillator type density. The total reation cross section of 11Li+12C is studied in detail and compacts with the results calculated by using the Cugnon parameterization nucleon-nucleon cross section. It is revealed that the increase of total reaction cross section 11Li+12C in low and medium energy region is resulted from the increase of elementary nucleon-nucleon cross section and the time scale, and from the decrease of the Pauli Blocking effect.
A folding model for the 16O+12C system is established.This model can well describe the elastic scattering between 16O and 12C nuclei.
Using the helicity angular distribution method we analyse the process e+e－→J/ψ→γ+X(JPC),X→BB. The angular and the projection angular distribution formulas for different spin-parity of the resonance X are obtained. With these formulas, we determine the spin of the resonance X through analysing experimental data.
A new neutron-deficient isotope 235Am was synthesized in the reaction of 238Pu (p, 4n) 235Am by using 35MeV proton bombarding 235Pu target. The Products were transported by the He-jet system. The Am was seperated from the reaction products using radiochemistry method. The y-ray of 23pu and X-ray of Np following EC decay of 235Am were observed. Based on the growth-decay cruve of X-ray of Np and the X-y coincidence measurements, the synthesis of 235Am was confirmed for the first time. The measured halflife of 35Am is 15±5min.
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