Properties of hyperon stars rotating at Keplerian frequency

The structure and properties of a Keplerian rotating hyperon star with an equation of state （EOS） investigated using the relativistic σ-ω-p model are examined by employing an accurate numerical scheme. It is shown that there is a clear rotating effect on the structure and properties, and that hyperon star matter cannot support a star with a mass larger than 1.9 M~, even a star rotating at the fastest allowed frequency. The constraints of the two known fastest rotating frequencies （716 Hz and 1122 Hz） on the mass and radius of a hyperon star are also explored. ~rthermore, our results indicate that the imprint of the rapid rotation of a hyperon star on the moment of inertia is clear; the backward equatorial redshift, the forward equatorial redshift and the polar redshift can be distinguished clearly, the forward equatorial redshift is always negative; and its figuration is far from a spherical symmetric shape.

Hyperon coupling dependence of hadron matter properties in relativistic mean field model

The properties of hadronic matter at β equilibrium in a wide range of densities are described by appropriate equations of state in the framework of the relativistic mean field model. Strange meson fields, namely the scalar meson field σ＊（975） and the vector meson field φ（1020）, are included in the present work. We discuss and compare the results of the equation of state, nucleon effective mass, and strangeness fraction obtained by adopting the TM1, TMA, and GL parameter sets for nuclear sector and three different choices for the hypcron couplings. We find that the parameter set TM1 favours the onset of hyperons most, while at high densities the GL parameter set leads to the most hyperon-rich matter. For a certain parameter set （e.g. TM1）, the most hyperon-rich matter is obtained for the hyperon potential model. The influence of the hyperon couplings on the effective mass of nucleon, is much weaker than that on the nucleon parameter set. The nonstrange mesons dominate essentially the global properties of dense hyperon matter. The hyperon potential model predicts the lowest value of the neutron star maximum mass of about 1.45 Msun to be 0.4--0.5 Msun lower than the prediction by using the other choices for hyperon couplings.

Gravitational waves from the axial perturbations of hyperon stars

The eigen-frequencies of the axial w-mode oscillations of hyperon stars are examined. It is shown that as the appearance of hyperons softens the equation of state of the super-density matter, the frequency of gravitational waves from the axial w-mode of hyperon star becomes smaller than that of a traditional neutron star at the same stellar mass. Moreover, the eigenfrequencies of hyperon stars also have scaling universality. It is shown that the EURO third-generation gravitational-wave detector has the potential to detect the gravitational-wave signal emitted from the axial w-mode oscillations of a hyperon star.

Hyperon-hyperon interaction in relativistic mean field model

By using the new experimental data of AA potential, this paper has performed a full calculation for strange hadronic matter with different strangeness contents as well as its consequences on the global properties of neutron star matter in relativistic mean field model. It finds that the new weak hyperon-hyperon interaction makes the equations of state much stiffer than the result of the previous strong hyperon hyperon interaction, and even stiffer than the result without consideration of hyperon-hyperon interaction. This new hyperon-hyperon interaction results in a maximum mass of 1.75M⊙ （where M⊙ stands for the mass of the Sun）, about 0.2-0.5M⊙ larger than the previous prediction with the presence of hyperons. After examining carefully the onset densities of kaon condensation it finds that this new weak version of hyperon-hyperon interaction favours the occurrence of kaons in comparison with the strong one.

Hyperon Effects on the Spin Parameter of Rotating Neutron Stars

Based on the equations of state from the relativistic mean field theory without and with the inclusion of strangeness-bearing hyperons, we study the dimensionless spin parameter j = cJ/（GM2） of uniformly rotat- ing neutron stars. It is shown that the maximum value of the spin parameter jmax of a neutron star rotating at the Keplerian frequency fK is .jmax - 0.7 when the star mass M 〉 0.SM⊙, which is sustained for various versions of equations of state without and with hyperons. The relationship between j and the scaled rotation frequency f /fK is found to be insensitive to the star mass or the adopted equation of state in the models without hyperons. However, the emergence of byperons in neutron stars will lead to an uncertainty of the spin parameter j, which in turn could generate a complexity in the theoretical study of the quasi-periodic oscillations observed in disk-accreting compact-star systems.

Influence of A Hyperons ^1S0 Superfluidity on the Direct Urca Processes with Hyperons

In the framework of the relativistic mean field theory （RMFT）,the relativistic energy losses of the directUrca processes with hyperons （Y-DURCA） for reactions A → p+e + ve and （?） → A + e + ve are studied in neutron stars.We calculate the energy gap of A hyperons and investigate the effects of the 1S0 superfluidity （SF） of A hyperons on theY-DURCA processes.The calculated results are in line with the recent experimental data ABaa ～ 1.01±0.20-0.11+0.18 MeV.The results indicate that the 1S0 SF of A hyperons exists in most density ranges of happening the two reactions.Thetheoretical cooling curves are in agreement with observation data.

