Neutral current effects in nuclei

We review the effects of weak neutral currents is nuclei and show how different nuclear processes can sensitively test gauge theory models of the weak and electromagnetic interactions. Our attention is focused principally on neutral current neutrino interactions in nuclei, although one chapter of our review is devoted to weak neutral current effects in polarized electron scattering off nuclei.     

远离β稳定线奇异核性质的理论研究

回顾了对远离β稳定线奇特核性质的理论研究现状，并用相对论平均场理论研究了远离β稳定线奇特核的性质．包括轻核的中子晕和质子晕、远离β稳定线核的壳效应和超重核的性质等.The present situation of studies on exotic nuclei far from the β stable line is simply reviewed and then the relativistic mean field study on these nuclei has been carried out. This includes studies on neutron halos and proton halos in light nuclei, on nuclear shell effects of nuclei far from the stability, and on the properties of superheavy nuclei.     

Nuclear threshold effects and neutron strength functions

The present work is devoted to study of spectroscopic aspects, in terms of neutron strength function, for the threshold effects with non-light nuclei. Relations to the neutron strength functions of the anomal effects observed at threshold of neutron analogue channel, in deuteron stripping reactions on A ≈ 90 mass target nuclei and in nucleon mirror reactions with A ≈ 30 nuclei, are established. It is proved that these threshold effects follow the mass dependance of the neutron strength functions.     

Quark antisymmetrization and deep-inelastic scattering : I. Nuclear quark momentum distributions

We consider the effects of quark antisymmetrization for quark momentum distributions. The simple convolution of nucleon momentum distributions in a nucleus and quark momentum distribution in a nucleon in general does not satisfy the Pauli principle. Antisymmetrizing the product of wave functions in momentum space introduces additional contributions. This paper extends the results for s-wave nuclei to p-wave nuclei, showing that the effects of antisymmetrization in that case are very small. The extension beyond the simple s-wave nuclei is important for the discussion of the role of antisymmetrization in the ratio of deep-inelastic structure functions for nuclei and nucleons.     

Nuclear shadowing and heavy-ion collisions at high energies

Nuclear shadowing effects for quarks and gluons are calculated using information on diffractive deep inelastic scattering on a nucleon. Role of these effects in interactions of hadrons and nuclei with nuclei at high energies is investigated. A decrease in particle densities for heavy-ion collisions in comparison with the Glauber model is predicted and nuclear modification factors are calculated. Distributions of gluons in nuclei are used to predict suppression of heavy quarkonia. The parameter-free calculation of J/ψ in DAu and AuAu collisions is in a good agreement with recent RHIC data. Predictions for heavy quarkonia suppression in heavy-ion collisions at LHC are formulated.     

晕核反应总截面和密度分布

利用考虑了量子修正、库仑修正、核子–核子碰撞同位旋效应和假定有效原子核密度分布后得到的改进的Glauber理论,计算了晕核与稳定核反应总截面,研究了晕核结构对反应总截面的影响.结果发现对于¹¹Be,¹⁴Be和¹¹Li等入射核,必须考虑它们的晕核结构和利用自由的核子–核子碰撞截面才能得到与实验符合的反应截面,并可依据反应总截面来确定晕核的密度分布和均方半径等信息.     

Ground state properties of 16O, 40Ca and 48Ca in a relativistic Hartree theory of nuclear matter

A relativistic field theory model of nuclear matter is solved in a Hartree approximation for finite nuclei. We show that the theory predicts small shell effects for the charge-density distributions in magic nuclei and is in agreement with recent electron scattering data. The effects of the small component of the relativistic wave function are investigated as well as the role of the isospin-dependent force generated by the rho field.     

Effects of rotation of fissioning nuclei in the angular distributions of prompt neutrons and gamma rays originating from the polarized-neutron-induced fission of 233U and 235U nuclei

The results of an experiment devoted to searches for effects of rotation of fissioning nuclei in the angular distributions of prompt neutrons and gamma rays originating from the polarized-neutron-induced fission of ²³³U nuclei are presented. The effects discovered in these angular distributions are opposite in sign to their counterparts in the polarized-neutron-induced fission of ²³⁵U nuclei. This is at odds with data on the relative signs of respective effects in the angular distribution of alpha particles from the ternary fission of the same nuclei and may be indicative of problems in the model currently used to describe the effect in question. The report on which this article is based was presented at the seminar held at the Institute of Theoretical and Experimental Physics and dedicated to the 90th anniversary of the birth of Yu.G. Abov, corresponding member of Russian Academy of Sciences, Editor in Chief of the journal Physics of Atomic Nuclei.     

Parity dependence in heavy-ion scattering

A range is defined for the effects of parity dependence in heavy-ion scattering. This range is shown to be related to the terms of the antisymmetrizer which exchange the largest number of nucleons between both nuclei. A simple formula, derived in the two-center harmonic oscillator model, gives an upper bound for the parity range. A criterion is proposed to determine whether a parity-dependent real part should be used in heavy-ion optical potentials. The most important parity effects should be expected in scattering between nuclei with neighbouring masses.     

