Nuclear symmetry energy from QCD sum rules

We calculated the nucleon self-energies in iso-spin asymmetric nuclear matter and obtained the nuclear symmetry energy by taking difference of these of neutron and proton. We find that the scalar （vector） self-energy part gives a negative （positive） contribution to the nuclear symmetry energy, consistent with the result from relativistic mean-field theories. Also, we found exact four-quark operator product expansion for nucleon sum rule. Among them, twist-4 matrix elements which can be extracted from deep inelastic scattering experiment constitute an essential part in the origin of the nuclear symmetry energy from QCD. Our result also extends early success of QCD sum rule in the symmetric nuclear matter to the asymmetric nuclear matter.     

Investigation on symmetry and characteristic properties of the fragmenting source in heavy-ion reactions through reconstructed primary isotope yields

In this report, a kinematical focusing technique will be briefly described, and using this technique, the primary hot isotope yields from the multiplicities of evaporated light particles, associated with isotopically identified intermediate mass fragments, are reconstructed. Symmetry energy and characteristic properties of the fragmenting source at the time of the intermediate mass fragment formation are extracted from these reconstructed primary isotope yields using a self-consistent manner. The extracted density-dependent symmetry energy is further compared with those experimentally extracted from other heavy-ion reactions in literatures. A direct connection between the freeze-out concept and transport model sim-ulations in a multifragmenting regime of heavy-ion colli-sions is also demonstrated quantitatively in the present work.     

Probing the density dependence of the symmetry energy with central heavy ion collisions

An improved isospin dependent Boltzmann Langevin model, in which the inelastic channels and momentum dependent interactions are incorporated, is used to investigate the high-density behavior of nuclear symmetry energy. By taking several forms of nuclear symmetry energy, we calculate the time evolutions of neutron over proton ratio, π ultiplicity and π-/π＋ ratio, and the kinetic energy and transverse momentum spectra of π-/π＋ ratio in the heavy ion collisions at 400A MeV. It is found that the neutron over proton ratio and π-/π＋ ratio are very sensitive to the nuclear symmetry energy, and the π- is more sensitive to the nuclear symmetry energy than the π＋. A supersoft symmetry energy results in a larger π-/π＋ ratio.     

Shear viscosity of nuclear matter

This paper reports my recent studyIll on the shear viscosity of neutron-rich nuclear matter from a relaxation time approach. An isospin- and momentum-dependent interaction is used in the study. Dependence of density, temperature, and isospin asymmetry of nuclear matter on its shear viscosity have been discussed. Similar to the symmetry energy, the symmetry shear viscosity is defined and its density and temperature dependence are studied.     

IMF production and symmetry energy in heavy ion collisions near Fermi energy

The symmetry energy at the time of the production of intermediate mass fragments （IMFs） is studied using experimentally observed IMF multiplicities combined with quantum statistical model calculations （QSM of Hahn and Stfcker）. The ratios of difference in chemical potentials between neutrons and protons relative to the temperature,（μt- μp） /T, and the double ratio temperature, T, were extracted experimentally in the reactions of 64＇7~Zn, 64Ni＋58＇64Ni, 112＇124Sn, 197Au, 232Th at 40A MeV. The extracted （μt- μp） / T scales linearly with Jwv, where fi~v is the asymmetry parameter, （N-Z）/A, of the emitting source and （μt- μp） / T = （11.1 ＋ 1.4）rNN -- 0.21 was derived. The experimentally extracted （μt-μp）/T and the double ratio temperatures are compared with those from the QSM calculations. The temperatures, T, and densities, p, extracted from the （μn - μp） / T values agreed with those from the double ratio thermometer which used the yield ratios of d, t, h and a particles. However the two analyses of the differential chemical potential analysis and the initial temperature analysis end up almost identical relation between T and p. T=5.25±0.75 MeV is evaluated from the （μn -μp） / T analysis, but no density determination was possible. From the extracted T value, the symmetry energy coefficient Esym=14.6±3.5 MeV is determined for the emitting source of T=5.25±0.75 MeV.     

