1997 Vol. 21, No. 3
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Using the data sample accumulated with the Beijing Spectrometer at the center-of-mass energy of 4.03GeV,we have analysed τ±τ±→e±+π±+nπ0+ν's(n=0,1,2)events.The branching ratios are given as Br(τ±→π±ντ)=(11.64±0.49+0.76－0.73%,Br(τ±→π±π0ντ)=(24.00±1.34+1.36－1.30%,Br(τ±→π±2π0ντ)=(9.39±1.68+1.69－1.66%.
The new neutron-rich isotope 175Er activity was produced via the reaction 176Yb(n,2p)by 14MeV neutron irradiation of natural ytterbium metals. When nuclide 175Er decayed to its daughter nuclide 175Tm, Tm characteristic X rays would be emitted with a certain ratio due to the internal conversions.So X-γ and γ-γ coincidence measurements were employed to successfully identify the neutron-rich isotope activities of rare-earth element from other rare-earth reaction products.And a partial decay scheme of 175Er has been proposed for the first time.
We used artificial neural networks(ANN) to distinguish superhigh energy cosmic-ray proton(p) and nucleus(N) with Monte Carlo family data in mountain emulsion chamber experiment.The result shows that when visible energy of a family is larger than 500TeV,about 80% of p and N can be correctly selected,and more than 70% can be selected in the region between 100 and 500TeV.
The measurement of the double differential cross sections of protons enritted from the reaction of 14.6MeV neutron with stainless steel was performed by using the multitelescope system at 16 angles from 25 to 165 deg with angular resolution of 12 deg on an average. The energy spectra,angular distributions and total cross section of proton emission have been obtained.
This paper is intended to discuss generally the method and procedure of diminsional regularization wihin the imaginary-time formalisim(ITF).As an example,we app it to calculate the thermodynamic potential of two-loop QED and the renormalization.
Identical one-quasiparticle and two-quasiparticle bands in neighboring odd-and even-mass nuclei are recognized.The intrinsic structure of identical bands is demonstrated by using the particle-number-conserving(PNC) treatment.The occurrence of almost identical moments of inertia is the result of competition among the shell effect (including shape variation),pairing(anti-alignment)effect and blocking (anti-pairing) effect.The observed moments of inertia of identical multi-quasiparticle bands are reproduced quite well by the PNC calculation.
Taking Z*σ and Eσ as the effective interactions in Hartree-Fock thoery,the comparison between the calculations by using two methods for treatment of pairing interaction is carried out.The validity and limits of the methods for reproducing the ground-state properties of the light nuclei from helium to oxygen are also discussed.
The ground state properties of the nuclei near Z=8 and Z=50 are investigated using the Skyrme-Hartree-Fock approach with new force parameters SK12,SK13 and SK14.The calculations show that the Skyrme-Hartree-Fock theory with above force parameters provides a good description on those isotopes.Among the three sets of force parameters,SK14,which has considersed the isospin dependence of the spin-orbit force,is the best one.SK14 is also successful in reproducing the charge shifts near Z=50.
The effective boson number is related to the effective valence nucleon pair number in the normal parity orbits for the first time.A new approach is suggested for calculating the effective valence nucleon pair number i.e. effective boson number in the light rare-earth region.
The structure of nucleus 11Be is investigated in terms of Particle-Vibrator Model (PVM).The low-lying states and electro-dipole transition of the first excied state to ground state of 11Be are calculated,and the results are in good agreement with experiments.The calculated wave-function of the ground state of 11Be shows that the parity inversion was caused by coupling of single particle motion with collective vebration of cove(10Be.The halo structure of 11Be is also explained reasonably in terms of the PVM.
The research survey of consistent dynamical and statistical description of fission is briefly introduced.The Channel theory of fission with diffusive dynamics based on Bohr channel theory and Fokker-Planck equation,and Kramers-Modified Bohr-Wheeler expression according to Strutinsky method given by P.Frobrich et al.are compared and analyzed.
Based on the relativistic hydrodynamic model,the dilepton production in the quark-gluon fireball is studied.It is found that with increasing initial temperature the total dilepton yield mconotonicly goes up aftera plateau for the quark-gluon fireball of zero baryon number and shows a peak for the baryon-rich quark-gluon fireball.Such a characteristics as a signal of the quark-gluon matter formation in the collision could be tested in future experiments at CERN and Brookhaven.
By an amplitudes analysis of the KKπ system in the J/ψ radiative decay to the K+K－π0 and the K0SK±π+ final states,we find that there is one 0－+ resonance (M=1467±3MeV,Γ=89±6MeV) and two 1++ resonances (M=1435±3MeV,Γ=59±5MeV; M=1497±2MeV,Γ=44±7MeV),which are consistent with the η(1440),the f1(1420),and the f1(1510).
A new group of protons at a laboratory energy of (4.07±0.05) MeV with half-life of (32±10)ms was discovered via observing the decay proton spectrum resulting from 32S+Ca reaction.By reaction channel analyses and comparing with theoretical prediction,this new proton radioactivity was assigned to arising from the beta-delayed proton decay of 69Kr produced in the 40Ca(32S,3n) reaction,corresponding to decay of the T=3/2 isobaric analog state in 69Br to the ground state of 68Se.Combining this measurement with Coulomb displacement energy calculation yields a mass excess for 69Kr of (－32.15±0.30)MeV. The partial decay scheme of 69Kr was proposed.
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