500 AMeV 56Fe诱发乳胶核反应弹核碎裂研究

通过利用日本放射线医学综合研究所( NIRS ) 重离子医用加速器( HIMAC) 产生的束流照射国产的核-4型原子核乳胶,对500 AMeV 56Fe诱发乳胶核反应粒子产生进行了研究。讨论了500 AMeV 56Fe诱发乳胶核反应弹核碎片的多重数分布,并与其他结果进行了比较。结果表明,弹核碎片平均多重数随靶核质量的增加而增加,与入射能量无关。A stack of domestic N-4 nuclear emulsion was exposed to 56Fe ions at 500 AMeV at the HIMAC of NIRS. Particle production was investigated in 56Fe-Em interactions. The multiplicity distribution of projectile fragments was given in this paper and compared with other experimental results of heavy ion induced nuclear reactions in nuclear emulsion. The results show that the multiplicity of projectile fragments increase with the increasing target mass, and thereis no dependence on the projectile energy.     

中能核反应中反应平面的确定

介绍并分析了中高能核反应过程中与反应平面相关的可观测量 ,以及确定核反应平面的各种方法 .这些方法包括裂变碎片方位角测量、类弹碎片测量、动量流球形张量、横向动量的方向性、方位角关联和Fourier谐波分析等 . Observables that related to the nuclear reaction plane in intermediate and relativistic energy heavy ion reactions are discussed. Reaction plane determination for intermediate and relativistic energy heavy ion reactions is presented. The methods include fission fragments measurement, projectile-like fragments measurement, kinetic flow-tensor, transverse momentum directivity, azimuthal correlation, Fourier series and etc.     

6 MeV/u 的19F+27Al 反应碎片的发射机制

重离子核反应中的碎片发射机制是近年来人们十分关注的研究课题。利用ΔE-E 探测器,测量了~6 MeV/u 的19F+27Al 反应中核电荷数Z = 2 ~13 的出射碎片。对产物的能谱、角分布、激发函数及能量自关联函数的分析表明,出射产物主要来自弹靶核深部非弹性碰撞所形成的转动的双核系统。In recent years, extensive studies have been made to understand the fragment emission mechanisms in low energy light heavy-ion reactions. These fragments are found to be emitted from quasielastic/projectile breakup, deep-inelastic and fusion-fission processes. Fragments of Z = 2~13 induced by the collision of 19F+27Al have been measured by ΔE-E telescope. The analysis of the energy spectra, angular distributions, excitation functions and energy auto-correlation functions of these fragments shows that the emission of fragments is coming from a rotational dinuclear system formed in the dissipative collision of the projectile and target nuclei.     

反质子物理

本文介绍反质子与核子和与原子核碰撞后各种物理现象．它与核子的散射获得的位势是吸引势和吸收型,与核的光学势是强吸收到．湮没后产生众多的介子和重子．以及在高能下湮没产生奇特性粒子、带粲的介子、重子．并探索获得混杂子、在核中存在反质子、其它新粒子的可能性． In this paper several physical phenomena of antiproton-nucleon and antiproton-necleus collision are discussed. The potential obtained from p-N scattering is attraction and absorption type. The optical potential of nucleus is strong absorption type. The annihilation happens after pp collision and thenproduces many kinds of meson, hadron, even produce some exotic particle and charmonium at high energy pp anihilation. Posibilities to find hybrids, antiproton and other particles in nucleus are also explored.     

Possible Way to Synthesize Superheavy Element Z=117

Within the framework of the dinuclear system model, the production of superheavy element Z = 117 in possible projectile-target combinations is analysed systematically. The calculated results show that the production cross sections are strongly dependent on the reaction systems. Optimal combinations, corresponding excitation energies and evaporation channels are proposed, such as the isotopes^248.249 Bk in ^48 Ca induced reactions in 3n evaporation channels and the reactions ^45Sc＋246.248Cm in 3n and 4n channels, and the system ^51 V＋ 244pu in 3n channel.     

Production of super-heavy nuclei in cold fusion reactions

A model for cold-fusion reactions related to the synthesis of super-heavy nuclei in collisions of heavy projectile-nuclei with a ²⁰⁸Pb target nucleus is discussed.In the framework of this model,the production of the com-pound nucleus by two paths,the di-nuclear system path and the fusion path,are taken into account simultaneously.The formation of the compound nucleus in the framework of the di-nuclear system is related to the transfer of nucle-ons from the light nucleus to the heavy one.The fusion path is linked to the sequential evolution of the nuclear shape from the system of contacting nuclei to the compound nucleus.It is shown that the compound nucleus is mainly formed by the fusion path in cold-fusion reactions.The landscape of the potential energy related to the fusion path is discussed in detail.This landscape for very heavy nucleus-nucleus systems has an intermediate state,which is linked to the formation of both the compound nucleus and the quasi-fission fragments.The decay of the intermediate state is taken into account in the calculation of the compound nucleus production cross sections and the quasi-fission cross sections.The values of the cold-fusion cross sections obtained in the model agree well with the experimental data.     