Direct Urca Processes with Hyperon-Hyperon Interactions

与相互作用从潜力的新试验性的数据推出了的一个弱重核子重核子( YY )，这篇论文在包括的相对论的吝啬的领域理论( RMFT )的框架执行了直接 Urca ( DURCA )进程的计算*并且介子，与与强壮的 YY 相互作用并且没有计算的结果比较(*，)介子包括了。在中子星物质，当强壮的 YY 相互作用供应吸引人的时，弱 YY 相互作用供应在重核子之间的另外的排斥相互作用。与弱 YY 相互作用，当比那些小时，重核子的有效群众比有强壮的 YY 相互作用的那些大(* ，) 包括的介子。阀值星为包含核子的 DURCA 过程集中， A 不对 YY 相互作用的力量敏感。弱 YY 相互作用为包含的 DURCA 过程导致更大的阀值群众吗？并且 0 比另外的二个盒子。仅仅当弱 YY 相互作用被使用时，包含 0 的过程能发生在中子星。弱 YY 相互作用能引进与更大的质量并且比强壮的 YY 相互作用的更快的冷却的与中子星的观察的协议。

Influence of Interactions on Populations for Hyperons in Neutron Stars

The numerical results of the populations for the baryon octet in neutron star matter have been presented by solving a set transcendental equations in the framework of the relativistic mean field approximation. The influence of the hyperon interactions on hyperon populations in neutron star matter is discussed. The results manifest that when the ratio of the hyperon-to-nucleon couplings increases, all hyperons appear towards low baryon density direction.

Influence of Hyperon-Hyperon Interaction on Properties of Hadronic Star

hadronic 星的全面性质上的重核子重核子相互作用的影响在相对论的吝啬的地(RMF ) 的框架被调查理论。为联合的某些重核子，更弱的重核子重核子相互作用能导致更重的 hadronic 星，它在 X 光检查二进制代码与重中子星的观察一致。我们发现有更大的群众的重核子的阀值密度被带到一有重核子重核子相互作用的增加的更低的价值。重核子星的存在的可能性与重核子重核子相互作用的考虑被检查。

Helicity Amplitude Analysis of η_c Decays into Hyperon-Antihyperon Pairs

他合法地为这些过程的振幅(Y：重核子) 被介绍，和为 η c 腐烂进。在这些腐烂测量重核子腐烂参数的敏感被评估基于他合法地振幅。用腐烂在实验测试钟不平等的前景被讨论。

Production and decay of polarized hyperon-antihyperon pairs

Polarized hyperon-antihyperon pairs shed light on various unresolved puzzles in contemporary physics:How the strong interaction confines quarks into hadrons, how accurately the Standard Model describes microcosmos and even why our universe consists of so much more matter than antimatter. Thanks to their weak, parity violating decays, hyperons reveal their spin properties. This can be exploited e.g. the decomposition of the electromagnetic structure of hyperons, precision tests of flavour symmetry and searches for CP violation. At the BESⅢ experiment at BEPC-Ⅱ, Beijing, China, hyperon-antihyperon pairs can be produced in abundance. Recently collected large data samples have triggered the development of new methods that provide unprecedented precision and a plethora of new results have emerged. When applied at future high-intensity facilities like PANDA and STCF, precision physics will be taken to a new level which can contribute to the solution to the aforementioned puzzles.

Transition density of the large mass hyperon star

The difference between the transition density of a larger mass hyperon star （for example, the neutron star PSR J1614-2230） and that of a smaller mass hyperon star is investigated in the framework of the relativistic mean field theory. We see that the transition density p0H increases with the increase of xw （i.e. the mass of the neutron star）. For the nucleons parts, the neutrons make the main contribution to the transition density as the baryon density P=p0H. With the increase of the xw （i.e. the mass of the neutron star）, the relative particle number density of neutrons decreases while that of protons increases. For the parts of hyperons, the ∧ and ≡. make the main contributions to the transition density as the baryon density p=p0H. The relative particle number density of A decreases while that of ≡ increases with the increase of the xw （i.e. the mass of the neutron star）. For the hyperons ∑-, ∑0 and E-, the total contributions are less than 16 per cent.

