A previously derived relativistic energy density functional for nuclei, based on low-energy in-medium chiral dynamics, is generalized to implement constraints from chiral SU(3) effective field theory and applied to $Λ$ hypernuclei. Density-dependent central and spin-orbit mean fields are calculated for a $Λ$ hyperon using the SU(3) extension of in-medium chiral perturbation theory to two-loop order. Long range $ΛN$ interactions arise from kaon-exchange and from two-pion-exchange with a $Σ$ hyperon in the intermediate state. Short-distance dynamics is encoded in contact interactions. They include scalar and vector mean fields reflecting in-medium changes of quark condensates, constrained by QCD sum rules. The $Λ$ single particle orbitals are computed for a series of hypernuclei from $^{13}_Λ$C to $^{208}_Λ$Pb. The role of a surface (derivative) term is studied. Its strength is found to be compatible with a corresponding estimate from in-medium chiral perturbation theory. Very good agreement with hypernuclear spectroscopic data is achieved. The smallness of the $Λ$-nuclear spin-orbit interaction finds a natural explanation in terms of an almost complete cancellation between short-range scalar/vector contributions and longer range terms generated by two-pion exchange.
We study strangeness dynamics in reactions relevant for the formation of multi-strange hypernuclei. In particular, we discuss the in-medium effects on elementary hyperon-nucleon ($YN$) channels, which are relevant for the production of hypernuclei at PANDA. The results indicate strong in-medium effects on $YN$-scattering, which might be important for hypernuclear studies at PANDA.
We take an approach to the $Λ$ nonmesonic weak decay in nuclei based on the exchange of mesons under the guidelines of chiral Lagrangians. The one pion and one kaon exchange are considered, together with the exchange of two pions, either correlated, leading to an important scalar-isoscalar exchange ($σ$-like exchange), or uncorrelated (box diagrams). A drastic reduction of the OPE results for the $Γ_n/Γ_p$ ratio is obtained and the new results are compatible with all present experiments within errors. The absolute rates obtained for different nuclei are also in fair agreement with experiment.
A previously introduced relativistic energy density functional, successfully applied to ordinary nuclei, is extended to hypernuclei. The density-dependent mean field and the spin-orbit potential are consistently calculated for a $Λ$ hyperon in the nucleus using the SU(3) extension of in-medium chiral perturbation theory. The leading long range $ΛN$ interaction arises from kaon-exchange and $2π$-exchange with $Σ$ hyperon in the intermediate state. Scalar and vector mean fields reflecting in-medium changes of the quark condensates are constrained by QCD sum rules. The model, applied to oxygen as…
We introduce a microscopic and relativistic theory describing free scattering and finite nuclei for the octet baryons in a consistent quantum field theoretical framework based on Dirac-Brueckner theory and nuclear mean-field. In a first quantitative approach - yet still heuristic for dealing with the $Λ$ hyperon - the quality of the description of finite (hyper)nuclei based on free meson exchange potentials is competitive with those from purely phenomenological relativistic mean-field calculations. In contrast to the latter our approach has the advantage of having a microscopic link to free in…
The $SU(3)$ meson exchange approach to interactions within the baryon octet and nuclear density functional theory are used to derive an \emph{ab initio} description of hypernuclear interactions. The density dependence of interactions is recast into a DFT with density dependent interaction vertices. The field-theoretical structure is retained by expressing the vertices as functionals of the matter field operators. Applications to infinite hypermatter and neutron star matter are discussed. A new approach is presented allowing to determine in-medium coupling constants out of the $NN$-vertex funct…
The production and structure of Λ hypernuclei are investigated in field theoretical models. The production in coherent p+A reactions is investigated by means of a resonance model. Results of exploratory calculations for associated strangeness production are presented for proton reactions on 40Ca. The target single particle wave functions are obtained from DDRH theory with density dependent Dirac-Brueckner meson-baryon vertices. The dependence of the in-medium vertices on density is discussed.
