We demonstrate the different effect of strange impurities ($Λ$ and $Ξ$) on the static properties of nuclei within the framework of the relativistic mean-field model. Systematic calculations show that the gluelike role of $Λ$ hyperon is universal for all $Λ$-hypernuclei considered. However, $Ξ^-$ hyperon has the gluelike role only for the protons distribution in nuclei, and for the neutrons distribution $Ξ^-$ hyperon plays a repulsive role. On the other hand, $Ξ^0$ hyperon attracts surrounding neutrons and reveals a repulsive force to the protons. Possible explanations of the above observation are discussed.
We analyze low-energy hyperon-nucleon scattering using an effective field theory in next-to-leading order. By fitting experimental cross sections for laboratory hyperon momenta below 200 MeV/c and using information from the hypertriton we determine twelve contact-interaction coefficients. Based on these we discuss the low-density expansion of hyperon mass shifts in the nuclear medium.
Relativistic mean-field theory with $δ$ meson, nonlinear isoscalar self-interactions and isoscalar-isovector cross interaction terms with parametrizations obtained to reproduce Dirac-Brueckner-Hartree-Fock calculations for nuclear matter is used to study asymmetric nuclear matter properties in $β$-equilibrium, including hyperon degrees of freedom and (hidden) strange mesons. Influence of cross interaction on composition of hyperon matter and electron chemical potential is examined. Softening of nuclear equation of state by the cross interactions results in lowering of hyperonization, although …
We present our attempts to determine the optical model potential $U_Σ= V_Σ-iW_Σ$ of the $Σ$ hyperon in nuclear matter. We analyze the following sources of information on $U_Σ$: $ΣN$ scattering, $Σ^-$ atoms, and final state interaction of $Σ$ hyperons in the $(π,K^+)$ and $(K^-.π)$ reactions on nuclear targets. We conclude that $V_Σ$ is repulsive inside the nucleus and has a shallow a tractive pocket at the nuclear surface. These features of $V_Σ$ are consistent with the Nijmegen model F of the hyperon-nucleon interaction.
Brueckner theory is used to investigate the properties of hyperons in nuclear matter. The hyperon-nucleon interaction is taken from chiral effective field theory at next-to-leading order with SU(3) symmetric low-energy constants. Furthermore, the underlying nucleon-nucleon interaction is also derived within chiral effective field theory. We present the single-particle potentials of Lambda and Sigma hyperons in symmetric and asymmetric nuclear matter computed with the continuous choice for intermediate spectra. The results are in good agreement with the empirical information. In particular, our…
We generalise the finite range momentum and density dependent Seyler-Blanchard nucleon-nucleon effective interaction to the case of interaction between two baryons. This effective interaction is then used to describe dense hadronic matter relevant to neutron stars in the nonrelativistic Thomas-Fermi approach. We investigate the behaviour of nuclear symmetry energy in dense nuclear and hyperon matter relevant to neutron stars. It is found that the nuclear symmetry energy always increases with density in hyperon matter unlike the situation in nuclear matter. This rising characteristic of the sym…
We have examined the contribution of the filled negative energy sea of hyperons to the energy/particle in nuclear matter at the one and two loop levels. While this has the potential to be significant, we find a strong cancellation between the one and two loop contributions for our chosen parameters so that hyperon effects can be justifiably neglected.
The interaction between hyperons and nucleons has a wide range of applications in strangeness nuclear physics and is a topic of continuing great interest. These interactions are not only important for hyperon-nucleon scattering but also essential as basic input to studies of hyperon-nuclear few- and many-body systems including hypernuclei and neutron star matter. We review the systematic derivation and construction of such baryonic forces from the symmetries of quantum chromodynamics within non-relativistic SU(3) chiral effective field theory. Several applications of the resulting potentials a…
We predict the energy per baryon in nuclear matter with non-zero fraction of $Λ$ hyperons. We include Dirac effects on the nucleons as well as the $Λ$ and describe how the latter is implemented. We use the nucleon-hyperon meson-exchange potentials from the Juelich group, the latest as well as an earlier version. The dependence of the results on the many-body framework and on the nucleon-hyperon interaction model is discussed.
