2006 Vol. 30, No. 6
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Abstract:
Based on the constrained relativistic mean field (RMF) theory, the superdeformed states of 196Pb are systematically investigated with four different interactions, TMA, PK1, NL3 and NL-SH. The potential surface, the quadruple deformation of ground and superdeformed states, and the excitation energies of superdeformed states are calculated. The results show that the shape of 196Pb is oblate for the ground state with deformation β2≈－0.15, and prolate for the superdeformed states with deformation β2≈0.60. The calculated excitation energy and the depth of the potential well of the superdeformed state are approximately equal to 4.5MeV and 1.6MeV, respectively. These results are in good agreement with the current experimental data. It indicates that RMF theory can well describe the energy of the band head of superdeformed rotational band in 196Pb.
Based on the constrained relativistic mean field (RMF) theory, the superdeformed states of 196Pb are systematically investigated with four different interactions, TMA, PK1, NL3 and NL-SH. The potential surface, the quadruple deformation of ground and superdeformed states, and the excitation energies of superdeformed states are calculated. The results show that the shape of 196Pb is oblate for the ground state with deformation β2≈－0.15, and prolate for the superdeformed states with deformation β2≈0.60. The calculated excitation energy and the depth of the potential well of the superdeformed state are approximately equal to 4.5MeV and 1.6MeV, respectively. These results are in good agreement with the current experimental data. It indicates that RMF theory can well describe the energy of the band head of superdeformed rotational band in 196Pb.
Abstract:
Partonic effects on two-particle transverse momentum correlations are studied for Au+Au collisions at \sqrt{s_{_{\rm NN}}}=130GeV in the Monte Carlo model, AMPT. This study demonstrates that in these collisions partonic interactions contribute significantly to the correlations. Additionally, model calculations are compared with data of the two-particle transverse momentum correlations measured by the STAR Collaboration at RHIC, and it is found that AMPT with string melting can well reproduce the measured centrality dependence of the two-particle transverse momentum correlations in Au+Au collisions at \sqrt{s_{_{\rm NN}}}=130GeV.
Partonic effects on two-particle transverse momentum correlations are studied for Au+Au collisions at \sqrt{s_{_{\rm NN}}}=130GeV in the Monte Carlo model, AMPT. This study demonstrates that in these collisions partonic interactions contribute significantly to the correlations. Additionally, model calculations are compared with data of the two-particle transverse momentum correlations measured by the STAR Collaboration at RHIC, and it is found that AMPT with string melting can well reproduce the measured centrality dependence of the two-particle transverse momentum correlations in Au+Au collisions at \sqrt{s_{_{\rm NN}}}=130GeV.
Abstract:
Recent results from BES and CLEOc experiments on hadron spectroscopy and charmonium decays using J/ψ, ψ′ and ψ′′ data samples collected in e+e－ annihilation are reviewed,including the study of the scalar particles in J/ψ radiative and hadronic decays, as well as in ψ′ and χc0 hadronic decays, and the study of the “ρπ puzzle”in J/ψ,ψ′, and ψ′′ decays. The new results on the light scalars and the new information on the hadronic decays of the ortho-charmonium states shed light on the understanding of QCD.
Recent results from BES and CLEOc experiments on hadron spectroscopy and charmonium decays using J/ψ, ψ′ and ψ′′ data samples collected in e+e－ annihilation are reviewed,including the study of the scalar particles in J/ψ radiative and hadronic decays, as well as in ψ′ and χc0 hadronic decays, and the study of the “ρπ puzzle”in J/ψ,ψ′, and ψ′′ decays. The new results on the light scalars and the new information on the hadronic decays of the ortho-charmonium states shed light on the understanding of QCD.
