Relativistic Few-Body Physics

I discuss different formulations of the relativistic few-body problem with an emphasis on how they are related. I first discuss the implications of some of the differences with non-relativistic quantum mechanics. Then I point out that the principle of special relativity in quantum mechanics implies that the quantum theory has a Poincaré symmetry, which is realized by a unitary representation of the Poincaré group. This representation can always be decomposed into direct integrals of irreducible representations and the different formulations differ only in how these irreducible representations are realized. I discuss how these representations appear in different formulations of relativistic quantum mechanics and discuss some applications in each of these frameworks.     

超核物理学进展

简要评述超核物理学近几年的发展,包括常规超核和非常规超核两个方面.对于包含通常超子的常规超核,重点介绍近来在日本KEK完成的一批超核实验及其理论分析.对其中关于超子杂质效应和超子平均自由路程等实验测量结果进行了理论分析,得到一些有意义的结果.并对奇异数为S=-2的Ξ超核的结构和性质进行了若干研究.对于包含C夸克或B夸克的其他味超核,以及可能的包含pentaquark的θ+超核也做了适当的介绍. Progress and recent status of experimental and theoretical investigations on hypernuclear physics are briefly reviewed, including conventional hypernuclear physics and unconventional hypernuclear physics. We introduce the recent progress of hypernuclear experiments in KEK, Japan and the studies of fine structure in γ-ray spectroscopy of Λ hypernuclei. The spin-flip transition between the ground-state spin doublet of light hypernuclei has been observed and the transition energy provides important..     

Recent Achievements in Hypernuclear Physics

In the last decade the hypernuclear physics community was committed to carrying on several third-generation experiments. Large data samples were collected on specific items, thanks to dedicated facilities and experimental apparatuses. The attention was focused on both high-resolution spectroscopy and decay mode study of single Λ-hypernuclei. Nowadays this phase is over but, until recently, important and to some extent unexpected results were achieved. Among others, the claim for the first observation of the neutron-rich hypernucleus \({^6_\Lambda{\rm H}}\) and the first experimental evidence for the hypernucleus two-nucleon induced weak decay raised strong interest.     

Experimental Activities in Few-Body Physics

Understanding the few-nucleon system remains one of the challenges in modern nuclear and hadron physics. Observables in few-nucleon scattering processes are sensitive probes to study the two and many-body interactions between nucleons in nuclei. In the past decades, several facilities provided a large data base to study in detail the three-nucleon interactions below the pion-production threshold by exploiting polarized proton and deuteron beams and large-acceptance detectors. Only since recently, the four-nucleon scattering process at intermediate energies has been explored. In addition, there is a focus to collect data in the hyperon-nucleon sector, thereby providing access to understand the more general baryon-baryon interaction. In this contribution, some recent results in the few-nucleon sector are discussed together with some of the preliminary results from a pioneering and exclusive study of the four-nucleon scattering process. Furthermore, this paper discusses the experimental activities in the hyperon sector, in particular, the perspectives of the hyperon program of PANDA.     

Recent Progress in Hypernuclear Physics

Hypernuclear physics has become very exciting owing to new epoch-making experimental data. The recent progress in theoretical and experimental studies of hypernuclei and discussion about the future development in this field are presented.     

Nuclear Few-Body Physics at FAIR

The FAIR facility, to be constructed at the GSI site in Darmstadt, will be addressing a wealth of outstanding questions within the realm of subatomic, atomic and plasma physics through a combination of novel accelerators, storage rings and innovative experimental set-ups. One of the key installations is the fragment separator Super-FRS that will be able to deliver an unprecedented range of radioactive ion beams (RIBs) in the energy range of 0?C1.5?GeV/u to the envisaged experiments collected within the NuSTAR collaboration. This will in particular permit new experimental investigations of nuclear few-body systems at extreme isospins, also reaching beyond the drip-lines, using the NuSTAR-R³B set-up. The outcome of pilot experiments on unbound systems are reported, as well as crucial detector upgrades.     

Few-Body Physics in a Many-Body World

The study of quantum mechanical few-body systems is a century old pursuit relevant to countless subfields of physics. While the two-body problem is generally considered to be well-understood theoretically and numerically, venturing to three or more bodies brings about complications but also a host of interesting phenomena. In recent years, the cooling and trapping of atoms and molecules has shown great promise to provide a highly controllable environment to study few-body physics. However, as is true for many systems where few-body effects play an important role the few-body states are not isolated from their many-body environment. An interesting question then becomes if or (more precisely) when we should consider few-body states as effectively isolated and when we have to take the coupling to the environment into account. Using some simple, yet non-trivial, examples I will try to suggest possible approaches to this line of research.     