Neutron stars provide unique conditions to study cold dense nuclear matter at extreme densities. Due to these extreme conditions additional hadronic degrees of freedom are expected to be populated,including hyperons. This talk will focus on the influence of hyperons on the neutron star equation ofstate. In particular the contribution of the lambda hyperon will be discussed, as a first approximation to describing exotic neutron star equations of state. The system under consideration is where the strong nuclear force is described by the exchange of mesons and applying the relativistic mean field…
We study the long range part of the $Λ$-hyperon optical potential in nuclei using Quantum Many Body techniques and flavor-SU(3) Chiral Lagrangians as starting point. More precisely, we study the contributions to the $Λ$-hyperon optical potential due to the long-range two-pion exchange, with $Σ$ and $Σ^*$ baryons in the internal baryonic lines and considering Nh and $Δ$h excitations. We also consider the contribution to the spin-orbit potentials that comes out from these terms. Our results support a natural explanation of the smallness of the $Λ$-nuclear spin-orbit interaction and shows the imp…
We calculate the magnetic moments of hyperons in dense nuclear matter by using relativistic quark models. Hyperons are treated as MIT bags, and the interactions are considered to be mediated by the exchange of scalar and vector mesons which are approximated as mean fields. Model dependence is investigated by using the quark-meson coupling model and the modified quark-meson coupling model; in the former the bag constant is independent of density and in the latter it depends on density. Both models give us the magnitudes of the magnetic moments increasing with density for most octet baryons. But…
In this article we will review the role and properties of hyperons in finite and infinite nuclear systems. In particular, we will revise different production mechanisms of hypernuclei, as well as several aspects of hypernuclear $γ$-ray spectroscopy, and the weak decay modes of hypernuclei. Then we will discuss the construction of hyperon-nucleon and hyperon-hyperon interactions on the basis of the meson-exchange and chiral effective field theories. Recent developments based on the so-called V$_{low\,\, k}$ approach and lattice QCD will also be adressed. Finally, we will go over some of the eff…
We present a novel approach to the density dependent mean field and the spin-orbit interaction of a $Λ$-hyperon in a nuclear many-body system, based on flavor-SU(3) in-medium chiral perturbation theory. The leading long-range $ΛN$-interaction arises from kaon exchange and from two-pion exchange with a $Σ$-hyperon in the intermediate state. The empirical $Λ$-nucleus potential depth of about $-28 $MeV is well reproduced with a single cutoff scale, $\bar Λ= 0.7 $GeV, effectively representing all short-distance (high-momentum) dynamics not resolved at scales characteristic of the nuclear Fermi mom…
The in-medium properties of a hyperon-nucleon potential, derived within chiral effective field theory and fitted to Lambda-N and Sigma-N scattering data, are investigated. Results for the single-particle potentials of the Lambda and Sigma hyperons in nuclear matter are reported, based on a conventional first-order Brueckner calculation. The Sigma-nucleus potential is found to be repulsive, in agreement with phenomenological information. A weak Lambda-nucleus spin-orbit interaction can be achieved by an appropriate adjustment of a low-energy constant corresponding to an antisymmetric Lambda-N -…
Using SU(3) chiral perturbation theory we calculate the density-dependent complex mean field $U_Σ(k_f)+ i W_Σ(k_f)$ of a $Σ$-hyperon in isospin-symmetric nuclear matter. The leading long-range $ΣN $-interaction arises from one-kaon exchange and from two-pion exchange with a $Σ$- or a $Λ$-hyperon in the intermediate state. We find from the $ΣN\to ΛN$ conversion process at nuclear matter saturation density $ρ_0 = 0.16 $fm$^{-3}$ an imaginary single-particle potential of $W_Σ(k_{f0}) =-21.5$ MeV, in fair agreement with existing empirical determinations. The genuine long-range contributions from i…
