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We have conducted a study of the femtoscopic correlation functions for the D 0 D ⁎ + and D + D ⁎ 0 channels that build the T c c state. We develop a formalism that allows us to factorize the scattering amplitudes outside the integrals in the formulas, and the integrals involve the range of the strong interaction explicitly. For a source of size of 1 fm, we find values for the correlation functions of the D 0 D ⁎ + and D + D ⁎ 0 channels at the origin around 30 and 2.5, respectively, and we see these observables converging to unity already for relative momenta of the order of 200 MeV. We conduct tests to see the relevance of the different contributions to the correlation function and find that it mostly provides information on the scattering length, but should the correlation functions be measured with the precision of the latest experiments, the effective range of the D 0 D ⁎ + could also be obtained. [ABSTRACT FROM AUTHOR]

We study the structure of single Λ -hypernuclei using the Hartree–Fock–Bogoliubov method. Finite range Gogny-type forces are used to describe the nucleon–nucleon and Λ -nucleon interactions. Three different Λ -nucleon Gogny forces are built. The unknown parameters of these forces are obtained by fitting the experimental binding energies of the 1s Λ single-particle state in various hypernuclei using the "Simulated Annealing Method". These forces are then used to calculate the binding energies of the other (1p, 1d, 1f, 1g) Λ single-particle states in the different hypernuclei. The predicted values are found to be in good agreement with the experimental data for the three forces constructed. In addition, we calculate also the root-mean-square radii of ground state Λ orbital, as well as several global properties of the hypernuclei considered such as their ground-state Hartree–Fock–Bogoliubov energy, their pairing energy and their quadrupole moment. [ABSTRACT FROM AUTHOR]

Elucidating the appropriate microscopic degrees of freedom within neutron stars remains an open question which impacts nuclear physics, particle physics and astrophysics. The recent discovery of the first non-trivial dibaryon, the d ⁎ ( 2380 ) , provides a new candidate for an exotic degree of freedom in the nuclear equation of state at high matter densities. In this paper a first calculation of the role of the d ⁎ ( 2380 ) in neutron stars is performed based on a relativistic mean field description of the nucleonic degrees of freedom supplemented by a free boson gas of d ⁎ ( 2380 ) . The calculations indicate that the d ⁎ ( 2380 ) would appear at densities around three times normal nuclear matter saturation density and comprise around 20% of the matter in the centre of heavy stars with higher fractions possible in the higher densities of merger processes. The d ⁎ ( 2380 ) would also reduce the maximum star mass by around 15% and have significant influence on the fractional proton/neutron composition. New possibilities for neutron star cooling mechanisms arising from the d ⁎ ( 2380 ) are also predicted. [ABSTRACT FROM AUTHOR]

Abstract: We construct two-meson exchange three-baryon potentials between two nucleons and one hyperon (NNY) consistent with the two body nucleon–hyperon (NY) J04 potential of the Jülich group. In particular, we focus on the NNΛ and forces since Λ and are the first hyperons expected to appear in microscopic calculations of neutron star matter. Brueckner–Hartree–Fock calculations of the hyperonic matter are then performed including the effect of these three-body forces. Our results show that at high densities the total contribution of the NNY force is repulsive making the resulting equation of state stiffer, as required from neutron star mass observations. [Copyright &y& Elsevier]

Abstract: We study the role played by hyperons on the hadron-star to quark-star conversion mechanism proposed recently by Berezhiani and collaborators. We find that the quantum nucleation of a quark matter drop inside hadron matter is faster when the presence of hyperons is taken into account in the hadron phase. As a consequence the conversion mechanism is then favored. [Copyright &y& Elsevier]