A covariant hyper-nuclear energy density functional (EDF) is derived from in medium nucleon meson vertex functionals, assuring the proper description of nuclear mean-field dynamics. The fundamental SU(3) coupling constants for the mean-field relevant vector (m=V) and scalar (m=S) interactions as functionals of the total baryon density are determined. Scalar and vector potentials and the resulting hyperon mean-fields in asymmetric nuclear matter are constructed and discussed, addressing also effects from three-body interactions. Λ- Σ^0 mixing in asymmetric nuclear through the coupling to the ba…
Hot hypernuclear matter is investigated in an explicit SU(3) quark model based on a mean field description of nonoverlapping baryon bags bound by the self-consistent exchange of scalar $σ, ζ$ and vector $ω, ϕ$ mesons. The $σ, ω$ mean fields are assumed to couple to the u,d-quarks while the $ζ, ϕ$ mean fields are coupled to the s-quark. The coupling constants of the mean fields with the quarks are assumed to satisfy SU(6) symmetry. The calculations take into account the medium dependence of the bag parameter on the scalar fields $σ, ζ$. We consider only the octet baryons $N,Λ,Σ,Ξ$ in hypernucle…
The contribution of ground state correlations (GSC) to the non--mesonic weak decay of $^{12}_Λ$C and other medium to heavy hypernuclei is studied within a nuclear matter formalism implemented in a local density approximation. We adopt a weak transition potential including the exchange of the complete octets of pseudoscalar and vector mesons as well as a residual strong interaction modeled on the Bonn potential. Leading GSC contributions, at first order in the residual strong interaction, are introduced on the same footing for all isospin channels of one-- and two--nucleon induced decays. Toget…
1s(Lambda) hypernuclear formation rates in stopped K- reactions on several p-shell targets are derived from hypernuclear formation spectra measured recently by the FINUDA Collaboration and are compared with calculated 1s(Lambda) formation rates based on a KbarN coupled channels chiral model. The calculated rates are about 15% of the derived rates, depending weakly on the depth of the threshold K- nuclear potential. The A dependence of the calculated rates is in fair agreement with that of the derived rates, showing a slight preference for a deep density dependent K- nuclear potential of depth …
We extend the No-Core Shell Model (NCSM) methodology to incorporate strangeness degrees of freedom and apply it to single-$Λ$ hypernuclei. After discussing the transformation of the hyperon-nucleon (YN) interaction into Harmonic-Oscillator (HO) basis and the Similarity Renormalization Group transformation applied to it to improve model-space convergence, we present two complementary formulations of the NCSM, one that uses relative Jacobi coordinates and symmetry-adapted basis states to fully exploit the symmetries of the hypernuclear Hamiltonian, and one working in a Slater determinant basis o…
We review the present activities related to hypernuclear production in hadronic in-medium reactions at intermediate energies. The status of theoretical predictions and experimental evidences for the in-medium formation of bound superstrange matter is discussed. Heavy-ion collisions and antiproton-induced reactions at energies close to strangeness production thresholds create the conditions of hypermatter formation. This allows to understand better in-medium hyperon interactions and sets constraints on the strangeness sector of the nuclear equation of state.