We extend a chiral effective field theory approach to the $Λ$-nuclei interaction with the inclusion of the decuplet baryons. More precisely, we study the contributions due to the long-range two-pion exchange, with $Σ$ and $Σ^*$ baryons in the internal baryonic lines considering Nh and $Δ$h excitations. In particular, central and spin-orbit potentials are studied. For the former, regularization is needed and physical values of the cut-off give a large attraction, becoming necessary to include the repulsion of other terms not considered here. For the latter, in a model-independent framework, the…
Adopting hyperon-nucleon and hyperon-nucleon-nucleon interactions parametrized in chiral effective field theory, single-particle potentials of the $Λ$ and $Σ$ hyperons are evaluated in symmetric nuclear matter and in pure neutron matter within the framework of lowest order Bruckner theory. The chiral NLO interaction bears strong $Λ$N-$Σ$N coupling. Although the $Λ$ potential is repulsive if the coupling is switched off, the $Λ$N-$Σ$N correlation brings about the attraction consistent with empirical data. The $Σ$ potential is repulsive, which is also consistent with empirical information. The i…
Brueckner theory is used to investigate the in-medium properties of a $Λ$-hyperon in nuclear and neutron matter, based on hyperon-nucleon interactions derived within SU(3) chiral effective field theory (EFT). It is shown that the resulting $Λ$ single-particle potential $U_Λ(p_Λ=0,ρ)$ becomes strongly repulsive for densities $ρ$ of two-to-three times that of normal nuclear matter. Adding a density-dependent effective $ΛN$-interaction constructed from chiral $ΛNN$ three-body forces increases the repulsion further. Consequences of these findings for neutron stars are discussed. It is argued that …
We present sets of equation of state (EOS) of nuclear matter including hyperons using an SU_f(3) extended relativistic mean field (RMF) model with a wide coverage of density, temperature, and charge fraction for numerical simulations of core collapse supernovae. Coupling constants of Sigma and Xi hyperons with the sigma meson are determined to fit the hyperon potential depths in nuclear matter, U_Sigma(rho_0) ~ +30 MeV and U_Xi(rho_0) ~ -15 MeV, which are suggested from recent analyses of hyperon production reactions. At low densities, the EOS of uniform matter is connected with the EOS by She…
The recent discoveries of massive neutron stars, such as PSR J$0348+0432$ and PSR J$1614-2230$, have raised questions about the existence of exotic matter such as hyperons in the neutron star core. The validity of many established equations of states (EoS's) like the GM1 and FSUGold are also questioned. We investigate the existence of hyperonic matter in the central regions of massive neutron stars using Relativistic Mean Field (RMF) theory with the recently proposed IUFSU model. The IUFSU model is extended by including hyperons to study the neutron star in $β$ equilibrium. The effect of diffe…
The structure of neutron stars is determined by the equation of state of the matter inside the star, which relies on the knowledge of nuclear interactions. While radii of neutron stars mostly depend on the equation of state of neutron matter at nuclear densities, their maximum mass can be drastically affected by the appearance of hyperons at higher densities in the inner core of the star. We summarize recent quantum Monte Carlo results on the calculation of the equation of state of neutron matter at nuclear and higher densities. We report about the development of realistic hyperon-nucleon inte…
Within the framework of quantum molecular dynamics transport model, the isospin and in-medium effects on the hyperon production in the reaction of $^{197}$Au + $^{197}$Au are investigated thoroughly. A repulsive hyperon-nucleon potential from the chiral effective field theory is implemented into the model, which is related to the hyperon momentum and baryon density. The correction on threshold energy of the elementary hyperon cross section is taken into account. It is found that the $Σ$ yields are suppressed in the domain of midrapidity and kinetic energy spectra with the potential. The hypero…
We analyze hyperon and nucleon mass shifts in nuclear matter using chiral perturbation theory. Expressions for the mass shifts that include strong interaction effects at leading order in the density are derived. Corrections to our results are suppressed by powers of the Fermi momentum divided by either the chiral symmetry breaking scale or the nucleon mass. Our work is relevant for neutron stars and for large hypernuclei.
