Properties Of Hypernuclei Research Articles

On the survey of nuclei and hypernuclei in multifragmentation

Multifragmentation reactions are dominating processes for the decomposition of highly excited nuclei leading to the fragment production in heavy-ion collisions. In high energy reactions strange particles are abundantly produced. We present a novel development of the Statistical multifragmentation model (SMM), namely, its generalization for the hyper-matter which is formed after the hyperon capture. This way, it is possible to describe its disintegration into normal and hyper-nuclei. Some properties of hyper-nuclei and their binding energies can be determined from the comparison of the isotope yields. The main focus of this method is to investigate strange and multi-strange hypernuclei since their properties are not easy to measure in traditional hyper-nuclei experiments.

Phase transition in hot Λ hypernuclei within the relativistic Thomas-Fermi approximation

A self-consistent description for hot $\Lambda$ hypernuclei in hypothetical big boxes is developed within the relativistic Thomas-Fermi approximation in order to investigate directly the liquid-gas phase coexistence in strangeness finite nuclear systems. We use the relativistic mean-field model for nuclear interactions. The temperature dependence of $\Lambda$ hyperon density, $\Lambda$ hyperon radius, excitation energies, specific heat, and the binding energies of $\Lambda$ hypernuclei from $^{16}_{\Lambda}$O to $^{208}_{\Lambda}$Pb in phase transition region are calculated by using the subtraction procedure in order to separate the hypernucleus from the surrounding baryon gas. The $\Lambda$ central density is very sensitive to the temperature. The radii of $\Lambda$ hyperon at high temperature become very large. In the relativistic Thomas-Fermi approximation with the subtraction procedure, the properties of hypernuclei are independent of the size of the box in which the calculation is performed. The level density parameters of hypernuclei in the present work are confirmed to be almost constant at low temperature. It is also found that the single-$\Lambda$ binding energies of $\Lambda$ hypernuclei are largely reduced with increasing temperature.

Equation of State of Dense Matter and Consequences for Neutron Stars

There is currently tremendous interest in the role of hyperons and other exotic forms of matter in neutron stars. This is particularly so following the measurement by Demorest et al. of a star with a mass almost 2 solar masses. Given that we know of no physical mechanism to stop the occurrence of hyperons at matter in beta–equilibrium above roughly 3 times nuclear matter density, we discuss the constraints on the possible maximum mass when hyperons are included in the equation of state. The discussion includes a careful assessment of the constraints from low energy nuclear properties as well as the properties of hypernuclei. The model within which these calculations are carried out is the quark-meson coupling (QMC) model, which is derived starting at the quark level.

Hyperonic mixing in five-baryon double-strangeness hypernuclei in a two-channel treatment

Properties of hypernuclei $_{\ensuremath{\Lambda}\ensuremath{\Lambda}}^{5}\mathrm{H}$ and $_{\ensuremath{\Lambda}\ensuremath{\Lambda}}^{5}\mathrm{He}$ are studied in a two-channel approach with explicit treatment of coupling of channels $^{3}\mathit{Z}+\ensuremath{\Lambda}+\ensuremath{\Lambda}$ and $\ensuremath{\alpha}+\ensuremath{\Xi}$. Diagonal $\ensuremath{\Lambda}\ensuremath{\Lambda}$ and coupling $\ensuremath{\Lambda}\ensuremath{\Lambda}\ensuremath{-}\ensuremath{\Xi}N$ interactions are derived within $G$-matrix procedure from Nijmegen meson-exchange models. Bond energy $\ensuremath{\Delta}{B}_{\ensuremath{\Lambda}\ensuremath{\Lambda}}$ in $_{\ensuremath{\Lambda}\ensuremath{\Lambda}}^{5}\mathrm{He}$ exceeds significantly that in $_{\ensuremath{\Lambda}\ensuremath{\Lambda}}^{5}\mathrm{H}$ due to the channel coupling. Diagonal $\ensuremath{\Xi}\ensuremath{\alpha}$ attraction amplifies the effect, which is sensitive also to $\ensuremath{\Lambda}$-core interaction. The difference of the $\ensuremath{\Delta}{B}_{\ensuremath{\Lambda}\ensuremath{\Lambda}}$ values can be an unambiguous signature of the $\ensuremath{\Lambda}\ensuremath{\Lambda}\ensuremath{-}\ensuremath{\Xi}N$ coupling in $\ensuremath{\Lambda}\ensuremath{\Lambda}$ hypernuclei. However, improved knowledge of the hyperon-nucleus potentials is needed for quantitative extraction of the coupling strength from future data on the $\ensuremath{\Lambda}\ensuremath{\Lambda}$ hypernuclear binding energies.

Relativistic mean-field approaches for light hypernuclei

We study the ground state properties of light hypernuclei theoretically using the relativistic mean-field theory with TM1 and NL-SH force parameters. It is found that these new parameters can satisfactorily reproduce the ground-state properties of the light hypernuclei even near the neutron drip-line. The parameter sets TM1 and NL-SH give a very similar description of hypernuclei. The properties of hypernuclei in baryon-hyperon systems are insensitive to the force parameters of effective nucleon-nucleon interactions. We also take into account the influence of pairing forces on the Λ hyperon and find that it leads to an even-odd effect in light hypernuclei.

Hypernuclei with meson-exchange hyperon-nucleon interactions

The properties of hypernuclei are studied in relativistic mean field theory, with effective σ coupling constants of hyperons obtained from a dynamic model for the YN interactions arising from the ππ and K K correlations. The properties of Λ-hypernuclei can be well described by fitting the omega coupling constant. A weaker effective ω coupling to the Σ might be required to form a nuclear bound state. The effective potentials of hyperons in hypernuclei are studied, especially the spin-orbit interaction of the hyperons.

Spectroscopy of Λ-hypernuclei

The present-day state of the theoretical and experimental studies on the spectroscopy of Λ-hypernuclei in the (K−, π−), (π+, K+), (K−, πγ) reactions is reviewed. The available experimental data and the main physical consequences of their analysis are discussed with particular emphasis on the tasks of further experimental studies of the spectroscopic properties of hypernuclei in the light of their importance in order to get a deeper insight into the structure of excited states and into hyperon-nucleon interactions.