In this study,the non-trival effect of the selection of reference particles for decay angle definitions is demonstrated when constructing the partial-wave amplitude of multi-body decays using helicity formalism.This i...In this study,the non-trival effect of the selection of reference particles for decay angle definitions is demonstrated when constructing the partial-wave amplitude of multi-body decays using helicity formalism.This issue is often ignored in the standard use case of helicity formalism.A new technique is proposed to test the selection of the particle ordering,and it can also be used as a generalized method to calculate the rotation operators that are used for the final-state alignment between different decay chains.Moreover,numerical validations are performed to support the arguments and to verify the effectiveness of the proposed technique.展开更多
The possible place to search for exotic states in J/ψ hadronic decays is in J/ψ →ρρπ. Because of the symmetry of identical particle and the symmetry of isospin, the physical analysis on this channel is quite com...The possible place to search for exotic states in J/ψ hadronic decays is in J/ψ →ρρπ. Because of the symmetry of identical particle and the symmetry of isospin, the physical analysis on this channel is quite complicated. In this paper, the method to use the partial wave analysis based on covariant helicity amplitude analysis to study the invariant mass spectrum of ρρπ and to find the evidence of exotic states in ρρπ spectrum is discussed. The decay amplitude for the decay sequence J/ψ→ρX, X →ρπ is given first. Then we discuss how to realize the identical particle symmetry and the isospin symmetry in the decay amplitude, which is the key point in the analysis of this channel. Then the total decay amplitude of this channel including all decay components is given. After that, how to identify the exotic states in the ρρπ spectrum is discussed. What is discussed in this paper is the theoretical basis on experimentally searching for exotic states at BEPC/BES.展开更多
The experimental observation indicates that the branching ratio of ψ＇→ρπ is very small while the ρ-π channel is a main one in J/ψ decays. To understand the puzzle, various interpretations have been proposed. M...The experimental observation indicates that the branching ratio of ψ＇→ρπ is very small while the ρ-π channel is a main one in J/ψ decays. To understand the puzzle, various interpretations have been proposed. Meanwhile according to the hadronic helicity selection rule, this decay mode should be suppressed. Numerical calculations are needed to determine how it is suppressed. We calculate the branching ratios of J/ψ→ρπ and ππ in the framework of QCD. The results show that the branching ratios are proportional to （mu＋md/MJ/ψ）^2 for the ρπ mode and （mu-md/MJ/ψ）^2 for the ππ mode which is isospin violated. The theoretical prediction of the ratio of J/ ψ→ρπ is smaller than data, but not too small to invoke a completely new mechanism. Thus the puzzle is still standing even though we learn much knowledge towards the puzzle and this will help to finally interpret the puzzle and then gain a deeper insight to the heavy quarkonia.展开更多
An exact quantum treatment reveals that signal and idler photon number operators are not well-behaved dynamical operators for studying photon statistics in parametric amplification/down-conversion processes. Contrary ...An exact quantum treatment reveals that signal and idler photon number operators are not well-behaved dynamical operators for studying photon statistics in parametric amplification/down-conversion processes. Contrary to expectations, the mean signal-idler photon number difference varies with time, while the corresponding signal-idler photon number cross-correlation function is complex and experiences an interference phenomenon driven by the interaction parameters. The intensity operators and related polarization operators of the polarized signal-idler photon pair in positive and negative helicity states are identified as the appropriate operators specifying a conservation law and the dynamical symmetry group (SU(1, 1)) of the parametric amplification process. The conservation of the mean positive and negative helicity photon intensity difference and the purely real positive-negative helicity intensity cross-correlation function correctly account for the simultaneous production of polarized signal and idler photons in positive and negative helicity states.展开更多
