2007 Vol. 31, No. 1
Display Method: |
Abstract:
Exotics belong to high multiplet of SU(3), so one can understand them by researching their non-exotic partners in the same multiplet. Here the possible 27-plet from flavor SU(3) symmetry are investigated. By fitting the mass spectrum and calculating the two-body partial hadronic decay widths of members, two set of 27-plet baryons with different parities are found. For the mass spectrum, all non-exotic members have their candidates in PDG except for a new Λ(1780). For the decay widths, the computing results show the approximate flavor SU(3) symmetry. The further analyzing and comparing with the results from other theoretical models can support the rationality of the 27-plet assignment.
Exotics belong to high multiplet of SU(3), so one can understand them by researching their non-exotic partners in the same multiplet. Here the possible 27-plet from flavor SU(3) symmetry are investigated. By fitting the mass spectrum and calculating the two-body partial hadronic decay widths of members, two set of 27-plet baryons with different parities are found. For the mass spectrum, all non-exotic members have their candidates in PDG except for a new Λ(1780). For the decay widths, the computing results show the approximate flavor SU(3) symmetry. The further analyzing and comparing with the results from other theoretical models can support the rationality of the 27-plet assignment.
Abstract:
Assuming X(3872) is a qcqc tetraquark and using its mass as input, we perform a schematic study of the masses of possible heavy tetraquarks using the color-magnetic interaction with the flavor symmetry breaking corrections.
Assuming X(3872) is a qcqc tetraquark and using its mass as input, we perform a schematic study of the masses of possible heavy tetraquarks using the color-magnetic interaction with the flavor symmetry breaking corrections.
Abstract:
Canonical quantizaion of the complex scalar field theory with boundaries is studied. Contrary to the previous discussions where the boundary conditions are taken as primary Dirac constraints, we shall study this problem in the classical solution space. Fadeev-Jackiw method is applied to get the commutation relations among the Fourier modes. Ambiguities in the Dirac method are avoided by using our approach.
Canonical quantizaion of the complex scalar field theory with boundaries is studied. Contrary to the previous discussions where the boundary conditions are taken as primary Dirac constraints, we shall study this problem in the classical solution space. Fadeev-Jackiw method is applied to get the commutation relations among the Fourier modes. Ambiguities in the Dirac method are avoided by using our approach.
Abstract:
Using the improved lattice Hamiltonian with massive Wilson quark and the variational method, we study the quark mass mq and the Wilson parameter r dependences of the quark condensate 〈ψψ〉in the two-dimensional SU(NC) lattice gauge theory. The numerical results show that when r is given, for NC=2,3,4,5,6,7, the value of 〈ψψ〉suba/(gNC3/2) decreases as mq increases. For NC>3, when mq is small, 〈ψψ〉suba/(gNC3/2) is almost independent of r; when mq is large, 〈ψψ〉suba/(gNC3/2)increases with increasing r. Particularly, when mq→0, our numerical results agree very well with Zhitnitsky's analytical weak coupling result in the continuum, which implys that our numerical results in the case of mq≠0 are reliable.
Using the improved lattice Hamiltonian with massive Wilson quark and the variational method, we study the quark mass mq and the Wilson parameter r dependences of the quark condensate 〈ψψ〉in the two-dimensional SU(NC) lattice gauge theory. The numerical results show that when r is given, for NC=2,3,4,5,6,7, the value of 〈ψψ〉suba/(gNC3/2) decreases as mq increases. For NC>3, when mq is small, 〈ψψ〉suba/(gNC3/2) is almost independent of r; when mq is large, 〈ψψ〉suba/(gNC3/2)increases with increasing r. Particularly, when mq→0, our numerical results agree very well with Zhitnitsky's analytical weak coupling result in the continuum, which implys that our numerical results in the case of mq≠0 are reliable.
Abstract:
We investigate the properties of polarization vectors for gauge bosons, including their forms with arbitrary polarization direction in laboratory frame, their different sum rules, and the projection operators they constitute. Then by some examples, we illustrate techniques in calculating processes involving gauge bosons. Our discussion is beneficial for the understanding of the essence of gauge bosons.
