2008 Vol. 32, No. 7
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It is shown that SU(2) QCD admits an dual Abelian-Higgs phase, with a Higgs vacuum of a type-II superconductor. This is done by using a connection decomposition for the gluon field and the random-direction approximation. Using a bag picture with soft wall, we presented a calculational procedure for the glueball energy based on the recent proof for wall-vortices [Nucl. Phys. B 741(2006)1].
We study the possible tetraquark interpretation of light scalar meson states a0(980), f0(980), κ,σ within the framework of the non-relativistic potential model. The wave functions of tetraquark states are obtained in a space spanned by
multiple Gaussian functions. We find that the mass spectra of the light scalar mesons can be well accommodated in the tetraquark picture if we introduce a three-body quark interaction in the quark model. Using the obtained multiple Gaussian wave functions, the decay constants of tetraquarks are also calculated within the ``fall apart'' mechanism.
We study the properties of QCD vacuum state in this paper. The
values of various local quark vacuum condensates, quark-gluon mixed
vacuum condensates, and the structure of non-local quark vacuum
condensate are predicted by the solution of Dyson-Schwinger
Equations in ``rainbow" approximation with three sets of different
parameters for effective gluon propagator. The light quark
virtuality is also obtained in a consistent way. Our all theoretical
results here are in good agreement with the empirical values used
widely in literature and many other theoretical calculations.
In this paper, we discuss a possibility of studying properties of dark energy in long baseline neutrino oscillation experiments. We consider two types of models of neutrino dark energy. For one type of models the scalar field is taken to be quintessence-like and for the other phantom-like. In these models the scalar fields couple to the neutrinos to give rise to spatially varying neutrino masses. We will show that the two types of models predict different behaviors of the spatial variation of the neutrino masses inside the Earth and consequently result in different signals in long baseline neutrino oscillation experiments.
We study the hadron-quark phase transition in the interior of neutron stars, and examine the influence of the nuclear equation of state on the phase transition and neutron star properties. The relativistic mean field theory with several parameter sets is used to construct the nuclear equation of state, while the
Nambu-Jona-Lasinio model is used for the description of the deconfined quark phase. Our results show that a harder nuclear equation of state leads to an earlier onset of a mixed phase of hadronic and quark matter. We find that a massive neutron star possesses a mixed phase core, but it is not dense enough to possess a pure quark core.
The efficiency for the detection and identification of photons with the ALICE PHOton Spectrometer PHOS has been studied with the Monte-Carlo generated data. In particular, the influence on the efficiency of the PHOS-module edge-effect and of the material in front of PHOS have been examined.
The reaction cross section of 17B on 12C target at (43.7±2.4)MeV/u has been measured at the Radioactive Ion Beam Line in Lanzhou (RIBLL). The root-mean-square matter radius (Rrms) was deduced to be (2.92±0.10)fm, while the Rrms of the core and the valence neutron distribution are 2.28fm and 5.98fm respectively. Assuming a ``core plus 2n'' structure in 17B, the mixed configuration of (2s1/2) and (1d5/2) of the valence neutrons is studied and the
s-wave spectroscopic factor is found to be (80±21)%.
A study of the dynamical fluctuation properties at various c.m. energies in e+e－ collisions is performed using the Monte Carlo method. The results suggest that, after the normalized factorial moments of 3-dimensional phase space are analyzed using an isotropical phase space partition, the NFM describing non-linear dynamical properties show a power-law scaling, i.e., the dynamical fluctuations in higher dimensional phase space are isotropic. For c.m. energies √s≤80 GeV, the scaling exponents φq increase rapidly with the c.m. energy and for c.m. energies √s>80GeV, the φq gradually saturate.
Based on the neutron induced fission fragment mass distribution data up to neutron energy 20MeV measured with the double kinetic energy method (KEM) and the radio active method (RAM), the systematics of fission fragment mass distribution was investigated by using 5 Gaussian model and the systematics parameters were obtained by fitting the experimental data. With the systematics, the yields of any mass A and at any energy in the region from 0 to 20MeV of neutron energy can be calculated. The calculated results could well reproduce the experimental data measured with KEM, but show some systematical deviation from the data measured by RAM, which reflects some systematical deviations between the two kinds of measured data. The error of systematics yield was calculated in an exact error transformation way, including from the error of the experimental yield data to the error of the discrete parameters, then to the systematics parameters, and at last to the yield calculated with systematics.
Using the isospin- and momentum-dependent hadronic transport model IBUU04, we have investigated the influence of the entrance-channel isospin asymmetry on the sensitivity of the pre-equilibrium neutron/proton ratio to symmetry energy in central heavy-ion collisions induced by high-energy radioactive beams. Our analysis and discussion are based on the dynamical simulations of the three
isotopic reaction systems 132Sn+124Sn, 124Sn+112Sn and 112Sn+112Sn which are of the same total proton number but different isospin asymmetry. We find that the kinetic-energy distributions of the pre-equilibrium neutron/proton ratio are quite sensitive to the density-dependence of symmetry energy at incident
beam energy E/A=400MeV, and the sensitivity increases as the isospin asymmetry of the reaction system increases.
