Highly correlated vacuum and the production of exotic clusters

We discuss the possibility of producing a new kind of nuclear system by putting a few antibaryons inside ordinary nuclei. The structure of such systems is calculated within the relativistic mean-field model assuming that the nucleon and antinucleon potentials are related by the G-parity transformation. The presence of antinucleons leads to decreasing vector potential and increasing scalar potential for the nucleons. As a result, a strongly bound system of high density is formed. Due to the significant reduction of the available phase space the annihilation probability might be strongly suppressed in such systems.     

Investigation of electron localization in harmonic emission from asymmetric molecular ion

We theoretically investigate the electron localization around two nuclei in harmonic emission from asymmetric molecular ion. The results show that the ionization process of electron localized around one nucleus competes with its transfer process to the other nucleus. By increasing the initial vibrational level, more electrons localized around the nucleus D+tend to transfer to the nucleus He2+so that the ionizations of electrons localized around the nucleus He2+increase. In this case, the difference in harmonic efficiency between He H2+and He D2+decreases while the difference in harmonic spectral structure increases. The evident minimum can be observed in the harmonic spectrum of He H2+compared with that in the spectral structure of He D2+, which is due to the strong interference of multiple recombination channels originating from two nuclei. Time-dependent nuclear probability density, electron-nuclear probability density, double-well model, and time-frequency maps are presented to explain the underlying mechanisms.     

Fusion suppression and sub-barrier breakup of weakly bound nuclei

The mechanism for the large suppression of complete fusion in the 9Be+208Pb reaction has been investigated through measurement of sub-barrier breakup of 9Be. Excluding breakup through the 8Be ground state, whose lifetime is too long, a prompt breakup component remains, having sufficient probability to explain the observed suppression of complete fusion. This appears to be associated with interactions at the nuclear surface. The fusion suppression is predicted to be almost proportional to the charge of the target nucleus, making it most significant in reactions with heavy nuclei.     

New Exact Solution of Dirac-Coulomb Equation with Exact Boundary Condition

It usually writes the boundary condition of the wave equation in the Coulomb field as a rough form without considering the size of the atomic nucleus. The rough expression brings on that the solutions of the Klein-Gordon equation and the Dirac equation with the Coulomb potential are divergent at the origin of the coordinates, also the virtual energies, when the nuclear charges number Z>137, meaning the original solutions do not satisfy the conditions for determining solution. Any divergences of the wave functions also imply that the probability density of the meson or the electron would rapidly increase when they are closing to the atomic nucleus. What it predicts is not a truth that the atom in ground state would rapidly collapse to the neutron-like. We consider that the atomic nucleus has definite radius and write the exact boundary condition for the hydrogen and hydrogen-like atom, then newly solve the radial Dirac-Coulomb equation and obtain a new exact solution without any mathematical and physical difficulties. Unexpectedly, the K value constructed by Dirac is naturally written in the barrier width or the equivalent radius of the atomic nucleus in solving the Dirac equation with the exact boundary condition, and it is independent of the quantum energy. Without any divergent wave function and the virtual energies, we obtain a new formula of the energy levels that is different from the Dirac formula of the energy levels in the Coulomb field.     

Nuclear absorption of stopped antiprotons: Multipion-nucleus interactions

It is proposed to use the nuclear absorption of stopped antiprotons to study the interaction arising when several pions enter a nucleus simultaneously. A model is constructed for the incoherent multipion-nucleus interaction, when the annihilation pions interact with the nucleus independently of each other. Energy spectra and the multiplicities of secondary particles generated after the antiproton absorption are compared with the experimental data. Distributions of the number of pions interacting with the nucleus are calculated as well as the distributions of residual nuclei with excitation energy, momentum, angular momentum and isotope yield. It is shown that the effect of the excitation of high-spin isomers must be observed in the antiproton absorption. The example of the two-nucleon absorption of η- and ω-mesons is used to discuss the possibility of investigating interactions of pionic resonances with nuclei during the process of the annihilation of antiprotons.     

