SUBRAT KUMAR BISWAL Institute Theoretical Physics, UCAS, China, Beijing-100190

1. Effects of the φ-meson on the hyperon production in the hyperon star SUBRAT KUMAR BISWAL Institute Theoretical Physics, UCAS, China, Beijing-100190

2. Plan of the talk • Introduction • Theoretical Formalism • hyperon puzzle • Calculation with various RMF parameter set • Results and discussions • Summary

3. INTORDUCTION • The matter inside the neutron star is very different form the terrestrial environment; therefore a good knowledge of EOS required to understand the properties of the neutron star. • Traditionally the core of the NS is modeled as a β-equilibrated neutron rich matter. • Due the large value of the density, new hadronic degrees of freedom are more likely to appear inside the core of the NS. • Hyperons may appear at a density 2-3 times the saturation density. • But the presences of the hyperon leads a softening the EOS , reduction of the maximum mass.

4. The recent observation of the PSRJ1614-2230 (1.97 SM) and PSR J0348+0432 ( 2.01 SM) , demand the stiff equation of state and intriguing the long back hyperon Puzzle. The presence of the hyperon in the neutron star was considered for the first time by Ambartsumyan in 1960. Three different mechanisms that could provide such additional repulsion 1. The repulsive hyperon-hyperon interaction (exchange of vector meson) 2. The inclusion of repulsive hyperonic three-body force 3. The possibility of the phase transition to the deconfinment quark matter

5. Theoretical formalisms We use the relativistic mean field formalism to calculate the EOS for the neutron and hyperon star. The interacting mesons are σωρ between the nucleons and σωρφ-mesons are between the hyperons.

7. The nucleon-meson interaction strengths are obtained by fitting with the saturation properties of the infinite nuclear matter and finite nuclear properties like charge radius, binding energies, excitation energy of monopole. We know little about the hyperon-hyperon interaction as there are less number of hyper-nuclei are synthesized in the laboratory. So we follow a phenomenological approaches to fit the hyperon-hyperon interaction from assumption of the effective potential. We use following expression to calculate the effective potential The different hyperon potentials are UΛ=-30 MeV, UΞ=-28 MeV, UΣ=+40 MeV. The xσY and xωY are fitted to reproduce the hyperon potential.

9. Fitted hyperon-meson coupling constant for various parameter sets xφΛ =xφΣ =xφΞ /2 = -0.4714 xωN

10. Mass vs radius of the neutron star for the various parameter sets . (c) FSU, IFSU, G1,FSU*,SINPA, SINPB,BSP (b) BSP, SINPA, FSU,SINPB,IFSU*

11. Effects of the φ-meson on the EOS of G1-parameter set

12. Variation of the maximum mass of the hyperon star with hyperon-meson Coupling constants

13. Mass vs radius of the hyperon star with different parameter sets

14. MN ( σ,ω,ρ) > MH ( σ,ω,ρ,φ) > MH ( σ, ω, ρ) (M/R)N ( σ,ω,ρ) > (M/R)H (σ,ω,ρ,φ) > (M/R)H (σ,ω,ρ)

15. Effects φ-meson on the relative hyperon production

16. Variation of the strangeness content of the hyperon star with coupling constants Phys. Rev. C 85, 065802 (2012).

17. Summary For study of the hyperon-hyperon interaction strength, we need lots of hyper-nuclear data. In summary, we study the properties of the neutron star with 25 parameter set of the RMF model and check their predictive capacity to reproduce the recent observation of the maximum mass. We have discussed how the different pair xσY and xωY , which reproduce same potential affect the maximum mass of the hyperon star So it is necessary not only constraint the potential depth but also the range of the hyperon-meson coupling constants go get more clear picture

18. The inclusion of the φ-meson increases the maximum mass of the hyperon star, mainly due to the pushing the threshold of the hyperon production to higher density. The variation of the strangeness content of the hyperon star with hyperon meson coupling constants are discussed.

19. THANKS