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
We perform a unified description of the experimental data of the π^(+)π^(-)and J/ψπ^(±)invariant mass spectra for e^(+)e^(-)→J/ψπ^(+)π^(-)and the D^(0)D^(*-)mass spectrum for e^(+)e^(-)→D^(0)D^(*-)π^(+)...We perform a unified description of the experimental data of the π^(+)π^(-)and J/ψπ^(±)invariant mass spectra for e^(+)e^(-)→J/ψπ^(+)π^(-)and the D^(0)D^(*-)mass spectrum for e^(+)e^(-)→D^(0)D^(*-)π^(+)at e^(+)e^(-)center-of-mass energies 4.23 and 4.26 GeV.The analysis takes into account open-charm meson loops that contain triangle singularities,the J/ψπ-DD^(*)coupled-channel interaction respecting unitarity,and the strong ππ-KK final state interaction using dispersion relations.The analysis leads to a precise determination of the Z_(c)(3900)pole with the pole mass and width(3880.7±1.7_(stat)±22.4_(syst))MeV and(35.9±1.4_(stat)±15.3_(syst))MeV,respectively,and hints at that the DD^(*)molecular and non-molecular components are of similar importance in the Z_(c)(3900)formation.展开更多
We study the lepton pair production via the Bethe-Heitler mechanism in the deuteron breakup reaction.The complete seven-fold differential cross section is calculated with final state interactions taken into account.Th...We study the lepton pair production via the Bethe-Heitler mechanism in the deuteron breakup reaction.The complete seven-fold differential cross section is calculated with final state interactions taken into account.The deuteron bound state is described by a relativistic covariant deuteron-nucleon vertex.The numerical results indicate that the differential cross section is highly dependent on the lepton's azimuthal angle in regions of small polar angles and exhibits sharp peaks in the distribution over the invariant mass of the generated lepton pair or the two nucleons in the final state.We demonstrate that such a nearly singular feature originates from the collinearity between the produced lepton or antilepton and the incident photon,and it is physically regularized by the lepton mass in our calculation.The final state interaction between the knocked-out nucleon and recoil nucleon redistributes the differential cross section over the missing momentum,with a significant enhancement at a large missing momentum and a suppression in the intermediate region.With a further decomposition of the final state interaction contribution,It is found that the on-shell term dominates the near quasi-elastic region,while the off-shell term dominates the other end.Additionally,we examine the contribution from the interference between the proton amplitude and neutron amplitude,which,as expected,is found negligible even if the proton-neutron rescattering is included.The results of this study can serve as inputs for the analysis and background estimation of multiple exclusive measurements at Jefferson Lab and future electron-ion colliders.展开更多
The η meson can be bound to atomic nuclei.Experimental search is discussed in the form of final state interaction for the reactions dp → 3 Heη and dd → 4 Heη.For the latter case tensor polarized deuterons were us...The η meson can be bound to atomic nuclei.Experimental search is discussed in the form of final state interaction for the reactions dp → 3 Heη and dd → 4 Heη.For the latter case tensor polarized deuterons were used in order to extract the s-wave strength.For both reactions complex scattering lengths are deduced： a 3 Heη = ± 10.7±0.8 ＋0.1 -0.5 ＋i· 1.5±2.6 ＋1.0-0.9 fm and a 4 Heη = [±（3.1±0.5）＋i·（0±0.5）] fm.In a two-nucleon transfer reaction under quasi-free conditions,p^ 27 Al → ^3 HeX,was investigated.The system X can be the bound 25 Mg η at rest.When a possible decay of an intermediate N （1535） is required,a highly significant bump shows up in the missing mass spectrum.The data give for a bound state a binding energy of 13.3±1.6 MeV and a width of σ=4.4±1.3 MeV.展开更多
We investigate the decay of a_1^+(1260) →π^+π^+π^-with the assumption that the a_1(1260) is dynamically generated from the coupled channel ρπ and KK~*interactions. In addition to the tree level diagrams that pro...We investigate the decay of a_1^+(1260) →π^+π^+π^-with the assumption that the a_1(1260) is dynamically generated from the coupled channel ρπ and KK~*interactions. In addition to the tree level diagrams that proceed via a_1^+(1260) →ρ~0π^+→π^+π^+π^-, we take into account also the final state interactions of ππ→ππ and KK →ππ. We calculate the invariant π^+π^-mass distribution and also the total decay width of a_1^+(1260) →π^+π^+π^-as a function of the mass of a_1(1260). The calculated total decay width of a_1(1260) is significantly different from other model calculations and tied to the dynamical nature of the a_1(1260) resonance. The future experimental observations could test of model calculations and would provide vary valuable information on the relevance of the ρπ component in the a_1(1260) wave function.展开更多
We propose one possible mechanism,i.e.,the vector meson （VV） rescattering effects,to interpret the near threshold narrow enhancement observed in J/ψ → γpp.The estimate indicates that these effects can give sizeab...We propose one possible mechanism,i.e.,the vector meson （VV） rescattering effects,to interpret the near threshold narrow enhancement observed in J/ψ → γpp.The estimate indicates that these effects can give sizeable contributions to this channel,and a destructive interference between different rescattering amplitudes is required to reproduce the line shape of the data.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