Low-energy antiproton annihilation in nuclei

The annihilation of 100 MeV antiprotons in atomic nuclei is studied in the frame of an intranuclear cascade model. It is found that the antiproton is annihilated about 1 fm inside the nucleus on the average. The energy released by the annihilation is carried by an average of 5 pions, which cascade throughout the nucleus. About 5% (10%) of the primordial pions are absorbed by the ⁴⁰Ca (¹⁰⁸Ag) target. The pions transfer around 5̃50 MeV (7̃00 MeV) to the nucleons and eject about one-fifth of the nucleons. The pion and proton cross sections are calculated. In particular, the relative transparency of the nucleus to high-energy pions (and not to pions in the Δ-resonance region) gives rise to a peculiar pion emission pattern. The time evolution of the baryon density and of the spectrum of the participant nucleons is investigated. It turns out that the cascade does not generate high energy density.     

H,He,Kr杂质在过渡金属和贵金属中的行为

本文以胶体模型为基础,利用密度泛函理论,局域密度近似研究了H,He和Kr在过渡金属Ni,Fe,Cr和贵金属Cu中的空位团复合体的电子结构、正电子湮没寿命。结果表明:随着复合体尺寸的增加,杂质的束缚态电子能级变浅,散射态电子在复合体内的平均密度变小,正电子在复合体内的几率增大,正电子湮没寿命增加。 关键词：     

正电子湮没参量及其所反映物质信息的探讨

本根据正电子在凝聚态物质中的湮没机制及捕获模型,讨论了正电子湮没参量——正电子寿命谱和多普勒线形等参量所反映的物质信息,给出了各正电子湮没参量与所反映的物质信息之间的定量关系。分析了在该体系中正电子寿命参量与局域电子密度、多普勒线形参量和角关联参量与电子动量密度分布和费米面之关联。     

Saturation of nuclear partons: Fermi statistics or nuclear opacity?

We derive the two-plateau momentum distribution of final state (FS) quarks produced in deep inelastic scattering (DIS) off nuclei in the saturation regime. The diffractive plateau, which dominates for small p, measures precisely the momentum distribution of quarks in the beam photon; the role of the nucleus is simply to provide an opacity. The plateau for truly inelastic DIS exhibits a substantial nuclear broadening of the FS momentum distribution. We discuss the relationship between the FS quark densities and the properly defined initial state (IS) nuclear quark densities. The Weizsäcker-Williams glue of a nucleus exhibits a substantial nuclear dilution, still soft IS nuclear sea saturates because of the anti-collinear splitting of gluons into sea quarks.     

Complete destruction of heavy nuclei by hadrons and nuclei

The total disintegration is considered of nuclei with atomic weights ～100 and 200 by high energy hadrons and He⁴, C¹² nuclei with a momentum of 4.5 GeV/c per nucleon. It is shown that mainly nucleons are emitted, and there is no residual nucleus the mass of which is comparable to that of the primary nucleus. The probability of total disintegration is considered as a function of projectile energy and mass. The multiplicity, energy and emission angle of particles are considered as well. It is shown that the density of nuclear matter in the overlap zone of colliding nuclei exceeds the usual one by a factor of ～4. A comparison is made with interaction models. A conclusion is drawn of the collective interaction mechanism (perhaps, of the shock wave type) of particle ejection from the target nucleus at the first stage of interaction and of explosive decay of the residual nucleus at the next one.     

Antiprotons for nuclear structure research

The interaction of antiprotons with nuclei is investigated in a model using the free space $\overline{p} N$ T-matrix and nuclear densities from HFB calculations. Elastic scattering and annihilation reactions are used as probes for nuclear sizes of exotic nuclei. The annihilation cross sections are related to the nuclear root-mean-square radii by a scaling law. A more detailed picture is obtained by detecting in coincidence a pion ejected from the annihilation zone.     