The J/ψ hadronic decays provide good laboratory to search for the hybrid states with exotic quantum numbers. A full Partial Wave Analysis （PWA） is performed to the generated Monte Carlo J/ψ→ ρηπ data, based on...The J/ψ hadronic decays provide good laboratory to search for the hybrid states with exotic quantum numbers. A full Partial Wave Analysis （PWA） is performed to the generated Monte Carlo J/ψ→ ρηπ data, based on the design of BESⅢ detector, to study the sensitivity of searching for a possible exotic state at BESⅢ.展开更多
A long-pulse plasma discharge for more than 30 min. was achieved on the Large Helical Device （LHD）. A plasma of ne = 0.8 × 10^19 m^-3 and T10 = 2.0 keV was sustained with PICH = 0.52 MW, PECH = 0.1 MW and avera...A long-pulse plasma discharge for more than 30 min. was achieved on the Large Helical Device （LHD）. A plasma of ne = 0.8 × 10^19 m^-3 and T10 = 2.0 keV was sustained with PICH = 0.52 MW, PECH = 0.1 MW and averaged PNBI = 0.067 MW. Total injected heating energy was 1.3 G J, which was a quarter of the prepared RF heating energy. One of the keys to the success of the experiment was a dispersion of the local plasma heat load to divertors, accomplished by shifting the magnetic axis inward and outward.展开更多
Topological insulators have a bulk band gap like a.n ordinary insulator and conducting states on their edge or surface which are formed by spin orbit coupling and protected by time-reversal sylnmetry. W＇e report theo...Topological insulators have a bulk band gap like a.n ordinary insulator and conducting states on their edge or surface which are formed by spin orbit coupling and protected by time-reversal sylnmetry. W＇e report theoretical analyses of tile electronic properties of three-dimensional topological insulator Bi2Sea film on different energies. We choose five different energies （ 123, -75, 0, 180. 350 meV） around the Dirac cone （ 113 meV）. When energy is close to the Dirac cone. the properties of wave function Inatch the topological insulator＇s halhnark perfectly. When energy is far way from tile Dirac cone, the halhnark of topological insulator is broken and the helical states disappear. The electronic properties of helical states are dug out fi＇om the calculation results. The spin-inomentum locking of the helical StatES are confirmed. A 3-fold symmetry of the helical states in Brillouin zone is also revealed. The penetration depth of tile helical states is two quintuple layers which can be identified from layer projection. Tile charge contribution on each quintuple layer depends on the energy, and has completely different behavior along K and M direction in Brillouin zone. From orbital projection, we can find that the maximum charge contribution of the helical states is p： orbit and the charge contribution on py and Px orbits have 2-fold symmetry.展开更多
基金This work was supported in part by National Key R&D Program of China(2017YFA0402103,2020YFA0406400)National Natural Science Foundation of China(11775122,11822506,11975015)Fundamental Research Funds for the Central Universities。
文摘In this study,the non-trival effect of the selection of reference particles for decay angle definitions is demonstrated when constructing the partial-wave amplitude of multi-body decays using helicity formalism.This issue is often ignored in the standard use case of helicity formalism.A new technique is proposed to test the selection of the particle ordering,and it can also be used as a generalized method to calculate the rotation operators that are used for the final-state alignment between different decay chains.Moreover,numerical validations are performed to support the arguments and to verify the effectiveness of the proposed technique.
基金The project supported in part by National Natural Science Foundation of China under Grant Nos, 10575002, 10421503, 10491306, and 10491300.Acknowledgments The authors acknowledge helpful discussions with H.Q Zheng and X.Y. Shen.
文摘The possible place to search for exotic states in J/ψ hadronic decays is in J/ψ →ρρπ. Because of the symmetry of identical particle and the symmetry of isospin, the physical analysis on this channel is quite complicated. In this paper, the method to use the partial wave analysis based on covariant helicity amplitude analysis to study the invariant mass spectrum of ρρπ and to find the evidence of exotic states in ρρπ spectrum is discussed. The decay amplitude for the decay sequence J/ψ→ρX, X →ρπ is given first. Then we discuss how to realize the identical particle symmetry and the isospin symmetry in the decay amplitude, which is the key point in the analysis of this channel. Then the total decay amplitude of this channel including all decay components is given. After that, how to identify the exotic states in the ρρπ spectrum is discussed. What is discussed in this paper is the theoretical basis on experimentally searching for exotic states at BEPC/BES.