We investigate the properties of polarization vectors for gauge bosons, including their forms with arbitrary polarization direction in laboratory frame, their different sum rules, and the projection operators they constitute. Then by some examples, we illustrate techniques in calculating processes involving gauge bosons. Our discussion is beneficial for the understanding of the essence of gauge bosons.
Abstract:
A new class of Hubbard-type models with open boundary conditions in one dimension is studied in the framework of coordinate Bethe ansatz method. The energy spectrum, integrable boundary conditions and the corresponding Bethe ansatz equations are derived.
A new class of Hubbard-type models with open boundary conditions in one dimension is studied in the framework of coordinate Bethe ansatz method. The energy spectrum, integrable boundary conditions and the corresponding Bethe ansatz equations are derived.
Abstract:
The YBJ-ARGO experiment is located in Tibet at 4300m a.s.l.. The data of this experiment under scalar mode can be used to study the solar modulation of cosmic ray flux at E>10GeV. The data during January 15—17, 2005 are analyzed, and a cosmic ray flux Forbush decrease after several X class solar flares has been observed. All detailed structures of the flux curves are similar to the results from neutron monitors. The maximum amplitudes of FD are about －6%, －6%, －4% and －3% with multiplicity greater than 1, 2, 3 and 4, respectively, i.e. the maximum amplitude of FD decreases as the energy of cosmic ray increases. These are the results about a FD measured at the same site (Yangbajing) with different cosmic ray energies for the first time.
The YBJ-ARGO experiment is located in Tibet at 4300m a.s.l.. The data of this experiment under scalar mode can be used to study the solar modulation of cosmic ray flux at E>10GeV. The data during January 15—17, 2005 are analyzed, and a cosmic ray flux Forbush decrease after several X class solar flares has been observed. All detailed structures of the flux curves are similar to the results from neutron monitors. The maximum amplitudes of FD are about －6%, －6%, －4% and －3% with multiplicity greater than 1, 2, 3 and 4, respectively, i.e. the maximum amplitude of FD decreases as the energy of cosmic ray increases. These are the results about a FD measured at the same site (Yangbajing) with different cosmic ray energies for the first time.
Abstract:
The reaction rate of non-leptonic quark weak interaction and the bulk viscosity of quark matter in the magnetic field are investigated. The approximation method for calculating the reaction rate in a weak magnetic field is improved, the results of the reaction rate of non-leptonic process and the bulk viscosity of quark matter are given. It is shown that the relationship between the bulk viscosity and the temperature in the weak magnetic field case is the same as that in the zero magnetic field case, but the magnitude of bulk viscosity is affected by the strength of the magnetic field.
The reaction rate of non-leptonic quark weak interaction and the bulk viscosity of quark matter in the magnetic field are investigated. The approximation method for calculating the reaction rate in a weak magnetic field is improved, the results of the reaction rate of non-leptonic process and the bulk viscosity of quark matter are given. It is shown that the relationship between the bulk viscosity and the temperature in the weak magnetic field case is the same as that in the zero magnetic field case, but the magnitude of bulk viscosity is affected by the strength of the magnetic field.
Abstract:
Radiative energy loss rate of heavy quark traversing through thermal dense matter which is formed in heavy ion collisions has been studied under an assumption of valid factorized method, in which light quark radiative spectrum is used to multiply an dead-cone factor depending on quark mass and energy. The numerical calculated results with energies at RHIC and LHC show that the heavy quark radiation spectra, obtained by extending light quark energy spectrum, are approximately consistent with that calculated under pQCD frame by Djordjecvic-Guulassy. The calculation is simplified by using of factorial dead cone factor and equivalent results can be obtained.
