H.323 Based Collaborative Environment for High Energy and Nuclear Physics

After having evaluated various H.323 products for these two years,KEK and Japanese HENP community started to move from ISDN(H.320)-based video conferencing environment into IP(H.323)-based one.Primary reason for the move is to cut down the ever increasing ISDN communication cost.At the same time the H.323 can offer us more powerful collaborative environment.In order to make KEK to be a center for the H.323-based collaborative environment in Japan,Picture Tel‘s LIVE GATEWAY as a H.320/H.323 gateway ,which is essential for the smooth transition,Cisco IP/VA 3510 as a H.323/MCU,and Cisco 2610 as a gatekeeper were installed at KEK in March 2001,And the transition started.In this paper,we‘ll describe the collaborative environment which our users can have,together with its operational results.     

Energy Loss of Fast Quarks in Nuclear Drell-Yan Dimuon Production

The energy loss effect in nuclear matter, which is another nuclear effect apart from the nuclear effects on the patton distribution as in the deep inelastic scattering process, can be measured best by the nuclear dependence of the high energy nuclear Drell-Yan process. By means of the quark energy loss parametrization given in literature and the nuclear patton distribution extracted only with lepton-nucleus deep inelastic scattering experimental data, measured Drell-Yan production cross sections are analysed for 800-GeV protons incident on a variety of nuclear targets from FNAL E866. The average energy loss of quarks are given by fitting the Fe/Be and W/Be Drell-Yan cross section ratios versus the incident patton momentum fraction.     

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.     

Nuclear Masses and Nuclear Shape Transitions in Z=50—71

Some parameters and the β equation of Johansson mass formula were modified.In the fit to the experimental masses and two-neutron separation energies (S_2n) of 640 nuclides in the region of 50≤Z≤71,four free parameters are presented.The root-mean-square deviation of the mass values and S_2n are 0.827MeV and 0.406MeV respectively.The characters of transition from spherical to deformed shapes (N>90) are also reproduced by the curves of S_2n.     

Nuclear β-decay. I

In order to clarify the validity of the theory of nuclearβ-transition a new formulation is given. The nuclear properties are contained in form factors, arising from a decomposition of the matrix element of the V-A operator for nuclear states. The connection of these form factors with nuclear physics matrix elements is tabulated. The total transition amplitude can be written as an integral over these form factors folded with off-shell amplitudes for elastic and inelastic electron scattering on nuclei.     

Nuclear β-decay. II

A general expression for the beta-decay transition amplitude is evaluated, using the decomposition of the nuclear current matrix element into beta-decay form factors as obtained in the previous paper. For the electron radial wave functions the finite nuclear size is taken into account. Formulas for the spectrum shape factor and the polarisation are calculated.     

Influence of Nuclear Deformation on the Potential Energy Surface in Di—Nuclear Model

Influence of the nuclear deformation on the potential energy surface(PES) in a di-nuclear system is studied in details.It is found that the PES shape changes greatly due to the deformation effect.The top point of the PES could be reduced significantly,which implies that the optimum excitation energy could also be reduced greatly and may enhance the fromation probability of the compound nucleus.The dynamical deformaiton as a function of the reaction time in the reaction process is dramatic.The Z/N ratios of fragments tend to follow that of the compound nucleus during the nucleon exchange process,but to fluctuate.     

Nuclear bound states of ω mesons

Models based on chiral SU(3)_l ⊗ SU(3)_r symmetry and vector meson dominance suggest an attractive potential for the ω meson in a nuclear medium. We discuss the feasibility of producing nuclear bound states of ω mesons using (d, ³He) and pion induced reactions on selected nuclear targets.     

Phase Transition of Hot Nuclear Matter

Based on the difference between the Ferm/distributions at zero temperature and at the finite temperature, we introduce the temperature-dependent three-body force (TBF) into the microscopic finite-temperature Brueckner-Hartree-Fock theory (FTBHF). In terms of the meson-exchange current approach, i.e. the one boson exchange (OBE) approximation, the exchange of four important mesons π, ρ, σ and ω axe considered. Using the FTBHF theory including TBF, we describe the critical temperature of the liquid-gas phase transition for symmetric nuclear matter and discuss its change trend with the increasing asymmetry parameter. Compared to the result excluding TBF, the value of the critical temperature turns out to be smaller.     

Limiting Temperatures for Finite Nuclear Systems

The mass dependence of the limiting temperatures for finite nuclear systems is investigated. Our study shows that the different parameter sets of Skyrme interaction and the form of surface tension can influence the limiting temperature obviously.     

xF （or y）-Dependence of Nuclear Absorption and Energy Loss Effects on J/ψ Production

By means of the nuclear parton distribution studied only with lepton deep-inelastic scattering experimental data, the J/ψ ＂normal nuclear absorption＂ and energy loss effects are studied in a GIauber formalism at HERA and RHIC energies. Assuming that the absorption cross section σabs increases with the charmonium-nucleon center of mass energy, the results reveal a significant dependence of the aabs on rapidity g at RHIC energies. The initial-state energy loss effect, which is found important only at HERA energies, is also considered, and its influence should be eliminated when we studied the absorption effect at low collision energies. Finally, we also present the theoretical prediction for LHC.     

Nuclear Physics with 10 PW laser beams at Extreme Light Infrastructure – Nuclear Physics (ELI-NP)

The field of the uncharted territory of high-intensity laser interaction with matter is confronted with new exotic phenomena and, consequently, opens new research perspectives. The intense laser beams interacting with a gas or solid target generate beams of electrons, protons and ions. These beams can induce nuclear reactions. Electrons also generate ions high-energy photons via bremsstrahlung processes which can also induce nuclear reactions. In this context a new research domain began to form in the last decade or so, namely nuclear physics with high power lasers. The observation of high brilliance proton beams of tens of MeV energy from solid targets has stimulated an intense research activity. The laser-driven particle beams have to compete with conventional nuclear accelerator-generated beams. The ultimate goal is aiming at applications of the laser produced beams in research, technology and medicine. The mechanism responsible for ion acceleration are currently subject of intensive research in many laboratories in the world. The existing results, experimental and theoretical, and their perspectives are reviewed in this article in the context of IZEST and the scientific program of ELI-NP.     

Dynamical Structure of Nuclear Excitation in Continuum

Dynamical structures of collective excitation in continuum are studied by calculating the isoscalar and isovector strength as well as transition density of nuclei near the drip-line such as ^28O and ^34Ca. It is found that for some excited states in continuum the proton and neutron transition density calculated from isoscalar and isovector excitation at some given energies may be different, which will affect the calculation of the polarization for nuclei with N≠Z.