Neutron halos in heavy nuclei-relativistic mean field approach

Assuming a simple spherical relativistic mean field model of the nucleus, we estimate the width of the antiproton-neutron annihilation (Γ_n) and the width of antiproton-proton (Γ_p) annihilation, in an antiprotonic atom system. This allows us to determine the halo factor f, which is then discussed in the context of experimental data obtained in measurements recently done on LEAR utility at CERN. Another quantity which characterizes the deviation of the average nuclear densities ratio from the corresponding ratio of the homogeneous densities is introduced too. It was shown that it is also a good indicator of the neutron halo. The results are compared to experimental data as well as to the data of the simple liquid droplet model of the nuclear densities. The single particle structure of the nuclear density tail is discussed also.     

Nuclear Energy Density Functional and the Nuclear α Decay

We study the nuclear α decay of heavy nuclei using nuclear energy density functionals. This allows us to write the structure of the nuclear α potential inside the parent nucleus in terms of the proton and neutron density profile of the daughter nucleus with ad hoc parameters which control the strength of the potential. We adopt the Skyrme force model, Gogny force model, and relativistic mean field model to get the nucleon density profiles inside heavy nuclei. This approach is then applied to get predictions for unknown decay halflives of heavy nuclei and our results are compared with other model predictions.     

Double-strangeness production with antiprotons

The production of double-strangeness by antiproton annihilation in nuclei will be an exciting way to investigate whether the formation of deeply bound antikaonic nuclear clusters occurs. The existence of deeply bound antikaonic nuclear clusters is a lively debated problem in hadron physics today, which can be solved only experimentally. At CERN with the Antiproton Decelerator (AD) and in future with the new FAIR facility at Darmstadt low energy antiprotons are available to perform this type of experiments. The use of antiprotons for the production of double-strangeness was recently discussed by Weise and Kienle and indeed, it would be very challenging to produce and study such “double-strange nuclei” in the view of the prediction of Akaishi and Yamazaki that double-antikaon bound nuclear systems with strangeness (S?=???2) will be formed with binding energies up to 200–300 MeV. Such binding energies might result in an increase of the average density to more than 3 times the average nuclear density. If such dense systems are created, conditions in the phase diagram might be reached where phase transition to kaon condensation or colour superconductivity will occur at low temperature.     

稳定和不稳定核巨共振性质的相对论研究

在相对论平均场的基态上自洽的相对论无规位相近似(RRPA)理论框架下,研究稳定核和不稳定核的巨共振性质.研究了稳定核²⁰⁸Pb,¹⁴⁴Sm,¹¹⁶Sn,⁹⁰Zr,⁴⁰Ca,¹⁶O和不稳定核Ca同位素链同位旋标量和同位旋矢量集体巨共振激发,并讨论了Dirac海负能核子态和矢量介子空间分量对核的巨共振性质的影响.研究的结果表明,Dirac海负能核子态和矢量介子空间分量对同位旋标量激发有贡献,特别是对重核,而对轻核它的贡献减弱,对于同位旋矢量激发的贡献可忽略.几组常用的相对论平均场非线性模型参量,不仅能成功的描述有限核的基态性质,也能很好地描述核的巨共振激发.对于N/Z极端情况下,同位旋矢量巨偶极激发模式存在低能集体激发,它是由于费密面附近弱束缚核子的激发和同位旋混杂效应 关键词： 相对论无规位相近似 核巨共振     