Basic quantities of the equation of state in isospin asymmetric nuclear matter

Based on the Hugenholtz-Van Hove theorem,six basic quantities of the EoS in isospin asymmetric nuclear matter are expressed in terms of the nucleon kinetic energy t(k),the isospin symmetric and asymmetric parts of the single-nucleon potentials U0(ρ,k)and Usym,i(ρ,k).The six basic quantities include the quadratic symmetry energy Esym,2(ρ),the quartic symmetry energy Esym,4(ρ),their corresponding density slopes L2(ρ)and L4(ρ),and the incompressibility coefficients K2(ρ)and K4(ρ).By using four types of well-known effective nucleon-nucleon interaction models,namely the BGBD,MDI,Skyrme,and Gogny forces,the density-and isospin-dependent proper-ties of these basic quantities are systematically calculated and their values at the saturation density ρ0 are explicitly given.The contributions to these quantities from t(k),U0(ρ,k),and Usym,i(ρ,k)are also analyzed at the normal nuclear density ρ0.It is clearly shown that the first-order asymmetric term U/sym,1(ρ,k)(also known as the symmetry potential in the Lane potential)plays a vital role in deter-mining the density dependence of the quadratic symmetry energy Esym,2(ρ).It is also shown that the contributions from the high-order asymmetric parts of the single-nucleon potentials(Usym,i(ρ,k)with i＞1)cannot be neglected in the calculations of the other five basic quantities.Moreover,by analyzing the properties of asymmetric nuclear matter at the exact saturation density ρsat(δ),the corresponding quadratic incompressibility coefficient is found to have a simple empirical relation Ksat,2 = K2(ρ0)-4.14L2(ρ0).     

Isospin dependence of nucleon effective masses in neutron-rich matter

In this talk,we first briefly review the isospin dependence of the total nucleon effective mass M Jinferred from analyzing nucleon-nucleus scattering data within an isospin-dependent non-relativistic optical potential model,and the isospin dependence of the nucleon E-mass M;E J obtained from applying the Migdal–Luttinger theorem to a phenomenological single-nucleon momentum distribution in nuclei constrained by recent electron-nucleus scatteringexperiments.Combining information about the isospin dependence of both the nucleon total effective mass and E-mass,we then infer the isospin dependence of nucleon k-mass using the well-known relation M_J~*=M_ J~(*1E).Implications of the results on the nucleon mean free path in neutron-rich matter are discussed.     

Investigating nuclear dissipation properties at large deformations via excitation energy at scission

Using the stochastic Langevin model coupled with a statistical decay model, we study nuclear dissipation properties at large deformations with excitation energy at scission (E*sc) measured in experiments. It is found that the postsaddle dissipation strength required to fit E*sc data is 12 ×1021 s-1 for 254;256Fm and 6 ×1021 s-1 for 189Au, which has a smaller postsaddle deformation than the former heavy nucleus, showing a rise of nuclear dissipation strength with increasing deformation.     

Constraints on symmetry energy and n/p effective mass splitting with improved quantum molecular dynamics model

A new version of improved quantum molecular dynamics model that includes standard Skyrme interactions has been developed. Based on the new code, four commonly used parameter sets, SLy4, Ski2, SkM＊ and Gs are adopted in the improved quantum molecular dynamics model and the isospin sensitive observables, namely isospin transport ratios, single and double ratios of the yields of neutrons and protons are investigated. The isospin transport ratios are strongly sensitive to the slope of symmetry energy, and are not very sensitive to the nucleon effective mass splitting. On the other hand, the high energy neutrons and protons yields ratios from reactions at different incident energies provide a good observable to the momentum dependence of nucleon effective mass splitting. By comparing our calculations with the data, we find that the constrained L value （the slope of density dependence of symmetry energy） is about -46 MeV when the Skyrme type interaction is considered in transport models, and the isospin diffusion data prefer to mn 〉 mp, but it is not a strong constraint with deep Z2 minimum.     

Spallation reaction and the probe of nuclear dissipation with excitation energy at scission

We study in the framework of the Langevin model the influence of initial excitation energy （E＊） of Hg compound nuclei （CNs） on the sensitivity of the excitation energy at scission （E~c） to the nuclear friction strength （fl）. It is shown that the sensitivity is enhanced substantially with increasing E＊. Moreover, we find that the significant sensitivity of E＊c to fl at high E＊ is little affected by a marked difference in the neutron-to-proton ratio ofa CN and in its size and fissility. Our findings suggest that, on the experimental side, a measurement of E~c in energetic proton-induced spallation reactions can provide not only a sensitive but also a robust probe of nuclear dissipation in fission of highly excited nuclei. Further development of a suitable approach to spallation reaction is discussed.     