In this study,the heavy to heavy decay of D^(0)_(s)→D^(*+)D^(-)is evaluated through the factorization approach by using the final state interaction as an effective correction.Under the factorization approach,this dec...In this study,the heavy to heavy decay of D^(0)_(s)→D^(*+)D^(-)is evaluated through the factorization approach by using the final state interaction as an effective correction.Under the factorization approach,this decay mode occurs only through the annihilation process,so a small amount is produced.Feynman's rules state that six meson pairs can be assumed for the intermediate states before the final meson pairs are produced.By taking into account the effects of twelve final state interaction diagrams in the calculations,a significant correction is obtained.These effects correct the value of the branching ratio obtained by the pure factorization approach from(2.41±1.37)×10^(-5)to(8.27土2.23)×10^(-5).The value obtained for the branching ratio of the D^(0)_(s)→D^(*+)D^(-)decay is consistent with the experimental results.展开更多
The discovery of Ξ_(cc)^(++)has inspired new interest in studying doubly heavy baryons.In this study,the weak decays of a doubly charmed baryon B_(cc)to a light baryon B and a charm meson D^(*)(either a pseudoscalar ...The discovery of Ξ_(cc)^(++)has inspired new interest in studying doubly heavy baryons.In this study,the weak decays of a doubly charmed baryon B_(cc)to a light baryon B and a charm meson D^(*)(either a pseudoscalar or a vector one)are calculated.Following our previous work,we calculate the short distance contributions under the factorization hypothesis,whereas the long distance contributions are modeled as the final state interactions,which are calculated with the one particle exchange model.We find that the B_(cc)→BD^(*)decays'branching ratios are obviously larger,as they receive contributions of more polarization states.Among the decays that we investigate,the following have the largest branching fractions:BR(Ξ_(cc)^(++)→∑^(+)D^(*+))∈[0.46%,3.33%]estimated with τΞ_(cc)^(++)=256 fs;BR(Ξ_(cc)^(+)→AD^(*+))∈[0.38%,2.63%]and BR(Ξ_(cc)^(+)→∑^(0)D^(*+))∈[0.45%,3.16%]with τΞ_(cc)^(++)=45 fs;and BR(Ω_(cc)^(+)→Ξ^(0)D^(+))∈[0.27%,1.03%),BR(Ω_(cc)^(+)→∑^(0)D^(*+))∈[0.07%,0.44%],and BR(Ω_(cc)^(+)→∑^(0)D^(*+))∈[0.06%,0.45%] with τ_(Ω_(cc))^(+)=75 fs.By comparing the decay widths of pure color commensurate channels with those of pure bow-tie ones we find that the bow-tie mechanism plays an important role in charm decays.展开更多
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 National Natural Science Foundation of China(Grant Nos.11975028,11974043,12361141819,12125507,11835015,12047503,and 12070131001)the Chinese Academy of Sciences(Grant Nos.XDB34030000,and YSBR-101)the NSFC and the Deutsche Forschungsgemeinschaft(DFG)through the funds provided to the Sino-German Collaborative Research Center TRR110“Symmetries and the Emergence of Structure in QCD”(Grant No.DFG Project-ID 196253076)。
文摘We perform a unified description of the experimental data of the π^(+)π^(-)and J/ψπ^(±)invariant mass spectra for e^(+)e^(-)→J/ψπ^(+)π^(-)and the D^(0)D^(*-)mass spectrum for e^(+)e^(-)→D^(0)D^(*-)π^(+)at e^(+)e^(-)center-of-mass energies 4.23 and 4.26 GeV.The analysis takes into account open-charm meson loops that contain triangle singularities,the J/ψπ-DD^(*)coupled-channel interaction respecting unitarity,and the strong ππ-KK final state interaction using dispersion relations.The analysis leads to a precise determination of the Z_(c)(3900)pole with the pole mass and width(3880.7±1.7_(stat)±22.4_(syst))MeV and(35.9±1.4_(stat)±15.3_(syst))MeV,respectively,and hints at that the DD^(*)molecular and non-molecular components are of similar importance in the Z_(c)(3900)formation.
基金Supported by the National Natural Science Foundation of China(12075003,12175117,12335006)。
文摘We study the lepton pair production via the Bethe-Heitler mechanism in the deuteron breakup reaction.The complete seven-fold differential cross section is calculated with final state interactions taken into account.The deuteron bound state is described by a relativistic covariant deuteron-nucleon vertex.The numerical results indicate that the differential cross section is highly dependent on the lepton's azimuthal angle in regions of small polar angles and exhibits sharp peaks in the distribution over the invariant mass of the generated lepton pair or the two nucleons in the final state.We demonstrate that such a nearly singular feature originates from the collinearity between the produced lepton or antilepton and the incident photon,and it is physically regularized by the lepton mass in our calculation.The final state interaction between the knocked-out nucleon and recoil nucleon redistributes the differential cross section over the missing momentum,with a significant enhancement at a large missing momentum and a suppression in the intermediate region.With a further decomposition of the final state interaction contribution,It is found that the on-shell term dominates the near quasi-elastic region,while the off-shell term dominates the other end.Additionally,we examine the contribution from the interference between the proton amplitude and neutron amplitude,which,as expected,is found negligible even if the proton-neutron rescattering is included.The results of this study can serve as inputs for the analysis and background estimation of multiple exclusive measurements at Jefferson Lab and future electron-ion colliders.
