Production of light nuclei and hypernuclei at High Intensity Accelerator Facility energy region

Heavy-ion collisions are powerful tools for studying hypernuclear physics.We develop a dynamical coalescence model coupled with an ART model(version1.0) to study the production rates of light nuclear clusters and hypernuclei in heavy-ion reactions,for instance,the deuteron(d),triton(t),helium(~3He),and hypertriton(_A^3H)in minimum bias(0-80%centrality)~6Li+^(12)C reactions at beam energy of 3.5A GeV.The penalty factor for light clusters is extracted from the yields,and the distributions of 0 angle of particles,which provide direct suggesetions about the location of particle detectors in the near future facility-High Intensity heavy-ion Accelerator Facility(HIAF) are investigated.Our calculation demonstrates that HIAF is suitable for studying hypernuclear physics.

Giant Monopole Resonance and Nuclear Incompressibility of Hypernuclei

The isoscalar giant monopole resonances（ISGMRs）of hypernucleiAA42Ca,AA（122）Sn,andAA（210）Pb are investigated using a fully self-consistent Skyrme-Hartree-Fock plus random phase approximation method.The Skyrme-type forces,SGII,No.5 and SAAl,are adopted to describe the nucleon-nucleon,A hyperon-nucleon and A hyperon-A hyperon（AA）interactions,respectively.For a given hyperon fraction,we find that effects of AA interaction on the properties of infinite symmetric nuclear matter and finite hypernuclei are very small.The ISGMR strengths are shifted to the high energy region when two A are added into normal nuclei.The changes are from two parts,one is due to the mean field calculations,and the other is from the residual interaction associated with A hyperons.The constrained energies are increased by about 0.5-0.7MeV,which consequently enhances the effective incompressibility modulus of hypernuclei.

Dynamical Structure of A≤4 Hypernuclei and Charge Symmetry Breaking

-The dynamical structure of A≤4 Λ-hypernuclei is studied by using thefew-body theoretical method.The AN interaction is taken to be the meson exchange po-tential with the single k,ω,η exchange diagrams and the box diagrams of π and πρ ex-change containing the intermediate state particles Σ,Δ.The Λ binding energy differenceof the mirror hypernuclei _Λ~4He and _Λ~4H is explained.It is shown that the root meansquare distances between the particles in the light hypernuclei are almost the same andthere does not exist any nuclear core.The relative motion between particles stay mainlyin 1S state.

Density-dependent relativistic mean field approach and its application to single-Λhypernuclei in oxygen hyperisotopes

The in-medium feature of nuclear force, which includes both nucleon-nucleon( NN) and hyperon-nucleon( ΛN) interactions, impacts the description of single-Λ hypernuclei. With the alternated mass number or isospin of hypernuclei, such effects may be unveiled by analyzing the systematic evolution of the bulk and single-particle properties. From a density-dependent meson-nucleon/hyperon coupling perspective, a new ΛN effective interaction in the covariant density functional(CDF) theory, namely, DD-LZ1-Λ1, is obtained by fitting the experimental data ofΛ separation energies for several single-Λ hypernuclei. It is then used to study the structure and transition properties of single-Λ hypernuclei in oxygen hyperisotopes, in comparison with those determined using several selected CDF Lagrangians. A discrepancy is explicitly observed in the isospin evolution of Λ1p spin-orbit splitting with various effective interactions, which is attributed to the divergence of the meson-hyperon coupling strengths with increasing density. In particular, the density-dependent CDFs introduce an extra contribution to reduce the value but enhance the isospin dependence of the splitting, which originates from the rearrangement terms of Λ self-energies. In addition, the characteristics of hypernuclear radii are studied along the isotopic chain. Owing to the impurity effect of theΛ hyperon, a size shrinkage is observed in the matter radii of hypernuclei compared with the cores of normal nuclei,and its magnitude is further elucidated to correlate with the incompressibility of nuclear matter. Moreover, there is a sizable model-dependent trend in which the Λ hyperon radii evolve with neutron number, which is decided partly by the in-medium NN interactions and core polarization effects.

Nonrelativistic mean-field description of the deformation of Λ hypernuclei

The deformations of light Λ hypernuclei are studied in an extended nonrelativistic deformed Skyrme-Hartree-Fock approach with realistic modern nucleonic Skyrme forces,pairing correlations,and a microscopical lambda-nucleon interaction derived from Brueckner-Hartree-Fock calculations.Compared to the large effect of an additional Λ particle on nuclear deformation in the light soft nuclei within relativistic mean field method,this effect is much smaller in the nonrelativistic mean-field approximation.