Two New Hyperon Coupling Models in the Light of the Massive Neutron Star PSR J0348+0432

In the context of the relativistic mean field theory,we propose two new hyperon coupling models,namely the limitation model and the potential well depth model,in the light of the observed data for the massive neutron PSR J0348+0432.The radius of PSR J0348+0432 given by the limitation model is found to be 12.52 km^12.97 km,while the radius given by the potential well depth model is found to be 12.19 km^12.89 km.We also calculate the gravitational redshift of PSR J0348+0432 within these two models,for which the limitation model gives 0.346~0.391 and the potential well depth model gives 0.350~0.409.Further exploration of these two models shows that,these two models are almost degenerate for neutron stars lighter than 1.85 M⊙,and start to give different results for massive neutron stars heavier than 1.85 M⊙.Therefore,the studies of massive neutron stars could be crucial for discriminating these two models and help deepen our understanding of hyper-nuclear interactions.

Transverse momentum dependence of differential directed flow of Λ hyperon within kaon covariant dynamics

The transverse momentum distributions of Λ's and proton's directed flows are investigated by using Quantum Molecular Dynamics model (QMD) within the framework of covariant kaon dynamics. The calculated results show that the transverse momentum distribution of differential directed flow of Lambda hyperons is dependent appreciably on the nuclear matter equation of states (EOS). The differential directed flow of Lambda hyperons calculated with soft EOS is consistent with the experimental data,whereas the discrepancy between the results obtained with hard EOS and experimental data increases with increasing the transverse momentum. Although the interaction acting on Λ's by nucleons in the dense medium is attractive,the analysis indicates,that the transverse momentum distribution of proton's directed flow is insensitive to the EOS. The results obtained with both hard and soft EOS are all roughly in agreement with the corresponding data.

Study of the s → dv■ rare hyperon decays in the Standard Model and new physics

FCNC processes offer important tools to test the Standard Model(SM)and to search for possible new physics.In this work,we investigate the s→dννrare hyperon decays in SM and beyond.We find that in SM the branching ratios for these rare hyperon decays range from 10^-14 to 10^-11.When all the errors in the form factors are included,we find that the final branching ratios for most decay modes have an uncertainty of about 5%to 10%.After taking into account the contribution from new physics,the generalized SUSY extension of SM and the minimal 331 model,the decay widths for these channels can be enhanced by a factor of 2~7.

Prospects for rare and forbidden hyperon decays at BESⅢ

The study of hyperon decays at the Beijing Electron Spectrometer Ⅲ （BESⅢ） is proposed to investigate the events of J/φ decay into hyperon pairs, which provide a pristine experimental environment at the Beijing Electron-Positron Collider Ⅱ. About 10^6-10^8 hyperons, i.e., ∧, ∑, ∈, and Ω, will be produced in the J/φ and φ（2S） decays with the proposed data samples at BESⅢ. Based on these samples, the measurement sensitivity of the branching fractions of the hyperon decays is in the range of 10^-5-10^-8. In addition, with the known center-of-mass energy and ＂tag technique＂, rare decays and decays with invisible final states can be probed.

Thermal protoneutron stars with hyperons

The properties of thermal protoneutron star matter including hyperons are investigated in the framework of the relativistic mean field theory (RMFT). In protoneuron star matter, with the increase of the temperature, the critical densities of hyperons decrease, the sequence for appearances of hyperons change, the abundances of hyperons as well as neutrinos increase, and the strong interactions between baryons get weaker. Meanwhile, the abundances of isospin multiple states for nucleons, Σ, and ■ become identical, leading to isospin saturated symmetric matter, respectively. Moreover, if a protoneutron star is born with higher temperature, it is less likely to convert to a black hole.

Rearrangement term with relativistic density-dependent hyperon potentials

An appropriate density dependence of hyperon potentials is important for the stiffening of the equation of state and massive neutron stars. To persist in covariance and thermodynamic consistency, the rearrangement term is indispensable. In this work, we derive the rearrangement term for hyperon potentials with arbitrary density- dependence. The importance of the rearrangement term is also exhibited in numerical instances.

Effect of the mesons σ~* and Φ and the variety of U_Σ^(N) on the transition density of hyperon stars

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

Hyperonic neutron stars: reconciliation between nuclear properties and NICER and LIGO/VIRGO results

Using an extended version of quantum hadrodynamics,I propose a new microscopic equation of state(EoS)that is able to correctly reproduce the main properties of symmetric nuclear matter at the saturation density,as well as produce massive neutron stars and satisfactory results for the radius and the tidal parameter.I show that this EoS can reproduce at least a 2.00 solar mass neutron star,even when hyperons are present.The constraints about the radius of a 2.00 M_(⊙) and the minimum mass that enables a direct Urea effect are also checked.