Radiative energy loss rate of heavy quark traversing through thermal dense matter which is formed in heavy ion collisions has been studied under an assumption of valid factorized method, in which light quark radiative spectrum is used to multiply an dead-cone factor depending on quark mass and energy. The numerical calculated results with energies at RHIC and LHC show that the heavy quark radiation spectra, obtained by extending light quark energy spectrum, are approximately consistent with that calculated under pQCD frame by Djordjecvic-Guulassy. The calculation is simplified by using of factorial dead cone factor and equivalent results can be obtained.
Abstract:
Assuming Θ+ interacts with nucleon or Θ+ by exchanging isoscalar mesons σ and ω, the equation of state of {p,n,Θ+} and possible metastable state are studied in the framwork of the density dependent relativistic hadron field theory(DDRH). The ratio of the proton isospin to the neutron isospin with different baryon densities and the effect of the Θ+ component on the binding energy per baryon of the system are also discussed. It is shown that when the binding energy per baryon of the system takes the maximal value, Θ+ might be bound in the nuclear matter.
Assuming Θ+ interacts with nucleon or Θ+ by exchanging isoscalar mesons σ and ω, the equation of state of {p,n,Θ+} and possible metastable state are studied in the framwork of the density dependent relativistic hadron field theory(DDRH). The ratio of the proton isospin to the neutron isospin with different baryon densities and the effect of the Θ+ component on the binding energy per baryon of the system are also discussed. It is shown that when the binding energy per baryon of the system takes the maximal value, Θ+ might be bound in the nuclear matter.
Abstract:
The neutron-rich nucleus 8He is selected by RIBLL from the breakup of 50MeV/u 13C on be target at HIRFL. The 2n-removal and 4n-removal cross section of 8He was measured by using the transmission method. The point that 4He is 8He core can be reduced from the experiment data via the Ogawa's theory.
The neutron-rich nucleus 8He is selected by RIBLL from the breakup of 50MeV/u 13C on be target at HIRFL. The 2n-removal and 4n-removal cross section of 8He was measured by using the transmission method. The point that 4He is 8He core can be reduced from the experiment data via the Ogawa's theory.
Abstract:
According to the hadronization program ART1.0 of AMPT Monte Carlo generator, the evolution picture of hadronization process is obtained. The radii of reaction area are then calculated based on the distribution picture of hadrons in different evolution time. Comparing the results with those obtained from the HBT momentum correlation, the freeze-out time is fixed finally. The result obtained is reasonable.
According to the hadronization program ART1.0 of AMPT Monte Carlo generator, the evolution picture of hadronization process is obtained. The radii of reaction area are then calculated based on the distribution picture of hadrons in different evolution time. Comparing the results with those obtained from the HBT momentum correlation, the freeze-out time is fixed finally. The result obtained is reasonable.
Abstract:
The isospin effect and isoscaling behaviors in projectile fragmentation reactions have been systematically investigated by a modified statistical abrasion-ablation (SAA) model. The normalized peak difference and reduced isoscaling parameters are found to decrease with (Zproj－Z)/Zproj or (Nproj－N)/Nproj exponentially and have no dependence on the size of reaction systems. It is pointed out that the reduced isoscaling parameters can be used as an observable to study excitation extent of system and asymmetric nuclear equation of state in heavy ion collisions.
The isospin effect and isoscaling behaviors in projectile fragmentation reactions have been systematically investigated by a modified statistical abrasion-ablation (SAA) model. The normalized peak difference and reduced isoscaling parameters are found to decrease with (Zproj－Z)/Zproj or (Nproj－N)/Nproj exponentially and have no dependence on the size of reaction systems. It is pointed out that the reduced isoscaling parameters can be used as an observable to study excitation extent of system and asymmetric nuclear equation of state in heavy ion collisions.
Abstract:
ARGO is a "full coverage" air shower detector currently under construction in Tibet, China. One of the main goals of this experiment is to search for possible gamma-ray bursts (GRBs) with E>10GeV. In this work, the sensitivity in observing a GRB (with a certain significance) by ARGO is found to be dependent on the flux of the GRB, the slope and the energy cutoff of its spectrum, as well as its time duration and the zenith angle at the observation.
