2002 Vol. 26, No. 8
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Based on the physical implication of the unusually large mass scale and long live time characteristics of J/ψ particle and on the understanding of the requirement of glueball production,we proposed an alternative mechanism of glueball production in J/ψ radiative decay: the glueball Gb could be formed via fusion of a pair of constituent gluons which are emitted whenever the constituent charm quark and anti-quark in J/ψ transit into current charm quark and anti-quark,and remained current charm quark-pair annihilates into a photon. After a brief discussion of model parameters,we evaluate the partial width Γ J/ψ→Gb+γ,and compare it with the result from the mechanism where the glueball is produced via hadronazation of two emitted gluons in the J/ψ radiative decay.
We calculate the effective mass and damping rate in φ63 theory at finite temperature by evaluating the real and imaginary parts of the one-loop self energies at the hard thermal loop (HTL) approximation. We show that there is thermal instability above a critical temperature Tc. The effective mass and damping rate are proportional to gT and gT respectively. We compare our results with those in hot QCD.
A method is developed to study the optimized BES data taking time after each injection. For current ψ′ data taking,the optimized data taking time is 3-5 hours. The method can be generalized to other experiments.
Based on the possibility that the life time of the lightest top squark 1(1) may be long enough and it may form a bound state with another quark before its decay has not been ruled out yet, we focus on the bound states of the lightest top squark 1(1) and a heavy quark Q(), and establish the Bethe Salpeter equation for the binding systems (c1) and (b1) (or their antiparticles) etc with QCD inspired kernel. We then investigate these systems and give their spectroscopy by means of instantaneous approximation.
We improve the coupled cluster method in lattice gauge theory based on the application of the random phase approximation. Using this method, we study the vacuum wavefunction and glueball mass of the 0－－ and 0++ in 3+1 D SU (3) lattice gauge theory by finding the solution of the Hamiltonian eigenvalue equation. The calculated results are satisfacting γ=m (0－－)/m(0++)=1.8578±0.0506.
The ratio of final baryon to meson and baryon antibaryon correlation in e+e－ annihilation are considered as sensitive observables to test the hadronizition models,because among the results obtainted in different popular hadronizition models,only those from JETSET event generator can fit experimental data by adjusting extra ad hoc parameters. We replace the color neutral flow connection,which is the results in large Nc limit and is used in JETSET,with the color separate connection,which is allowed by PQCD,and calculate these observables. We compare the obtained results with those from the standard JETSET7.4 code and the available experimental data. We find that the results and the relevant properties are consistent with data. This shows that the consistency of the data with the results from the standard JETSET7.4 code for these properties does not mean that the traditional color neutral flow is the only color connection selected by NPQCD. The 100% color separate connection is also possible.
The squeezing property of states generated by the excitation on the SUq(1,1) even and odd q coherent states (a+mqα>eq and a+m qα>oq) is numerically studied. It is shown that for small q, the state a+m qα>eq and state a+mqα>oq can exhibit strong q squeezing, and as r2 increases the q squeezing function Δe1(Δo1) exhibits a wonderful oscillating phenomenon of increasing amplitude and increasing period. As m increases and q decreases, the amplitude of Δe1(Δo1) increases greatly. As q decreases, the period of Δe1(Δo1) increases but is independent of m.
Through measuring prompt γ-rays emitted in the spontaneous fission of 252Cf with higher statistic data,level structures in the neutron rich,odd A107Ru nucleus have been re investigated. New level scheme of 107Ru has been established. The ground state band was extended with spin up to 27 2h. The νh11/2 band structure observed in our previous publication has been confirmed and extended. These results clear up the inconsistence between our earlier work and results from another experiment published recently. A collective band built on (9/2－) level has been observed for the first time. Some important features of the level scheme have been discussed.
By irradiation of an enriched target of 96Ru with 40Ca and using a helium-jet fast tape transport system in combination with X-γ and γ-γ coincidence measurements,the very neutron deficient isotope 133Sm was produced and studied. A simple(EC+β+) decay scheme of
The yield of light charged particles (LCPs) emitted at forward angles is investigated in the reactions of Si target bombarded by the fragments produced in the fragmentation of 69AMeV 36Ar. It is found that the yield of LCPs increases with decreasing the neutron number of fragment isotopes,and for the lighter fragments,the effect is more prominent. Moreover the yield of LCPs decrease with the increase of the proton number of fragments with the same isospin. It indicates that the yield of LCPs is very sensitive to the structure of the nuclei near the proton drip line. It can be regarded as a possible probe to explore the structure of proton rich nuclei and a new way to provide an evidence for existing proton halo.
Lifetimes of the excited states in light rare-earth nucleus 130Ce have been measured using heavy ion reaction 116Sn(16O,2n)130Ce at beam energy of 73MeV through analyzing the Doppler-broadened line shapes. The reduced transition probabilities B(E2) are extracted from these measurements. The experimental results show that the previously reported anomalously high B(E2) value has not been observed in the present work. The transition quadrupole moment for the yrast band varies with spin and corresponds to a triaxial deformation with γ≈7°.
The reaction of 139La(82Se, x)136Ba was used in this experiment. The nuclide 136Ba was produced via the transfer reaction channel. Some new γ rays of 136Ba were measured and a new isomer state at 10+ was observed. The half life of this isomer is 94ns based on its time spectrum. According to the intensities of gamma transition and gamma-gamma coincidence relationship, the scheme of 136Ba is suggested.
A phenomenological energy modified transparency function in Glauber model is presented. The reaction cross sections for a lot of light nuclear reaction systems such as:12—14C,6Li, 7Be,8B+12C and 6Li, 7Be,8B+9Be,20Ne+12C,12C+27Al at the energy range from 10MeV/u to 1000MeV/u have been calculated. The most of the calculated results reproduce the experimental data very well.
