Effect of the mesons σ* and Φ and the variety of U(N)Σ on the transition density of hyperon stars

The effect of the mesons σ* and φ and the variety of U(N)Σ on the transition density of hyperon stars is examined within the framework of relativistic mean field theory for the baryon octet {n,p,∧,∑-,∑0,∑+,Ξ- and Ξ0} system.It is found that,compared with that without considering the mesons δ* and φ,the transition density of hyperon stars decreases,the critical baryon density that hyperons Σ-,Σ0,Ξ+,Ξ- and Ξ0 appears to decrease too,but for A the effect is not obvious.As U(N)Σ goes up,the critical baryon density of Σ+,Σ0 and Σ- increases,that of Ξ0 decreases and that of A and Ξ- is fixed.In addition,it is found that the variety of U(N)Σ almost does not influence the transition density.     

Effect of σ*,φ Mesons on the Neutron Star Matter at Finite Temperature

Within the RMF approach, considering the contribution of σ*,φ mesons and baryon octet {n,p,Λ,Σ^－,Σ⁰,Σ⁺,Ξ^－,Ξ⁰}, some properties of neutron star matter have been investigated in the temperature region between 5—15MeV. It is found that when the contributions of σ*,φ mesons are included, (1) the critical baryon density decreases (but for the Λ hyperon, the effect is not obvious), but the number of hyperons increases; (2) the equation of state becomes soft at higher energy density; (3) the maximum mass decreases while the corresponding radius increases; (4) the central density, the central energy density, and the central pressure all become smaller. At T=5MeV and 10MeV and for Σ⁰,Ξ⁰,Σ⁺, the σ*,φ mesons make critical baryon density greatly decrease; but at T=15MeV, 20MeV, and 25MeV, the effect is not obvious. However, for Λ,Σ^－,Ξ^－ hyperons, at all the above temperatures, the effect is not obvious.     

Influence of the weakly interacting light U boson on the properties of massive protoneutron stars

Considering the octet baryons in relativistic mean field theory and selecting entropy per baryon S=l,we calculate and discuss the influence of U bosons on the equation of state,mass-radius,moment of inertia and gravitational redshift of massive protoneutron stars(PNSs).The effective coupling constant gu of U bosons and nucleons is selected from 0 to 70 GeV~(-2).The results indicate that U bosons will stiffen the equation of state(EOS).The influence of U bosons on the pressure is more obvious at low density than high density,while the influence of U bosons on the energy density is more obvious at high density than low density.The U bosons play a significant role in increasing the maximum mass and radius of PNS.When the value of gu changes from 0 to 70 GeV~(-2),the maximum mass of a massive PNS increases from 2.11M_⊙ to 2.58M_⊙,and the radius of a PNS corresponding to PSR J0348+0432 increases from 13.71 km to 24.35 km.The U bosons will increase the moment of inertia and decrease the gravitational redshift of a PNS.For the PNS of the massive PSR J0348+0432,the radius and moment of inertia vary directly with gu,and the gravitational redshift varies approximately inversely with gu.     

Effect of f0(975) and φ(1020) Mesons on Neutron Star Mater

In the RMF approach, considering the contributions of the σ^* and φ mesons and the hyperons in the baryon octet {N,P,Λ,∑^－,∑⁰,∑⁺,Ξ^－,Ξ⁰}, the properties of neutron star matter have been investigated. It is found that with the contributions of the σ^* and φ mesons, the critical baryon density of hyperon appearance decreases, the number of hyperons increases, the transition density ρ_0H of hyperon stars decreases, the equation of state turns soft, the maximum mass of neutron star decreases and the corresponding radius increases, the central density, the central energy density and the central pressure are all reduced.     

Influence of Entropy on Composition and Structure of Massive Protoneutron Stars

Adjusting the suitable coupling constants in relativistic mean field (RMF) theory and focusing on thermal effect of an entropy per baryon (S) from 0 to 3, we investigate the composition and structure of massive protoneutron stars corresponding PSR J1614-2230 and PSR J0348+0432. It is found that massive protoneutron stars (PNSs) have more hyperons than cold neutron stars. The entropy per baryon will stiffen the equation of state, and the influence on the pressure is more obvious at low density than high density, while the influence on the energy density is more obvious at high density than low density. It is found that higher entropy will give higher maximum mass, higher central temperature and lower central density. The entropy per baryon changes from 0 to 3, the radius of a PNS corresponding PSR J0348+0432 will increase from 12.86 km to 19.31 km and PSR J1612-2230 will increase from 13.03 km to 19.93 km. The entropy per baryon will raise the central temperature of massive PNSs in higher entropy per baryon, but the central temperature of massive PNSs maybe keep unchanged in lower entropy per baryon. The entropy per baryon will increase the moment of inertia of a massive protoneutron star, while decrease gravitational redshift of a massive neutron star.     

