We investigate the properties of the η-nucleus interaction by postulating the N*(1535) dominance for ηN system. Since the mass gap of N* and N is very close to the η meson mass,there is the possibility of the level...We investigate the properties of the η-nucleus interaction by postulating the N*(1535) dominance for ηN system. Since the mass gap of N* and N is very close to the η meson mass,there is the possibility of the level crossing between the N*-h and η modes in finite density. We postulate the N*(1535) resonance for the ηN system and consider quite distinct N* properties in finite density which are predicted by two independent chiral models. We find that we can obtain clearer information on the in-medium N* properties and also on the η-nucleus interaction through the formation of the η-mesic nuclei by (π,N) reactions under the appropriate experimental conditions,which can be performed at existing and/or forthcoming facilities like J-PARC.展开更多
In this study,we explore the possibilities of the formation of bound states of neutral pseudoscalar mesonsη,η',D^(0),B^(0),B^(0)and K^(0)and the vector meson ϕ,with the nuclei^(12)C,^(16)O,^(40)Ca,and 208 Pb,cal...In this study,we explore the possibilities of the formation of bound states of neutral pseudoscalar mesonsη,η',D^(0),B^(0),B^(0)and K^(0)and the vector meson ϕ,with the nuclei^(12)C,^(16)O,^(40)Ca,and 208 Pb,calculating their binding energy and absorption decay width.To calculate the optical potentials of these mesons in different nuclei under study,we use the chiral SU(3)hadronic mean field model,in which the properties of nucleons in the medium are modified through the scalar isoscalar fieldsσandζand scalar-isovector fieldδ.The scalar-isovector fieldδaccounts for the finite isospin asymmetry of different nuclei having asymmetry in the number of protons and neutrons.The binding energy and absorption decay width of mesons are calculated for the ground state and some possible excited states of the nuclei.In the chiral(3)model,the mesonsη,η',D^(0),B^(0),B^(0)and K^(0)are observed to have a significant negative mass shift up to nuclear saturation density,which leads to the possibility of bound states at least for ground states and some excited states for heavy nuclei.For the pseudoscalar singlet η' and vector meson ϕ,the mass shift obtained are found to be small,and bound states are not formed.The present calculations are compared with those of different studies conducted in the field and are useful in understanding the outcomes from different experimental facilities focusing on this area of research.展开更多
The binding energies εη and widths Гη of wmesic nuclei are calculated. We parameterize the η self-energy in the nuclear medium as a function of energy and density. We find that the single-particle energies are se...The binding energies εη and widths Гη of wmesic nuclei are calculated. We parameterize the η self-energy in the nuclear medium as a function of energy and density. We find that the single-particle energies are sensitive to the scattering length, and increase monotonically with the nucleus. The key point for the study of η-nucleus bound states is the η-nuclear optical potential. We study the s-wave interactions of η mesons in a nuclear medium and obtain the optical potential Uη ≈ -72 MeV. Comparing our results with the previous results, we find that the ηN scattering length aηN is indeed important to the calculations. With increasing nuclear density the effective mass of the η meson decreases.展开更多
基金Grant for Scientific Research from the Japan Society for the Promotion of Science(18-8661)
文摘We investigate the properties of the η-nucleus interaction by postulating the N*(1535) dominance for ηN system. Since the mass gap of N* and N is very close to the η meson mass,there is the possibility of the level crossing between the N*-h and η modes in finite density. We postulate the N*(1535) resonance for the ηN system and consider quite distinct N* properties in finite density which are predicted by two independent chiral models. We find that we can obtain clearer information on the in-medium N* properties and also on the η-nucleus interaction through the formation of the η-mesic nuclei by (π,N) reactions under the appropriate experimental conditions,which can be performed at existing and/or forthcoming facilities like J-PARC.
文摘植物多样性与植物竞争强度和生态位重叠度的关系会随环境发生变化。为探究上述关系在若尔盖地区的表现形式,于2021年8月对若尔盖地区典型的水生、湿生、湿生—中生和中生植物群落进行调查,构建了新的植物竞争强度(Competition intensity,CI)公式并进行测算,计算了植物群落的植物多样性指数(包括物种丰富度、Shannon⁃Weiner指数、Simpson指数和Pielou均匀度指数)和生态位重叠度(Niche overlap of species,NOS),分析了植物群落物种多样性指数与CI和NOS的关系。结果表明:1)从水生到中生生境,植物多样性指数均呈增加趋势(P<0.05);2)湿生—中生生境的CI显著高于湿生生境(P<0.05),湿生生境的NOS高于水生生境(P<0.05);CI与NOS无显著相关性,但在湿生生境中两者呈倒抛物线关系(P<0.05)。3)整体来看,植物群落的物种丰富度与CI呈抛物线关系(P<0.05),与NOS无显著关系(P>0.05);Shannon⁃Weiner指数、Simpson指数和Pielou均匀度指数均与NOS呈线性正相关(P<0.05),与CI无显著关系(P>0.05);从单个生境看,湿生—中生生境的Simpson指数、Shannon⁃Weiner指数和Pielou均匀度指数与CI呈线性负相关(P<0.05),其余生境的上述多样性指数与CI无显著关系(P>0.05);各生境的植物多样性指数均与NOS无显著相关性(P>0.05)。本研究表明,从水生到中生生境,若尔盖地区的植物多样性呈增加趋势,但植物多样性与物种竞争强度和生态位重叠度的关系较复杂。本研究结果有助于理解若尔盖高原植物多样性的形成机制。
文摘In this study,we explore the possibilities of the formation of bound states of neutral pseudoscalar mesonsη,η',D^(0),B^(0),B^(0)and K^(0)and the vector meson ϕ,with the nuclei^(12)C,^(16)O,^(40)Ca,and 208 Pb,calculating their binding energy and absorption decay width.To calculate the optical potentials of these mesons in different nuclei under study,we use the chiral SU(3)hadronic mean field model,in which the properties of nucleons in the medium are modified through the scalar isoscalar fieldsσandζand scalar-isovector fieldδ.The scalar-isovector fieldδaccounts for the finite isospin asymmetry of different nuclei having asymmetry in the number of protons and neutrons.The binding energy and absorption decay width of mesons are calculated for the ground state and some possible excited states of the nuclei.In the chiral(3)model,the mesonsη,η',D^(0),B^(0),B^(0)and K^(0)are observed to have a significant negative mass shift up to nuclear saturation density,which leads to the possibility of bound states at least for ground states and some excited states for heavy nuclei.For the pseudoscalar singlet η' and vector meson ϕ,the mass shift obtained are found to be small,and bound states are not formed.The present calculations are compared with those of different studies conducted in the field and are useful in understanding the outcomes from different experimental facilities focusing on this area of research.
文摘The binding energies εη and widths Гη of wmesic nuclei are calculated. We parameterize the η self-energy in the nuclear medium as a function of energy and density. We find that the single-particle energies are sensitive to the scattering length, and increase monotonically with the nucleus. The key point for the study of η-nucleus bound states is the η-nuclear optical potential. We study the s-wave interactions of η mesons in a nuclear medium and obtain the optical potential Uη ≈ -72 MeV. Comparing our results with the previous results, we find that the ηN scattering length aηN is indeed important to the calculations. With increasing nuclear density the effective mass of the η meson decreases.
