利用手征SU(3)夸克模型研究轻超核_Λ~5He,_Λ~4He和_Λ~4H的结合能

利用手征SU(3)夸克集团模型,通过共振群方法(RGM)得到非定域的YN相互作用势和Λ超子与壳心核的相互作用势,并用其计算了轻Λ超核5ΛHe,4ΛHe和4ΛH的结合能.计算结果表明,手征SU(3)夸克集团模型不仅能较好地描述Λp散射,也能较好地描述轻Λ超核的结合能.由于利用共振群方法(RGM)直接抽取的非定域YN相互作用势更为准确,因此计算得到的轻Λ超核5ΛHe,4ΛHe和4ΛH的结合能更符合实验数据,同时,这也为将来研究超核和多夸克体系确定了一套更为精确的模型参数.     

裂变碎片靶室在直接测量重Λ超核寿命中的应用

介绍了一种新的直接测量重超核寿命的方法. 并对其中用到的一个重要探测设备——裂变碎片靶室——在托马斯.杰斐逊国家实验室用²⁵²Cf放射源进行了测试. 该靶室的单模块时间分辨率为～163ns. 在此分辨率的基础上, 计算机模拟表明用此方法测到的超核寿命误差将在9.6ps左右.     

Shell-model Study of Neutron-rich A-hypernucleus 10ΛLi

We investigate a Σ-mixing probability of a neutron-rich A-hypernucleus ~(10)_ΛLi by using microscopic shell-model calculations considering a Λ-Σ coupling in the first order perturbation.The theoretical Σ-mixing probability in ~(10)_Li is found to be about 0.48%,due to the appearance of multi-configuration Σ Nuclear excited states which can be strongly coupled with the A ground state in ~(10)_Li.     

Six quark cluster effects and Λ-binding energy difference between the mirror hypernuclei Λ 4 He and Λ 4 He

The lambda binding energy difference between two mirror hypernuclei _Λ ⁴ He and _Λ ⁴ He is studied by incorporating the quark structure of nucleons, specially the six quark cluster effects. A small contribution in the binding energy difference (59 keV in the non-relativistic quark model and 29 keV in the bag model) is obtained in the present work.     

Investigation of Λ+c- and Λb-Hypernuclei in Relativistic Mean-Field Model

We investigate the properties of Λc+- and Λb-hypernuclei within the framework of the relativistic mean-fieldmodel (RMF). It is found that no Λc+ bound states can exist if the Λc+ potential well depth |Uλc+| in nuclear matter isless than 10 MeV. If |Uλc+| is less than 20 MeV, Λc+ cannot bind to the heavier nuclei with atomic number larger than100. We suggest it is preferable to search the Λc+-hypernuclei from medium-heavy nuclear systems in experiment. Verysmall spin-orbit splitting for the Λc+ in hypernuclei is also observed, and for the Λb it is nearly zero.     

奇异性核物理前沿问题

简要评述奇异性核物理的几个前沿问题,包括Λ超核能谱精细结构与ΛN相互作用提取问题,自由YN势的改进问题、K核问题、Σ超子-核势问题、Λ超子-Λ超子相互作用强度问题、中子星内部奇异粒子成分问题等。     

Polarization effect on the spin symmetry for anti-Lambda spectrum in ^16O＋∧ system

^The polarization effect on the spin symmetry for anti-Lambda spectrum in 16 O＋Λ system has been studied in relativistic mean-field theory.The PK1 effective interaction is used for nucleon-meson couplings and G-parity symmetry with a reduction factor ξ = 0.3 is adopted for anti-Lambda-meson couplings.The energy differences between spin doublets in the anti-Lambda spectrum are around 0.10-0.73 MeV for p Λ state.The dominant components of the Dirac spinor for the anti-Lambda spin doublets are found to be near identical.It indicates that the spin symmetry is still well-conserved against the polarization effect from the valence antiLambda hyperon,which leads to a highly compressed cold nucleus with the central density up to 2 - 3 times of saturated density.     

Physics prospects at J-PARC

We have held an inauguration ceremony of the Japan Proton Accelerator Research Complex （JPARC） on July 6,2009,celebrating the completion of its construction.Now,the beam commissioning of the 50 GeV main proton synchrotron is in progress to improve the beam intensity and quality.A lot of important experimental programs in Nuclear Physics are waiting for the beam.In this report,I introduce some examples.     

hypernuclei based on the ESC04 model

Structures of S=−2 many-body states (double-Λ and Ξ hypernuclei) are investigated on the basis of G-matrix interactions derived from the recently-developed extended-soft-core model (ESC04d). ΛΛ–ΞN mixing effects in ⁶_ΛΛHe, ⁵_ΛΛH and ⁵_ΛΛHe are investigated with use of three-body models. Possible Ξ hypernuclei are investigated systematically with Ξ-core folding potentials derived from ΞN G-matrix interactions. A four-body narrow Ξ⁰–Ξ⁻ mixed state, specific to ESC04d, is discussed.     

夸克平均场模型研究有限核及超核

采用组分夸克模型描述重子,首先由自由核子及超子的性质定出模型参数,进一步考虑核介质中重子性质的变化,核介质中的介子平均场直接与重子内部的组分夸克相互作用.夸克平均场模型已被用于研究有限核及超核的性质,能够给出令人满意的有限核及超核的性质,该模型也预言了核介质中核子体积的膨胀及核子有效质量的降低. The quark mean field model, which describes the baryon by using the constituent quark model, is applied to study the properties of finite nuclei and hypernuclei. The meson mean fields couple directly with the quarks and change the properties of baryons in nuclear medium. The quark mean field model provides satisfactory results on the properties of spherical nuclei and hypernuclei. It also predicts an increasing size of the nucleon as well as a reduction of the effective mass in the nuclear environment.