Universality test of short range nucleon-nucleon correlations in nuclei with strange and charmed probes

Understanding the EMC effect and its relation to the short-range nucleon-nucleon correlations(SRC)in nuclei is a major challenge for modem nuclear physics.One of the key aspects of the connection between these phenomena is the universality.The universality states that the SRC is responsible for the EMC effect and that the modification of the partonic structure of the SRC is the same in different nuclei.The flavor dependence of the universal-ity is one of the unanswered questions.The investigations conducted to date have demonstrated the existence and universality of the SRC for light u and d quarks.Recently,it was suggested that the universality for heavy flavors can be studied through their deep subthreshold production in yA and eA collisions.In this paper,we discuss an alternative possibility to access the strange and gluon high-A"structure of the SRC and to establish universality for heavy flavors using nuclear semi-inclusive deep inelastic scattering(nSIDIS),which probes different quark flavor combinations depending on the final state hadron.The specific reaction can be"tagged"by observation of a strange or charmed particle registered in coincidence with the scattering lepton.The universality of the SRC can be tested in the kinematic region,i.e.,X>1,where the contribution to the cross section from SRC becomes dominant.Exploring the strangeness,charmonium,and open charm will shed light on the role of quarks and gluons in nuclei,thereby developing an understanding of how nuclei emerge within QCD.     

研究重元素原子谱学性质的可能性

论述了重元素,特别是超重元素原子谱学的重要意义。指出了对这些元素原子谱学进行研究的必要性。探讨了通过核反应产生重元素的几率和产额, 以及可能的收集方法,表明了这可为重元素原子谱学研究提供必要的条件。 同时也简单描述了研究重原子谱学的方法——激光共振电离法。 The importance of the atomic spectroscopy of heavy elements,especially the superheavy elements has been briefly reviewed. It is pointed that studies of the atomic spectroscopy of very heavy elements is necessary from the atomic physics and the identification of new superheavy elements. The production probability and yields of heavy elements in the heavy ion induced reactions were discussed. And the possible collection methods for heavy residue of reactions were also retrospected. Those techniques which have been used in the heavy ion reactions and superheavy element identifications will provide some possible support to the studies of heavy element spectroscopy.     

Strangeness by Thermal Model Simulation at RHIC

The local temperature effect on strangeness enhancement in relativistic heavy ion collisions is discussed in the framework of the thermal model in which the K^＋ /h^＋ ratio becomes smaller with increasing freeze-out temperature. Considering that most strangeness particles of final-state particles are from the kaon meson, the temperature effect may play a role in strangeness production in hot dense matter where a slightly different temperature distribution in different areas could be produced by jet energy loss. This phenomenon is predicted by thermal model calculation at RHIC energy. The /Ф ratio in central Au＋Au collisions at 200GeV from the thermal model depends on the freeze-out temperature obviously when γs is different. It should be one of the reasons why strangeness enhancements of and Ф are different though they include two strange quarks. These results indicate that thermodynamics is an important factor for strangeness production and the strangeness enhancement phenomenon.     

Antiproton production in heavy-ion collisions at subthreshold energies

Within the framework of the Lanzhou quantum molecular dynamics model,the deep subthreshold antiproton production in heavy-ion collisions has been investigated thoroughly.The elastic scattering,annihilation and charge exchange reactions associated with antiproton channels are implemented in the model.The attractive antiproton potential extracted from the G-parity transformation of nucleon selfenergies reduces the threshold energies in meson-baryon and baryon-baryon collisions,and consequently enhances the antiproton yields to some extent.The calculated invariant spectra are consistent with the available experimental data.The primordial antiproton yields increase with the mass number of the colliding system.However,annihilation reactions reduce the antiproton production which becomes independent of the colliding partners.Anti-flow phenomena of antiprotons correlated with the mean field potential and annihilation mechanism is found by comparing them with the proton flows.Possible experiments at the high-intensity heavy-ion accelerator facility(HIAF) in China are discussed.     

Double strangeness production in antiproton annihilation on nuclei

The recent data on double strangeness production after antiproton annihilation on nuclei are analyzed within the conventional picture of the reaction, namely annihilation on a single nucleon, followed by rescattering of the products in the nucleus, assumed to proceed in a hadronic phase. General expressions for single and double strangeness are derived within this picture. The relevant parameters are determined, as far as possible, from the single strangeness production yields and are used to predict double strangeness production yields. The later are compared with experiment and found consistent with the conventional picture. However, the data seem to indicate that the strangeness production in the primordial annihilation is different from what it is in nucleon-antinucleon reactions. An estimate of theΞ production rate is also performed. It is shown that the latter is much less sensitive to the rescattering process than in theΛ production case.     