This paper presents the Extended-Soft-Core (ESC) potentials ESC04a-d for baryon-baryon channels with total strangeness $S=-2$. For these channels no experimental scattering data exist, and alsothe information from hypernuclei is very limited.The potential models for $S=-2$ are based on SU(3) extensions of potential models for the $S=0,-1$ sectors, which are fitted to experimental data. Flavor su(3)-symmetry is broken 'kinematically'by the masses of the baryons and the mesons.Moreover, in ESC04a,b aldo the coupling constants are broken, albeit in a well defined way using the $^3P_0$ quark-antiq…
We evaluate the antikaon spectral density in isospin symmetric nuclear matter. The in-medium antikaon-nucleon scattering process and the antikaon propagation is treated in a self consistent and relativistic manner where a maximally scheme-independent formulation is derived by performing a partial density resummation in terms of the free-space antikaon-nucleon scattering amplitudes. The latter amplitudes are taken from a covariant and chiral coupled-channel SU(3) approach which includes s-, p- and d-waves systematically. Particular care is taken on the proper evaluation of the in-medium mixing …
The theoretical status of the hyperon-nucleon and hyperon-hyperon interactions is reviewed, paying a special attention to chiral effective field theories. Results on hyperons in dense matter are presented and the consequences for the properties of neutron stars are analyzed.
We evaluate the antikaon and hyperon spectral functions in a self-consistent and covariant many-body approach. The computation is based on coupled-channel dynamics derived from the chiral SU(3) Lagrangian. A novel subtraction scheme is developed that avoids kinematical singularities and medium-induced power divergencies all together. Scalar and vector mean fields are used to model nuclear binding and saturation. The effect of the latter is striking for the antikaon spectral function that becomes significantly more narrow at small momenta. Attractive mass shifts of about 30 and 40 MeV are predi…
The purpose of this note is to report predictions of the binding energy of the $Λ$ hyperon in nuclear matter using the latest version of the Juelich nucleon-nucleon meson-exchange potential. Results from a conventional Brueckner calculation are compared with previously reported values. A calculation including Dirac effects on the $Λ$ single-particle potential is also presented. Issues encountered in Dirac calculations with nucleon-hyperon potentials are discussed.
Superfluidity of $Λ$ and $Σ^-$ admixed in neutron star (NS) cores is investigated realistically for hyperon ($Y$)-mixed NS models obtained using a $G$-matrix-based effective interaction approach. Numerical results for the equation of state (EOS) with the mixing ratios of the respective components and the hyperon energy gaps including the temperature dependence are presented. These are meant to serve as physical inputs for $Y$-cooling calculations of NSs. By paying attention to the uncertainties of the EOS and the $YY$ interactions, it is shown that both $Λ$ and $Σ^-$ are superfluid as soon as …
We have developed a formalism for microscopic Brueckner-type calculations of dense nuclear matter that includes all types of baryon-baryon interactions and allows to treat any asymmetry on the fractions of the different species (n, p, $Λ$, $Σ^0$, $Σ^+$, $Σ^-$, $Ξ^-$ and $Ξ^0$). We present results for the different single-particle potentials focussing on situations that can be relevant in future microscopic studies of beta-stable neutron star matter with strangeness. We find the both the hyperon-nucleon and hyperon-hyperon interactions play a non-negligible role in determining the chemical pote…
Three-body forces acting on a $Λ$ hyperon in a nuclear medium are investigated, with special focus on the so-called hyperon puzzle in neutron stars. The hyperon-nucleon two-body interaction deduced from SU(3) chiral effective field theory is employed at next-to-leading order. Hyperon-nucleon three-body forces are approximated using saturation by decuplet baryons and are transcribed to density-dependent effective two-body interactions. These together are taken as input in a Brueckner-Bethe-Goldstone equation with explicit treatment of the $ΛN\leftrightarrowΣN$ and $ΛNN\leftrightarrowΣNN$ couple…
