The equation of state for the nucleonic and hyperonic core of neutron stars

We re-examine the equation of state for the nucleonic and hyperonic inner core of neutron stars that satisfies the 2M⊙ observations as well as the recent determinations of stellar radii below 13 km, while fulfilling the saturation properties of nuclear matter and finite nuclei together with the constraints on the high-density nuclear pressure coming from heavy-ion collisions. The recent nucleonic FSU2R and hyperonic FSU2H models are updated in order to improve the behaviour of pure neutron matter at subsaturation densities. The corresponding nuclear matter properties at saturation, the symmetry energy, and its slope turn out to be compatible with recent experimental and theoretical determinations. We obtain the mass, radius, and composition of neutron stars for the two updated models and study the impact on these properties of the uncertainties in the hyperon-nucleon couplings estimated from hypernuclear data. We find that the onset of appearance of each hyperon strongly depends on the hyperon-nuclear uncertainties, whereas the maximum masses for neutron stars differ by at most 0.1M⊙, although a larger deviation should be expected tied to the lack of knowledge of the hyperon potentials at the high densities present in the centre of 2M⊙ stars. For easier use, we provide tables with the results from the FSU2R and FSU2H models for the equation of state and the neutron star mass-radius relation

Equation of state for nucleonic and hyperonic neutron stars with mass and radius constraints

We obtain a new equation of state for the nucleonic and hyperonic inner core of neutron stars that fulfils the 2 M⊙ observations as well as the recent determinations of stellar radii below 13 km. The nucleonic equation of state is obtained from a new parameterization of the FSU2 relativistic mean-field functional that satisfies these latest astrophysical constraints and, at the same time, reproduces the properties of nuclear matter and finite nuclei while fulfilling the restrictions on high-density matter deduced from heavy-ion collisions. On the one hand, the equation of state of neutron star matter is softened around saturation density, which increases the compactness of canonical neutron stars leading to stellar radii below 13 km. On the other hand, the equation of state is stiff enough at higher densities to fulfil the 2 M⊙ limit. By a slight modification of the parameterization, we also find that the constraints of 2 M⊙ neutron stars with radii around 13 km are satisfied when hyperons are considered. The inclusion of the high magnetic fields present in magnetars further stiffens the equation of state. Hyperonic magnetars with magnetic fields in the surface of ~1015 G and with values of ~1018 G in the interior can reach maximum masses of 2 M⊙ with radii in the 12-13 km range

Open-charm mesons in nuclear matter at finite temperature beyond the zero-range approximation

The properties of open charm mesons, D, D, D{sub s}, and D{sub s} in nuclear matter at finite temperature are studied within a self-consistent coupled-channel approach. The interaction of the low-lying pseudoscalar mesons with the ground-state baryons in the charm sector is derived from a t-channel vector-exchange model. The in-medium scattering amplitudes are obtained by solving the Lippmann-Schwinger equation at finite temperature including Pauli blocking effects, baryon dressing, as well as D, D, D{sub s}, and D{sub s} self-energies taking their mutual influence into account. We find that the in-medium properties of the D meson are affected by the D{sub s}-meson self-energy through the intermediate D{sub s}Y loops coupled to DN states. Similarly, dressing the D meson in the DY loops has an influence over the properties of the D{sub s} meson

Impact of a thermal medium on D mesons and their chiral partners

We study D and Ds mesons at finite temperature using an effective field theory based on chiral and heavy-quark spin-flavor symmetries within the imaginary-time formalism. Interactions with the light degrees of freedom are unitarized via a Bethe-Salpeter approach, and the D and Ds self-energies are calculated self-consistently. We generate dynamically the D*0(2300) and Ds*(2317) states, and study their possible identification as the chiral partners of the D and Ds ground states, respectively. We show the evolution of their masses and decay widths as functions of temperature, and provide an analysis of the chiral-symmetry restoration in the heavy-flavor sector below the transition temperature. In particular, we analyse the very special case of the D-meson, for which the chiral partner is associated to the double-pole structure of the D*0(2300)

Strange and charm mesons at fair

We study the properties of strange and charm mesons in hot and dense matter within a self-consistent coupled-channel approach for the experimental conditions of density and temperature expected for the CBM experiment at FAIR/GSI. The in-medium solution at finite temperature accounts for Pauli blocking effects, mean-field binding of all the baryons involved, and meson self-energies. We analyse the behaviour in this hot and dense environment of dynamically-generated baryonic resonances together with the evolution with density and temperature of the strange and open-charm meson spectral functions. We test the spectral functions for strange mesons using energy-weighted sum rules and finally discuss the implications of the properties of charm mesons on the Ds0(2317) and the predicted X(3700) scalar resonances.Molina Peralta, Raquel, [email protected] ; Nieves Pamplona, Juan Miguel, [email protected] ; Oset Báguena, Eulogio, [email protected]