Abstract:
The lg Ne-Nμ relationship has been studied from 4.4×104 events (total observation time is 2.9×106s)collected from Mt. Liang Wang Array (24.5°N, 102.9°E, 2720m above sea level). In order to study the mass composition at the knee, Monte-Carlo simulations for the EAS development and detection under same event selection criteria as used in the experimental data have been performed. The result shows that the mass composition of primary cosmic rays has no obvious change and the dominant component is light nuclei around the knee.
The lg Ne-Nμ relationship has been studied from 4.4×104 events (total observation time is 2.9×106s)collected from Mt. Liang Wang Array (24.5°N, 102.9°E, 2720m above sea level). In order to study the mass composition at the knee, Monte-Carlo simulations for the EAS development and detection under same event selection criteria as used in the experimental data have been performed. The result shows that the mass composition of primary cosmic rays has no obvious change and the dominant component is light nuclei around the knee.
Abstract:
Using the method of QCD factorization, we calculate the branching ratio and the CP violation for pure annihilation decay BS→π＋π－ in the Standard Model. Meanwhile, we employ an effective gluon mass resulted in the study of the infrared behaviour of gluon propagators to avoid the soft endpoint divergence. We find that the CP-averaged branching ratio is about 1.24×10－7, and the penguin diagram contributions is dominant in this process. The direct CP violation parameter is about －0.05, while the mixing-induced CP asymmetry is a quite large number of 0.18. Once these quantities can be measured in the future LHC-b experiments, studying such a process will enrich our knowledge on the dynamics of the charmless hadronic decay of B-meson and the property of gluon.
Using the method of QCD factorization, we calculate the branching ratio and the CP violation for pure annihilation decay BS→π＋π－ in the Standard Model. Meanwhile, we employ an effective gluon mass resulted in the study of the infrared behaviour of gluon propagators to avoid the soft endpoint divergence. We find that the CP-averaged branching ratio is about 1.24×10－7, and the penguin diagram contributions is dominant in this process. The direct CP violation parameter is about －0.05, while the mixing-induced CP asymmetry is a quite large number of 0.18. Once these quantities can be measured in the future LHC-b experiments, studying such a process will enrich our knowledge on the dynamics of the charmless hadronic decay of B-meson and the property of gluon.
Abstract:
If all the supersymmetry particles (sparticles) except a light Higgs boson are too heavy to be directly produced at the Large Hadron Collider (LHC), a possible way to reveal evidence for supersymmetry is through their virtual effects in other processes. We examine such supersymmetric QCD effects in bottom pair production associated with a light Higgs boson at the LHC. We find that if the relevant sparticles (gluinos and squarks) are too heavy to be directly produced well above the TeV scale, they can still have sizable virtual effects in this process. For large tanβ, such residual effects can alter the production rate by over 40 percent,which should be observable in future measurements of this process at the LHC.
If all the supersymmetry particles (sparticles) except a light Higgs boson are too heavy to be directly produced at the Large Hadron Collider (LHC), a possible way to reveal evidence for supersymmetry is through their virtual effects in other processes. We examine such supersymmetric QCD effects in bottom pair production associated with a light Higgs boson at the LHC. We find that if the relevant sparticles (gluinos and squarks) are too heavy to be directly produced well above the TeV scale, they can still have sizable virtual effects in this process. For large tanβ, such residual effects can alter the production rate by over 40 percent,which should be observable in future measurements of this process at the LHC.
Abstract:
Classical and quantum oscillators of sextic anharmonicity are analytically solved up to the n-th power of ε(weak-coupling constant) by using the multiple-scale perturbation theory. Differing from Taylor series solution, the frequency shift appears in all orders of oscillations no matter it is in the classical or quantum case. So the multiple-scale perturbation theory is an approximate method to deal with the weak-coupled anharmonic oscillation and is better than the Taylor series approach.
Classical and quantum oscillators of sextic anharmonicity are analytically solved up to the n-th power of ε(weak-coupling constant) by using the multiple-scale perturbation theory. Differing from Taylor series solution, the frequency shift appears in all orders of oscillations no matter it is in the classical or quantum case. So the multiple-scale perturbation theory is an approximate method to deal with the weak-coupled anharmonic oscillation and is better than the Taylor series approach.