中能重离子碰撞中K介子产生动力学研究(英文)

基于兰州量子分子动力学(LQMD)模型研究了阈能附近K介子(K0和K+)产生动力学机制。LQMD模型能够较好地描述中能重离子碰撞中K介子产额分布。通过拟合K介子动能谱分布,计算中采用了排斥的K-核子相互作用势。该光学势增强了高动量K介子产生,而降低了K介子总产额。结合实验数据比较,在高密区域给出了较软的对称核物质状态方程。对称能的软硬对K0/K+比值起着重要作用,特别是在阈下区域。而K介子光学势对K0/K+比值激发函数影响不明显。     

Doubly strange hypernuclei at PANDA

The FAIR project aims to investigate several fields of physics: QCD, nuclear structure, astrophysics, atomic physics, plasma physics and their applications. In particular, the high-energy storage ring (HESR) will allow high-precision measurements in the antiproton momentum range from 1.5 to 15?GeV/c. Inside HESR, the PANDA experiment will study the charm and strangeness physics, the form factor in the time-like region and other topics like the crossed-channel Compton scattering. The study of the strangeness will be focused onto the doubly strange systems (hypernuclei and hyperatoms) produced with a new technique starting from the antiproton-nucleus reaction.     

Charge and strangeness transfer in multiparticle production

A simple explicit model for charge production is found to agree well with available data. This model combined with unitarity gives a realistic estimate for the suppression of two-body charge exchange scattering. Similar considerations are applied to strangeness transfer.     

Spectra and multiplicities of n, p, d, t, K, π from antiproton annihilation in Cu and U

Inclusive energy spectra of neutrons, protons, deuterons, tritons, charged kaons and pions following antiproton annihilation at rest in copper and uranium have been measured. The determined multiplicity charged kaons is compared to recent measurements and indicates an enhancement of strangeness production. Ratios of directly emitted neutrons and protons have been determined for copper and uranium to 3.0±0.6 and 3.2±0.5, respectively.     

Sum rules for strangeness exchange reactions with nuclei

Within the framework of a constituent quark model we derive energy-weighted sum rules for strangeness exchange (analog) and spin-strangeness exchange (generalized Gamow-Teller) reactions in the limit of small momentum transfer. The target nucleus is treated as a system of non-communicating 3-quark clusters. We also calculate the branching between the SU(3) octet and decouplet channels and we consider double strangeness exchange reactions.     

Isospin effect in peripheral heavy-ion collisions at Fermi energies

The isospin effect in peripheral heavy-ion collisions was thoroughly investigated within the framework of the Lanzhou quantum molecular dynamics (LQMD) transport model. A coalescence approach was used to recognize the primary fragments formed in nucleus-nucleus collisions. The secondary decay process of these fragments was described using the statistical code GEMINI. The production mechanism and isospin effect of the projectile-like and target-like fragments were analyzed using the combined approach. It was found that the isospin migration from the high-isospin density to the low-density matter occurred in the neutron-rich nuclear reactions, i.e., ⁴⁸Ca+²⁰⁸Pb, ⁸⁶Kr+⁴⁸Ca/²⁰⁸Pb/¹²⁴Sn, ¹³⁶Xe+²⁰⁸Pb, ¹²⁴Sn+¹²⁴Sn, and ¹³⁶Xe+¹³⁶Xe. A hard symmetry energy was available for creating the neutron-rich fragments, particularly in the medium-mass region. The isospin effect of the neutron-to-proton (n/p) ratio of the complex fragments was reduced when the secondary decay process was included. However, a soft symmetry energy enhanced the n/p ratio of the light particles, particularly at kinetic energies greater than 15 MeV/nucleon.     

Measurement of strange-quark contributions to the nucleon's form factors at Q(2) = 0.230 (GeV/c)(2)

We report on a measurement of the parity-violating asymmetry in the scattering of longitudinally polarized electrons on unpolarized protons at a Q2 of 0.230 (GeV/c)(2) and a scattering angle of theta (e) = 30 degrees - 40 degrees. Using a large acceptance fast PbF2 calorimeter with a solid angle of delta omega = 0.62 sr, the A4 experiment is the first parity violation experiment to count individual scattering events. The measured asymmetry is A(phys)=(-5.44+/-0.54(stat)+/-0.26(sys))x10(-6). The standard model expectation assuming no strangeness contributions to the vector form factors is A(0) = (-6.30+/-0.43) x 10(-6). The difference is a direct measurement of the strangeness contribution to the vector form factors of the proton. The extracted value is G(s)(E) + 0.225G(s)(M) = 0.039+/-0.034 or F(s)(1) + 0.130F(s)(2) = 0.032+/-0.028.