2002 Vol. 26, No. 07
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The construction of BEPCⅡ/BESⅢ is under plan. Both the accelerator and detector will have much better performance than BEPCⅠ/BESⅡ. Under certain assumptions on 1P1 and η′c decay modes and branching ratios and on the BESⅢ detector performance,and assuming 3×109 ψ(2S) events data sample,the simulation shows that clear signals of 1P1 and η′c can be identified with rather low background.
A cutting rule for the correlation functions of higher twist amplitudes,which is proposed on the naive parton level by Jaffe,is justified for its valid when considering QCD corrections. Using the collinear time ordered perturbation theory,we show that this cutting rule is held at any orders of ans(μ2) provided all initial parton operators are separable on the light-cone direction y－.
In this paper we first emphasize the importance of the Pomeron (IP) for its asymptotically saturation of the unitarity condition alone. After proper modified the field theory model for IP developed by Landshoff and Nochtmann,we argue that the exchange of IP in high energy h-h′ scattering embodies the hypothesis of the maximum non-perturbative strong interaction reaction (MNSIR) in which a constituent quark converts into a current quark and emits a color octet nonperturbative glue. We think the IP is composed from the conjugated pair of such glue. In the circle of non-perturbative fundamental entities in QCD,we argue that there should exist a new member_the constituent gluon,it should be emerged in high energy h-h′ strong-soft processes,and the gluballs are produced via two constituent gluons fusion. Finally,we conjecture there may be an averaged dual relation between the glueballs and the Pomeron,but this correspondence may become as multi-to-one homologue.
We analyze the decay Ds→φπ with QCD factorization in the heavy quark limit. The nonfactorizable contributions,including hard spectator contribution,are discussed and numerical results are presented. Our predictions on the branching ratio of the decay are in agreement with the experiment. We also use a pure phenomenological method to estimate the branching ratio for Ds→φπ with the existing D0→K*π data.
We study the production and decay of the neutral top-pion π0t in topcolor-assisted technicolor (TC2) theory. Our results show that, except for the dominant decay modes b, c and gg, the πt0 can also decay into γγ and Zγ modes. It can be significantly produced at high energy linear e+e－ collider (LC) experiments via the processes e+e－→π0t γ and e+e－→Zπt0. We further calculate the production cross sections of the processes e+e－→γπt0→γc and e+e－→Zπt0→Zc. We find that the signatures of the neutral top-pion πt0 can be detected via these processes.
The cross sections of 185Re(n,2n) 184gRe,185Re(n,2n)184mRe and 191Ir(n,2n) 190Ir reactions induced by 14.7MeV neutrons were measured by the activation method. The experimental results for the reactions are (1817±85)mb,(390±18)mb and (2038±82)mb, respectively. And the excitation curves of these reactions were calculated by using the code HFTT in neutron energy range from 7 MeV to 18 MeV.
The measurement of total reaction cross section is of great importance in studying the structure and reaction mechanisms of exotic nuclei produced by radioactive nuclear beam (RNB). The measurements of the total reaction cross section of fragments produced by 20Ne (80MeV/u)+9Be(3mm) on Si target at intermediate energies were performed on RIBLL by using the transmission method which is the most convenient and credible method in use. The setting-up of the telescope detectors is introduced. And the experimental procedure and experimental results are also described. From the results, we can see the trends of the total cross sections with neutron number in each nuclear isotope chain. The results for some exotic nuclei predicted by theories, such as 12N,17F and 17Ne, are compared with those of their neighbors. And our results show that 12N has an exotic structure, but 17F and 17Ne have not.
The role of momentum dependence equation of state on the nuclear stoppings coming from the isospin dependence of the mean field (one-body dissipation) is studied by using the isospin dependence quantum molecular dynamics (IQMD). A detail study indicates that the difference between the nuclear stoppings coming from the isospin dependence of the mean field (symmetry potential) and the isospin independence of the mean field in the presence of momentum dependence interaction is larger than that without momentum dependence interaction. But the important point is that the enhancement of the difference between nuclear stoppings from the isospin dependence of two-body dissipation is larger than that from the isospin dependence of one-body dissipation in the presence of momentum dependence interaction. Namely in comparison with each other, the momentum dependence equation of state enhances the sensitivity of nuclear stopping on the isospin dependence of in-medium nucleon-nucleon cross section and reduces the sensitivity of the nuclear stopping on the symmetry potential, leading to that the nuclear stopping depends strongly on the isospin dependence of nucleon-nucleon cross section and weakly on the symmetry potential. In this case, one can make use of the nuclear stopping as a probe for extracting the information of in-medium N-N cross section in HIC if MDI is taken into account.