The effects of nuclear medium on the residue, mass and self energy of the positive and negative parity $Σ$, $Λ$ and $Ξ$ hyperons are investigated using the QCD sum rule method. In the calculations, the general interpolating currents of hyperons with an arbitrary mixing parameter are used. We compare the results obtained in medium with those of the vacuum and calculate the shifts in the corresponding parameters. It is found that the shifts on the residues in nuclear matter are over all positive for both the positive and negative parity hyperons, except for the positive parity $Σ$ hyperon that t…
The role of the isoscalar hyperon Lambda in probing the density dependence of the nuclear symmetry energy is studied in multi-Lambda hypernuclei, hyperon-rich matter and neutron stars in relativistic models. Relationships between the properties of three types of objects and the neutron thickness in 208Pb are established with respect to the isoscalar-isovector coupling that modifies the density dependence of the symmetry energy. The exotic isotopes far from the neutron drip line can be stabilized by filling in considerable Lambda hyperons. The difference of the binding energy of multi-Lambda hy…
We study the trend of the nuclear symmetry energy in relativistic mean-field models with appearance of the hyperon and quark degrees of freedom at high densities. On the pure hadron level, we focus on the role of $Λ$ hyperons in influencing the symmetry energy both at given fractions and at charge and chemical equilibriums. The softening of the nuclear symmetry energy is observed with the inclusion of the $Λ$ hyperons that suppresses the nucleon fraction. In the phase with the admixture of quarks and hadrons, the equation of state is established on the Gibbs conditions. With the increase of th…
The properties of $Σ$-hyperons in pure $Σ$ matter are studied with the finite-density quantum chromo-dynamics sum rule (QCDSR) approach. The $ΣΣ$ nuclear potential $U_Σ$ is most likely strongly attractive, it could be about -50 MeV or even more attractive at normal nuclear density. If this prediction is the case, the interactions between $Σ$-hyperons should play crucial roles in the strange nuclear matter, when there are multi-$Σ$ hyperons. The bound state of double-$Σ$ maybe exist.
We study the effect of rotation on global properties of neutron star with a hyperon core in an effective chiral model with varying nucleon effective mass within a mean field approach. The resulting gross properties of the rotating compact star sequences are then compared and analyzed with other theoretical predictions and observations from neutron stars. The maximum mass of the compact star predicted by the model lies in the range $(1.4-2.4) ~M_{\odot}$ at Kepler frequency $Ω_K$, which is consistant with recent observation of high mass stars thereby reflecting the sensitivity of the underlying…
The chiral version of the QMC model, in which the effect of gluon and pion exchanges is included self-consistently, is applied to the hyperons in a nuclear medium. The hyperfine interaction due to the gluon exchange plays an important role in the in-medium baryon spectra, while the pion-cloud effect is relatively small. At the quark mean-field level, the $Λ$ feels more attractive force than the Σor Ξin matter.
We propose a dynamical mechanism which provides an interaction between the spins of hyperons and antihyperons and the vorticity of the baryon current in noncentral high energy nuclear collisions. The interaction is mediated by massive vector and scalar bosons which is well known to describe the nuclear spin-orbit force. It follows from the Foldy-Wouthuysen transformation and leads to a strong-interaction Zeeman effect. The interaction may explain the difference in polarizations of $Λ$ and $\barΛ$ hyperons as measured by the STAR Collaboration at the BNL Relativistic Heavy Ion Collider. The sig…
In this work, masses and radii of neutron stars are considered to investigate the effect of nuclear symmetry energy to the astrophysical observables. A relativistic mean field model with density-dependent meson-baryon coupling constants is employed in describing the equation of state of dense nuclear matter, and the density dependencies of the symmetry energies are quoted from the recent phenomenological formulae obtained from the heavy ion data at subnuclear saturation densities. Since hyperons can take part in the $β$-equilibrium of the dense matter inside neutron stars, we include hyperons …
