远离稳定线丰中子核素的合成和研究

远离稳定线丰中子核素的合成和其衰变性质及核结构研究在过去几年中得到了迅速的发展，已成为原子核物理最为活跃的前沿领域之一。本文综述各质量区丰中子远离核的生成和鉴别，重点讨论丰中子远离核奇异衰变性质和核结构研究的重要进展，并简要介绍丰中子远离核研究在天文物理学中的重要作用。     

重离子碰撞中的介子——兰州重离子冷却储存环上可能实验的讨论

讨论了在兰州重离子加速装置冷却储存环上开展介子产生的实验研究的可能性和进行π和η介子产生研究的意义在 ＣＳＲ能量区域内, 核子可以激发为Δ和 Ｎ,因此, 在研究热密核物质的状态方程时, 考虑Δ和Ｎ自由度是重要的． 观察重离子碰撞中产生的介子可以提供热密核物质的状态方程, 从而可以提供核内物质分布以及 Ｎ在核物质中传播的信息． 建议建造一个测量介子的实验装置, 以开展该领域的研究.The possibilities for experimental study of meson production at Cooling Storage Ring (CSR) of Lanzhou are discussed. It is shown that the study of production of the pion and eta mesons at CSR is of significance. Nucleon can be excited to Δ and N * at CSR energy region. Therefore, it is important to consider the degree of Δ and N * in the study of the equation of states of hot and dense matter. The produced mesons in heavy ion collisions can provide information on...     

在线同位素分离器和丰中子核β衰变

简要介绍了在线同位素分离器的原理以及在奇异核β衰变核谱学中的应用。着重介绍了芬兰Jyv（ae）skyl（ae）大学的离子制导型在线同位素分离器,并对在该装置上开展的丰中子Ag同位素的β^-衰变研究进行了综述。Isotope Separator on Line is briefly introduced with emphasis on the basic concept and features related to the production of exotic nuclei and β decay spectroscopy. The Ion Guide Isotope Separator on Line （IGISOL）at the University of Jyv（ae）skyl（ae）, Finland is presented in detail with experimental results on the decay of neutron-rich silver isotopes produced in proton induced symmetric fission.     

利用深部非弹反应对Z≈56,N≈80区核激发态的探索性研究

通过410MeV ⁸²Se轰击天然Ba靶引起的深部非弹反应布居产生了类弹和类靶余核的激发态,利用在束γ谱学方法测量了它们的退激γ.通过γ–γ符合测量估计了类弹、类靶余核激发态的产生截面,在多个类靶余核中观测到了新γ跃迁,并建立了¹³⁶Ba的新能级纲图,说明利用深部非弹反应研究Z≈56,N≈80区高自旋态是有效、可行的.     

丰中子核8He在Si靶上的反应总截面的测量

利用HIRFL 50MeV/u ¹³C束流在Be靶上碎裂,RIBLL选择出丰中子放射性次级束流⁸He,实验测量了25—40MeV/u ⁸He在²⁸Si靶上的反应总截面.采用双参数HO密度分布形式,通过微观Glauber模型拟合⁸He实验数据,发现⁸He具有扩展的中子密度分布.实验结果与Warner反应总截面实验和Alkhazov弹性散射实验结果较好地符合.     

丰中子核6He在28Si靶上的反应总截面测量

实验测量了20—40MeV u的轻丰中子核6He在Si靶上的反应总截面,并且结合6He的高能实验数据,采用双参数HO密度分布形式用Glauber模型计算得到较好的拟合.与Warner的实验数据比较,反应总截面数据系统性好,并与能量有明显的依赖关系. Total reaction cross section (σt) was measured for neuton rich nuclei 6He on 28Si target from about 20 to 40 MeV/u and compared with Warner s experimental data. It is found that the total cross section of 6He on 28Si depends on the energy and it can be fitted well by Glauber model using two term HO density distribution from high energy data of 6He.     

利用反应时间分析多核子转移反应中丰中子核的产生机制

在改进的量子分子动力学(ImQMD)模型框架下,研究了136 Xe+198 Pt体系的多核子转移反应过程.给出了不同弹靶接触时间下二分裂碎片的总动能-质量分布,发现准弹性碰撞、深度非弹性碰撞和准裂变反应事件可以采用弹靶接触时间进行粗略的划分.分析了不同弹靶接触时间下类靶碎片的双微分截面分布以及Ba同位素的产生截面分布,...     

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.     

幻数和幻数的最新科研成果简介

 自从德国核物理学家迈耶用轨道和自旋相互作用来解释原子核的结构,并建立了“壳层模型”,由此而获得１９６３年诺贝尔奖后,物理学界一直认为,幻数是固定不变的。而近日,日本科学家发现了新的幻数,说明幻数不是固定不变的。本文仅就这一问题简介如下： 一、什么是幻数 众所周知,一切物质都是由分子构成;分子又是由原子组成;原子都是由带正电的原子核和带负电的电子组成;原子核是由带正电的质子和不带电的中子组成。不同元素的原子,其原子核质量和原子核中质子、中子的多少是不同的。在质子数、中子数是某个特定数值或两者均为这一数值时,原子核的稳定性就比平均值大。这些数值被称为“幻数”。     