ARGO is a "full coverage" air shower detector currently under construction in Tibet, China. One of the main goals of this experiment is to search for possible gamma-ray bursts (GRBs) with E>10GeV. In this work, the sensitivity in observing a GRB (with a certain significance) by ARGO is found to be dependent on the flux of the GRB, the slope and the energy cutoff of its spectrum, as well as its time duration and the zenith angle at the observation.
Abstract:
In this paper, we describe a series of performance tests for the RPC prototypes of the BESⅢ muon detector. A new type of bakelite plate is made and the resistivity of samples is measured at different temperatures. Eight RPC prototypes are built and their performance as a function of the bakelite resistivity is studied. The rate capability of these chambers in the streamer mode is also studied by using a 137Cs γ source. The results show that RPCs made of the new type of bakelite fulfill the requirements of the BESⅢ muon detector.
In this paper, we describe a series of performance tests for the RPC prototypes of the BESⅢ muon detector. A new type of bakelite plate is made and the resistivity of samples is measured at different temperatures. Eight RPC prototypes are built and their performance as a function of the bakelite resistivity is studied. The rate capability of these chambers in the streamer mode is also studied by using a 137Cs γ source. The results show that RPCs made of the new type of bakelite fulfill the requirements of the BESⅢ muon detector.
Abstract:
We briefly introduce the components of liquid scintillator used in neutrino experiment in this paper. The set-up, principles and methods of light yield and attenuation measurements for liquid scintillator are described, and liquid scintillator samples with different components are measured. We also studied the factors which affect the light yield and attenuation length of liquid scintillator. The measurement of our liquid scintillator sample shows it can meet the requirement of neutrino experiment.
We briefly introduce the components of liquid scintillator used in neutrino experiment in this paper. The set-up, principles and methods of light yield and attenuation measurements for liquid scintillator are described, and liquid scintillator samples with different components are measured. We also studied the factors which affect the light yield and attenuation length of liquid scintillator. The measurement of our liquid scintillator sample shows it can meet the requirement of neutrino experiment.
Abstract:
We present the results of experiments on the passive magnetic shield for HXMT main detectors. The magnetic shielding case made of permalloy reduces the maximum gain variations of detectors to 6% on the ground. Together with the automatic gain control system, the magnetic shield system will limit the gain variations of in-flight detectors to 1%, and limit the background variations to 0.1%.
We present the results of experiments on the passive magnetic shield for HXMT main detectors. The magnetic shielding case made of permalloy reduces the maximum gain variations of detectors to 6% on the ground. Together with the automatic gain control system, the magnetic shield system will limit the gain variations of in-flight detectors to 1%, and limit the background variations to 0.1%.
Abstract:
The Fumili minimization method was used in the calibration for the calorimeter counter on HRS at Hall-A in Jefferson Jlab(JLab) for the data of small angle GDH experiment. Due to a large set of kinematics and changes in hardware settings, different calibrations were needed for the calorimeter detector. The resolution of the calorimeter for the scattering electron was about 0.06GeV when its momentum was at 1.0GeV.
The Fumili minimization method was used in the calibration for the calorimeter counter on HRS at Hall-A in Jefferson Jlab(JLab) for the data of small angle GDH experiment. Due to a large set of kinematics and changes in hardware settings, different calibrations were needed for the calorimeter detector. The resolution of the calorimeter for the scattering electron was about 0.06GeV when its momentum was at 1.0GeV.
Abstract:
This paper studies the high order effect in bunch compressing. There exists the limit of high order effect which is from RF accelerating field and bunch compressor, the bunch length obtained from high order theory is longer than that from linear theory, the initial uniform distribution bunch is easier to compress than the initial Gaussian distribution. Finally, a numerical simulation has been carried out, and the results agree with the theory well.
This paper studies the high order effect in bunch compressing. There exists the limit of high order effect which is from RF accelerating field and bunch compressor, the bunch length obtained from high order theory is longer than that from linear theory, the initial uniform distribution bunch is easier to compress than the initial Gaussian distribution. Finally, a numerical simulation has been carried out, and the results agree with the theory well.