The properties of compact stars and their formation processes depend on many physical ingredients. The composition and the thermodynamics of the involved matter is one of them. We will investigate here uniform strongly interacting matter at densities and temperatures, where potentially other components than free nucleons appear such as hyperons, mesons or even quarks. In this paper we will put the emphasis on two aspects of stellar matter with non-nucleonic degrees of freedom. First, we will study the phase diagram of baryonic matter with strangeness, showing that the onset of hyperons, as tha…
We study the effects of anisotropic pressure on properties of the neutron stars with hyperons inside its core within the framework of extended relativistic mean field. It is found that the main effects of anisotropic pressure on neutron star matter is to increase the stiffness of the equation of state, which compensates for the softening of the EOS due to the hyperons. The maximum mass and redshift predictions of anisotropic neutron star with hyperonic core are quite compatible with the result of recent observational constraints if we use the parameter of anisotropic pressure model $h \le 0.8$…
The dynamics of light hypernuclei and nuclear clusters produced in $^{197}$Au+$^{197}$Au collisions has been investigated thoroughly with a microscopic transport model. All possible channels of hyperon production and transportation of hyperons in nuclear medium are implemented into the model. The light complex fragments are recognized with the Wigner density approach at the stage of freeze out in nuclear collisions. The isospin diffusion in the collisions is responsible for the neutron-rich cluster formation. The collective flows of nuclear clusters are consistent with the experimental data fr…
We have studied quasielastic charged current hyperon production induced by $\barν_μ$ on free nucleon and the nucleons bound inside the nucleus. The calculations are performed for several nuclear targets like $^{12}C$, $^{40}Ar$, $^{56}Fe$ and $^{208}Pb$ which are presently being used in various oscillation experiments using accelerator neutrinos. The inputs are the hyperon-nucleon transition form factors determined from neutrino-nucleon scattering as well as from semileptonic decays of neutron and hyperons using SU(3) symmetry. The calculations for the nuclear targets are done in local density…
The relativistic nucleus-nucleus collisions can produce hypernuclei and low-temperature hyper-matter as a result of hyperon capture by nuclear residues and free nucleons. We use the transport, coalescence and statistical models to describe the whole process, and point at the important advantages of such reactions: A broad variety of formed hypernuclei in masses and isospin allows for investigating properties of exotic hypernuclei, as well as the hypermatter both at high and low temperatures. The abundant production of multi-strange nuclei that can give an access to multi-hyperon systems and st…
The work presents the recent developments in Quantum Monte Carlo calculations for nuclear systems including strange degrees of freedom. The Auxiliary Field Diffusion Monte Carlo algorithm has been extended to the strange sector by the inclusion of the lightest among the hyperons, the $Λ$ particle. This allows to perform detailed calculations for $Λ$ hypernuclei, providing a microscopic framework for the study of the hyperon-nucleon interaction in connection with the available experimental information. The extension of the method for strange neutron matter, put the basis for the first Diffusion…
We study the equation of state of hyperon-rich matter for neutron stars using an extended relativistic mean-field model. We take special care of the recently proposed non-linear behaviour of the vector field which gives a much better description of Dirac-Brueckner calculations. The hyperon-hyperon interaction is also implemented by introducing additional meson exchanges. These new terms avoid the instability found at high densitites in previous works while keeping the excellent description for finite nuclear systems. We also demonstrate within the mean-field approach that the presence of hyper…
The possibility of existence of hyperons in the recently measured $2M_\odot$ pulsar PSRJ1614-2230 is explored using a diverse set of nuclear equations of state calculated within the relativistic mean-field models. Our results indicate that the nuclear equations of state compatible with heavy-ion data allow the hyperons to exist in the PSRJ1614-2230 only for significantly larger values for the meson-hyperon coupling strengths. The maximum mass configurations for these cases contain sizable hyperon fractions ($\sim 60%$) and yet masquared their counterpart composed of only nucleonic matter.