Abstract:
From the κ symmetric action of IIB string in AdS3×S3 background given by Rahmfeld and Rajaraman, we derive the equations of motion. Then using the twisted dual transformation which was introduced by Hou et al. We construct the flat currents, and hence conserved non-local charge with one free parameter, for the Green-Schwarz superstring in AdS3×S3. Thus we show the AdS3×S3 string is integrable.
From the κ symmetric action of IIB string in AdS3×S3 background given by Rahmfeld and Rajaraman, we derive the equations of motion. Then using the twisted dual transformation which was introduced by Hou et al. We construct the flat currents, and hence conserved non-local charge with one free parameter, for the Green-Schwarz superstring in AdS3×S3. Thus we show the AdS3×S3 string is integrable.
Abstract:
We propose a dark energy model with single dynamical scalar field and fixed background vector field, in which the parameter w can cross －1 during the evolution of the universe. It is found that in certain cases w can cross －1 and transition from decelerating to accelerating occur at z≈0.2 and z≈1.7 respectively, which is consistent with the observations.
We propose a dark energy model with single dynamical scalar field and fixed background vector field, in which the parameter w can cross －1 during the evolution of the universe. It is found that in certain cases w can cross －1 and transition from decelerating to accelerating occur at z≈0.2 and z≈1.7 respectively, which is consistent with the observations.
Abstract:
140Tb and 141Dy were produced via fusion evaporation in the reaction 40Ca+106Cd. Their β-delayed proton decays were studied by means of “p-γ” coincidence in combination with a He-jet tape transport system, including half-lives, proton energy spectra, γ-transitions following the proton emissions, and the branching ratios to the low-lying states in the grand-daughter nuclei. The ground-state spins and parities of 140Tb and 141Dy were extracted as 7± and 9/2±, respectively, by fitting the experimental data with a statistical model calculation. The configuration-constrained nuclear potential energy surfaces (NPES) of 140Tb and 141Dy were calculated by using the Woods-Saxon Strutinsky method, which indicate the ground-state spins and parities of 140Tb and 141Dy to be 7+and 9/2－, respectively. In addition, the configuration-constrained NPES of 143Dy was also calculated by using the same method. From the NPES a 1/2+ ground state and a 11/2－ isomer with the excitation energy of 198keV were found. The calculated results are consistent with our experimental data on the decay of 143Dy reported in Eur. Phys. J., 2003, A16: 347—351.
140Tb and 141Dy were produced via fusion evaporation in the reaction 40Ca+106Cd. Their β-delayed proton decays were studied by means of “p-γ” coincidence in combination with a He-jet tape transport system, including half-lives, proton energy spectra, γ-transitions following the proton emissions, and the branching ratios to the low-lying states in the grand-daughter nuclei. The ground-state spins and parities of 140Tb and 141Dy were extracted as 7± and 9/2±, respectively, by fitting the experimental data with a statistical model calculation. The configuration-constrained nuclear potential energy surfaces (NPES) of 140Tb and 141Dy were calculated by using the Woods-Saxon Strutinsky method, which indicate the ground-state spins and parities of 140Tb and 141Dy to be 7+and 9/2－, respectively. In addition, the configuration-constrained NPES of 143Dy was also calculated by using the same method. From the NPES a 1/2+ ground state and a 11/2－ isomer with the excitation energy of 198keV were found. The calculated results are consistent with our experimental data on the decay of 143Dy reported in Eur. Phys. J., 2003, A16: 347—351.
Abstract:
Based on the opinion that the γ-matrices in Dirac equation have structure and are decomposable, we decompose the γ-matrices into the direct product of the operators in the spin space and the particle-antiparticle space. By using this method, we attain a complete set of commutative operators, a set of quantum numbers and the correspondingly eigen solutions of the Hamiltonian for a charged Dirac particle moving in a uniform constant magnetic field. In addition, the dynamic supersymmetry of the Hamiltonian is unveiled. Spin symmetry breaking and particle-antiparticle symmetry breaking are discussed, and the supersymmetric group operator of the degenerate spin subspace resulting from the spin residual supersymmetry is found.
