1992 Vol. 16, No. 1
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The L3 calorimeter beam test data were analyzed.An e/π separation scheme including "key cut" and "Δ cut" is suggested.We show that,using the scheme,in the energy range 4—20GeV,e/π separation is better than 93.7%.
When an ion beam pass through the Penning trap an electron cloud is produced.The distributions of the electron density,electron temperature,drift angular velocity of electrons,diffusion flow density of electrons and electric potential in the electron cloud are discussed by means of the fluid equations of the motion of electrons.
The three family fermions can not be accommolated the Grand Unified Theories(GUTs)if only one extra Z0 boson exists.The minimal GUTs with three families should include two extra Z0 bosons which belong to the different broken scales.Georg's argument on heavy Dirac fermions has been realized.These Dirac fermions should not be bizarre.Frampton's SU(9) model should be essentially same as its SU(7) model.The difficulty of the proton decay may be resolved.
In high energy reactions the production of Spin 3/2 baryons is strongly suppressed in comparison with that of 1/2 baryons.We show that it results from the flavor conservation,so that the strangeness suppression factor λ=
Chiral Ward-Takahashi identities with composite fields are applied to investigate mass spectra in (2+1) dimensional chiral Gross-Neveu model.The fermion mass and bound state spectra are obtained,which are in agreement with large-N expansion in the lowest approximation.When the chiral symmetry is an approximate one,we obtain the PCAC.
The increase of the width of the momentum distribution of He fragments with decreasing He-multiplicity in relativistic 16O fragmentation at 2GeV/N to 200GeV/N is analyzed.The result shows that with decreasing He-multiplicity the surface-excitation energy of the projectile-spectator increases,which is the reason of the increase of the width of the momentum distribution.Although the incident energy changes the projectile-spectator obtains the same excitation energy under the same geometric conditions.This gives the limiting fragmentation behavior of the He-multiplicity distribution.
The enhancement of K+/π+ ratio in the high energy heavy-ion collision is believed to be a possible signature of the quark gluon plasma.Based on the Participant Nucleon Model and the concept of the formation time of secondary particles,the K+/π+ ratio in the central collision of Si(14.5GeV/c) and Au are calculated by Monte Carlo simulation.The following secondary collisions are considered.πN→K+Y、ππ→KK and the single charge exchange reaction between pions and nucleons.The calculation results show that the increased K+/π+ ratio caused by these secondary collisions is not enough to explain the experimental data observed by the E802 group at BNL.
We discuss the time evolution of the colour screening and J/ψ、χ and ψ' suppression by the quark-gluon plasma within the non-relativistic confining potential model.
The cross sections for the 50Ti(n,α)47Ca,46Ti(n,p)46Sc、48Ti(n,p)48Sc and 58Ni(n,2n)57Ni 58Ni(n,p)58m+gCo reactions have been measured by using the activation method relative to the cross sections of the 27Al(n,α)24Na reaction in the neutron energy range of 13.50—14.81MeV.The neutron energies were determined by the cross section ratios of the 90Zr(n,2N) 89m+gZr and 93Nb (n,2n) 92mNb reactions.The results obtained are compared with the published and to be published data of several authors.
The high spin states of 125Ba populated via the 109Ag(19F,3n) reaction are measured by using a BGO Compton suppressed HPGe detector array.The negative and positive parity bands built respectively on the h11/2 and g7/2 neutron hole states are extended to 35/2－ and 23/2+.Backbending occurs in both signature branches of the negative band at the frequencies close to that of the 124Ba yrast band.An onset of backbending in the positive band has been seen.
In order to describe the quasi-elastic knockout reactions such as (p,2p) by a method with higher accuracy,the multiple-scattering proposed by the previous work has been developed in this paper based on the time-independent multiple-scattering theory.In particular,T matrix element is expanded as a series form of multiple-scattering terms,Tfi=M(1)M+T(2)M+...It is proved that T(1)M is almost equivalent to the total effects of the first three orders of the Born series.It means that one can only keep the first term,T(1)M and obtain good results.On the other hand,the calculations of T(1)M is simple relatively.As an example,excellent results have been produced by the present method for the pure Coulomb interaction,such as the (e,2e) reactions of atomic hydrogen,and 6Li(p,2p)5He, reactions.
By the Holstein-Primakoff boson expansion,an hermitian supplementary term with finite form is introduced into the IBM hamiltonian to describe the cross shell excitations.The method of intrinsic condensate is generalized to treat the intruder states.According to this scheme,the low-lying spectra of the Sn isotopes are calculated.Both the vibrational spectra and the additional rotational spectra are obtained.
A formula for the calculation of the cross sections,of nuclear transition to continuum states induced by direct radiative capture of intermediate-energy proton is deduced.The transition amplitude includes two terms corresponding to potential-scattering to potential-scattering transitions and potential-scattering to resonance-scatting transitions,respectively.The model is compard with available experimental data of the 11B(p,γ19)12C reaction,and the results show that the direct capture mechanism is capable to account for the main features of the measured data within the reasonable parameter scope,and,in the present case,the contributions from two terms are of the same order of magnitude.The physical significance of the results is also discussed.
The validity of the quantum group SUq(2) expression for the nuclear rotational spectrum is investigated thoroughly.Analyses (including the Mallmann plots,the relations for the I(I+1) expansion coefficients,energy spectra,etc.)definitely display a systematical deviation of the SUq(2) prediction from the experimental data available for the even-even rare-earth and actinide nuclei.Only within a limited range of angular momentum the SUq(2) expression is suitable for rotational spectra.A significant angular momentum dependence of q-deformation parameter is found.The q-deformation is derectly related to the nuclear softness.
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