Meson Effect in the Proto Neutron Star PSR J0348+0432

The effect of mesons f ₀(975) (named as f), ?(1020) (named as ?) and δ on the moment of inertia of the PNS PSR J0348+0432 is examined in the framework of the relativistic mean field theory considering the baryon octet. It is found that the energy density ε and pressure p will increase considering the mesons δ whereas will decrease as the mesons f and ? being considered. When the mesons f,? and δ are considered, the energy density and pressure will all decrease. It is also found that the contribution of mesons f, ? and δ to the central energy density is only the central energy density’s 0.06 ～0.6% whereas the contribution of mesons f, ? and δ to the central pressure is the central pressure’s 4 ～7%. For the radius, it will decrease when the contributions of mesons f, ? and δ are considered. The moment of inertia I will increase considering the mesons δ whereas will decrease as the mesons f and ? being considered. When the mesons f, ? and δ are all considered, the moment of inertia will decrease. It is found that the contribution of mesons f and ? to moment of inertia is 4 ～9 times larger than that of mesons δ. Our results show that the mesons f, ? and δ contribute to the moment of inertia’s 2 ～5%.     

The Σ Well Depth and the Proto Neutron Star Matter

The effect of the Σ well depth $U_{\varSigma}^{(N)}$ on a proto neutron star (PNS) is examined within the framework of relativistic mean field theory for the baryon octet system. It is found that the well depth $U_{\varSigma}^{(N)}$ will affect the structures of the PNS. With the well depth $U_{\varSigma}^{(N)}$ growing from 0 to 30 MeV, the field strength of meson ρ, the chemical potentials of electrons and neutrons, the relative number density of p, e, μ, Λ, Ξ ⁰, the mass and the pressure of a PNS all increase while the relative number density of n, Ξ ^?, Σ ^?, Σ ⁰, Σ ⁺ decrease. It is also found that the larger changes of the hyperon coupling constants, which is connected to the Σ well depth $U_{\varSigma}^{(N)}$ , will lead to the smaller changes in the neutron star mass and this shows the mass of PNS is not very sensitive to the hyperon coupling constants.     

Mixing of scalar meson and baryon-baryon interaction

At quark level,we study the effect of ideal mixing of singlet σ 0 and octet σ 8 scalar mesons on baryon-baryon interaction in the chiral SU(3) quark model.We solve the resonating group method equation for scattering process and bound state.The results show that the binding energy of deuteron and nucleonnucleon and hyperon-nucleon scattering data can be reasonably described for ideal mixing.Taking the same parameters we used in the scattering calculation,we further investigate the possible dibaryons and find the binding energy of (ΩΩ) ST =00 and (Ξ *Ω) ST =0 1 2 can be reduced a lot for ideal mixing.     

Thermal Dynamics Behavior of Protoneutron Star Matter

In the relativistic σ-ω model, including the vacuum fluctuation of nucleons and σ mesons, the effect of the temperature to the composition and equation of state of protoneutron star matter, nucleon effective mass and chemical potential of neutrons and electrons are studied. We find that the influence of the temperature on the equation of state of protoneutron star matter is indeed small, however, its influence on the composition of protoneutron star, which will contribute to the evolution of protoneutron star, cannot be neglected in low density region. The chemical potentials of neutrons and electrons also depend on the temperature in almost the same density region.     

Self-consistent description of finite nuclei based on a relativistic quark model

Relativistic Hartree equations for spherical nuclei have been derived from a relativistic quark model of the structure of bound nucleons which interact through the (self-consistent) exchange of scalar (σ) and vector (ω and ϱ) mesons. The coupling constants and the mass of the σ-meson are determined from the properties of symmetric nuclear matter and the rms charge radius in ⁴⁰Ca. Calculated properties of static, closed-shell nuclei from ¹⁶O to ²⁰⁸Pb are compared with experimental data and with results of Quantum Hadrodynamics (QHD). The dependence of the results on the nucleon size and the quark mass is investigated. Several possible extensions of the model are also discussed.     

Self-consistent hartree description of finite nuclei in a relativistic quantum field theory

Relativistic Hartree equations for spherical nuclei are derived from a relativistic nuclear quantum field theory using a coordinate-space Green function approach. The renormalizable field theory lagrangian includes the interaction of nucleons with σ, ω, ρ and π mesons and the photon. The Hartree equations represent the “mean-field” approximation for a finite nuclear system. Coupling constants and the σ-meson mass are determined from the properties of nuclear matter and the rms charge radius in ⁴⁰Ca, and pionic contributions are absent for static, closed-shell nuclei. Calculated charge densities, neutron densities, rms radii, and single-nucleon energy levels throughout the periodic table are compared with data and with results of non-relativistic calculations. Relativistic Hartree results agree with experiment at a level comparable to that of the most sophisticated non-relativistic calculations to date. It is shown that the Lorentz covariance of the relativistic formalism leads naturally to density-dependent interactions between nucleons. Furthermore, non-relativistic reduction reveals non-central and non-local aspects inherent in the Hartree formalism. The success of this simple relativistic Hartree approach is attributed to these features of the interaction.     