High-density QCD and saturation of nuclear partons

We review the recent finding of the two-plateau momentum distribution of sea quarks in deep inelastic scattering off nuclei in the saturation regime. The diffractive plateau which dominates for small p measures precisely the momentum distribution of quarks in the beam photon, the rôle of the nucleus is simply to provide an opacity. The plateau for truly inelastic DIS exhibits a substantial nuclear broadening of the momentum distribution. Despite this nuclear broadening, the observed final-state and initial-state sea quark densities do coincide exactly. We emphasize how the saturated sea is generated from the nuclear-diluted Weizsäcker-Williams because of the anti-collinear splitting of gluons into sea quarks.Received: 30 September 2002, Published online: 22 October 2003PACS: 11.80.La Multiple scattering - 13.87.-a Jets in large-Q ² scattering - 24.85. + p Quarks, gluons, and QCD in nuclei and nuclear processe     

用正电子湮没技术研究USY沸石的“二次孔”结构

测量了NaY及USY沸石的正电子寿命谱．得到NaY沸石有四个寿命分量：两个短寿命分量和两个长寿命分量．两个长寿命分量中，τ₃，τ₄分别是o-Ps在β笼和超笼中的湮没．USY沸石有五个寿命分量：两个短寿命分量和三个长寿命分量，三个长寿命分量中，τ₃为o-Ps在笼中的湮没，τ₄，τ₅分别为o-Ps在“二次微孔”和“二次中孔”中的湮没．与NaY沸石相比，在真空中，USY的τ₄增加到 关键词：     

Focusing of high-energy particles in the electrostatic field of a homogeneously charged sphere and the effective momentum approximation

The impact of the strongly attractive electromagnetic field of heavy nuclei on electrons in quasi-elastic (e, e') scattering is often accounted for by the effective momentum approximation. This method is a plane wave Born approximation which takes the twofold effect of the attractive nucleus on initial- and final-state electrons into account, namely the modification of the electron momentum in the vicinity of the nucleus, and the focusing of electrons towards the nuclear region leading to an enhancement of the corresponding wave function amplitudes. The focusing effect due to the attractive Coulomb field of a homogeneously charged sphere on a classical ensemble of charged particles incident on the field is calculated in the highly relativistic limit and compared to results obtained from exact solutions of the Dirac equation. The result is relevant for the theoretical foundation of the effective momentum approximation and describes the high-energy behavior of the amplitude of continuum Dirac waves in the potential of a homogeneously charged sphere. Our findings indicate that the effective momentum approximation is a useful approximation for the calculation of Coulomb corrections in (e, e') scattering off heavy nuclei for sufficiently high electron energies and momentum transfer.     

Nuclear density functional theory

An understanding of atomic nuclei is crucial for a complete nuclear theory, for the nuclear astrophysics, for performing new experimental tasks, and for various other applications. Within a density functional theory, the total binding energy of the nucleus is given by a functional of the nuclear density matrices and their derivatives. The variation of the energy density functional with respect to particle and pairing densities leads to the Hartree-Fock-Bogoliubov equations. The “Universal Nuclear Energy Density Functional” (UNEDF) SciDAC project to develop and optimize the energy density functional for atomic nuclei using state-of-the-art computational infrastructure, is briefly described. The ultimate goal is to replace current phenomenological models of the nucleus with a well-founded microscopic theory with minimal uncertainties, capable of describing nuclear data and extrapolating to unknown regions.     

The determination of the Coulomb energy of a nuclear system at the scission point upon fission

The dependence of the Coulomb energy of deformed nuclei on the shape and the nuclear matter density distribution is considered. For an ellipsoidal shape of the nucleus and a homogeneous distribution of nuclear matter, the result was obtained in a simple analytical form convenient for further use. Separate attention was paid to the consideration of a Fermi-like distribution of nuclear matter using different shapes of the nucleus that reflect several different kinds of collective motions. After these considerations, the dependence of the Coulomb energy of the fission products at the scission point of binary fission reactions on configurations, shapes and nuclear matter distributions was investigated. Calculation of the dependence of the shape of the nuclei deformation parameters at the scission point from their total kinetic energies was made in detail. Finally, the influence of shell effects on the mass yield of fission products is discussed. The text was submitted by the authors in English.