In the last years auxiliary field diffusion Monte Carlo has been used to assess the properties of hypernuclear systems, from light- to medium-heavy hypernuclei and hyper-neutron matter. One of the main findings is the key role played by the three-body hyperon-nucleon-nucleon interaction in the determination of the hyperon separation energy of hypernuclei and as a possible solution to the hyperon puzzle. However, there are still aspects of the employed hypernuclear potential that remain to be carefully investigated. In this paper we show that the isospin dependence of the Lambda-NN force, which…
When the $\bar{K}N$ system is submerged in nuclear medium the $\bar{K}N$ scattering amplitude and the final state branching ratios exhibit a strong energy dependence when going to energies below the $\bar{K}N$ threshold. A sharp increase of $\bar{K}N$ attraction below the $\bar{K}N$ threshold provides a link between shallow $\bar{K}$-nuclear potentials based on the chiral $\bar{K}N$ amplitude evaluated at threshold and the deep phenomenological optical potentials obtained in fits to kaonic atoms data. We show the energy dependence of the in-medium $K^{-}p$ amplitude and demonstrate the impact …
The $A$-dependence of the bond energy $ΔB_{ΛΛ}$ of the ${ΛΛ}$ hypernuclear ground states is calculated in a three-body ${Λ+ Λ+ {^{A}Z}}$ model and in the Skyrme-Hartree-Fock approach. Various ${ΛΛ}$ and $Λ$-nucleus or ${ΛN}$ potentials are used and the sensitivity of $ΔB_{ΛΛ}$ to the interactions is discussed. It is shown that in medium and heavy ${ΛΛ}$ hypernuclei, $ΔB_{ΛΛ}$ is a linear function of $r_Λ^{-3}$, where $r_Λ$ is rms radius of the hyperon orbital. It looks unlikely that it will be possible to extract ${ΛΛ}$ interaction from the double-$Λ$ hypernuclear energies only, the additional…
We have constructed the leading order hyperon-nucleon potential in a chiral Effective Field Theory approach. The chiral potential consists of one-pseudoscalar-meson exchanges and non-derivative four-baryon contact terms. The hyperon-nucleon interactions are derived using SU(3) symmetry, the nucleon-nucleon interaction is not considered explicitly since it can not be described well with a leading order chiral Effective Field Theory. We solve a regularized Lippmann-Schwinger equation and show that a good description of the available hyperon-nucleon scattering data is possible with five free para…
The $ΛN$ and $ΣN$ interactions are considered at next-to-leading order in SU(3) chiral effective field theory. Different options for the low-energy constants that determine the strength of the contact interactions are explored. Two variants are analysed in detail which yield equivalent results for $ΛN$ and $ΣN$ scattering observables but differ in the strength of the $ΛN \to ΣN$ transition potential. The influence of this difference on predictions for light hypernuclei and on the properties of the $Λ$ and $Σ$ hyperons in nuclear matter is investigated and discussed. The effect of the variation…
We develop a method for calculating the doublet splittings of select ground-state single $Λ$-hypernuclei. This hypernuclear spectroscopy is conducted by supplementing the self-consistent single-particle equations with an effective interaction, which follows directly from the underlying lagrangian,to simulate the residual particle-hole interaction. Our previous investigation, performed using only the leading-order contributions to the particle-hole interaction, was inadequate. In the present work, this method is improved upon by increasing the level of truncation in the residual interaction to …
It is shown that an enhancement in the spectral function near 2$m_π$ threshold in the I=J=0 channel is a good signal of the partial restoration of chiral symmetry in nuclear medium. Several experiments are discussed to detect the enhancement, which uses hadron-nucleus and photo-nucleus reactions.
We discuss partial restoration of chiral symmetry in nuclear medium, which is realized as an effective reduction of the quark condensate in nuclear medium. We derive the in-medium Weinberg-Tomozawa relation. We also give a brief calculation of the in-medium quark condensate based on chiral perturbation theory. We conclude that the density dependence of the quark condensate beyond the linear density comes from the vertex correction of the chiral field insertion and nucleon correlations.