Critical phenomena of a nuclear system in alternative ZM models

Alternative versions of the ZM model are xtended to asymmetric nuclear matter by including ρ meson degree of freedom in the Lagrangian ,The extended models are then used to study the thermodynamical properties of asymmetric nuclear matter at finite temperature.The critical temperature for a liquid-gas phase transition in nuclear matter and its dependence on asymmetry parameter are calculated,The liniting temperature Tlim,which reflects Coulomb instability of hot nuclei,is studied.The calculated results are compared with that given by the original ZM model.     

Impact of initial fluctuations and nuclear deformations in isobar collisions

Relativistic isobar(9644Ru+9644Ru and 9640Zr+9640Zr)collisions have revealed intricate differences in their nuclear size and shape,inspiring unconventional studies of nuclear structure using relativistic heavy ion collisions.In this study,we investigate the relative differences in the mean multiplicity(R)and the second-(Rε2)and third-order eccentricity(Rε3)between isobar collisions using initial state Glauber models.It is found that initial fluctuations and nuclear deformations have negligible effects on Rin most central collisions,while both are important for the Rε2and Rε3,the degree of which is sensitive to the underlying nucleonic or sub-nucleonic degree of freedom.These features,compared to real data,may probe the particle production mechanism and the physics underlying nuclear structure.     

相对论重离子核反应产生的中子能量和通量的固体径迹测定

在苏联杜布纳联合核子研究所同步稳相加速器上用CR-39探测器测量了44GeV ~(12)C+Cu(厚靶)核反应产生的中子能量和通量。测量表明.这一核反应释放的中子的平均能量为15.8±2.8MeV,当入射重离子数目为6×10~(11)时,与~(12)C束成～70°方向,距靶～60cm处的中子积分通量为(4.5±0.3)×10~9cm~2。这一方法可用来测量相对论重离子核反应释放的中子的角分布和每个入射重离子或每次核反应可产生的中子平均数目。     

Role of nuclear energy in environment, economy, and energy issues of the 21st century – Growing energy demand in Asia and role of nuclear

The economic growth of recent Asia is rapid, and the GDP and the energy consumption growth rate are about 8–10% in China and India. The energy consumption forecast of Asia in this century was estimated based on the GDP growth rate by Goldman Sachs. As a result, about twice in India and Association of South East Asian Nations (ASEAN) and about 1.5 times in China of SRES B (Special Report on Emission Scenarios) are forecasted. The simulation was done by Grape Code to analyze the impact of energy increase in Asia. As for the nuclear plant in Asia, it is expected 1500 GWe in 2050 and 2000 GWe in 2100, in the case of the environmental constrain. To achieve this nuclear utilization, there are two important aspects, technically and institutionally.

A. Development of the CANDLE core and/or the Breed and Burn core.

B. The establishment of the stable nuclear fuel supply system like “Asian nuclear fuel supply organization”.

Asymmetric neutron stars in the presence of vacuum fluctuations

The asymmetric neutron stars are investigated in a relativistic effective model with vacuum fluctuations(VF) taken into account. Due to the VF effects, various properties of the neutron matter become ‘softened' comparing to that obtained in the FSUGold model, and the maximum mass of the enpelT neutron stars is reduced from1.71 M to 1:35M.     

Density isomer of nuclear matter in an equivalent mass approach

The equation of state of symmetric nuclear matter is studied with an equivalent mass model. The equivalent mass of a nucleon has been expanded to order 4 in density. We first determine the first-order expansion coefficient in the quantum hadron dynamics, then calculate the coefficients of the second to fourth order for the given binding energy and incompressibility at the normal nuclear saturation density. It is found that there appears a density isomeric state if the incompressibility is smaller than a critical value. The model dependence of the conclusion has also been checked by varying the first-order coefficient.     