Single-particle energies of the Λc charmed baryon are obtained in several nuclei from the relevant self-energy constructed within the framework of a perturbative many-body approach. Results are presented for a charmed baryon-nucleon (YcN) potential based on a SU(4) extension of the meson-exchange hyperon-nucleon potential ˜A of the Jülich group. Three different models (A, B, and C) of this interaction, which differ only on the values of the couplings of the scalar σ meson with the charmed baryons, are considered. Phase shifts, scattering lengths, and effective ranges are computed for the three models and compared with those predicted by the YcN interaction derived by Haidenbauer and Krein [Eur. Phys. A 54, 199 (2018)] from the extrapolation to the physical pion mass of recent results of the HAL QCD Collaboration. Qualitative agreement is found for two of the models (B and C) considered. Our results for Λc nuclei are compatible with those obtained by other authors based on different models and methods. We find a small spin-orbit splitting of the p-, d-, and f-wave states as in the case of single Λ hypernuclei. The level spacing of Λc single-particle energies is found to be smaller than that of the corresponding one for hypernuclei. The role of the Coulomb potential and the effect of the coupling of the ΛcN and ΣcN channels on the single-particle properties of Λc nuclei are also analyzed. Our results show that, despite the Coulomb repulsion between the Λc and the protons, even the less attractive one of our YcN models (model C) is able to bind the Λc in all the nuclei considered. The effect of the ΛcN-ΣcN coupling is found to be almost negligible due to the large mass difference of the Λc and Σc baryons. [ABSTRACT FROM AUTHOR]

The equation of state of neutron matter is affected by the presence of a magnetic field due to the intrinsic magnetic moment of the neutron. Here we study the equilibrium configuration of this system for a wide range of densities, temperatures, and magnetic fields. Special attention is paid to the behavior of the isothermal compressibility and the magnetic susceptibility. Our calculation is performed using both microscopic and phenomenological approaches of the neutron matter equation of slate, namely the Brueckner-Hartree-Fock (BHF) approach using the Argonne V18 nucleon-nucleon potential supplemented with the Urbana IX three-nucleon force, the effective Skyrme model in a Hartree-Fock description, and the quantum hadrodynamic formulation with a mean-field approximation. All these approaches predict a change from completely spin polarized to partially polarized matter that leads to a continuous equation of state. The compressibility and the magnetic susceptibility show characteristic behaviors which reflect that fact. Thermal effects tend to smear out the sharpness found for these quantities at T = 0. In most cases a thermal increase of △T = 10 MeV is enough to hide the signals of the change of polarization. The set of densities and magnetic field intensities for which the system changes it spin polarization is different for each model. However, we found that under the conditions examined in this work there is an overall agreement between the three theoretical descriptions. [ABSTRACT FROM AUTHOR]

Only one-third of the nucleons in 208Pb occupy the saturation density area. Consequently, nuclear observables related to the average properties of nuclei, such as masses or radii, constrain the equation of state not at the saturation density but rather around the so-called crossing density, localized close to the mean value of the density of nuclei: p ≈ 0.11 fm-3. This provides an explanation for the empirical fact that several equation of state quantities calculated with various functionals cross at a density significantly lower than the saturation one. The third derivative M of the energy per unit of volume at the crossing density is constrained by the giant monopole resonance measurements in an isotopic chain rather than the incompressibility at saturation density. The giant monopole resonance measurements provide M = 1100 ± 70 MeV (6% uncertainty), whose extrapolation gives K∞ = 230 ± 40 MeV (17% uncertainty). [ABSTRACT FROM AUTHOR]

We review the current status and recent progress of microscopic many-body approaches and phenomenological models, which are employed to construct the equation of state of neutron stars. The equation of state is relevant for the description of their structure and dynamical properties, and it rules also the dynamics of core-collapse supernovae and binary neutron star mergers. We describe neutron star matter assuming that the main degrees of freedom are nucleons and hyperons, disregarding the appearance of quark matter. We compare the theoretical predictions of the different equation-of-state models with the currently available data coming from both terrestrial laboratory experiments and recent astrophysical observations. We also analyze the importance of the nuclear strong interaction and equation of state for the cooling properties of neutron stars. We discuss the main open challenges in the description of the equation of state, mainly focusing on the limits of the different many-body techniques, the so-called "hyperon puzzle," and the dependence of the direct URCA processes on the equation of state. [ABSTRACT FROM AUTHOR]

The properties of the D and D charmed mesons in normal nuclear matter density are studied within a coupled channel approach using a t-channel vector-meson exchange mechanism as driving force. The in-medium scattering amplitudes are obtained by solving the Lippmann-Schwinger equation including Pauli blocking effects and medium self-energies in a self-consistent way. [ABSTRACT FROM AUTHOR]