文摘The η meson can be bound to atomic nuclei.Experimental search is discussed in the form of final state interaction for the reactions dp → 3 Heη and dd → 4 Heη.For the latter case tensor polarized deuterons were used in order to extract the s-wave strength.For both reactions complex scattering lengths are deduced： a 3 Heη = ± 10.7±0.8 ＋0.1 -0.5 ＋i· 1.5±2.6 ＋1.0-0.9 fm and a 4 Heη = [±（3.1±0.5）＋i·（0±0.5）] fm.In a two-nucleon transfer reaction under quasi-free conditions,p^ 27 Al → ^3 HeX,was investigated.The system X can be the bound 25 Mg η at rest.When a possible decay of an intermediate N （1535） is required,a highly significant bump shows up in the missing mass spectrum.The data give for a bound state a binding energy of 13.3±1.6 MeV and a width of σ=4.4±1.3 MeV.
基金Supported by the National Natural Science Foundation of China under Grant Nos.11475227 and 11735003supported by the Youth Innovation Promotion Association CAS(No.2016367)
文摘We investigate the decay of a_1^+(1260) →π^+π^+π^-with the assumption that the a_1(1260) is dynamically generated from the coupled channel ρπ and KK~*interactions. In addition to the tree level diagrams that proceed via a_1^+(1260) →ρ~0π^+→π^+π^+π^-, we take into account also the final state interactions of ππ→ππ and KK →ππ. We calculate the invariant π^+π^-mass distribution and also the total decay width of a_1^+(1260) →π^+π^+π^-as a function of the mass of a_1(1260). The calculated total decay width of a_1(1260) is significantly different from other model calculations and tied to the dynamical nature of the a_1(1260) resonance. The future experimental observations could test of model calculations and would provide vary valuable information on the relevance of the ρπ component in the a_1(1260) wave function.
基金Supported by National Natural Science Foundation of China (10675131,10491306)Chinese Academy of Sciences (KJCX3-SYW-N2)Ministry of Science and Technology of China (2009CB825200)
文摘We propose one possible mechanism,i.e.,the vector meson （VV） rescattering effects,to interpret the near threshold narrow enhancement observed in J/ψ → γpp.The estimate indicates that these effects can give sizeable contributions to this channel,and a destructive interference between different rescattering amplitudes is required to reproduce the line shape of the data.
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In this study,the heavy to heavy decay of D^(0)_(s)→D^(*+)D^(-)is evaluated through the factorization approach by using the final state interaction as an effective correction.Under the factorization approach,this decay mode occurs only through the annihilation process,so a small amount is produced.Feynman's rules state that six meson pairs can be assumed for the intermediate states before the final meson pairs are produced.By taking into account the effects of twelve final state interaction diagrams in the calculations,a significant correction is obtained.These effects correct the value of the branching ratio obtained by the pure factorization approach from(2.41±1.37)×10^(-5)to(8.27土2.23)×10^(-5).The value obtained for the branching ratio of the D^(0)_(s)→D^(*+)D^(-)decay is consistent with the experimental results.
基金National Natural Science Foundation of China(11765012,12075126)。
文摘The discovery of Ξ_(cc)^(++)has inspired new interest in studying doubly heavy baryons.In this study,the weak decays of a doubly charmed baryon B_(cc)to a light baryon B and a charm meson D^(*)(either a pseudoscalar or a vector one)are calculated.Following our previous work,we calculate the short distance contributions under the factorization hypothesis,whereas the long distance contributions are modeled as the final state interactions,which are calculated with the one particle exchange model.We find that the B_(cc)→BD^(*)decays'branching ratios are obviously larger,as they receive contributions of more polarization states.Among the decays that we investigate,the following have the largest branching fractions:BR(Ξ_(cc)^(++)→∑^(+)D^(*+))∈[0.46%,3.33%]estimated with τΞ_(cc)^(++)=256 fs;BR(Ξ_(cc)^(+)→AD^(*+))∈[0.38%,2.63%]and BR(Ξ_(cc)^(+)→∑^(0)D^(*+))∈[0.45%,3.16%]with τΞ_(cc)^(++)=45 fs;and BR(Ω_(cc)^(+)→Ξ^(0)D^(+))∈[0.27%,1.03%),BR(Ω_(cc)^(+)→∑^(0)D^(*+))∈[0.07%,0.44%],and BR(Ω_(cc)^(+)→∑^(0)D^(*+))∈[0.06%,0.45%] with τ_(Ω_(cc))^(+)=75 fs.By comparing the decay widths of pure color commensurate channels with those of pure bow-tie ones we find that the bow-tie mechanism plays an important role in charm decays.