Strange and charm mesons at fair

We study the properties of strange and charm mesons in hot and dense matter within a self-consistent coupled-channel approach for the experimental conditions of density and temperature expected for the CBM experiment at FAIR/GSI. The in-medium solution at finite temperature accounts for Pauli blocking effects, mean-field binding of all the baryons involved, and meson self-energies. We analyse the behaviour in this hot and dense environment of dynamically-generated baryonic resonances together with the evolution with density and temperature of the strange and open-charm meson spectral functions. We test the spectral functions for strange mesons using energy-weighted sum rules and finally discuss the implications of the properties of charm mesons on the Ds0(2317) and the predicted X(3700) scalar resonances.Molina Peralta, Raquel, [email protected] ; Nieves Pamplona, Juan Miguel, [email protected] ; Oset Báguena, Eulogio, [email protected]

Interaction of vector mesons with baryons and nuclei

After some short introductory remarks on particular issues on the vector mesons in nuclei, in this paper, we present a short review of recent developments concerning the interaction of vector mesons with baryons and with nuclei from a modern perspective using the local hidden gauge formalism for the interaction of vector mesons. We present results for the vector-baryon interaction and in particular for the resonances which appear as composite states, dynamically generated from the interaction of vector mesons with baryons, taking also the mixing of these states with pseudoscalars and baryons into account. We then venture into the charm sector, reporting on hidden charm baryon states around 4400 MeV, generated from the interaction of vector mesons and baryons with charm, which have a strong repercussion on the properties of the J/Psi N interaction. We also address the interaction of K* with nuclei and make suggestions to measure the predicted huge width in the medium by means of transparency ratio. The formalism is extended to study the phenomenon of J/psi suppression in nuclei via J/psi photo-production reactions

The properties of antikaons in hot and dense matter

[eng] Understanding the behavior of matter under extreme conditions of density and temperature, such as those found in neutron stars or in heavy-ion collisions, requires a good knowledge on the modification of the properties of hadrons in the nuclear medium. In particular, the in-medium effects on antikaons have received much attention over the last years, especially after the speculation of the possible existence of an antikaon condensed phase in neutron stars and the analysis of the experimental data coming from the programs developed at SIS-GSI, SPS-CERN and RHIC-BNL. The purpose of this thesis is to present a self-consistent calculation of the antikaon properties in dense and hot matter in order to explore the typical conditions found in heavy-ion collisions at GSI, studying the possible implications that the inclusion of the in-medium effects at finite temperature on the antikaon optical potential would have on the K-/ K+ ratio. Solving the Bethe-Goldstone equation for G-matrix, we obtain the K- optical potential from the K- N effective interaction in nuclear matter at T=0 taking, as a bare meson-baryon interaction, the meson-exchange potential of the Julich group. The momentum dependence and the effect of higher partial waves of the K- N effective interaction, beyond the L=0 component, are studied using this microscopic and self-consistent calculation. Afterwards, the model is extended by incorporating finite temperature effects in order to adapt our calculations to the experimental conditions in heavy-ion collisions. In the rank of densities studied, the finite temperature K- optical potential shows a smooth behavior if we compare it to the T=0 outcome. Finally, our model is applied to the study of the ratio between K- and K+ produced at GSI with T around 70 MeV in the framework of thermal models. Different approaches for the K- self-energy are taken into account so as to analyze the effects on the determination of this ratio

Open charm in nuclear matter at finite temperature

We study the properties of open-charm mesons ($D$ and $\bar {D}$) in nuclear matter at finite temperature within a self-consistent coupled-channel approach. The meson-baryon interactions are adopted from a type of broken SU(4) s-wave Tomozawa-Weinberg terms supplemented by an attractive scalar-isoscalar attraction. The in-medium solution at finite temperature incorporates Pauli blocking effects, mean-field binding on all the baryons involved, and $\pi$ and open-charm meson self-energies in a self-consistent manner. In the $DN$ sector, the $\Lambda_c$ and $\Sigma_c$ resonances, generated dynamically at 2593 MeV and 2770 MeV in free space, remain close to their free-space position while acquiring a remarkable width due to the thermal smearing of Pauli blocking as well as from the nuclear matter density effects. As a result, the $D$ meson spectral density shows a single pronounced peak for energies close to the $D$ meson free-space mass that broadens with increasing matter density with an extended tail particularly towards lower energies. The $\bar D$ potential shows a moderate repulsive behavior coming from the dominant I=1 contribution of the $\bar D N$ interaction. The low-density theorem is, however, not a good approximation for the $\bar D$ self-energy in spite of the absence of resonance-hole contributions close to threshold in this case. We speculate the possibility of $D$-mesic nuclei as well as discuss some consequences for the $J/\Psi$ suppression in heavy-ion collisions, in particular for the future CBM experiment at FAIR

The in-medium (K)over-barN interaction within a chiral unitary approach

The s- and p-wave contributions to the K¯N interaction in dense nuclear matter are obtained using a chiral unitary approach. We perform a self-consistent calculation of the K¯ self-energy including Pauli blocking effects, meson self-energies modified by short-range correlations and baryon binding potentials. We find that the on-shell factorization cannot be applied to evaluate the in-medium corrections to p-wave amplitudes. Furthermore, the Λ and Σ develop a mass shift of -30 MeV at saturation density while the Σ∗ width increases to 80 MeV. We conclude that no deep and narrow K¯ bound states could be observed