Statistical multifragmentation of nuclei: (I). Formulation of the model

A statistical formulation of the multifragmentation of finite nuclei is given. The approach considers the generalization of the liquid-drop model for hot nuclei and allows one to calculate thermodynamic quantities characterizing the nuclear ensemble at the disassembly stage. It is shown how to determine probabilities of definite partitions of finite nuclei and how to apply a Monte Carlo method. The importance of including finite-size effects is shown by comparison with infinite-like systems.     

Scattering of slow neutrons by bound nuclei

TheT-operator for scattering of slow neutrons by a system of bound nuclei is calculated up to quadratic terms in the scattering length. Binding effects as well as effects of multiple scattering have to be included in order to avoid inconsistencies. For the discussion of binding effects one can adopt methods developed by Dietze and Nowak [1] for treating scattering by an elastically bound nucleus. In particular the case of coherent elastic scattering is discussed: we show how the corrections can be expressed in terms of correlation functions and that binding effects are most important for scattering by light nuclei.     

Shape transitions in proton-rich Ho and Tm isotopes

Total Routhian Surface (TRS) calculations have been performed for even-even nuclei along proton drip line to study nuclear ground-state deformations, as well as the odd proton nuclei Ho and Tm isotopes. The drip line nuclei show the expected shape transition with the shell e?ects. Ground-state shape changes from prolate to oblate at 143Ho and 145Tm in these two isotopes, which is due to the γ instability around N =76.     

r-过程路径核β——衰变半衰期的估算

分析了20 < A < 190范围内丰中子核β衰变的实验数据,根据半衰期随质子数、中子数以及衰变能变化所呈现的壳效应和对效应等特点,提出了一种有效估算丰中子核β衰变寿命的公式。新的计算公式形式简单包含了较少的参数、计算量小。用该公式能较为准确地再现丰中子核的β衰变半衰期。用RIKEN最新测量丰中子核半衰期检验了该公式的外推能力,本工作可以为r-过程研究提供可靠的输入数据。Experimental data of the β--decay half-lives for the nuclei with atomic number between 20 and 190 are investigated. We have systematically studied the shell effects and pairing effects on β--decay half-lives versus the decay energy Q and nucleon numbers (Z, N). An empirical formula has been proposed to calculate the β--decay half-lives of neutron-rich nuclei. The empirical formula is simple and has relatively few parameters. Experimental β--decay half-lives of the neutron-rich nuclei are well reproduced by the new formula. In addition, the extrapolating capacity of this formula has been checked with the very recent experimental data from RIKEN. The predicted half-lives for r-process relevant nuclei with the current formula can be served as the reliable input of r-process model calculations.     

Identical bands: two steps forward

The identical bands phenomenon has been studied in detail both experimentally and theoretically. A first step has been done by analysing the distributions of the fractional changes in the dynamical moments of inertia of superdeformed nuclei. They showthat there is a clear excess of identical bands in superdeformed nuclei compared to normally-deformed nuclei at low spin. Furthermore, this difference can be traced back to some special properties of superdeformed bands. The second step consists in the precise lifetime measurements that have been performed in superdeformed nuclei of the rare earth region. The derived quadrupole moments support the picture that alignments and deformation effects cancel in identical bands.     

Nuclear effects in photoproduction and leptoproduction where are they? Are they Negligible?

We discuss nuclear effects in hadronic final states in photoproduction and leptoproduction on nuclei. Whereas the final states in photoproduction and leptoproduction on free nucleons are similar, striking differences are predicted for the case of nuclear targets, the differences being largest in multiplicity correlations. Quantitative predictions are given for the cases of practical interest: photoproduction and muonproduction on emulsion nuclei, and neutrino-production in neon and propanefreon bubble chambers. Neutrino-production on nuclei is emphasized as offering the most direct test of the formation length hypotheses.     

Interaction potential between two 16O nuclei derived from the Skyrme interaction

The energy functional for the Skyrme density-dependent force is used to calculate the interaction potential between two ¹⁶O nuclei. A two-centre harmonic oscillator potential is employed to construct the density and kinetic energy density of the ground state of the combined system and of the separated nuclei. The antisymmetrization effects are investigated. The relative motion of the nuclei is taken approximately into account and the energy dependence of the potential derived from the Skyrme force is presented.     

Mass differences and neutron pairing in Ca,Sn and Pb isotopes

Various estimates of the even-odd effect of the mass shell of atomic nuclei are considered.Based on the experimental mass values of the Ca,Sn,and Pb isotopes,the dependence of the energy gap on the neutron number is traced and the relationship of this characteristic to the properties of external neutron subshells is shown.In nuclei with closed proton shells,effects directly related to neutron pairing and effects of nucleon shells are discussed.     

Pionic field and renormalization of the axial coupling constant in nuclei

The renormalization of the axial coupling constant in nuclei is related by PCAC to the exchange effects in the pionic vertex. Using an optical potential as a model for the pion source function, it is shown that in large nuclei the renormalization arises from the short range correlations. The analogy between this problem and that of an electric dipole inside a dielectric medium is pointed out.