Neutron--Antineutron Oscillations at the Surface of Nuclei

We discuss some aspects of possible neutron--antineutron oscillations in nuclei. The phenomenon occurs mostly at the surface of nuclei, and hence {\sl i)} is not very sensitive to medium corrections and {\sl ii)} makes use of the antinucleon-nucleus interaction in a region probed by experiments at CERN.Comment: Contr. Oak Ridge Workshop on Workshop on Baryon Instability, Latex, 4 pages, comments to [email protected]

Quasinuclear N N states

We present an interpretation of recent experimental results on nucleon-anti-nucleon annihilation reactions of the type N{bar N} {yields} {pi}X, which have yielded evidence for a new tensor meson AX (here called X{sub 2}) with J{pi}{sup C}(I{sup G}) = 2{sup ++}(0{sup +}). The branching ratios for producing X{sub 2} from N{bar N} atomic states of orbital angular momentum L = 0,1, as well as its preference for decay into {rho}{rho} and {pi}{pi} rather than K{bar K} channels, are consistent with the identifications of X{sub 2} as a {sup 13}P{sub 2}{minus}{sup 13}F{sub 2} bound state of the N{bar N} potential. We suggest further key test of this interpretation. 21 refs

Nuclear physics with strange particles

Recent progress in the understanding of strange particle interactions with nuclear systems is reviewed. We discuss the relative merits of various reactions such as (K/sup -/, ..pi../sup +-/), (..pi../sup +/, K/sup +/), or (..gamma.., K/sup +/) for hypernuclear production. The structure of /sub ..lambda..//sup 13/C is analyzed in some detail, in order to illustrate the role of the ..lambda..N residual interaction and approximate dynamical symmetries in hypernuclear structure. Recent results on the single particle states of a ..lambda.. in heavy systems, as revealed by (..pi../sup +/, K/sup +/) reaction studies, are used to extract information on the density dependence and effective mass which characterize the ..lambda..-nucleus mean field. Finally, we develop the idea the K/sup +/-nucleus scattering at low energies is sensitive to the subtle ''swelling'' effects for nucleons bound in nuclei. 64 refs., 13 figs

Exotic atoms and hypernuclei

Recent progress is reviewed in hypernuclear and exotic atom physics. A discussion of quasiatomic and very energetic ..gamma.. rays from the anti pp atom, and their possible relevance to the multiquark baryonium states is included. Also summarized is the most recent results on the study of ..lambda.. and ..sigma.. hypernuclei, in particular the proposals for the central and spin-orbit components of the single particle potentials and the spin-spin term in the ..lambda.. N residual interaction, as revealed by hypernuclear spectra and ..gamma.. ray transitions. 39 references

Strangeness production with protons and pions

We discuss the spectrum of physics questions related to strangeness which could be addressed with intense beams of protons and pions in the few GeV region. We focus on various aspects of strangeness production, including hyperon production in pp collisions, studies of hyperon-nucleon scattering, production of hypernuclei in proton and pion-nucleus collisions, and spin phenomena in hypernuclei

Hypernuclei and interactions of kaons with nuclei

Recent experimental and theoretical progress in hypernuclear physics is reviewed. Different models for hyperon-nucleus central and spin-orbit potentials are compared: several models yield a very small spin-orbit strength for the ..lambda.., as experimentally observed, but differ considerably in their predictions for the ..sigma... The new data on the /sup 13/C hypernuclear spectrum, as obtained in the (K/sup -/, ..pi../sup -/) strangeness exchange reaction at 800 MeV/c, are discussed. It is shown how one extracts constraints on the ..lambda..-nucleus and effective ..lambda..-nucleon ineractions from the data. The new BNL data on the (K/sup -/, ..pi../sup +/) reaction at 720 MeV/c, leading to ..sigma..-hypernuclear states, are examined. The case of /sup 6/Li(K/sup -/, ..pi../sup +/)/sup 6/H is discussed in some detail, and some speculations concerning the (K/sup -/, ..pi../sup +/) reaction on other targets are presented. The physical mechanisms which may lead to unusually narrow ..sigma.. excitations in some systems are examined. Finally, the physics motivations for several future hypernuclear experiments which are already under development, such as (K/sup -/, ..pi../sup -/..gamma..) and ..pi../sup + -/, K/sup +/) studies, or under preliminary consideration, for instance, the (K/sup -/, K/sup +/) reaction producing S=-2 hypernuclei are reviewed

Widths of Ξ\Xi Hypernuclear States

The $\Lambda$ and neutron decay widths of $\Xi$ hypernuclear states, based on calculated \Xi N \to \lala mixing amplitudes, are estimated. The widths which result from using the Nijmegen Model D interaction are sufficiently small, of order 1.5 MeV, that experiments to observe $\Xi$ hypernuclear states using the $(K^-,K^+)$ reaction may be feasible.Comment: 20 pages, LaTex with one postscript figure in accompanying file, to appear in Progress of Theoretical Physics Supplement No. 11

Limits on \boldmath n {\bar n} oscillations from nuclear stability

The relationship between the lower limit on the nuclear stability lifetime as derived from the non disappearance of `stable` nuclei ($T_{d}~\gtrsim~5.4~\times~10^{31}$ yr), and the lower limit thus implied on the oscillation time $(\tau_{n \bar n})$ of a possibly underlying neutron-antineutron oscillation process, is clarified by studying the time evolution of the nuclear decay within a simple model which respects unitarity. The order-of-magnitude result $\tau_{n \bar n} \approx 2 (T_{d}/\Gamma_{\bar n})^{1/2} > 2 \times 10^{8}$ sec, where $\Gamma_{\bar n}$ is a typical $\bar n$ nuclear annihilation width, agrees as expected with the limit on $\tau_{n \bar n}$ established by several detailed nuclear physics calculations, but sharply disagreeing by 15 orders of magnitude with a claim published recently in Phys. Rev. CRAP.Comment: 8 pages; this PRC version (accepted for publication, November 4 1999) differs from the original version only by a few minor editorial change

The influence of strength of hyperon-hyperon interactions on neutron star properties

An equation of state of neutron star matter with strange baryons has been obtained. The effects of the strength of hyperon-hyperon interactions on the equations of state constructed for the chosen parameter sets have been analyzed. Numerous neutron star models show that the appearance of hyperons is connected with the increasing density in neutron star interiors. The performed calculations have indicated that the change of the hyperon-hyperon coupling constants affects the chemical composition of a neutron star. The obtained numerical hyperon star models exclude large population of strange baryons in the star interior.Comment: 18 pages, 22 figures, accepted to be published in Journal of Physics G: Nuclear and Particle Physic

Loosely bound hyperons in the SU(3) Skyrme model

Hyperon pairs bound in deuteron like states are obtained within the SU(3) Skyrme model in agreement with general expectations from boson exchange models. The central binding from the flavor symmetry breaking terms increases with the strangeness contents of the interacting baryons whereas the kinetic non-linear $\sigma$-model term fixes the spin and isospin of the bound pair. We give a complete account of the interactions of octet baryons within the product approximation to baryon number $B=2$ configurations.Comment: 35 pages REVTEX including 2 figs, with 3 further figs available on request from [email protected] or from [email protected] SI-94-TP3S2; STPHY-Th/94-