A new fit of a chirally motivated coupled-channels model for meson-baryon interactions is presented including the recent SIDDHARTA data on the 1s level characteristics of kaonic hydrogen. The kaon-nucleon amplitudes generated by the model are fully consistent with our earlier studies. We argue that a sharp increase of the real part of the in-medium $K^{-}p$ amplitude at subthreshold energies provides a link between the shallow $\bar{K}$-nuclear optical potentials obtained microscopically from threshold $\bar{K}N$ interactions and the phenomenological deep ones deduced from kaonic atoms data. T…
We investigate nuclear matter, i.e. the nuclear equation-of-state (EOS) as well as the relativistic mean fields in the chiral limit. The investigations are based on a chiral nucleon-nucleon EFT interaction where the explicit and implicit pion mass dependence is known up to next-to-leading order. The nuclear bulk properties are found to remain fairly stable in the chiral limit. Based on the same interaction the in-medium scalar condensate is derived, both in Hartree-Fock approximation as well as from the Brueckner G-matrix, making thereby use of the Hellman-Feynman theorem. Short distance physi…
It is argued that the chiral partners of the lowest-lying hadrons are hadronic molecules and not three-quark or quark-antiquark states, respectively. As an example the case of a_1 as the chiral partner of the rho is discussed. Deconfinement -- or as a precursor large in-medium widths for hadronic states -- is proposed as a natural way to accommodate for the fact that at chiral restoration the respective in-medium spectra of chiral partners must become degenerate. Ingredients for a systematic and self-consistent in-medium calculation are presented with special emphasis on vector-meson dominance…
After giving brief discussions on the chiral condensate in hot and/or dense hadronic matter and the significance of the $σ$ meson in QCD, we discuss the importance of experiments using nuclear targets including ones with electro-magnetic probes for obtaining clearer confirmation of the existence of the $σ$ meson and for exploring the possible restoration of chiral symmetry in nuclear medium.
We discuss medium modifications of the unitarized pion-pion interaction in the nuclear medium. We incorporate both the effects of chiral symmetry restoration and the influence of collective nuclear pionic modes, originating from the p-wave coupling of the pion to delta-hole configurations. We show how the resulting strong enhancement of the sigma-meson spectral function is related to large fluctuations of the condensate associated with the partial restoration of chiral symmetry.
We consider two methods to find the effective parameters of the pion traversing a nuclear medium. One is the first order chiral perturbation theoretic evaluation of the pion pole contribution to the two-point function of the axial-vector current. The other is the exact, first order virial expansion of the pion self-energy. We find that, although the results of chiral perturbation theory are not valid at normal nuclear density, those from the virial expansion may be reliable at such density. The latter predicts both the mass-shift and the in-medium decay width of the pion to be small, of about …
Using heavy-baryon chiral perturbation theory, we have calculated all the diagrams up to two-loop order which contribute to the S-wave pion self-energy in symmetric nuclear matter. Some subtleties related to the definition of pion fields are discussed. The in-medium pion mass is turned out to be increased by only (5 - 6) per cents in normal nuclear matter density, without any off-shell ambiguity.
An accurate assessment of the hyperon-nucleon interaction is of great interest in view of recent observations of very massive neutron stars. The challenge is to build a realistic interaction that can be used over a wide range of masses and in infinite matter starting from the available experimental data on the binding energy of light hypernuclei. To this end, accurate calculations of the hyperon binding energy in a hypernucleus are necessary. We present a quantum Monte Carlo study of $Λ$ and $ΛΛ$ hypernuclei up to $A=91$. We investigate the contribution of two- and three-body $Λ$-nucleon force…
The Density Dependent Relativistic Hadron Field (DDRH) theory, previously introduced and applied to isospin nuclei, is extended to hypernuclei by including the octet hyperons. Infinite matter Dirac-Brueckner theory for octet baryons and the derivation of in-medium DDRH baryon-meson vertices is discussed. From the properties of Dirac-Brueckner interactions it is found that hyperon and nucleon self-energies and vertices are related by the ratios of free space coupling constants. This leads to simple scaling laws for the in-medium hyperon and nucleon vertices. The model is applied in relativistic…
In order to assess the relevance of chiral dynamics in the scalar sector we address two recent problems: radiative decay of the $ϕ$, for which there are quite recent data from Frascati, and the modification of the $σ$ properties in the nuclear medium seen through the $π^0 π^0$ photoproduction in nuclei.