A test of GOR model and PCAC relations through the Meson-Baryon σ-terms and the BBS coupling constants

A set of SU (3) invariant BBS coupling constants with the same D/F ratio as the baryon masses is obtained through the meson-baryon σ-terms, by the use of GOR Model and PCAC Relations. The possible role of the scalar mesons in determining the meson-baryon σ-terms is also analysed.     

Radiative Decays of (0+,1+) Strange-Bottom Mesons

In this article, we assume that the (0⁺,1⁺) strange-bottom mesons are the conventional b\bar{s} mesons, and calculate the electromagnetic coupling constants d, g₁, g₂, and g₃ using the light-cone QCD sum rules. Then we study the radiative decays B_{s0 →} B_s* γ, B_{s1→ ^{Bs* γ,}} B_{s1 →} B_s* γ, and B_s1→ B_{s0 ^γ}, and observe that the widths are rather narrow. We can search for the (0⁺,1⁺) strange-bottom mesons in the invariant B_s π⁰ and B_s*π⁰ mass distributions in the strongdecays or in the invariant B_s*γ and B_s^γ mass distributions in the radiative decays.     

Nucleons from skyrmions with vector mesons

We use a chirally gauged non-linear σ-model with minimal breaking to describe spin 0 and spin 1 mesons. Contrary to current claims, we argue that this model is similar in nature with the recently proposed models based on concepts of a hidden local symmetry. We show that classically the model exhibits stable hedgehog baryons and this without resorting to Skyrme's fourth order term. All the parameters of the model are fixed by the meson masses and coupling constants. The bulk properties of the nucleon andΔ-isobar are found to be in good agreement with the experimental results.     

Sum rules in perturbation theory

Sum rules derived from isospin current algebra are examined in perturbation theory for nucleons interacting with neutral pseudoscalar mesons and isovector pions. It is shown that the well-known sum rules for electromagnetic isovector form factors of nucleons and pions are correct in zero and second order of the meson-nucleon coupling constant.     

Effects of σ* and Φ mesons on the surface redshift of a neutron star

The effects of σ and Φ mesons on the surface redshift of a neutron star have been investigated within the framework of relativistic mean field theory for the baryon octet {n,p,Λ,Σ,Σ 0,Σ +,Ξ,Ξ 0 } system.It is found that compared with those without considering the contributions of σ and Φ mesons,the surface redshift decreases and that corresponding to the maximum value of the mass also decreases from 0.2540 to 0.2236,about by 12%.Meanwhile,it is also found that including σ and Φ mesons,the M/R and that corresponding to the maximum mass decrease.     

Baryon ＋ Baryon→（ΩΩ）J^π=0＋ ＋ X Cross Section Calculation

The cross sections of Ω Ξ→（ΩΩ）J^π=0 K(K^*) and Ω Ω→（ΩΩ）J^π=0 η‘(φ) are studied by using an effective Hamiltonian method.For the two pseudo-scalar meson production processes,the cross sections are still in the order of several μbs,but for the two vector meson production processes,the cross sections are about 10 times larger than those in pseudo-scalar meson production case when the coupling constants of vector meson fields are fixed according to gNNρ and fNNρ in NN scattering and the SU(3) relation.     

Abnormal nuclear matter and pion condensation

The possibility of nuclear matter undergoing a combined phase transition into abnormal matter and a pion condensate is investigated. Various lagrangians for the meson (σ and π_i) fields, based on the σ-models, are used in mean-field approximation, and the entire system (mesons + nucleons) is treated fully relativistically. Equilibrium conditions of nuclear matter are obtained with NN repulsion, parametrized by the excluded volume approximation. It turns out that the formation of abnormal matter depends crucially on the choice of the σ-model lagrangian and considerably less on the additional pion condensate.     

Deep processes in nuclei and in-medium dressing of the nucleons and mesons

K⁺ scattering and quasielastic electron scattering from nuclei are expected to provide information about the nucleons and mesons in the inner regions of nuclei. The K⁺- nucleus cross sections and the quasielastic electron-nucleus response functions have been calculated taking into account the same in-medium dressing of the nucleons and the same coupling of the σ and ω mesons to the polarization of nuclear matter. We obtain a good agreement with experimental data for the two processes.     

ρ-A1 mixing in pion induced reaction

The dynamical evolution of the heavy-ion collision is described by a transport equation of QMD type evolving nucleons, N* and Δ resonances, Λ′s and Σ baryons, furthermore, π′s, η′s, ρ′s, σ′s, ω′s and kaons with their isospin degrees of freedom. The input cross sections and resonance parameters of the model are fitted to the available nucleon-nucleon and pion-nucleon cross sections. One consequence of the chiral restoration is the mixing of parity partners. We look for a possible signature of the mixing of vector and axialvector mesons in heavy-ion collisions. We suggest an experimental method for its observation.