We calculate the contribution to the polarization of $Λ$ hyperons in relativistic nuclear collisions at high energy from the decays of $Σ^*(1385)$ and $Σ^0$, which are the predominant sources of $Λ$ production besides the primary component, as a function of the $Λ$ momentum. Particularly, we estimate the longitudinal component of the mean spin vector as a function of the azimuthal angle in the transverse plane, assuming that primary $Σ^*$ and $Σ^0$ polarization follow the predictions of local thermodynamic equilibrium in a relativistic fluid. Provided that the rapidity dependence around midrap…
Using a extended version of the Quantum Hadrodynamics (QHD), I propose a new microscopic equation of state (EoS) able to correctly reproduce the main properties of symmetric nuclear matter at the saturation density, as well produce massive neutron stars and satisfactory results for the radius and the tidal parameter $Λ$. I show that even when hyperons are present, this EoS is able to reproduce at least 2.00 solar masses neutron star. The constraints about the radius of a $2.00M_\odot$ and the minimum mass that enable direct Urca effect are also checked.
We discuss the properties of baryons within the framework of the in-medium modified SU(3) Skyrme model. The modification is performed by a minimal way, the medium functionals in the SU(2) sector being introduced. These functionals are then related to nuclear matter properties near the saturation point. The modifications in the SU(3) sector are performed with the additional changes of kaon properties in nuclear matter. The results show that the properties of baryons in the strange sector are sensitive to the in-medium modifications of the kaon properties. The consistency of the in-medium modifi…
Nuclear effective interactions are considered as a vital tool to guide into the region of the high degree of isospin asymmetry and density. We take varieties of parameter sets of the RMF model to show the parametric dependence of the hyperon star properties. We add $ϕ_0$-meson to $σ$-$ω$-$ρ$ model. The effects of $ϕ_0$-meson on the equation of state and consequently on the maximum mass of the hyperon star are discussed. Due to the inclusion of $ϕ_0$-meson the threshold density of different hyperon production shift to higher density region. The effects of the hyperon-meson coupling constants on…
Using the SU6 quark-model baryon-baryon interaction recently developed by the Kyoto-Niigata group, we calculate NN, Lambda N and Sigma N G-matrices in ordinary nuclear matter. This is the first attempt to discuss the Lambda and Sigma single-particle potentials in nuclear medium, based on the realistic quark-model potential. The Lambda potential has the depth of more than 40 MeV, which is more attractive than the value expected from the experimental data of Lambda-hypernuclei. The Sigma potential turns out to be repulsive, the origin of which is traced back to the strong Pauli repulsion in the …
The existence of 2 Msun pulsars puts very strong constraints on the equation of state (EOS) of neutron stars (NSs) with hyperon cores, which can be satisfied only by special models of hadronic matter. The radius-mass relation for these models is sufficiently specific that it could be subjected to an observational test with future X-ray observatories. We want to study the impact of the presence of hyperon cores on the radius-mass relation for NS. We aim to find out how, and for which particular stellar mass range, a specific relation R(M), where M is the gravitational mass, and R is the circumf…
We determine the equation of state (EOS) of nuclear matter with the inclusion of hyperons in a self-consistent manner by using a Modified Quark Meson Coupling Model (MQMC) where the confining interaction for quarks inside a baryon is represented by a phenomenological average potential in an equally mixed scalar-vector harmonic form. The hadron-hadron interaction in nuclear matter is then realized by introducing additional quark couplings to $σ$, $ω$, and $ρ$ mesons through mean-field approximations. The effect of a nonlinear $ω$-$ρ$ term on the equation of state is studied. The hyperon couplin…
This paper presents the Extended-Soft-Core (ESC) potentials ESC08c for baryon-baryon channels with total strangeness S=-2. The potential models for S=-2 are based on SU(3) extensions of ESC potential models for the S=0 and S=-1 sectors, which are fitted to experimental data. Flavor SU(3)-symmetry is broken only kinematically by the masses of the baryons and the mesons. For the S=-2 channels no experimental scattering data exist, and also the information from hypernuclei is rather limited. Nevertheless, in the fit to the S=0 and S=-1 sectors information from the so called NAGARA event and the $…
The phase diagram of nuclear matter is extended to strangeness and antimatter. It offers fascinating features for heavy ion physics and astrophysics. We will discuss some regions of this phase diagram as strange matter at zero temperature, hypermatter at high densities and the antiworld at high densities and strangeness fraction.