The temperature dependence of the chiral condensate in isospin-symmetric nuclear matter at varying baryon densities is investigated starting from a realistic free energy density of the correlated nuclear many-body system. The framework is thermal in-medium chiral effective field theory which permits a systematic calculation of the quark mass dependence of the free energy density. One- and two-pion exchange processes, virtual $Δ(1232)$-isobar excitations and Pauli blocking corrections are treated up to and including three-loop order. It is found that nuclear matter remains in the Nambu-Goldston…
A significant drop of the vector meson masses in nuclear matter is observed in a chiral SU(3) model due to the effects of the baryon Dirac sea. This is taken into account through the summation of baryonic tadpole diagrams in the relativistic Hartree approximation. The appreciable decrease of the in-medium vector meson masses is due to the vacuum polarisation effects from the nucleon sector and is not observed in the mean field approximation.
We present the first ab initio coupled-cluster calculations of medium-mass nuclei with explicit chiral three-nucleon (3N) interactions. Using a spherical formulation of coupled cluster with singles and doubles excitations including explicit 3N contributions, we study ground states of 16,24-O, 40,48-Ca and 56-Ni. We employ chiral NN plus 3N interactions softened through a similarity renormalization group (SRG) transformation at the three-body level. We investigate the impact of all truncations and quantify the resulting uncertainties---this includes the contributions from triples excitations, t…
In these lectures I make an introduction to chiral unitary theory applied to the meson baryon interaction and show how several well known resonances are dynamically generated, and others are predicted. Two very recent experiments are analyzed, one of them showing the existence of two $Λ(1405)$ states and the other one providing support for the $Λ(1520)$ resonance as a quasibound state of $Σ(1385) π$. The use of chiral Lagrangians to account for the hadronic interaction at the elementary level introduces a new approach to deal with the modification of meson and baryon properties in a nuclear me…
Recently developed chiral effective field theory models provide excellent descriptions of the bulk characteristics of finite nuclei, but have not been tested with other observables. In this work, densities from both relativistic point-coupling models and mean-field meson models are used in the analysis of meson-nucleus scattering at medium energies. Elastic scattering observables for 790 MeV/$c$ $π^{\pm}$ on $^{208}$Pb are calculated in a relativistic impulse approximation, using the Kemmer-Duffin-Petiau formalism to calculate the $π^{\pm}$ nucleus optical potential.
We study the use of truncated normal-ordered three-nucleon interactions in ab initio nuclear structure calculations starting from chiral two- plus three-nucleon Hamiltonians evolved consistently with the similarity renormalization group (SRG). We present three key steps: (i) a rigorous benchmark of the normal-ordering approximation in the importance-truncated no-core shell model (IT-NCSM) for 4-He, 16-O, and 40-Ca; (ii) a direct comparison of the IT-NCSM results with coupled-cluster calculations at the singles and doubles level (CCSD) for 16-O; and (iii) first applications of SRG-evolved chira…
The constraints imposed by chiral symmetry on hadron correlation functions in nuclear medium are discussed. It is shown that these constraints imply some structure of the in-medium hadron correlators, lead to the cancellation of the order $ρm_π$ term in the in-medium nucleon correlator and result in the effect of mixing of the chiral partners correlators, reflecting the phenomena of partial restoration of chiral symmetry. The different scenarios of such restorations are briefly discussed.