We have extracted the nuclear asymptotic normalization coefficients for the virtual transitions 12B 11B+n and 13C 12C+n via two transfer reactions 11B(d,p) 12B and 12C(d, p) 13C. With these coefficients, root-mean-square radii for the valence neutron in 12B and 13C have been calculated. Our results show that the second (Jπ=2－), third (Jπ=1－) excited states in 12B, and the first (Jπ=1/2+) excited state in 13C are neutron halo states, whereas the third (Jπ=5/2+) excited state in 13C is a neutron skin state. The retard effects of the Coulomb potential and the orbital angular momentum on halo formation have been quantitatively examined. A unified scaling law for the mean-square radius versus the effective nucleon separation energy is established for the systems with a neutron or proton in a weekly bound state.
In this serial work, the Brueckner-Hatree-Fock approach has been extended by intro- ducing isospin degree of freedom and by including ground-state correlations in neutron and proton mass operators. The obtained isospin dependent extended Brueckner-Hatree-Fock approach has been applied to investigate the single-particle properties and their isospin depndence of isospin-asymmetric nuclear matter. The effect of a microscopic three-body force on the properties of asymmetric nuclear matter and its connection to the relativistic corrections from relativistic mean field theory as well Dirac Brueckner-Hartree-Fock approach have also been studied. In this paper, the isospin dependent extended Brueckner-Hartree-Fock approcach has been derived explicitly.
The quark effect in the two baryon systems is studied by making an analysis of the quark exchange terms. The results point out that the quark effect becomes visible only when the two baryon clusters are close to each other. So its influence is much more important in the S waves than in P waves, and the expectation value of the permutation operator in the spin-flavor-color space plays significant role. For some spin-flavor states, the Pauli Blocking Effect is very serious, there should be a big repulsive core radius between these two baryons. But for some other spin-flavor states, the quark exchange effect is favorable for mixing the two baryon clusters together to form dibaryon. Therefore the data of the phase shifts of the baryon-baryon scattering and the binding energies of the two baryon systems are cardinal in examining the quark effect.
We first review the non-Abelian transport theory and its mean field dynamics. The theory is then applied for studying the color electric dynamics of cold and dense quark matter at large chemical potential, and color conductivity with non-perturbation effect is obtained. Finally, we compare the results at large chemical potential with that at high temperature, and discuss possible applications in the field of astrophysics.
It is important to measure the quenching factor of recoiled nuclei of detector for direct detection of WIMP. Energy calibration of CsI(Tl) crystal detector for measuring quenching factor of recoiled nuclei induced by incident neutron beam has been done with low-energy X-ray sources such as 109Cd and 133Ba and the linearity of energy response of experimental system is obtained. The equivalent energy deposited in CsI(Tl) crystal of a single photoelectron of PMT has been measured. The time of integration of current signals is optimized for different X-ray source energys.
In a high current RFQ accelerator, it is required to tightly control the beam losses and beam emittance growth. For this reason, it is demanded to accurately measure and to correctly analyze field distribution and mode components, and eventually, to tune the RF field to reach its design values. LebView is a widely used software platform for the automatic measurement and data processing. In this paper, we present our code development on this platform for the RFQ measurement and analysis, including some applications of the codes.
The mouse melanoma cells (B16), human cervical squamous carcinoma cells (HeLa), Chinese hamster pulmonary cells V79, and human hepatoma cells (SMMC-7721) were collected for studing. The cells of 5×105/ml were seeded in 35mm diameter petri dish and allowed to grow one day, and then the medium in petri dishes was removed away, the cells were washed once with phosphate-bufferd saline (PBS), petri dishes was covered with 4μm thickness Mylar film. The cells were irradiated by 12C ion beam with LETs of 125.5, 200, 700keV/μm in water generated from HIRFL (Heavy Ion Research Facility in Lanzhou). For 60Co γ-ray experiment, the cells of 5×104/ml were grown in 20ml culture flasks including 1.5ml cell suspension and directly used for irradiation. Following irradiation, the cells were trypsinized, counted, plated at appropriate densities in growth medium and then seeded in 60mm diameter culture dishes. Each dish was filled 4ml standard medium, and incubated for 8-12 days at 37℃ incubator containing 5% CO 2. The cultures were then rinsed with PBS buffer at pH6.8, fixed with Carnoy′s fluid, stained for 8min with Giemsa (1∶20,pH6.8), and colonies containing more than 50 cells were scored. Their relative biological effectivenesses (RBE) were investigated. The results show that RBE depends on cellular types and increases with increasing of cellular survival level when LET is at 125.5keV/μm, and decreases with increasing LET when LET≥125.5keV/μm.
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