We describe the algorithm to reconstruct the charged tracks for BESⅢ main drift chamber at BEPCⅡ, including the track finding and fitting. With a new method of the Track Segment Finder (TSF), the results of present study indicate that the algorithm can reconstruct the charged tracks over a wide range of momentum with high efficiency, while improving the robustness against the background noise in the drift chamber. The overall performances, including spatial resolution, momentum resolution and secondary vertices reconstruction efficiency, etc. satisfy the requirements of BESⅢ experiment.
GEANT3 and GEANT4 are the detector simulation software programs that are widely used in most nuclear and particle physics experiments. ROOT is a program for framework, data analysis, online and offline software. Detector description is an important function in all these programs. Due to different detector construction methods and respective detector data representative, it is difficult to exchange the detector data among them. A new method based on GDML is developed to automatically convert the detector data among ROOT, GEANT4 and GEANT3. Any existing detector geometry in one program can be mapped to the geometry in the other two programs. In the software development of an experiment, different applications can share and reuse the same detector description. The application of this method in the PHENIX experiment upgrade and PHENIX Forward Vertex Silicon detector design is introduced.
In a storage ring, asymmetry of the β function with momentum deviation is the main reason for asymmetry of the dynamic aperture. This paper applies simulation method based on AT code in Matlab to investigate sensitivity of the β function beating and the tune shift to quadrupole field error with the presence of bending field error in the Shanghai Synchrotron Radiation Facility (SSRF) storage ring. Sextupole effect on the variation trend is analyzed. Dynamics of the lattice for working points close to and away from the second order structural resonance stop-band are compared. These results show that the β function beating with momentum deviation doesn't lie in the influence of the second order structural resonance stop-bands completely, but it is relevant to lattice structure.
The beam dynamic code PARMELA was used to simulate the transportation process of accelerating electrons in S-band SW linacs with different energies of 2.5, 6 and 20MeV. The results indicated that in the ideal condition, the percentage of electron beam loss was 50% in accelerator tubes. Also we calculated the spectrum, the location and angular distribution of the lost electrons. Calculation performed by Monte Carlo code MCNP demonstrated that the radiation distribution of lost electrons was nearly uniform along the tube axis, the angular distributions of the radiation dose rates of the three tubes were similar, and the highest leaking dose was at the angle of 160° with respect to the axis. The lower the energy of the accelerator, the higher the radiation relative leakage. For the 2.5MeV accelerator, the maximum dose rate reached 5% of the main dose and the one on the head of the electron gun was 1%, both of which did not meet the eligible protection requirement for accelerators. We adopted different shielding esigns for different accelerators. The simulated result showed that the shielded radiation leaking dose rates fulfilled the requirement.
An updated main coupler has been designed for the superconducting accelerator of Free Electron Laser (FEL) project under construction in Peking University. A capacitive structure is chosen for the main coupler. Numerical investigation using CST Microwave Studio demonstrates the cold window part. The other nonstandard structures such as holding rods and antenna are also optimized. The coupler uses a 95% purity Al2O3 ceramic cold window. The VSWR (Vottage Standing Wave Ratio) is 1.02 at 1.3GHz and the frequency bandwidth is 45MHz with VSWR<1.1. The electric field intensity is 8.5×10－2kV/mm around the window with 20kW Continuous Wave (CW) transmitted power. The Qext is designed variable from 5×106 to 1×107.
This paper presents the analytical and simulation responses of the closed orbit distortion in the SSRF storage ring to random and plane wave like magnet vibrations respectively. It is shown that the use of girder is very beneficial in the view of suppressing this response function. Effect of the independently supported gradient bending magnets to the closed orbit response is given. An analytic formula is written to give a rough estimate of the closed orbit distortion due to ground motion, taking into account the closed orbit response function and girder transfer function. As an example, the result of SSRF case is given.
In high gain harmonic generation (HGHG) free electron laser (FEL), with the right choice of parameters of the modulator undulator, the dispersive section and the seed laser, one may make the spatial bunching of the electron beam density distribution correspond to one of the harmonic frequencies of the radiator radiation, instead of the fundamental frequency of the radiator radiation in conventional HGHG, thus the radiator undulator is in harmonic operation (HO) mode. In this paper, we investigate HO of HGHG FEL. Theoretical analyses with universal method are derived and numerical simulations in ultraviolet and deep ultraviolet spectral regions are given. It shows that the power of the 3rd harmonic radiation in the HO of HGHG may be as high as 18.5% of the fundamental power level. Thus HO of HGHG FEL may obtain short wavelength by using lower beam energy.
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