Relativistic Hypernuclei: Old Problems and New Prospects

The first experiments with relativistic hypernuclei (Bowen; Khorozov and Lukstins) were done many years ago. They demonstrated not only that such extremely difficult experiments are manageable but also their great advantage, a possibility of observing and studying independently the production and weak decay of hypernuclei: the points of the production and decay of relativistic hypernuclei are separated by tens of centimeters instead of some microns in classical experiments. At the same time these first experiments revealed a huge problem with selection of the proper trigger.Recently we proposed to explore a unique feature of the ⁹Be nucleus: after removing a neutron from its ground state several groups of alpha-particles appear from different excited states of a residual nucleus ⁸Be. Detection of the correlated pair of -particles produced in a vacuum volume at a distance of some 40 cm from target is an unambiguous signal of nonmesonic decay of hypernucleus ¹⁰ Be(++n+n) or ¹⁰ Be(++n+p). In this particular case it is possible to take exclusive decay rates (on different excited states of ⁸Be^*). This open a way for a phenomenological analysis of matrix elements of the four-baryon weak interaction.The experiment is approved for new accelerator Nuclotron at JINR, Dubna.     

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.     

Physics prospects at J-PARC

We have held an inauguration ceremony of the Japan Proton Accelerator Research Complex (J-PARC) 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.     

Study of excited nucleon states at EBAC: status and plans

We present an overview of a research program for the excited nucleon states in Excited Baryon Analysis Center (EBAC) at Jefferson Lab. Current status of our analysis of the meson production reactions based on the unitary dynamical coupled-channels model is summarized, and the N~* pole positions extracted from the constructed scattering amplitudes are presented. Our plans for future developments are also discussed.     

Study of excited nucleon states at EBAC: status and plans

We present an overview of a research program for the excited nucleon states in Excited Baryon Analysis Center （EBAC） at Jefferson Lab. Current status of our analysis of the meson production reactions based on the unitary dynamical coupled-channels model is summarized, and the N＊ pole positions extracted from the constructed scattering amplitudes are presented. Our plans for future developments are also discussed.     

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.     

兰州冷却储存环上可开展的强子物理研究

介绍了当前强子物理的研究现状和兰州冷却储存环的能量特点,以及国内强子物理专家的分析和建议。在兰州冷却储存环上,可利用中能轻离子束核反应产生强子激发态研究强子内部夸克态的结构和性质、强子性质随核环境的变化和手征对称破缺与部分恢复。尤其是通过兰州冷却储存环上限能区附近的P＋P反应,研究奇异夸克的不对称性和形状因子,寻找超子激发态和pentaquark的实验证据,发现双重子态的实验事例。 According to both the development on badrons physics and the aspect of Lanzhou cooling storage ring （CSR） and based on the analysis and propositions given by experts in China, we propose some hadrons physics program at CSR. The hadron spectroscopy produced in light nucleus collisions at CSR used to probe the quark and gluon structure of hadrons, to study the modification of the hadron properties in nuclear matter and to investigate the spontaneous breaking of the chiral symmetry and its partial restoration. Especially, the proton-proton collisions at beam energies per proton below 2.8 GeV at CSR should be used to measure the strangeness asymmetry and strange form lector, to probe the existence of hyperon and pentaquarks and to find the evidence for the existence of dibaryon.     

Hypernuclear physics for neutron stars

The role of hypernuclear physics for the physics of neutron stars is delineated. Hypernuclear potentials in dense matter control the hyperon composition of dense neutron star matter. The three-body interactions of nucleons and hyperons determine the stiffness of the neutron star equation of state and thereby the maximum neutron star mass. Two-body hyperon–nucleon and hyperon–hyperon interactions give rise to hyperon pairing which exponentially suppresses cooling of neutron stars via the direct hyperon URCA processes. Nonmesonic weak reactions with hyperons in dense neutron star matter govern the gravitational wave emissions due to the r-mode instability of rotating neutron stars.     

The Role of One Single Lambda Hyperon on Binding Energy Difference of Hypernuclear Mirror Pair

Investigation on isospin symmetry in light Lambda hypernuclei is one of the most important issues in hypernuclear physics. In order to know the influences introduced by a single Lambda hyperon, we study the binding energy difference of mirror hypernuclear pair with mass A=16, 18, 28, 40, and 42 using a time-odd triaxial relativistic mean field theory. Effects as the spin-orbit interaction, the time-odd component of vector fields, the core polarization, the proton-neutron mass difference, and the center-of-mass energy correction are self-consistently considered. Compared to the reported results of ordinary nuclei, the binding energy difference of mirror hypernuclei shows trivial change. With core polarization modified by an impurity hyperon, the isospin nonconserving effect between proton and neutron is hardly reduced for nuclei in study.     

Probing new physics in B → J/ψπ~0 decay

We calculate the branching ratio of B → J/ψπ0 with a mixed formalism that combines the QCDimproved factorization and the perturbative QCD approaches.The result is consistent with experimental data.The quite small penguin contribution in B → J/ψπ0 decay can be calculated with this method.We suggest two methods to extract the weak phase β.One is through the dependence of the mixing induced CP asymmetry SJ/ψπ0 on the weak phase β,the other is from the relation of the total asymmetry ACP with the weak phase β.Our results show that the deviation ΔSJ/ψπ0 of the mixing induced CP asymmetry from sin（-2β） is of O（10-3） and has much less uncertainty.The above O（10-3） deviation can provide a good reference for identifying new physics.