Abstract:
Two rings will be constructed in the current tunnel to increase the luminosity of BEPCⅡ. There will be approximately 460 magnet power supplies in the rings and transport line. Most magnet power supplies require 1×10－4 control precision and stability. Only the dipole power supply requires 5×10－5 control precision and stability. Using a PSC/PSI for the control of a high precision prototype PS, it has been proven that the PSI can meet the requirement of 5×10－5 precision and stability. For easy integration and maintenance, we decided to use the same hardware and software for the control of all PS in the rings and transport line. So, the control of all power supplies will be based on the PSC/PSI modules and the EPICS toolkits. This paper describes the application of the PSC/PSI for the BEPCⅡ power supply control. The status of application software development and power supply control is discussed.
Two rings will be constructed in the current tunnel to increase the luminosity of BEPCⅡ. There will be approximately 460 magnet power supplies in the rings and transport line. Most magnet power supplies require 1×10－4 control precision and stability. Only the dipole power supply requires 5×10－5 control precision and stability. Using a PSC/PSI for the control of a high precision prototype PS, it has been proven that the PSI can meet the requirement of 5×10－5 precision and stability. For easy integration and maintenance, we decided to use the same hardware and software for the control of all PS in the rings and transport line. So, the control of all power supplies will be based on the PSC/PSI modules and the EPICS toolkits. This paper describes the application of the PSC/PSI for the BEPCⅡ power supply control. The status of application software development and power supply control is discussed.
Abstract:
BPM system newly designed at HLS Linac has been installed and applied in beam based experiments. This paper introduces the structure of BPM system, signal processing module, mapping results and measurement results of beam based experiment. The BPM system has a dynamic range of not less than 40dBm, beam position resolution of less than 100μm, horizontal sensitivity of 1.61dB/mm and vertical sensitivity of 1.51dB/mm. The results of experiment between corrector strength and BPM shows that the newly designed BPM system can acquire the beam positions information correctly, and the horizontal and vertical correction coefficients of the correctors are 0.46mm/A and 0.58mm/A respectively, and the horizontal and vertical beam positions at BPM are 0.83mm and －0.57mm respectively with the default value of correctors.
BPM system newly designed at HLS Linac has been installed and applied in beam based experiments. This paper introduces the structure of BPM system, signal processing module, mapping results and measurement results of beam based experiment. The BPM system has a dynamic range of not less than 40dBm, beam position resolution of less than 100μm, horizontal sensitivity of 1.61dB/mm and vertical sensitivity of 1.51dB/mm. The results of experiment between corrector strength and BPM shows that the newly designed BPM system can acquire the beam positions information correctly, and the horizontal and vertical correction coefficients of the correctors are 0.46mm/A and 0.58mm/A respectively, and the horizontal and vertical beam positions at BPM are 0.83mm and －0.57mm respectively with the default value of correctors.
Abstract:
Perovskite oxides LaFe1－xCrxO3 were synthesized by solid state reaction method. X-ray powder diffraction was tested to characterize the crystalline structure of the samples. The result indicates that the samples are single orthorhombic phase. The lattice parameter decreases with the Chromium concentration. The extend X-ray absorption fine structures (EXAFS) of the Fe K-edge as a function of doping level x show that the Fe-La bonds distance decreases dramatically. This suggests that Lanthanum is very important for the stability of the whole LaFe1－xCrxO3 structure.
Perovskite oxides LaFe1－xCrxO3 were synthesized by solid state reaction method. X-ray powder diffraction was tested to characterize the crystalline structure of the samples. The result indicates that the samples are single orthorhombic phase. The lattice parameter decreases with the Chromium concentration. The extend X-ray absorption fine structures (EXAFS) of the Fe K-edge as a function of doping level x show that the Fe-La bonds distance decreases dramatically. This suggests that Lanthanum is very important for the stability of the whole LaFe1－xCrxO3 structure.
