2006 Vol. 30, No. 04
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Recently BESⅡ collaboration observed an enhancement near the pp invariant mass spectrum. Using the covariant tensor formalism, here we provide theoretical formulae for the partial wave analysis (PWA) of the ψ radiative decay channels ψ→γpp, γΛΛ, γ∑∑,γΞΞ. By performing the Monte Carlo simulation, we give the angular distributions for the photon and proton in the process of J/ψ→γ pp, which may serve as a useful reference for the future PWA on these channels.
In the SU(2) singlet down type vectorlike quark model, there exist a tree level coupling zsb of b→sZ* and an additional D quark. In the framework we evaluate the D quark effects on B→Xsγ by running the Wilson coefficients of the effective Hamiltonian with the renormalization scale from mD to weak scale.Using the recent measurements for B→Xsl+l－,we extract rather stringent constraints on the size and CP violating phase of zsb,and find that the zero point of the forward-backward asymmetry may have large deviation from that of the standard model and is very sensitive to zsb, and therefore, it can be useful in probing the new physics.
The three-body decay B0(Bs)→γνν can occur via penguin and box diagrams in the Standard Model (SM). These channels are useful to determine the decay constant fB (fBs) and B (Bs) meson wave function. Using the B meson wave function determined in hadronic B (Bs) decays, we calculate and get the branching ratio of order 10－9 and 10－8 for B0 and Bs decay, respectively. They agree with previous calculations.
We study one of the most important reactions 2H(d,γ)4He with an astrophysical interest. A phenomenological model is adopted where the D-state component of the colliding deuterons and D-components in 4He ground state are considered. Woods-Saxon potential parameters are obtained by reproducing the binding energy of d-d system and d-d elastic scattering phase shifts calculated by the resonating group method. A comparison of theoretical results with the experiment data is made at the energy range Ec.m.<3MeV. In particular, rather good agreement with the experiment data of the astrophysical S-factor can be obtained below 500keV. Due to the lack of experiment data at the energies around 0—20keV required in the investigation of the stellar nucleosynthesis, an theoretical extrapolation of the S-factor down to stellar energies is performed.
Nuclear properties of stannum isotopes have been studied by the self-consistent shell-model-like approach in the framework Relativistic Mean Field theory, i.e., RMF+SLAP, and compared with the results from the non self-consistent RMF+SLAP* in which the influence of the pairing correlations on the mean field has been neglected. It is shown that the RMF+SLAP method can reproduce correctly the change of the quadrupole deformation as a function of pairing strength, the binding energy, one-and two-neutron separation energies and quadrupole deformation of stannum isotopes. The importance in treating the pairing correlations and block effect correctly has been emphasized.
Based on the experimental data of the total, the nonelastic and the elastic cross sections and the elastic scattering angular distributions for n+58Ni reactions, a set of parameters for a neutron optical model potential is obtained in the incident neutron energy region from 0.8—150MeV. Then reaction cross sections, angular distributions, energy spectra, gamma-ray production cross sections and gamma-ray production energy spectra are calculated in terms of the optical model, the distorted wave Born approximation theory, the Hauser-Feshbach theory, the exciton model and the cascade mechanism inside nuclear. The results are analyzed and compared with the existing experimental data and other evaluated data from ENBF/B-6. They are in agreement with each other within error bars.
The clear shell effect of the pairing strength is proved based on the frame of the relativistic mean filed theory. With the same theory, the closed shell problem of the superheavy isotope chain around Z=96—102 is studied. The results show that N=184 for neutron is a closed shell. According to the study, a new method to check the shell closure is given.
Within the Boltzmann-Langevin equation , the neutron cluster production cross sections in the reactions induced by 14Be, 8He,6He,11Li,17B,11Be,19C on 12C at 35MeV/u were studied. The experimental data for 4n production cross section from 14Be+12C at 35MeV/u can be reproduced. It is found that the production cross section of neutron cluster is large in the reaction that the projectile has more halo nucleons. And the projectiles with big mass number are easy to produce the neutron cluster, when they have the same number of halo nucleons. The neutron cluster is probably mainly from the halo nucleons of projectile.
It was based on the comparisons of the variance properties of fragment multiplicities FM's and nuclear stoppings R's for the neutron-halo colliding system with those of FZ's and R's for the proton-halo colliding system with the increases of beam energy in more detail, the closely correlations between the reaction mechanism and the inner structures of halo-nuclei is found. From above comparisons it is found that the variance properties of fragment multiplicities and nuclear stopping with the increases of beam energy are quite different for the neutron-halo and proton-halo colliding systems, such as the effects of loosely bound neutron-halo structure on the fragment multiplicities and nuclear stopping are obviously larger than those for the proton-halo colliding system. This is due to that the structures of halo-neutron nucleus 11Li is more loosely than that of the proton-halo nucleus 23Al in this paper. In this case, the fragment multiplicity and nuclear stopping of halo nuclei may be used as a possible probe for studying the reaction mechanism and the correlation between the reaction mechanism and the inner structure of halo-nuclei.