The in-medium properties of a baryon-baryon interaction for the strangeness $S=-2$ sector derived within chiral effective field theory up to next-to-leading order are investigated. The considered $ΞN$ interaction is in line with available empirical constraints on the $ΛΛ$ $S$-wave scattering length and on $ΞN$ elastic and inelastic cross sections. In particular, there are no near-threshold bound states in the $ΞN$ system. A conventional $G$-matrix calculation for this interaction is performed and reveals that the single-particle potential of the $Ξ$-hyperon in nuclear matter is moderately attr…
In this talk I present recent developments in chiral dynamics of hadrons and hadrons in a medium addressing the following points: interaction of the octet of pseudoscalar mesons with the octet of baryons of the nucleon, showing recent experimental evidence on the existence of two $Λ(1405)$ states, the interaction of the octet of pseudoscalar mesons with the decuplet of baryons of the $Δ$, with particular emphasis on the $Λ(1520)$ resonance, dynamically generated by this interaction. Then I review the interaction of kaons in a nuclear medium and briefly discuss the situation around the claims o…
The temperature dependence of the chiral condensate in isospin-symmetric nuclear matter at varying baryon density is investigated using thermal in-medium chiral effective field theory. This framework provides a realistic approach to the thermodynamics of the correlated nuclear many-body system and permits calculating systematically the pion-mass dependence of the free energy per particle. One- and two-pion exchange processes, $Δ(1232)$-isobar excitations, Pauli blocking corrections and three-body correlations are treated up to and including three loops in the expansion of the free energy densi…
The constraints imposed by chiral symmetry on hadron correlation functions in nuclear medium are discussed. It is shown that these constraints implies the certain structure of the in-medium hadron correlators and lead to the cancellation of the order $ρm_π$ term in the in-medium nucleon correlator. We also consider the effect of mixing of the chiral partners correlaton functions arising from the interaction of nuclear pions with corresponding interpolating currents. It reflects the phenomena of partial restoration of chiral symmetry. The different scenarios of such restoration are briefly disc…
The properties of eta-nucleus interaction and their experimental consequences are investigated with eta-nucleus optical potentials obtained by postulating the N*(1535) dominance for eta-N system. The N*(1535) properties in nuclear medium are evaluated by two kinds of chiral effective models based on distinct pictures of N*(1535). We find that these two models provide qualitatively different optical potentials of the eta meson, reflecting the in-medium properties of N*(1535) in these models. In order to compare these models in physical observables, we calculate spectra of (d,3He) reactions for …
The s-wave isoscalar amplitude for pion-pion scattering in a nuclear medium is evaluated using a nonperturbative unitary coupled channels method and the standard chiral Lagrangians. The method has proved successful to describe the pion-pion properties in the scalar isoscalar channel up to 1.2 GeV giving rise to poles in the t matrix for the f0(980) and the sigma. The extension of the method to the nuclear medium implies not only the renormalization of the pions in the medium, but also the introduction of interaction terms related to contact terms in the pion-nucleon to pion-pion-nucleon intera…
We use the recently proposed In-Medium Similarity Renormalization Group (IM-SRG) to carry out a systematic study of closed-shell nuclei up to $\nuc{Ni}{56}$, based on chiral two- plus three-nucleon interactions. We analyze the capabilities of the IM-SRG by comparing our results for the ground-state energy to Coupled Cluster calculations, as well as to quasi-exact results from the Importance-Truncated No-Core Shell Model. Using chiral two- plus three-nucleon Hamiltonians whose resolution scales are lowered by free-space SRG evolution, we obtain good agreement with experimental binding energies …
In this review article, we give overview on the extended chiral quark models. In particular, how these models are extended to include the higher-order interactions, quantized fields, logarithmic potential and the effect of these modifications on hadron properties at hot and dense mediums. In addition, how we deal with non-normalization of the Nambu-Jona-Lasinio (NJL) model by using mid-point technique. Therefore, the extended quark models give satisfied results in comparison with lattice QCD at finite temperature and baryonic chemical potential. The extra effort is needed to deal with chiral q…