Isobaric single charge-exchange reactions, changing nuclear charges by one unit but leaving the mass partitions unaffected, have been for the first time investigated by peripheral collisions of 112Sn ions accelerated up to 1 A GeV at the GSI facilities. The high-resolving power of the FRS spectrometer allows us to obtain (p , n) -type isobaric charge-exchange cross sections with an uncertainty of 3.5% and to separate quasi-elastic and inelastic components in the missing-energy spectra of the ejectiles. The inelastic component is associated to the excitation of the Δ(1232) isobar resonance and the emission of pions in s-wave both in the target and projectile nucleus, while the quasi-elastic contribution is associated to the nuclear spin-isospin response of nucleon-hole excitations. An apparent shift of the Δ-resonance peak of ∼63 MeV is observed when comparing the missing-energy spectra obtained from the measurements with proton and carbon targets. A detailed analysis, performed with a theoretical model for the reactions, indicates that this observation can be simply interpreted as a change in the relative magnitude between the contribution of the excitation of the resonance in the target and in the projectile. [ABSTRACT FROM AUTHOR]

We study the effects of a strong magnetic field on the proton and neutron spin polarization and magnetic susceptibility of asymmetric nuclear matter within a relativistic mean-field approach. It is shown that magnetic fields B~1016-1017 G have noticeable effects on the range of densities of interest for the study of the crust of a neutron star. Although the proton susceptibility is larger for weaker fields, the neutron susceptibility becomes of the same order or even larger for small proton fractions and subsaturation densities for B>1016 G. We expect that neutron superfluidity in the crust will be affected by the presence of magnetic fields. [ABSTRACT FROM AUTHOR]

We present calculations of the energy per particle of pure neutron and symmetric nuclear matter with simplified Argonne nucleon-nucleon potentials for different many-body theories. We compare critically the Brueckner-Hartree-Fock results to other formalisms, such as the Brueckner-Bethe-Goldstone expansion up to third order, self-consistent Green's functions, auxiliary field diffusion Monte Carlo, and Fermi hypernetted chain. We evaluate the importance of spin-orbit and tensor correlations in the equation of state and find these to be important in a wide range of densities. [ABSTRACT FROM AUTHOR]

The symmetry energy contribution to the nuclear equation of state impacts various phenomena in nuclear astrophysics, nuclear structure, and nuclear reactions. Its determination is a key objective of contemporary nuclear physics, with consequences for the understanding of dense matter within neutron stars. We examine the results of laboratory experiments that have provided initial constraints on the nuclear symmetry energy and on its density dependence at and somewhat below normal nuclear matter density. Even though some of these constraints have been derived from properties of nuclei while others have been derived from the nuclear response to electroweak and hadronic probes, within experimental uncertainties-they are consistent with each other. We also examine the most frequently used theoretical models that predict the symmetry energy and its slope parameter. By comparing existing constraints on the symmetry pressure to theories, we demonstrate how contributions of three-body forces, which are essential ingredients in neutron matter models, can be determined. [ABSTRACT FROM AUTHOR]

Abstract: We study the quark deconfinement phase transition in hot β-stable hadronic matter. Assuming a first order phase transition, we calculate the enthalpy per baryon of the hadron–quark phase transition. We calculate and compare the nucleation rate and the nucleation time due to thermal and quantum nucleation mechanisms. We compute the crossover temperature above which thermal nucleation dominates the finite temperature quantum nucleation mechanism. We next discuss the consequences for the physics of proto-neutron stars. We introduce the concept of limiting conversion temperature and critical mass for proto-hadronic stars, and we show that proto-hadronic stars with a mass could survive the early stages of their evolution without decaying to a quark star. [Copyright &y& Elsevier]

Abstract: The properties of spin polarized neutron matter are studied both at zero and finite temperature within the framework of the Brueckner–Hartree–Fock formalism, using the Argonne v18 nucleon–nucleon interaction. The free energy, energy and entropy per particle are calculated for several values of the spin polarization, densities and temperatures together with the magnetic susceptibility of the system. The results show no indication of a ferromagnetic transition at any density and temperature. [Copyright &y& Elsevier]