Abstract:
Coherent X-ray scatter technology or energy-dispersive X-ray diffraction has been used for many years as a method to measure the atomic planar spacings in a crystalline substance. In this paper, this method has been shown to be of particular use when the requirement is to differentiate between low Z materials where transmission techniques provide very little contrast. We applied this technique to the detection and identification of explosives. Energy-dispersive detectors were used to collect coherent scatter spectra at a small angles (6.5°). It is shown that the information from these `signatures' can be used to determine whether an explosive sample is present or not. The geometrical configuration of the collimation and the position of the subject must be take into careful consideration when optimizing the capabilities of such a system.
Coherent X-ray scatter technology or energy-dispersive X-ray diffraction has been used for many years as a method to measure the atomic planar spacings in a crystalline substance. In this paper, this method has been shown to be of particular use when the requirement is to differentiate between low Z materials where transmission techniques provide very little contrast. We applied this technique to the detection and identification of explosives. Energy-dispersive detectors were used to collect coherent scatter spectra at a small angles (6.5°). It is shown that the information from these `signatures' can be used to determine whether an explosive sample is present or not. The geometrical configuration of the collimation and the position of the subject must be take into careful consideration when optimizing the capabilities of such a system.
Abstract:
A new algorithm of segmenting contour series of images is presented, which can achieve three dimension reconstruction with parametric recognition in Reverse Engineering based on X-ray CT. First, in order to get the nested relationship between contours, a method of a certain angle ray is used. Second, for realizing the contour location in one slice, another approach is presented to generate the contour tree by scanning the relevant vector only once. Last, a judge algorithm is put forward to accomplish the contour match between slices by adopting the qualitative and quantitative properties. The example shows that this algorithm can segment contour series of CT parts rapidly and precisely.
A new algorithm of segmenting contour series of images is presented, which can achieve three dimension reconstruction with parametric recognition in Reverse Engineering based on X-ray CT. First, in order to get the nested relationship between contours, a method of a certain angle ray is used. Second, for realizing the contour location in one slice, another approach is presented to generate the contour tree by scanning the relevant vector only once. Last, a judge algorithm is put forward to accomplish the contour match between slices by adopting the qualitative and quantitative properties. The example shows that this algorithm can segment contour series of CT parts rapidly and precisely.
Abstract:
The energy transfer of proton with energies of 10－300keV in Kapton/Al was simulated with TRIM and SRIM2003. Irradiating test parameter of energy was chosen based on the simulated results. The ground simulation tests of proton irradiations for Kapton/Al films were conducted by using the space synthesis irradiating facility under vacuum at room temperature. The key functional groups in the Kapton/Al films were analyzed quantitatively by means of the surface infrared spectrum technique. The damage cross section of typical molecular bonds was obtained from the variation of the absorbance at the characteristic peaks of key functional groups. The analysis results have shown that the average damage cross section is strongly dependent on the electron energy loss, which is agreement with the simulation results by TRIM. This indicates that the electron energy loss plays an important role in the damage of Kapton/Al by keV proton irradiation. From the tendency of the solar absorptance and the simulation results it can be seen that the proton irradiation effects have the maximum value near the incident energy of 80keV.
The energy transfer of proton with energies of 10－300keV in Kapton/Al was simulated with TRIM and SRIM2003. Irradiating test parameter of energy was chosen based on the simulated results. The ground simulation tests of proton irradiations for Kapton/Al films were conducted by using the space synthesis irradiating facility under vacuum at room temperature. The key functional groups in the Kapton/Al films were analyzed quantitatively by means of the surface infrared spectrum technique. The damage cross section of typical molecular bonds was obtained from the variation of the absorbance at the characteristic peaks of key functional groups. The analysis results have shown that the average damage cross section is strongly dependent on the electron energy loss, which is agreement with the simulation results by TRIM. This indicates that the electron energy loss plays an important role in the damage of Kapton/Al by keV proton irradiation. From the tendency of the solar absorptance and the simulation results it can be seen that the proton irradiation effects have the maximum value near the incident energy of 80keV.
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