Data analysis in relativistic nuclear physics using neural network

Two neural network algorithms for data analysis in relativistic nuclear physics are presented. A neural network technique (Hopfield method) is used in order to reconstruct particle tracks starting from a data set obtained with a coordinate detector system. An algorithm for circles recognition using deformable templates is carried out and its performances are studied. The technical limitations of the detectors, which in real situation prevent the possibility to reconstruct hits right on the circle, and presence of the noise points are taken into account.     

A correlated-basis-functions approach to realistic nuclear matter

The method of correlated basis functions is adapted to the nuclear-matter problem with two-nucleon potentials containing tensor as well as central components. Procedures are described for evaluating through three-body cluster order the energy expectation value with respect to a constrained trial ground-state wave function incorporating tensor and central correlations, and for calculating in two-body cluster approximation the second-order perturbation correction in a basis of likewise-correlated functions. Results for the 5100, 5200, Gammel-Christian-Thaler and Hamada-Johnston potentials are presented and dissected.     

A relativistic quantum field theory for rotating nuclear matter

The relativistic quantum field theory of Walecka is extended to rotating nuclear systems using a mean-field Thomas-Fermi approximation. Self-bound systems exhibit centrifugal stretching and a maximum angular frequency. Systems constrained to a cylindrical box develop central holes for large angular frequencies.     

On line nuclear orientation: From technique to new physics

Conclusion Since the first results continuous improvements and further developments of OLNO have been carried out; e.g. the sensitivity has been increased by the realization of particle detection. On—line nuclear orientation has evolved to a unique technique to study a broad range of physics topics from very fundamental interactions to applied material science. This has been proven by the results that already have been obtained. Apart from the well established low temperature NO technique, also the development of in—beam polarization methods is taking place. At NICOLE fine opportunities exist to work out specific and unique physics problems. Benefit can be taken of the high production rates at ISOLDE as compared to the other OLNO systems.     

Quantum theoretical physics is statistical and relativistic

We present a new theoretical framework for the quantum mechanism. We base it on a strict deterministic behavior of single systems. The conventional QM equation, however, is found to describe statistical results of many classical systems. We will see, moreover, that a rigorous synthesis of our theory requires relativistic kinematics.So, QM is not only a classical statistical theory, it is, of necessity, a relativistic theory. The equation of our theory does not just duplicate QM, it indicates an inherent nonlinearity in QM which is subject to experimental verification. We show, therefore, that conventional QM is a corollary of classical deterministic principles. We suggest this concept of nature conflicts with that prevalent in modern physics.     

核聚变中的核物理问题

采用标准的量子力学方位阱加库伦位垒,计算了氘-氘聚变截面。给出了0．2～280keY能区内的截面数据。与实验符合得很好。此模型说明了不可用Breit-Wigner公式来讨论轻核聚变反应。将此模型运用于束缚态带电粒子之间的核反应。可以解释一系列“异常现象”。并展现了开发不带强放射性的聚变能的前景。     

A free-electron laser generated gamma-ray beam for nuclear physics

The High Intensity Gamma Ray Source (HIγS), a collaborative project between TUNL and the Duke Free Electron Laser Laboratory, is described. An initial experiment and plans for a future research program are discussed briefly.     

One- and two-photon physics with relativistic heavy ions

The physics of peripheral collisions with relativistic heavy ions (PCRHI) is reviewed. One- and two-photon processes are discussed.     

QCD spin physics: Status and prospects for relativistic heavy-ion collider

We review some of the recent developments in QCD spin physics and highlight the spin physics program now underway at RHIC.     

Detectors and techniques in relativistic heavy ion physics

In collisions of heavy ions at relativistic energies highly excited nuclear matter is produced. Hadronic and electromagnetic probes are investigated in order to study the composition and the thermodynamical properties of the short-liver interaction volume and its expansion characteristics. The ultimate goal is to identify signals for a phase transition of hadronic matter to the quark-gluon plasma state. Because of the high multiplicity of particles in the final state various experimental techniques and analysis methods have been development in order to study exclusive signals with electromagnetic and hadronic probes. A selection of detector concepts which have been applied in heavy ion reactions at the CERN SPS will be presented here.     

A new trend in nuclear physics development

<正>Atomic nuclei comprise a principal level of material structure.Nuclear physics,in itself an substantial area of study,serves as a link between atomic physics and particle physics.The main research areas of nuclear physics involve strong interaction,weak interaction,and electromagnetic interaction.     

Dissipative relativistic fluid dynamics for nuclear collisions

In the context of the Müller-Israel-Stewart second-order theory for dissipative fluids due to Grad, we analyze the effects of thermal conduction and viscosity in heavy ion collisions. We contrast the results to those of the first-order theory due to Eckart and to Landau and Lifshitz and to those of perfect (ideal) fluid due to Euler. We study the energy density and entropy density evolution of a pion gas produced in the heavy ion collisions. The truncated version of the second-order theory is used to find the dissipative quantities.     

Random versus realistic interactions for low-lying nuclear spectra

We compare the shell-model results for realistic interactions with those obtained for various ensembles of random matrix elements. We show that, although the quantum numbers of the ground states in the even-even nuclei have a high probability ( approximately 60%) to be J(pi)T = 0(+)0, the overlap of those states with the realistic wave functions is very small in average. The transition probabilities B(E2) predicted with random interactions are also too small. The presence of the regular pairing is shown to be a significant element of realistic physics not reproduced by random interactions.     

Optimized δ expansion for relativistic nuclear models

The optimized δ-expansion is a nonperturbative approach for field theoretic models which combines the techniques of perturbation theory and the variational principle. This technique is discussed in the λφ⁴ model and then implemented in the Walecka model for the equation of state of nuclear matter. The results obtained with the δ expansion are compared with those obtained with the traditional mean field, relativistic Hartree and Hartree-Fock approximations. Received: 17 March 1997 / Revised version: 27 August 1997     

A generalized quantum kinetic equation for models of relativistic nuclear dynamics

Zubarev’s method of non-equilibrium statistical operator is applied to problems of relativistic kinetic theory. Within this method, a generalized relativistic quantum kinetic equation for the relativistic Wigner function is derived with taking into account the drift term of the Vlasov type and the collision integral of the second order in particle interaction. It is shown that this result holds as well for gauge invariant theories in the case of slowly changing fields. An advantage of the developed approach is exemplified by the consideration of relativistic nuclear matter within the Walecka and Nambu-Jona-Lasinio models. Typical relativistic effects like retardation, spin degrees of freedom and antiparticle evolution are taken into consideration.     

A relativistic quantum field theoretical model for nuclear slab collision dynamics

We treat the dynamics of colliding nuclear slabs in a relativistic quantum field theory by using the relativistic mean field approximation. Starting from Walecka's lagrangian, the nucleons are represented by single-particle spinors determined by a Dirac equation that contains a repulsive mean vector meson field and an attractive mean scalar meson field. Both fields satisfy Klein-Gordon equations whose source terms are again determined by the nucleon spinors. The two equal nuclear slabs are translationally invariant in two transverse dimensions and consist of spin and isospin symmetric nuclear matter. By specification of appropriate initial conditions for the collision, we numerically solve the system of coupled Dirac and Klein-Gordon equations for lab energies per nucleon up to 420 MeV. For small energies the results are similar to TDHF results. The time dependence of the density distribution, the mean meson fields, and the damping of the collision are studied. At the highest bombarding energy retardation effects are taken into account.