Abstract: We study the energy per particle of symmetric nuclear matter and pure neutron matter using realistic nucleon–nucleon potentials having noncentral tensor and spin–orbit components, up to three times the empirical nuclear matter saturation density, . The calculations are carried out within the frameworks of the Brueckner–Bethe–Goldstone (BBG) and correlated basis functions (CBF) formalisms, in order to ascertain the accuracy of the methods. The two hole-line approximation, with the continuous choice for the single particle auxiliary potential, is adopted for the BBG approach, whereas the variational Fermi hypernetted chain/single operator chain theory, corrected at the second order perturbative expansion level, is used in the CBF one. The energies are then compared with the available quantum and variational Monte Carlo results in neutron matter and with the BBG, up to the three hole-line diagrams. For neutron matter and potentials without spin–orbit components all methods, but perturbative CBF, are in reasonable agreement up to . After the inclusion of the LS interactions, we still find agreement around , whereas it is spoiled at larger densities. The spin–orbit potential lowers the energy of neutron matter at by per nucleon. In symmetric nuclear matter, the BBG and the variational results are in agreement up to . Beyond this density, and in contrast with neutron matter, we find good agreement only for the potential having spin–orbit components. [Copyright &y& Elsevier]

We investigate the possibility that the low mass companion of the black hole in the source of GW190814 was a strange quark star. This possibility is viable within the so-called two-families scenario in which neutron stars and strange quark stars coexist. Strange quark stars can reach the mass range indicated by GW190814, M∼(2.5-2.67)  M⊙ due to a large value of the adiabatic index, without the need for a velocity of sound close to the causal limit. Neutron stars (actually hyperonic stars in the two-families scenario) can instead fulfill the presently available astrophysical and nuclear physics constraints which require a softer equation of state. In this scheme it is possible to satisfy both the request of very large stellar masses and of small radii while using totally realistic and physically motivated equations of state. Moreover it is possible to get a radius for a 1.4  M⊙ star of the order or less than 11 km, which is impossible if only one family of compact stars exists. [ABSTRACT FROM AUTHOR]

Background: The recent accurate measurement of the mass of two pulsars close to or above 2M⊙ has raised the question of whether such large pulsar masses allow for the existence of exotic degrees of freedom, such as hyperons, inside neutron stars. Purpose: In the present work, we will investigate, within a phenomenological relativistic mean field approach, how the existing hypernuclei properties may constrain the neutron star equation of state and confront the neutron star maximum masses obtained with equations of state calibrated to hypernuclei properties with the astrophysical 2M⊙ constraint. Method: The study is performed using a relativistic mean field approach to describe both the hypernuclei and the neutron star equations of state. Unified equations of state are obtained. A set of five models that describe 2M⊙ when only nucleonic degrees of freedom are employed. Some of these models also satisfy other well-established laboratory or theoretical constraints. Results: The Λ-meson couplings are determined for all the models considered, and the Λ potential in symmetric nuclear matter and Λ matter at saturation are calculated. Maximum neutron star masses are determined for two values of the Λ-ω meson coupling, gωΛ=2gωN/3 and gωΛ=gωN, and a wide range of values for gϕΛ. Hyperonic stars with the complete baryonic octet are studied, restricting the coupling of the Σ and Ξ hyperons to the ω,ρ, and σ mesons due to the lack of experimental data, and maximum star masses calculated. Conclusions: We conclude that, within a phenomenological relativistic mean field approach, the currently available hypernuclei experimental data and the lack of constraints on the asymmetric equation of state of nuclear matter at high densities set only a limited number of constraints on the neutron star matter equation of state using the recent 2M⊙ observations. It is shown that the Λ potential in symmetric nuclear matter takes a value of ~30-32MeV at saturation for the gωΛ coupling given by the SU(6) symmetry, being of the order of the values generally used in the literature. On the other hand, the Λ potential in Λ matter varies between -14 and -8 MeV, taking for vector mesons couplings the SU(6) values, at variance with generally employed values between -1 and -5 MeV. If the SU(6) constraint is relaxed and the vector meson couplings to hyperons are kept to values not larger than those of nucleons, then values between -13 and +9 MeV are obtained. [ABSTRACT FROM AUTHOR]