Production of dileptons with intermediate masses in an expanding quark-gluon matter

1 INTRODUCTIONIn recent years, both the HELlOS-3 and NA38/NA50 Collaborations have observedenhancement of the dilepton yield in the IMR (between aam and about 2.5 GeV) incentral S W and S U collisions as compared to that in proton-induced reactions. Preliminary data from the NA50 Collaboration also show significant enhancement, i.e., incentral Ph Pb .ollisions.111 There are at least three possible sources for this enhancement: the contribution from initial charmed hadronic decays…     

Nuclear power technologies at the stage of sustainable nuclear power development

It is not simple to solve the problem of competitiveness of nuclear power technologies in evolutionary upgrading the conventional nuclear power plants (NPP) such as light water reactors (LWR), which requires high expenditure for safety. Moreover, the existing LWRs cannot provide nuclear power (NP) for a long time (hundreds of years) because the efficiency of use of natural uranium is low and closing the nuclear fuel cycle (NFC) for those reactors is not expedient.The highlighted problem can be solved in the way of use of innovative nuclear power technology in which natural uranium power potential is used effectively and the intrinsic conflict between economic and safety requirements has been essentially mitigated.The technology that is most available and practically demonstrated is the use of reactors SVBR-100 — small power multi-purpose modular fast reactors (100 MWe) cooled by lead-bismuth coolant (LBC). This technology has been mastered for nuclear submarines’ reactors in Russia.High technical and economical parameters of the NPP based on RF SVBR-100 are determined from the fact that the potential energy stored in LBC per a volume unit is the lowest.The compactness of the reactor facility SVBR-100 that results from integral arrangement of the primary circuit equipment allows realizing renovation of power-units LWRs, the vessels’ lifetime of which has been expired. So due to this fact, high economical efficiency can be obtained.The paper also validates the economical advantage of launching the uranium-fueled fast reactors with further changeover to the closed NFC with use of plutonium extracted from the own spent nuclear fuel in comparison with launching fast reactors directly with on uranium-plutonium fuel on the basis of plutonium extraction from spent nuclear fuel of LWRs.     

Particulate matter in exhaled breath condensate: A promising indicator of environmental conditions

Assessing the retention of aerosol particles in the human lung, one of the most important pathways of absorption, is a demanding issue. At present, there is no direct biomarker of exposure for the respiratory system. The collection of exhaled breath condensate (EBC) constitutes a new non-invasive method for sampling from the lung. However, the heterogeneity of the sample due to particulate matter suspended in the condensed phase may influence the quality of analytical results in occupational assessments.The main objective of the study was to confirm the presence of particulate matter in the condensate, to investigate how large the particles in suspension could be and to determine their elemental contents relative to those of EBC matrix.This paper reports on preliminary nuclear microprobe data of particulate matter in EBC. The sizes and the elemental contents of particles suspended in EBC of workers of a lead processing industry and in EBC of non-exposed individuals were inspected. Results demonstrated that EBC of workers contain large aerosol particles, isolated and in agglomerates, contrasting with non-exposed individuals. The particles contained high concentrations of Cl, Ca, Zn and Pb that are elements associated to the production process. These elements were also present in the EBC matrix although in much lower levels, suggesting that a fraction of the inhaled particulate matter was solubilised or their size-ranges were below the nuclear microprobe resolution. Therefore, the morphological characterization of individual particles achieved with nuclear microprobe techniques helped describing EBC constituents in detail, to comprehend their origin and enabled to delineate methodological procedures that can be recommended in occupational assessments. These aspects are critical to the validation of EBC as a biomarker of exposure to metals for the respiratory system.     

Improved nuclear mass formula with an additional term from the Fermi gas model

Nuclear mass is a fundamental property of nuclear physics and a necessary input in nuclear astrophysics.Owing to the com-plexity of atomic nuclei and nonperturbative strong interactions,conventional physical models cannot completely describe nuclear binding energies.In this study,the mass formula was improved by considering an additional term from the Fermi gas model.All nuclear masses in the Atomic Mass Evaluation Database were reproduced with a root-mean-square deviation(RMSD)of～1.86 MeV(1.92 MeV).The new mass formula exhibits good performance in the neutron-rich nuclear region.The RMSD decreases to 0.393 MeV when the ratio of the neutron number to the proton number is ≥1.6.