基金Supported by National Natural Science Foundation of ChinaSpecial Fund of Education Ministry of China for the PhD Programs
文摘The experimental observation indicates that the branching ratio of ψ＇→ρπ is very small while the ρ-π channel is a main one in J/ψ decays. To understand the puzzle, various interpretations have been proposed. Meanwhile according to the hadronic helicity selection rule, this decay mode should be suppressed. Numerical calculations are needed to determine how it is suppressed. We calculate the branching ratios of J/ψ→ρπ and ππ in the framework of QCD. The results show that the branching ratios are proportional to （mu＋md/MJ/ψ）^2 for the ρπ mode and （mu-md/MJ/ψ）^2 for the ππ mode which is isospin violated. The theoretical prediction of the ratio of J/ ψ→ρπ is smaller than data, but not too small to invoke a completely new mechanism. Thus the puzzle is still standing even though we learn much knowledge towards the puzzle and this will help to finally interpret the puzzle and then gain a deeper insight to the heavy quarkonia.
文摘An exact quantum treatment reveals that signal and idler photon number operators are not well-behaved dynamical operators for studying photon statistics in parametric amplification/down-conversion processes. Contrary to expectations, the mean signal-idler photon number difference varies with time, while the corresponding signal-idler photon number cross-correlation function is complex and experiences an interference phenomenon driven by the interaction parameters. The intensity operators and related polarization operators of the polarized signal-idler photon pair in positive and negative helicity states are identified as the appropriate operators specifying a conservation law and the dynamical symmetry group (SU(1, 1)) of the parametric amplification process. The conservation of the mean positive and negative helicity photon intensity difference and the purely real positive-negative helicity intensity cross-correlation function correctly account for the simultaneous production of polarized signal and idler photons in positive and negative helicity states.
基金Supported by National Natural Science Foundation of China (10575002,10721063,10521003,10625524)
文摘The J/ψ hadronic decays provide good laboratory to search for the hybrid states with exotic quantum numbers. A full Partial Wave Analysis （PWA） is performed to the generated Monte Carlo J/ψ→ ρηπ data, based on the design of BESⅢ detector, to study the sensitivity of searching for a possible exotic state at BESⅢ.
基金supported in part by the JSPS-CAS Core-University Program in the field of Plasma and Nuclear Fusion
文摘A long-pulse plasma discharge for more than 30 min. was achieved on the Large Helical Device （LHD）. A plasma of ne = 0.8 × 10^19 m^-3 and T10 = 2.0 keV was sustained with PICH = 0.52 MW, PECH = 0.1 MW and averaged PNBI = 0.067 MW. Total injected heating energy was 1.3 G J, which was a quarter of the prepared RF heating energy. One of the keys to the success of the experiment was a dispersion of the local plasma heat load to divertors, accomplished by shifting the magnetic axis inward and outward.
文摘Topological insulators have a bulk band gap like a.n ordinary insulator and conducting states on their edge or surface which are formed by spin orbit coupling and protected by time-reversal sylnmetry. W＇e report theoretical analyses of tile electronic properties of three-dimensional topological insulator Bi2Sea film on different energies. We choose five different energies （ 123, -75, 0, 180. 350 meV） around the Dirac cone （ 113 meV）. When energy is close to the Dirac cone. the properties of wave function Inatch the topological insulator＇s halhnark perfectly. When energy is far way from tile Dirac cone, the halhnark of topological insulator is broken and the helical states disappear. The electronic properties of helical states are dug out fi＇om the calculation results. The spin-inomentum locking of the helical StatES are confirmed. A 3-fold symmetry of the helical states in Brillouin zone is also revealed. The penetration depth of tile helical states is two quintuple layers which can be identified from layer projection. Tile charge contribution on each quintuple layer depends on the energy, and has completely different behavior along K and M direction in Brillouin zone. From orbital projection, we can find that the maximum charge contribution of the helical states is p： orbit and the charge contribution on py and Px orbits have 2-fold symmetry.