The new nuclide 259Db and its α decay chain are systematically studied in the framework of the relativistic mean field (RMF) theory with NL3 and TM1 effective interactions. The nuclide 259Db and its α-decay daughter nuclei are calculated in a RMF framework with and without the pairing correlation. With the pairing gaps obtained from the RCHB, the deformed RMF+BCS has been carried out for these nuclei. It has been found that the DRMF+BCS well reproduces the data and implies that the new nuclide 259Db and its α decay daughter nuclei are highly deformed. The α-decay energy Qα for different channel has been given and it seems that the ground state to ground state Qα values from DRMF+BCS reproduce the data well. Furthermore the single particle levels of the α decay chain are studied carefully and the explanation for the stability is also presented.
In this paper, we presented a x rescaling parameters' empiric formula of the extended x rescaling model, where we have established the connection between the rescaling parameters and the mean binding energy in nucleus. By using the formula, we can get the x rescaling parameters for various nuclei with A≥12, and thus further calculate the relevant nuclear process and make out prediction.
We have applied the theory of the single-particle Schrodinger fluid to the nuclear collective motion of axially deformed nuclei. A counter example of an arbitrary number of independent nucleons in the anisotropic harmonic oscillator potential at the equilibrium deformation has been also given. Moreover, the ground states of the doubly even nuclei in the s-d shell 20Ne,24Mg,28Si,32S and 36Ar are constructed by filling the single particle states corresponding to the possible values of the number of quanta of excitations nx,ny, and nz. Accordingly, the cranking-model, the rigid-body model and the equilibrium-model moments of inertia of these nuclei are calculated as functions of the oscillator parameters ωx,ωyand ωz which are given in terms of the non deformed value ω00 , depending on the mass number A, the number of neutrons N, the number of protons Z, and the deformation parameter β. The calculated values of the cranking-model moments of inertia of these nuclei are in good agreement with the corresponding experimental values and show that the considered axially deformed nuclei may have oblate as well as prolate shapes and that the nucleus 24Mg is the only one which is highly deformed. The rigid body model and the equilibrium model moments of inertia of the two nuclei 20Ne and 24Mg are also in good agreement with the corresponding experimental values.
superdeformed bands in the A～190 region are systematically analyzed by using the twoparameter expansion of quantum group Uqp(u2) Model. The calculated results of E2 transition γ ray energies are in agreement with experimental data. According to three different methods for the spin assignment of rotational bands, the spin values of the band head I0 of the yrast SD bands in 194Hg(1) and 194Pb(1) are assigned. Furthermore, the physical meaning of the nuclear softness is discussed, and these nuclear softness values of a signature partner are almost equal.
Using the dynamical transport model RQMD, the HBT size parameters and event anisotropy are studied for Au+Au non central collisions at RHIC energy. We find that the HBT size parameters reflect the source geometry at freeze out for such non central collisions and the HBT size parameters as a function of m t are insensitive to the pressure developed during the early stage of the collisions.
Detection of dark matter using CsI(Tl) scintillating crystal as the detector has gathered more and more interests. In this paper, the quenching factor of nuclear recoils induced by incident neutron beam was measured based on Pulse Shape Discrimination (PSD) method to identify events of nuclear recoils from background. It is shown that the quenching factor increases with the decreased recoil energy in the range of 7 keV to 132 keV. This result shows the great advantage of CsI(Tl) crystal detector in detecting of dark matter.
BESⅡ detector has been upgraded from 1995, the TOF time resolution is about 180ps for Bhabha events, a big improvement compared with 330ps of BESⅠ. With the upgrade of the detector, the software including calibration, reconstruction and Monte Carlo (M.C.) simulation needs corresponding improvement, especially for M.C. simulation. Using 50M J/ψ data taken in the last two years at BESⅡ, we studied the TOF resolution carefully, and made some improvements for TOF MC simulation. After such an improvement, we compared the TOF resolutions between real data and M.C. data and found they agree with each other.
Resonantly coupled RFQ is commonly used as the low energy accelerating structure for an intense beam proton linac. It is essential that the field distribution meets the design requirement in order to minimize the beam losses. Based on the RFQ transmission line model, a study on the field tuning was conducted on the cold model RFQ, focusing on the characteristics of the resonantly coupled RFQ structure. A satisfactory result was achieved in the field stabilization, and it also demonstrated the validity of the RFQ tuning code on the platform of LabVIEW.
A modulator type pulse generator which is based on Blumlein Pulse Forming Net and pulsed transformer, constructed by us is described in this paper. This generator can deliver pulse of 300kV to a load, and it has an output impedance of 100Ω and a pulse width of 500ns. It can operate steadily at pulse repetition rates as high as 100Hz. Three kinds of cathodes are studies on this pulse generator, and the diode can deliver electron beam pulse of nearly 300kV, pulse width 500ns and repetition frequency 50Hz.
We propose a build to low-energy γ-ray beam line (SLEGS-Ⅰ) at the Shanghai Synchrotron Radiation Facility (SSRF). By Compton back scattering (BCS) of infrared or far-infrared laser lights from 3.5 GeV electrons circulating in the storage ring of SSRF, high intense quasi-monochromatic BCS γ-rays with high linear or circular polarization ranging 1-25MeV will be produced. It can be widely applied to fundamental researching fields of nuclear physics, nuclear astrophysics and related applications. In this paper, we briefly present the outline of BCS theory and the properties of BCS γ-ray with numerical compution based on the major parameters of SSRF storage ring.
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