In-medium chiral perturbation theory is used to calculate the density dependence of the quark condensate $<\bar qq>$. The corrections beyond the linear density approximation are obtained by differentiating the interaction contributions to the energy per particle of isospin-symmetric nuclear matter with respect to the pion mass. Our calculation treats systematically the effects from one-pion exchange (with $m_π$-dependent vertex corrections), iterated $1π$-exchange, and irreducible $2π$-exchange including intermediate $Δ(1232)$-isobar excitations, with Pauli-blocking corrections up to three-loo…
We compute the binding energies, radii, and densities for selected medium-mass nuclei within coupled-cluster theory and employ the "bare" chiral nucleon-nucleon interaction at order N3LO. We find rather well-converged results in model spaces consisting of 15 oscillator shells, and the doubly magic nuclei 40Ca, 48Ca, and the exotic 48Ni are underbound by about 1 MeV per nucleon within the CCSD approximation. The binding-energy difference between the mirror nuclei 48Ca and 48Ni is close to theoretical mass table evaluations. Our computation of the one-body density matrices and the corresponding …
The constraints imposed by chiral symmetry on hadron correlation functions in nuclear medium are discussed. It is shown that these constraints imply a certain structure for the in-medium hadron correlators and lead to the cancelation of the order $ρm_π$ term in the in-medium nucleon correlator. We also consider the effect of mixing of the chiral partners correlation functions arising from the interaction of nuclear pions with corresponding interpolating currents. It reflects the phenomena of partial restoration of chiral symmetry. The different scenarios of such restoration are briefly discuss…
Exploiting operator relations in QCD, we derive a novel and model-independent formula relating the in-medium quark condensate <bar-q q>* to the decay constant F*_t and the wave function renormalization constant Z* of the pion in the nuclear medium. Evaluating Z* at low density from the iso-scalar pion-nucleon scattering data, it is concluded that the enhanced repulsion of the s-wave isovector pion-nucleusinteraction observed in the deeply bound pionic atoms implies directly the reduction of the in-medium quark condensate. The knowlege of the in-medium pion mass is not necessary to reach this c…
This paper is devoted to the interplay between p-wave, s-wave pion-nucleon/ nucleus interaction and in-medium pion-pion interaction with special emphasis on the role of the nuclear pionic scalar density driving a large amount of chiral symmetry restoration. In particular we show that the $πNN$ coupling constant and the Goldberger-Treiman relation are preserved in the nuclear medium within certain conditions. We also discuss the related problem of the in-medium pion-pion strength function.
We study the two-pion propagator in the nuclear medium. This quantity appears in the $π-π$ T-matrix and we show that it also enters the QCD scalar susceptibility. The medium effects on this propagator are due to the influence of the individual nucleon response to a scalar field through their pion clouds. This response is appreciably increased by the nuclear environment. It produces an important convergence effect between the scalar and pseudoscalar susceptibilities, reflecting the reshaping of the scalar strengh observed in $2π$ production experiments. While a large modification of the $σ$ pro…
An Extended Chiral Mean-Field Model with Medium-Modified Thermal Mesons for Hot and Dense Hadronic Matter
Center for Nuclear Research, Department of Physics, Kent State University（肯特州立大学物理系核研究中心）；Punjab, 144216, India（印度旁遮普邦）；Department of Physics, University of Houston（休斯顿大学物理系）
In this talk I report on selected topics of hadron modification in the nuclear medium using the chiral unitary approach to describe the dynamics of the problems. I shall mention how antikaons, $η$, and $ϕ$ are modified in the medium and will report upon different experiments done or planned to measure the $ϕ$ width in the medium.
A recently introduced relativistic nuclear energy density functional, constrained by features of low-energy QCD, is extended to describe the structure of hypernuclei. The density-dependent mean field and the spin-orbit potential of a $Λ$-hyperon in a nucleus, are consistently calculated using the SU(3) extension of in-medium chiral perturbation theory. The leading long-range $ΛN$ interaction arises from kaon-exchange and $2π$-exchange with a $Σ$-hyperon in the intermediate state. Scalar and vector mean fields, originating from in-medium changes of the quark condensates, produce a sizeable {\em…
We report neutron star predictions based on our most recent equations of state. These are derived from chiral effective field theory, which allows for a systematic development of nuclear forces, order by order. We utilize high-quality two-nucleon interactions and include all three-nucleon forces up to fourth order in the chiral expansion. Our ab initio predictions are restricted to the domain of applicability of chiral effective field theory. However, stellar matter in the interior of neutron stars can be up to several times denser than normal nuclear matter at saturation, and its composition …
