Analysis of (π K<Superscript>+</Superscript>) and (K<Superscript>-</Superscript>, K<Superscript>+</Superscript>) hypernuclear production spectra in distorted-wave impulse approximation

We study the hyperon-nucleus potential with distorted-wave impulse wave approximation (DWIA) using the Green's function method. In order to include the nucleon and hyperon potential effects in Fermi averaging, we introduce the local optimal momentum approximation of target nucleons. We can describe the quasi-free Λ , Σ and Ξ production spectra in a better way than in the standard Fermi-averaged t -matrix treatments.     

Correlations in hypernuclear matter

We investigate short-range correlations in nuclear and hypernuclear matter. Self-energies due to short-range correlations and their influence on the nucleon and Λ -hyperon spectral functions are described in an approach accounting for a realistic treatment of mean-field dynamics and a self-consistently derived quasi-particle interaction. Landau-Migdal theory is used to derived the short-range interaction from a phenomenological Skyrme energy density functional, subtracting the long-range pionic contributions to the nucleonic spectral functions. We discuss our results for different hyperon-baryon ratios to show the influence of strangeness on the correlations in hypernuclear matter.     

_Λ~6Li超核的基态能量

本文将谐振子乘积态为基的方法推广应用于组分集团自旋非零的系统．用此方法和α＋ｐ＋Λ三集团模型详细研究了Λ６Ｌｉ超核的基态结构特征．计算结果表明，此方法可以较好地适用于组分集团自旋非零的系统．     

Exchange reactions with Dick Dalitz

An account is given of the close collaboration of Dick Dalitz with the European K⁻ Collaboration over many decades in many aspects of hypernuclear physics. In particular, emphasis is given to the topics of double hypernuclei and the discovery and resolution of p-wave Λ strangeness exchange states. A brief review of early work on non-mesonic decays of hypernuclei is also given.     

Hypernuclear physics for neutron stars

The role of hypernuclear physics for the physics of neutron stars is delineated. Hypernuclear potentials in dense matter control the hyperon composition of dense neutron star matter. The three-body interactions of nucleons and hyperons determine the stiffness of the neutron star equation of state and thereby the maximum neutron star mass. Two-body hyperon–nucleon and hyperon–hyperon interactions give rise to hyperon pairing which exponentially suppresses cooling of neutron stars via the direct hyperon URCA processes. Nonmesonic weak reactions with hyperons in dense neutron star matter govern the gravitational wave emissions due to the r-mode instability of rotating neutron stars.     

Hypernuclear physics legacy and heritage of Dick Dalitz

The major contributions of Richard H. Dalitz to hypernuclear physics, since his first paper in 1955 to his last one in 2005 covering a span of 50 years during which he founded and led the theoretical study of hypernuclei, are reviewed from a personal perspective. Topical remarks on the search for quasi-bound -nuclear states and on kaon condensation are made.     

First observation of the ΣN decay of the S = - 2 system

An event emitting a Σ^- -hyperon from a Ξ^- -hyperon nuclear capture at rest has been observed in a hybrid-emulsion experiment. The event has been analyzed as the first observation of the weak decay of the S = - 2 system.     

A-dependence of the γ- and p-induced production of the Λ(1520) from nuclei

Using results of a recent calculation of the Λ(1520) in the nuclear medium, which show that the medium width is about five times the free width, we study the A-dependence of the Λ(1520) production cross-section in the reactions γA → K⁺Λ(1520)A^′ and pA → pK⁺Λ(1520)A^′. We find a sizable A-dependence in the ratio of the nuclear cross-sections for heavy nuclei with respect to a light one due to the large value of the Λ(1520) width in the medium, showing that devoted experiments, easily within reach in present facilities, can provide good information on that magnitude by measuring the cross-sections studied here.     

Mass number dependence in Λ–hypernuclei by means of the Hypervirial Theorems

The Hypervirial Theorems are applied to a wide class of single particle nuclear potentials, in order to study the mass number dependence of various quantities in Λ-hypernuclei. A very efficient model is assumed for the radius parameter of the potentials and the limitations of the whole method are discussed. Received: 27 November 1998     

On the ΔI= 1/2 rule in the ΛN→NN reaction

It is shown that the mass dependence of the Λ-lifetime in heavy hypernuclei is sensitive to the ratio of neutron-induced to proton-induced non-mesonic decay rates R _n/R p. A comparison of the experimental mass dependence of the lifetimes with the calculated ones for different values of R _n/R p leads to the conclusion that this ratio is larger than 2 on the confidence level of 0.75. This suggests that the phenomenological ΔI= 1/2 rule might be violated for the nonmesonic decay of the Λ-hyperon. Received: 31 March 1999