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
Multi-meson final states such as γp →pπ0π0 and γp →pπ0η have been investigated with the Crystal-Barrel/TAPS experiment at ELSA. Baryon cascades via △π and △η and also via higher mass baryon resonances are...Multi-meson final states such as γp →pπ0π0 and γp →pπ0η have been investigated with the Crystal-Barrel/TAPS experiment at ELSA. Baryon cascades via △π and △η and also via higher mass baryon resonances are clearly observed. Based on this data and on data from other reactions a partial wave analysis has been performed from which partial decay widths of various N＊ and △＊ states into the different pπ0π0 and pπ0η decay channels have been determined, leading partly to unexpected results. In addition, polarisation observables have been investigated. The beam asymmetry X has been determined for both reactions and double polarisation data using a longitudinally polarised target and a circularly or linearly polarised photon beam has been taken. Given the angular coverage of the Crystal-Baxrel/TAPS experiment this data covers almost the full angular range and phase space. This data will provide new and important information for the partial wave analyses and bring us one step closer towards a complete experiment.展开更多
The phenomenon of the near ppˉ-threshold enhancement observed in the J/ψ → γ pp decay is studied by using the enhancement factor method with a simpler one-pion-exchange potential between p and p. The Jost function...The phenomenon of the near ppˉ-threshold enhancement observed in the J/ψ → γ pp decay is studied by using the enhancement factor method with a simpler one-pion-exchange potential between p and p. The Jost function caused by the mentioned potential is perturbatively calculated in the zero-th order approximation, and the corresponding enhancement factor is obtained. It is found that such a final state interaction offers an important contribution to the decay width near the ppˉ-threshold, although it is not large enough. To explain the decay data, a phenomenological factor G（p） with the form of 285500/（m 2 π ＋ p 2 ） should be introduced. A further calculation including the p-dependent bare T -matrix, a more realistic N ˉ N potential and the contribution from the higher-order wave functions would provide a better understanding of the decay data and even the existence of the baryonium ppˉ. The near ppˉ-threshold behavior of the decay width in the J/ψ →π 0 pp process is also discussed.展开更多
Analytical formulae for the phase space factors and three-momenta of three-and four-body final states are derived for all sets of independent kinematic variables containing invariant mass variables.These formulae will...Analytical formulae for the phase space factors and three-momenta of three-and four-body final states are derived for all sets of independent kinematic variables containing invariant mass variables.These formulae will help experimental physicists to perform data analysis.As an example,we show how to use these formulae to distinguish the different mechanisms of the e+p→e+J/ψ+p process when searching the signals of P_(c) states in the energy region of the Electron-Ion collider at China(EicC).展开更多
The azimuthal distributions of final-state particles and fragments produced in high-energy nucleus-nucleus collisions are described by a modified multisource ideal gas model which contains the expansions and movements...The azimuthal distributions of final-state particles and fragments produced in high-energy nucleus-nucleus collisions are described by a modified multisource ideal gas model which contains the expansions and movements of the emission sources. The transverse structures of the sources are given in the transverse plane by momentum components Px and Py, and described by parameters in the model. The results of the azimuthal distributions, calculated by the Monte Carlo method, are in good agreement with the experimental data in nucleus-nucleus collisions at high energies.展开更多
The final-state energy spectrum in the electromagnetic dissociation is calculated by asimple method.The final-state energy curves obtained from the calculation are in agreementwith the experimental data of <sup>...The final-state energy spectrum in the electromagnetic dissociation is calculated by asimple method.The final-state energy curves obtained from the calculation are in agreementwith the experimental data of <sup>28</sup>Si into p+<sup>27</sup>Al at an energy of 14.6 GeV/u.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Supported by German Science Foundation (DFG) in the frame of the SFB/TR16
文摘Multi-meson final states such as γp →pπ0π0 and γp →pπ0η have been investigated with the Crystal-Barrel/TAPS experiment at ELSA. Baryon cascades via △π and △η and also via higher mass baryon resonances are clearly observed. Based on this data and on data from other reactions a partial wave analysis has been performed from which partial decay widths of various N＊ and △＊ states into the different pπ0π0 and pπ0η decay channels have been determined, leading partly to unexpected results. In addition, polarisation observables have been investigated. The beam asymmetry X has been determined for both reactions and double polarisation data using a longitudinally polarised target and a circularly or linearly polarised photon beam has been taken. Given the angular coverage of the Crystal-Baxrel/TAPS experiment this data covers almost the full angular range and phase space. This data will provide new and important information for the partial wave analyses and bring us one step closer towards a complete experiment.
基金Supported by National Natural Science Foundation of China (10675022, 10975018, 10975038, 11035006, 11165005, 11175020)Fundamental Research Funds for the Central UniversitiesKey-project by the Chinese Academy of Sciences (KJCX3-SYW-N2)
文摘The phenomenon of the near ppˉ-threshold enhancement observed in the J/ψ → γ pp decay is studied by using the enhancement factor method with a simpler one-pion-exchange potential between p and p. The Jost function caused by the mentioned potential is perturbatively calculated in the zero-th order approximation, and the corresponding enhancement factor is obtained. It is found that such a final state interaction offers an important contribution to the decay width near the ppˉ-threshold, although it is not large enough. To explain the decay data, a phenomenological factor G（p） with the form of 285500/（m 2 π ＋ p 2 ） should be introduced. A further calculation including the p-dependent bare T -matrix, a more realistic N ˉ N potential and the contribution from the higher-order wave functions would provide a better understanding of the decay data and even the existence of the baryonium ppˉ. The near ppˉ-threshold behavior of the decay width in the J/ψ →π 0 pp process is also discussed.
基金Supported by the Fundamental Research Funds for the Central Universitiesthe National Key R&D Program of China (2020YFA0406400)the Key Research Program of the Chinese Academy of Sciences (XDPB15)。
文摘Analytical formulae for the phase space factors and three-momenta of three-and four-body final states are derived for all sets of independent kinematic variables containing invariant mass variables.These formulae will help experimental physicists to perform data analysis.As an example,we show how to use these formulae to distinguish the different mechanisms of the e+p→e+J/ψ+p process when searching the signals of P_(c) states in the energy region of the Electron-Ion collider at China(EicC).
基金Project supported by the National Natural Science Foundation of China （Grant Nos 10275042 and 10475054）, the Shanxi Provincial Natural Science Foundation （Grant No 20021006）, and the Shanxi Provincial 1Foundation for Returned 0verseas Scholars.
文摘The azimuthal distributions of final-state particles and fragments produced in high-energy nucleus-nucleus collisions are described by a modified multisource ideal gas model which contains the expansions and movements of the emission sources. The transverse structures of the sources are given in the transverse plane by momentum components Px and Py, and described by parameters in the model. The results of the azimuthal distributions, calculated by the Monte Carlo method, are in good agreement with the experimental data in nucleus-nucleus collisions at high energies.
基金The project supported by Shanxi Provincial Foundation of Leading Man in ScienceShanxi Provincial Foundation of Scholarly ExchangeChina National Education Committee Foundation of Scholarly Exchange
文摘The final-state energy spectrum in the electromagnetic dissociation is calculated by asimple method.The final-state energy curves obtained from the calculation are in agreementwith the experimental data of <sup>28</sup>Si into p+<sup>27</sup>Al at an energy of 14.6 GeV/u.