Based on the opinion that the γ-matrices in Dirac equation have structure and are decomposable, we decompose the γ-matrices into the direct product of the operators in the spin space and the particle-antiparticle space. By using this method, we attain a complete set of commutative operators, a set of quantum numbers and the correspondingly eigen solutions of the Hamiltonian for a charged Dirac particle moving in a uniform constant magnetic field. In addition, the dynamic supersymmetry of the Hamiltonian is unveiled. Spin symmetry breaking and particle-antiparticle symmetry breaking are discussed, and the supersymmetric group operator of the degenerate spin subspace resulting from the spin residual supersymmetry is found.
Abstract:
A computer code OMHFISO, based on optical model and Hauser-Feshbach theory with width fluctuation correction (WHF), is made for calculating neutron reactions of isomer target below 5MeV, in which both the incoming and outgoing particles can be n, p, d, t, 3He and 4He. Up to now, there are only few people to calculate the complete set of neutron nuclear data of isomer target. In this work, neutron nuclear data of six isomer targets of unstable isotopes 90Rb and 91,93,96,97,98Y are calculated, and reasonable results in physics are obtained.
A computer code OMHFISO, based on optical model and Hauser-Feshbach theory with width fluctuation correction (WHF), is made for calculating neutron reactions of isomer target below 5MeV, in which both the incoming and outgoing particles can be n, p, d, t, 3He and 4He. Up to now, there are only few people to calculate the complete set of neutron nuclear data of isomer target. In this work, neutron nuclear data of six isomer targets of unstable isotopes 90Rb and 91,93,96,97,98Y are calculated, and reasonable results in physics are obtained.
Abstract:
In this paper we derive the Θ production cross section in high energy proton-proton collisions in the relativistic framework through using effective hadronic couplings. Both the nucleon and N*(1710) propagations are taken into account in the intermediate states. The one π and one ρ exchange mechanisms are considered and the commonly accepted coupling constants and form factors are used in the calculation. We find that ρ exchange is dominant in these processes and the N*(1710) propagation in the intermediate state is important,which increases the Θ production cross section by a factor of a few tens at center of mass energy 4GeV.
In this paper we derive the Θ production cross section in high energy proton-proton collisions in the relativistic framework through using effective hadronic couplings. Both the nucleon and N*(1710) propagations are taken into account in the intermediate states. The one π and one ρ exchange mechanisms are considered and the commonly accepted coupling constants and form factors are used in the calculation. We find that ρ exchange is dominant in these processes and the N*(1710) propagation in the intermediate state is important,which increases the Θ production cross section by a factor of a few tens at center of mass energy 4GeV.
Abstract:
A dark matter search experiment is being carried out with ultra-low energy HPGe detector at Y2L underground laboratory in Korea. Before the system was set up, the active shielding, CsI(Tl) anti-Compton detector, was studied for its performance. By using some radioactive source and recorded data with an FADC, the pulse shape was studied to get a better energy resolution and further PSD method application. The relative light output of crystal at different particle incident positions were compared for setting the threshold for CsI(Tl) detector. The internal background of the crystal was measured with an HPGe detector and the content of 137Cs and 134Cs isotopes were obtained. An about 18-day test run has been finished and the veto efficiency of CsI crystal anti-Compton detector is about 31% and the event rate of background spectrum of HPGe detector is about 133cpd. Further methods have to be explored to suppress the background level.