Recalibration of the binding energy of hypernuclei measured in emulsion experiments and its implications

TheΛseparation energy forΛhypernuclei,denoted BΛ,measured in 1967,1968,and 1973 are recalibrated using the current best estimates of the mass of particles and nuclei.The recalibrated BΛare systematically larger(except in the case ofΛ~6He)than the originally published values by about 100 keV.The effect of this level of recalibration is very important for light hypemuclei,especially for the hypertriton.The early BΛvalues measured in1967,1968,and 1973 are widely used in theoretical research,and the new results provide better constraints for the conclusions of such studies.

Structure of A=11 double-Λ hypernuclei studied with three-body forces

The energy levels and AA bond energy of the double-A hypernucleus nBe are calculated considering two- and three-nucleon forces. The interactions between the constituent particles are contact interactions that reproduce the low-energy binding energy of the nuclei. Effective action is constructed to involve the three-body forces. In this paper, we compare the binding energy result that is obtained with the experimental and other modern nucleon- nucleon potentials. The results of all the schemes agree very well, showing the high accuracy of our present ability to calculate the many-nucleon bound state with three-body forces. The experimental value of BAA（Be）=20.83 MeV seems to be more compatible with our calculated value of BAA（Be）=-19.31 MeV in comparison with the calculated result of 18.23 MeV by Hiyama et al.

Production of Λ-hypernuclei in A(p,K^+)ΛB reactions

The production of A-hypernuclei in the A（p,K^＋）AB reaction is investigated in the framework ofthe distorted wave impulse approximation（DWIA）. The total cross sections and differential cross sections for various nuclear targets are calculated with an elementary process pN → NKA where the additional contributions from the N（1535） resonance and the final state interaction between p and A are included. The dependence of the production cross sections of A-hypernuclei on the phenomenological nuclear density and the nucleon number in the target, as well as the distortion effect of the incident proton and outgoing kaon, are also explored. It is shown that the distortion effect tends to decrease the cross sections by a factor of about 3--10. The production cross sections are sensitive to the adopted nuclear density.

STABILITY OF J~π=O^+ DOUBLE ∧ HYPERNUCLEI(A=4)

The discovery of Be has aroused many researchers’ interest in studying double ∧ hypernuclei. In general, they use a variational method, and choose a phenomenological potential to diseuss the 3-body He(α-∧-∧) or 4-body Be (α-α-∧-∧) problems. Their results can explain the double ∧ hypernuclei He and Be observed in experiments. Up to now, H has not been found in experiment.

γ-ray Spectroscopy of Hypernuclei:Recent KEK Results and Future Plans at J-PARC

In this proceeding,we will first outline the experimental setup and main results of the most recent hypernuclear γ-ray spectroscopy experiment (KEK-E566) performed at KEK-PS K6 beam line. The main feature and characteristics of this type of research will be emphasised. After that,the approved experimental proposal (E13) at J-PARC facility will be introduced briefly.

Properties of deformed Λ hypernuclei

The properties of Be and B isotopes and the corresponding Λ hypernuclei are studied by using a deformed Skyrme Hartree-Fock approach with realistic nucleonic Skyrme forces, pairing correlations, and a microscopically determined lambda-nucleon interaction based on Brueckner-Hartree-Fock calculations of hypernuclear matter. The results suggest that the core nuclei and the corresponding hypernuclei have similar deformations with the same sign.

Massive neutron stars and A-hypernuclei in relativistic mean field models

Based on relativistic mean field（RMF） models, we study finite A-hypernuclei and massive neutron stars. The effective N-N interactions PK1 and TM1 are adopted, while the N-A interactions are constrained by reproducing the binding energy of A-hyperon at 1 s orbit of Λ^40Ca. It is found that the A-meson couplings follow a simple relation, indicating a fixed A potential well for symmetric nuclear matter at saturation densities, i.e., around VΛ=-29.786 MeV. With those interactions, a large mass range of Λ-hypernuclei can be described well. Furthermore,the masses of PSR J1614-2230 and PSR J0348＋0432 can be attained adopting the Λ-meson couplings gσΛ/gσN≥0.73,gωΛ/gωN≥0.80 for PK1 and gσΛ/gσN≥0.81,gωΛ/gωN≥0.90 for TM1, respectively. This resolves the hyperon puzzle without introducing any additional degrees of freedom.

