Progress in p-shell A hypernuclear spectroscopy

The strangeness nuclear physics is an important branch of nuclear physics. The spectroscopic study of A hypernuclei has been used as a tool for investigating the A-N interaction as well as probing the nuclear interior structure. In this paper some high-lights and open questions in the spectroscopic study of p-shell A hypernuclei are presented.     

裂变碎片靶室在直接测量重A超核寿命中的应用(英文)

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~(252)Cf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.     

Note on spin–orbit interactions in nuclei and hypernuclei

A detailed comparison is made between the spin–orbit interactions in Λ hypernuclei and ordinary nuclei. We argue that there are three major contributions to the spin–orbit interaction: (1) a short-range component involving scalar and vector mean fields; (2) a “wrong-sign” spin–orbit term generated by the pion exchange tensor force in second order; and (3) a three-body term induced by two-pion exchange with excitation of virtual Δ(1232)-isobars (à la Fujita–Miyazawa). For nucleons in nuclei the long-range pieces related to the pion-exchange dynamics tend to cancel, leaving room dominantly for spin–orbit mechanisms of short-range origin (parametrized, e.g., in terms of relativistic scalar and vector mean fields terms). In contrast, the absence of an analogous 2π-exchange three-body contribution for Λ hyperons in hypernuclei leads to an almost complete cancellation between the short-range (relativistic mean-field) component and the “wrong-sign” spin–orbit interaction generated by second order π-exchange with an intermediate Σ hyperon. These different balancing mechanisms between short- and long-range components are able to explain simultaneously the very strong spin–orbit interaction in ordinary nuclei and the remarkably weak spin–orbit splitting in Λ hypernuclei.     

Application of the HKS in the identification of kaons produced in the reaction （e,e＇K^＋）

At Jefferson Laboratory the experiment E02-017 was carried out to investigate the fission associated with kaons in the hypernuclei-producing interaction p（e,K^＋e＇）A. The newly installed high resolution kaon spectrometer （HKS） in Hall C was used as a key instrument to identify kaons. This paper introduces the HKS hardware and describes the way the kaons are identified. Maintaining most of the kaons （nearly 100%） in the data, HKS identifies kaons with a purity of -67% in this experiment. The resolution of the kaon target time reconstructed by HKS reaches 0.42 ns.     

Polarization effect on the spin symmetry for anti-Lambda spectrum in ~(16)O+■ 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.     

CSR上可能的超核物理研究

对近年来超核物理在理论上及实验上的进展作了简介, 结合即将建成的兰州重离子加速器, 给出了一些可行性的超核物理研究.     

Some Effects on A Single Particle Energies

With the phenomenological Λ-nucleus potentials of Woods-Saxon shape,the effects of the mass-number dependence of the shrinkage,the effective mass mΛ^* and the charge-symmetry breaking (CSB) on the single particle energies are discussed.It is found that the single particle energies are not sensitive to the effective mass mΛ^*.But the radius parameter depended on the mass number (ro(Ac)=r1 r2Ac^-2/3) can substantially improve the results.We also found that CSB effect is significant for heavy hypernuclei with a large neutron excess.     

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 Bogoliubov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. Halos in the relativistic continuum Hartree Bogoliubov (RCHB) theory are investigated，including giant halo in the even N Ca isotope near neutron drip line，halos in hypernuclei and the hyperon halos in 153ΛC.     

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

The production of A-hypernuclei in the A(p,K+)ΛB reaction is investigated in the framework of the 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 Λ-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.     

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

The Λ separation energy for Λ hypernuclei,denoted B_Λ,measured in 1967,1968,and 1973 are recalibrated using the current best estimates of the mass of particles and nuclei.The recalibrated B_Λ are systematically larger(except in the case of _Λ~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 B_Λ values measured in1967,1968,and 1973 are widely used in theoretical research,and the new results provide better constraints for the conclusions of such studies.