A dark matter search experiment is being carried out with ultra-low energy HPGe detector at Y2L underground laboratory in Korea. Before the system was set up, the active shielding, CsI(Tl) anti-Compton detector, was studied for its performance. By using some radioactive source and recorded data with an FADC, the pulse shape was studied to get a better energy resolution and further PSD method application. The relative light output of crystal at different particle incident positions were compared for setting the threshold for CsI(Tl) detector. The internal background of the crystal was measured with an HPGe detector and the content of 137Cs and 134Cs isotopes were obtained. An about 18-day test run has been finished and the veto efficiency of CsI crystal anti-Compton detector is about 31% and the event rate of background spectrum of HPGe detector is about 133cpd. Further methods have to be explored to suppress the background level.
Abstract:
The time-of-flight detector of the Beijing Spectrometer Ⅲ(BESⅢ) is built with long and narrow plastic scintillator bars, with each being 2.3m long and 6cm wide. The time resolution of prototypes wrapped with aluminum film has been studied for various thickness of the scintillator using a test beam at the Institute of High Energy Physics in Beijing, China. In this paper, the position-dependent time resolution of the scintillator with a thickness of 4cm, 5cm and 6cm is presented and compared with a Monte Carlo simulation, the results show that the bar with a thickness of 5cm has the best performance.
The time-of-flight detector of the Beijing Spectrometer Ⅲ(BESⅢ) is built with long and narrow plastic scintillator bars, with each being 2.3m long and 6cm wide. The time resolution of prototypes wrapped with aluminum film has been studied for various thickness of the scintillator using a test beam at the Institute of High Energy Physics in Beijing, China. In this paper, the position-dependent time resolution of the scintillator with a thickness of 4cm, 5cm and 6cm is presented and compared with a Monte Carlo simulation, the results show that the bar with a thickness of 5cm has the best performance.
Abstract:
The Experiment of RF modulation at the HLS(Hefei Light Source) is introduced. The 4%—8% AM(Amplitude Modulation) or the 2°—3° PM(Phase Modulation) with the modulated frequency closed to the longitudinal synchrotron oscillation frequency improves the beam lifetime. The experiment also finds out the intensity of the beam spectrum reduced after applying the RF modulation, which shows that the modulation is useful for suppressing the coupled-bunch instability.
The Experiment of RF modulation at the HLS(Hefei Light Source) is introduced. The 4%—8% AM(Amplitude Modulation) or the 2°—3° PM(Phase Modulation) with the modulated frequency closed to the longitudinal synchrotron oscillation frequency improves the beam lifetime. The experiment also finds out the intensity of the beam spectrum reduced after applying the RF modulation, which shows that the modulation is useful for suppressing the coupled-bunch instability.
Abstract:
This paper describes the beam commissioning process of BEPCⅡ Injector Linac. Aiming at the beam design goal and the beam physics characteristics of this injector linac, the beam commissioning method has been proposed, and some problems met in the beam commissioning process have been analyzed and studied. In addition, the preliminary beam commissioning results have been obtained.
This paper describes the beam commissioning process of BEPCⅡ Injector Linac. Aiming at the beam design goal and the beam physics characteristics of this injector linac, the beam commissioning method has been proposed, and some problems met in the beam commissioning process have been analyzed and studied. In addition, the preliminary beam commissioning results have been obtained.
Abstract:
A numerical simulation method for coupler design is proposed. It is based on the matching procedure for the 2π/3 structure given by Dr. R. L. Kyhl. Microwave Studio EigenMode Solver is used for such numerical simulation. The simulation for a coupler has been finished with this method and the simulation data are compared with experimental measurements. The results show that this numerical simulation method is feasible for coupler design.
A numerical simulation method for coupler design is proposed. It is based on the matching procedure for the 2π/3 structure given by Dr. R. L. Kyhl. Microwave Studio EigenMode Solver is used for such numerical simulation. The simulation for a coupler has been finished with this method and the simulation data are compared with experimental measurements. The results show that this numerical simulation method is feasible for coupler design.