超核物理学进展

简要评述超核物理学近几年的发展,包括常规超核和非常规超核两个方面.对于包含通常超子的常规超核,重点介绍近来在日本KEK完成的一批超核实验及其理论分析.对其中关于超子杂质效应和超子平均自由路程等实验测量结果进行了理论分析,得到一些有意义的结果.并对奇异数为S=-2的Ξ超核的结构和性质进行了若干研究.对于包含C夸克或B夸克的其他味超核,以及可能的包含pentaquark的θ+超核也做了适当的介绍.

统一框架下对超核_Λ~5He,_Λ~9Be,_(ΛΛ)He^6和_(ΛΛ)Be^(10)基态结合能的研究

用α集团模型和少体理论方法研究了超核5ΛΗe,9ΛΒe,6ΛΛΗe和10ΛΛΒe的基态结合能.所采用的α-α势符合低能α-α散射实验及8Be的基态共振能量,Λ-α势是用Λ-N势及α粒子密度分布函数拟合5ΛΗe的基态结合能的实验值得到的,Λ-Λ势是通过拟合6ΛΛΗe基态结合能的实验值而得到的.用一组α-α势,Λ-α势和Λ-Λ势统一描述这4个超核的基态结合能并得到了合理的结果.

_Λ~5He超核中α粒子的扭曲对结合能B_Λ的影响

在α粒子集团模型下，采用Rayleigh－Ritz变分法，计算了He超核的结合能．由于考虑了Λ超子和α粒子的扭曲作用，使得被扭曲的He超核的结合能BΛ增加，在不同的几种Λ－N相互作用势和α粒子密度分布下，结合能BΛ的增加值ΔB≈0．1～1．0MeV．所以He超核中的扭曲效应是不应被忽视的．

在折叠模型下对超核_Λ^(13)C基态结构的研究

用集团结构模型、折叠模型和少体理论方法,从基态结合能和集团间的均方根半径方面研究了13ΛC超核的基态结构,计算结果与实验值符合较好.

奇特核和超核中的晕现象

讨论奇特核和超核中的各种晕现象 .根据密度相关零程对力的相对论连续谱Hartree Bo goliubov理论给出的计算结果 ,预言了中子滴线附近的Ca原子核中可能存在着巨晕 ,并简要介绍了O ,Ni,Zr ,Sn和Pb等一些质子幻数核从质子滴线到中子滴线之间的原子核基态性质 .随后给出超核内的晕现象研究 ,如Ca超核内的中子晕和153ΛC内的单Λ超子晕 .

多Λ超核基态性质的研究

依据多Λ超核在高能重离子碰撞或天体物理中实现的可能性,以Ca为例,用相对论连续谱Hartree-Bogoliubov理论研究了系统的基态性质,包括每重子结合能、重子均方根半径和超核物质半径以及单粒子能谱等。研究表明,随着超子数目的增加,超核的每重子结合能和超子均方根半径变化趋势平缓,在5100ΛCa等一些超核内超子2s1/2和1d5/2能级排列有明显的反转,丰质子区和总核子数不变的多Λ钙超核滴线所对应的最大超子数分别为6和22。

Λ－N介子交换势和超核的Λ超子结合能

用Λ－Ｎ介子交换势计算的Λ超子结合能，重新确定介于交换势中参数Ｐ，获得改进了的Λ－Ｎ介子交换势．用此改正的Λ－Ｎ势计算Λ－Ｐ弹性散射截面与ｓ波相移以及，，，，，，和中Λ超子的结合能，计算结果和实验值基本符合。

滴线原子核中的晕现象——中子晕、超子晕、巨晕和形变晕

描述了相对论连续谱Hartree Bogoliubov理论框架下的多种可能的晕现象。预言了中子滴线附近的Ca原子核中可能存在着巨晕 ,并简要介绍了O、Ni、Zr、Sn和Pb等一些质子幻数核从质子滴线到中子滴线之间的原子核基态性质。随后给出超核内的晕现象研究 ,如Ca超核内的中子晕和153ΛC内的单Λ超子晕。此外 ,还讨论了形变晕等奇特现象。