CSR上可能的超核物理研究

对近年来超核物理在理论上及实验上的进展作了简介, 结合即将建成的兰州重离子加速器, 给出了一些可行性的超核物理研究.     

Panel Session on the Future of Few-Body Physics

During the 22nd European Few-Body Conference, a session was devoted to a panel discussion on the future of few-body physics. The panel members were Charlotte Elster, Jaume Carbonell, Evgeny Epelbaum, Nasser Kalantar-Nayestanaki, and Jean-Marc Richard. The session was chaired by Ben Bakker. After presentations by the panel members, several topics were discussed with the audience. The conclusions of this discussion are presented in this paper.     

Few-Body Aspects of the Near Threshold Pseudoscalar Meson Production

During the last decade large samples of data have been collected on the production of the ground-state pseudoscalar mesons in collisions of proton or deuteron beam with hydrogen or deuterium target. These measurements have been performed in the vicinity of the kinematical threshold for meson production where only a few partial waves in both initial and final state are expected to contribute to the production process. This simplifies significantly the interpretation of the data, yet still appears to be challenging due to the three or four particle final state systems with a complex hadronic potential. We review experiments and phenomenology of the near threshold production of the ground-state mesons in the few-body final states as for example: nucleus-meson and nucleon-nucleon-meson, and report on the status of the search of the mesic-nuclei (a meson-nucleus bound states). Experimental advantages of measurements close to the kinematical threshold are discussed, and general features of the production mechanism of the η and η′ mesons in the nucleon-nucleon collisions are presented emphasising results of measurements of spin and isospin dependence of the production cross sections.     

Relativistic Covariance of Light-Front Few-Body Systems in Hadron Physics

We study the light-front covariance of a vector-meson decay constant using a manifestly covariant fermion field theory model in (3 + 1) dimensions. The light-front zero-mode issues are analyzed in terms of polarization vectors and method of identifying the zero-mode operator and of obtaining the light-front covariant decay constant is discussed.     

Stochastic Variational Approach to Few-Body Problems in Condensed Matter Physics

The stochastic variational method is a powerful approach to solve few-body problems. The application of the stochastic variational approach to few-body problems in condensed matter physics is presented. The examples include calculation of energy spectra of atoms in magnetic field, confined atoms and trapped Fermi gases.     

The Few-Body Approximation in Nuclear,Atomic, and Molecular Physics

The quantum theory of few-body scattering based on Faddeev-Yakubovsky integral and differential equa¬tions is applied to calculations of various processes (elastic, inelastic, atom exchange, and dissociative) in nuclear, atomic, and molecular physics. Analytical solutions of these equations are presented for various limiting cases. The methods used for solving the integral and differential systems of equations are discussed.     

Few-Body Physics in Chiral Effective Field Theory: Recent Developments

Chiral effective field theory provides a systematic tool to study few-nucleon dynamics based on the approximate and spontaneously broken chiral symmetry of QCD. I discuss applications of this method to nuclear forces and few-nucleon dynamics. Various related topics including recent advances in nuclear lattice simulations are also addressed.     

Hypernuclear physics

The contributed papers submitted to the session C Hypernuclear and kaon physics and not presented orally at the Conference are briefly reviewed here.Rapporteur talk at the symposium Mesons and Light Nuclei IV, Bechyn, Czechoslovakia September 5–10, 1988.     

Hypernuclear spectroscopy

Conclusions The main difference between the- nucleus and the nucleon-nucleus interaction is in the spin dependence. The spin-spin and spin-orbit interaction is an order of magnitude weaker for the-nucleus than for the nucleon-nucleus system. If we want to emphasize the difference between hypernuclei and nuclei in an oversimplifying manner, we may say that the particle in the nucleus behaves like a spinless neutron.This radical difference in the behaviour of particles and nucleons in nuclear matter presents a sensitive test for the models of nuclear matter. Hypernuclear spectroscopy if studied in detail, a program just begun, promises to give valuable information on the effective properties of the quasiparticles in the nucleus and their interactions, both basic ingredients of nuclear models.Rather surprisingly, hypernuclei live long enough to observe individual states, as can be deduced from the berylium results. These results should be verified as soon as possible. If they are confirmed, this will challenge experimentalists to determine the -nucleus interaction in the same way as done for particles and the theorists to explain why the strong decay of particles in the nucleus is hindered.Invited talk at the symposium Mesons and Light Nuclei, Liblice, Czechoslovakia, June 1981.