1997 Vol. 21, No. 10
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Using the data obtained in the period of June 1990-October 1993,the shadowsof the Sun and the Moon have been detected at 5.7σ and 7.1σ levels respectively inthe 10TeV cosmic ray flux by the Tibet air shower array at an altitude of 4300mabove sea level. The shadow of the Sun is found to be deflected away from the Sunby 0.62°to the west and 0.22° to the south by the interplanetary magnetic field.The correlations between the shadow of the Sun and Solar activity and its asymmetryare studied in Detail. A new qualitative explanation to the shift and yearly variation ofthe Sun's shadow is presented.
The quasi-elastic scattering angular distributions of 19F+208Pb system at energies of 88,91,93,96 and 102 MeV have been measured by means of ionization chamber △E-E telescope. The optical potential parameters of the system were obtained from the fit of the angular distributions of the elastic scattering with ECIS code, and the phenomenon of the " threshold anomaly" is clearly observed. The angular distributions and the excitation functions of the products C, N and O from transfer reactions were also obtained. The slope factor k were deduced from the relations between the transfer probabilities and the closest distances for three main transfer channels. The κ values agree with the semi-classical calculation for the single nucleon transfer reaction, but are smaller than the calculation for the mufti-nucleon transfer reactions, and depend on theincident energies. The "slope anomaly. and the energy dependence of κ can not be explained by the semiclassical theory.
Delayed coincidence method was used to measure the lifetimes of the isomeric states in 117Xe.Two halflives of T1/2=(59±20) ns and T1/2=(16.5±8.0) ns have been extracted from the coincidence time spectrum between the 401keV(15/2－→11/2－) and the 205keV(7/2－→5/2＋) transitions,and are assigned to the 11/2－ and 7/2－ states respectively.
Some results of the studies on the properties of BSO crystals are reported, inclu- ding excitation spectrum and fluorescent spectrum, light yield, decay time and radiation hardness .
A new detection system was constructed by means of combination of a coincidence and an anticoincidence. The γ-ray energy signals detected by a HPGe detector were in coincidence with energy-loss signals of β rays detected by a 4πΔEβ detector, then the coincidence output were in anticoincidence with the positron-annihilating 511 keV γ signals detected by a large BGO detector. This system may reduces the Compote background for γ-spectrum measurement by about one order of magnitude. With strong suppression to the detection of the decaying γ rays from neutron-deficient isotopes, the detection of the decaying γ rays from neutron-rich isotopes can keep a higher efficiency of (46±3)% compared to single-spectrum measurement. This system was used for determining the half-life of the neutron-rich isotope 208Hg. A new value of 41.5-4.1 +5.0min was obtained, which is in agreement with the earlier value obtained by radiochemical milking method, but the measurement error was substantially improved.
The O(αs) corrections to the inclusive semi-tauonic B decay are calculated inone-generation-technicolor model. Comparing the theorretical prediction with the recentexperimental results, we present lower constraint on masses of the chargedcolor-singlet and color-octet pseudo Goldstone bosons, mp>43GeV, MP8>77GeV.
The terms up to one order derivative of Wigner function are retained when the semi-classical limit of transport equation of quarks is taken. The semi-classical transport equation is expanded in the color space and the spin space. The transport equations of color single spin scalar and color singlet spin vector are obtained. The non-Abelian natures of QGP are discussed though comparing our results with non-Abelian plasma.
A concept of particle-group correlations is proposed in this paper. In according with the new concept, a new method of collective Dow measurement is constructed. Using the new method, the particle-group correlations arising from collective flow are studied with 4. data lbr 2.1A GeV Ne+NaF collisions at the Bevalac streamer chamber. Comparing with the Monte Garlo results, the collectivity of the particles in the final state of this collision is inferred in the range from 75% to 95%.
(1+1) dimensional relativistic hydrodynamics equation with a source term iacludiag the quarktfragment effects a is numerically solved and the evolution of the energy density, flow rapidity and baryon number density as the characteristic values of the phase transition which is possible to be produced in the nuclear collisions at extreme high energy are also analysed. The quark-fragment effects in the source term are described by using the phenomenal SU(3 ) string model with a flavor dynamics. The numerical results are compared with Kajantie's, s data. It illustrates indirectly that the results are in agreement with the experimental data. The physics picture of our model presented in this paper shows that this phenomenological self-consistent model is reasonable.
Based upon the relativistic bydrodynatnics, it is pointed out that although the recent data on the first single-photon spectrum show a linearity, it does not mean that in an ultra-relativistic auclei-auclei collision the system reaches equilibrium at some temperature in whole, making use of a new dynamical mechanism for hadronztion. phase transition, the evaluating results predict that if the phase transition from QGP to badronic matter is of first-order, for higher colliding energies (e.g.>200GeV/u) the photon spectra would show some concave curvature, which may be a possible signature for diagaosiog QGP.
With the Skyrme force E and Hamree-Fock approximation, the sbucture of neutron rich isotopes of Li and Be are studied. Special attention is paid to the neutron pairing interaction, which is treated with a particle number conservation method. Close connection between the neutron padding interaction and the double neutron halo is demons trated.
The parity-violating asymmetry A is calculated for, quasielastic electron scattering of 12C and 40Ca. In this work, we use a relativistic mean field model of the nuclear matter response. The contdbudon of strange quarks to A is studied.
Based on the relationship between electron induced deep inelastic scattering and forward virual photon compote scattering, the spin dependent structure function of nucleon and its first moment are expressed in terms of total absorption cross section of virtual photon which are calculated numerically in SU(6) quark model by use of helicity amplitudes. With the theoretical cross sections, the first moment of proton spin dependent structure function is predicted, and then quark polarization is deduced from the predicted moment. The experimental measurements of EMC and SLAC are reproduced thcoretically.
Using ρ/ω mixing and thermos field dynamics, the neutmntproton mass difference in thermal environrnent is calculated and the finite density dependence of the neutroniproton mass difference is analyzed.
The radioactive nuclide 186Hf has been produced via multinucleon transfer reaction by 60MeV/u 18O ion irradiation of the natural tungsten. The radiochemical separation was performed to isolate the hafnium from tungsten and the complex mixture of the reaction products. The activity of the hafnium was measured using a HPGe detector The new neutron-rich isotope 186Hf has been identified for the first time by measuring the growth and decay of the 737.5keV γ-ray from its daughter 186Ta. The half-life of 186Hf was determined to be (2.6±1.2) min.
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