The rapidity distribution of protons produced in nucleus-nucleus collisions at the Alternating Gradient Synchrotron (AGS) and the Super Proton Synchrotron(SPS) energies are analyzed by the three-fireball model.The calculated results with Monte Carlo method are in agreement with the experimental data of Au-Au collisions at different centralities at 6, 8, and 10.8A GeV, Pb-Pb collisions at 158AGeV/c, and S-S collisions at 200A GeV/c.
The BESⅢ experiment uses about 1200m2 of resistive plate chambers(RPCs), which will all be tested in a cosmic test station before installation. The test facility is made of 3 streamer-tube chambers with a track reconstruction resolution of 2—3mm. Trigger is also provided by the streamer-tube chambers covering an area of 4m2. A total of 8 RPCs can be tested simultaneously.
A definition for the statistical significance of a signal in an experiment is proposed by establishing a correlation between the observed p-value and the normal distribution integral probability, which is suitable for both counting experiment and continuous test statistics. The explicit expressions to calculate the statistical significance for both cases are given.
CSR, a new accelerator project under the construction to upgrade the existing heavy ion cyclotron system in Lanzhou, is a double cooling-storage-ring system. It consists of a main ring and an experimental ring. The heavy ion beams from the cyclotron system will be accumulated and accelerated first in the main ring, then extracted to produce radioactive ion beams or high-Z beams, and finally to be send to the second ring for internal-target experiments.
This paper presents the structural and electromagnetic design of a C-band cavity type beam position monitor, with working frequency of 5.712GHz. We use MAFIA to simulate electromagnetic field, the results show that the waveguide coupling scheme can reject the common mode TM010 effectively. Some major parameters which may affect TM110 frequency are calculated. A homodyne cicuit has been designed, which converts microwave signal to low-frequency output.
Two superconducting magnet complexes are used in BEPCⅡ interaction region. The corresponding quench protection system divides all related faults into two classes and takes different protection actions according to the urgency degree. Since BEPCⅡ has two operating modes and the superconducting magnets use different power supplies in different operating modes, the quench protection system must take the mode switching into consideration.
Superconducting (SC) RF technology is an excellent choice for International Linear Collider (ILC), and the whole cost of ILC is closely related to the gradient of SC cavity. However, the gradient of Nb SC cavity is limited by SRF critical magnetic field at present. So it is very necessary to optimize the cavity shape to decrease the ratio of surface peak magnetic field and accelerating gradient (Hp/Eacc). A serial of new cavity shapes have been proposed including Low Loss shape and Re-Entrant shape etc. Low Loss shape has lower Hp/Eacc than Re-Entrant shape, so theoretically Low Loss shape can reach higher gradient. In this paper, an optimal design is illustrated. Then a Low Loss SC Cavity shape and its calculation results are presented, and finally these results are compared with TESLA 800 cavity and Re-Entrant Cavity.
Based on the radiation characteristics of the bend magnet source, the output characteristics of the BSRF-3B3 beamline was analyzed and discussed. The result is the foundation of adjustment and diagnosis of the beamline. A calculation model is provided to analyze characteristics of beamlines attached to bend magnet sources.
Irradiation of 110keV proton beam with exposure ranging from 1.0×1011to 1.0×1017p/cm2 onto the thermal control coatings of 6 different materials was performed, the changes of thermal properties were investigated and the surface chemical structure was analyzed by X-ray photoelectron spectroscopy XPS. It showed that the thermal properties of all the specimens was no obvious change and the surface chemical structure such as the chemical shift and elemental ratios changed little with the proton exposure less than 1.0×1014p/cm2.Nevertheless, the thermal properties and surface chemical structure changed significantly with the proton exposure over 1.0×1014p/cm2, for all the specimens the elemental ratio of C increased while the element ration of O decreased on the other hand. It is revealed that the proton irradiation with proper energy and fluence could improve the thermal properties of some thermal control coating of low solar absorptance.The changes both of the physics property and the surface chemical structure of the thermal control coatings resulting from the proton irradiation took place in phase.
Geometrical optimizations of two fullerenes, C60 and C70, have been performed by means of density-functional theory techniques. Based on the Gelius model, ultraviolet photoelectron spectra (UPS) of C60 and C70 have been simulated. We have shown how the different local arrangements of carbon atoms of C70 are responsible for the spectra. Our calculated spectra are in good agreement with the experimental counterparts.
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