Abstract:
The dominant frequency in an inward-emitting coaxial virtual cathode oscillator is solved analytically based on the steady-state relativistic-fluid-Maxwell equations. Full three-dimensional numerical simulation with the PIC method is carried out using the TS3 module of the MAFIA code. The frequency spectrum and the output power are obtained by monitoring the five propagating modes in the cylindrical output waveguide. The result shows that when the anode reflector exists, the frequency spectrum can be improved effectively by the formed quasi-cavity and hence the corresponding energy conversion efficiency can be enhanced.
The dominant frequency in an inward-emitting coaxial virtual cathode oscillator is solved analytically based on the steady-state relativistic-fluid-Maxwell equations. Full three-dimensional numerical simulation with the PIC method is carried out using the TS3 module of the MAFIA code. The frequency spectrum and the output power are obtained by monitoring the five propagating modes in the cylindrical output waveguide. The result shows that when the anode reflector exists, the frequency spectrum can be improved effectively by the formed quasi-cavity and hence the corresponding energy conversion efficiency can be enhanced.
Abstract:
In this paper, we introduce the Bunch-by-bunch tracing-measurement system in HLS, and describe some results of experiments and analyses. Using an in-phase gate signal for simulating beam signal and a frequency divided signal of RF for supplying external trigger of ADC, we test the reliability and the stability of this system. By this system, we trace and record a full process of injection, ramping, RF decreasing, closed orbit correcting, wiggler charging, adding skew-quadrupole and opening for users. The tune shift and the coupled bunch instability during the full process have been shown in the end.
In this paper, we introduce the Bunch-by-bunch tracing-measurement system in HLS, and describe some results of experiments and analyses. Using an in-phase gate signal for simulating beam signal and a frequency divided signal of RF for supplying external trigger of ADC, we test the reliability and the stability of this system. By this system, we trace and record a full process of injection, ramping, RF decreasing, closed orbit correcting, wiggler charging, adding skew-quadrupole and opening for users. The tune shift and the coupled bunch instability during the full process have been shown in the end.
Abstract:
The accelerating tube is the core of a linac. The capture efficiency is usually about 50% by ordinary design method in the electron linac for irradiation processing. Nearly half of the injected electrons are lost in the tube, resulting in strong radiation and additional heat load on the accelerating cavity, as well as a bad effect on vacuum. In this paper, a constant gradient accelerating structure is chosen to accelerate the electron beam, and the designed phase velocity is linearly increased along the tube. By adjusting the size of the accelerating cavity and the phase velocity function, a high capture efficiency is reached. After a series of simulations, we obtain a 90% capture efficiency, while the accelerator length is not increased due to the bunching process.
The accelerating tube is the core of a linac. The capture efficiency is usually about 50% by ordinary design method in the electron linac for irradiation processing. Nearly half of the injected electrons are lost in the tube, resulting in strong radiation and additional heat load on the accelerating cavity, as well as a bad effect on vacuum. In this paper, a constant gradient accelerating structure is chosen to accelerate the electron beam, and the designed phase velocity is linearly increased along the tube. By adjusting the size of the accelerating cavity and the phase velocity function, a high capture efficiency is reached. After a series of simulations, we obtain a 90% capture efficiency, while the accelerator length is not increased due to the bunching process.
Abstract:
X-ray imaging at hight energies has been used for many years in many fields. Conventional X-ray imaging is based on the different absorption within a sample. It's difficult to distinguish different tissues of a biological sample because of their small difference in absorption. In this paper, we use the diffraction enhanced imaging(DEI)method. We took images of absorption, extinction,scattering and refractivity. In the end, we presented pictures of high resolution with all these information combined.
X-ray imaging at hight energies has been used for many years in many fields. Conventional X-ray imaging is based on the different absorption within a sample. It's difficult to distinguish different tissues of a biological sample because of their small difference in absorption. In this paper, we use the diffraction enhanced imaging(DEI)method. We took images of absorption, extinction,scattering and refractivity. In the end, we presented pictures of high resolution with all these information combined.
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