8 pages and 6 figures. To appear in the proceedings of the Theoretical nuclear physics school "Exotic Nuclei: New Challenges", Les Houches (France) May 7-18, 2007
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 short-range} spin-orbit interaction. The model, when applied to oxygen as a test case, provides a natural explanation for the smallness of the effective $Λ$ spin-orbit potential: an almost complete cancellation between the background contributions (scalar and vector) and the long-range terms generated by two-pion exchange.
The weak decays of hyperons and hypernuclei are studied from the chiral symmetry viewpoint. The soft pion relations are useful in understanding the isospin properties of the weak hyperon decays. Recent development on the short-range part of the $\Lam N\to NN$ weak transitions shows fairly good account of the weak decays of hypernuclei, though it fails to explain the $n/p$ ratio. The $\pip$ decays of light hypernuclei are studied in the soft pion approach. They are related to the $\DI=3/2$ amplitudes of the nonmesonic decay.
We adopt the Hartree-Fock (HF) method in the proton-neutron-$Λ$ (p-n-$Λ$) formalism and the nucleon-$Λ$ Tamm-Dancoff Approximation (N$Λ$ TDA) to study the energy spectra of medium-mass hypernuclei. The formalism is developed for a potential derived from effective field theories which includes explicitly the 3-body $NNN$ forces plus the $YN$ LO potential. The energy spectra of selected medium-mass hypernuclei are presented and their properties discussed. The present calculation is the first step of a project devoted to {\it ab initio} studies of hypernuclei in medium and heavy mass regions. Thi…
We develop a chiral SU(3) symmetric relativistic mean field (RMF) model with a logarithmic potential of scalar condensates. Experimental and empirical data of symmetric nuclear matter saturation properties, bulk properties of normal nuclei, and separation energies of single- and double-$Λ$ hypernuclei are well explained. The nuclear matter equation of state (EOS) is found to be softened by $σζ$ mixing which comes from determinant interaction. The neutron star matter EOS is further softened by $Λ$ hyperons.
We study the medium modifications of baryon properties in nuclear many-body systems, especially in $Λ$ hypernuclei. The nucleon and the $Λ$ hyperon are described in the Friedberg-Lee model as nontopological solitons which interact through the self-consistent exchange of scalar and vector mesons. The quark degrees of freedom are explicitly considered in the model, so that the medium effects on baryons could be investigated. It is found that the model can provide reasonable descriptions for nuclear matter, finite nuclei, and $Λ$ hypernuclei. The present model predicts a significant increase of t…
We report quantum Monte Carlo calculations of single-$Λ$ hypernuclei for $A<50$ based on phenomenological two- and three-body hyperon-nucleon forces. We present results for the $Λ$ separation energy in different hyperon orbits, showing that the accuracy of theoretical predictions exceeds that of currently available experimental data, especially for medium-mass hypernuclei. We show the results of a sensitivity study that indicates the possibility to investigate the nucleon-isospin dependence of the three-body hyperon-nucleon-nucleon force in the medium-mass region of the hypernuclear chart, whe…
We develop a chiral SU(3) RMF model for octet baryons, as an extension of the recently developed chiral SU(2) RMF model with logarithmic sigma potential. For Sigma-meson coupling, strong repulsion(SR) and weak repulsion(WR) cases are examined in existing atomic shift data of Sigma^-. In both of these cases, we need an attractive pocket of a few MeV depth around nuclear surface.
The structure of single-$Λ$ hypernuclei is studied using the chiral hyperon-nucleon potentials derived at leading order (LO) and next-to-leading order (NLO) by the Jülich--Bonn--Munich group. Results for the separation energies of $Λ$ single-particle states for various hypernuclei from $^5_Λ$He to $^{209}_{\,\,\,\,\,Λ}$Pb are presented for the LO interaction and the 2013 (NLO13) and 2019 (NLO19) versions of the NLO potentials. It is found that the results based on the LO potential show a clear tendency for overbinding while those for the NLO13 interaction underbind most of the considered hyper…
Light hypernuclei with an $α$ cluster substructure of the core nucleus are studied using an accurate cluster approach (the Hyper-THSR wave function) in combination with a density-dependent $Λ$ hyperon-nuclear interaction derived from chiral SU(3) effective field theory. This interaction includes important two-pion exchange processes involving $ΣN$ intermediate states and associated three-body mechanisms as well as effective mass and surface terms arising in a derivative expansion of the in-medium $Λ$ self-energy. Applications and calculated results are presented and discussed for $_Λ^9$Be and …
The characteristic and selective nature of the electro-magnetic production of Lambda-hypernuclei in exciting states is demonstrated assuming the medium-mass targets 28Si, 40Ca, and 52Cr. Formalism of DWIA is used adopting the Saclay-Lyon, Kaon-MAID, Adelseck-Saghai, and Williams-Ji-Cotanch models for the elementary amplitudes and various nuclear and hypernuclear wave functions. The elementary amplitudes are discussed in detail presenting their basic properties and comparison with data. The unique features of the electro-magnetic production of Lambda-hypernuclei shown on examples are the slecti…
We have made a new evaluation of the Lambda decay width in nuclear matter within the Propagator Method. Through the Local Density Approximation it is possible to obtain results in finite nuclei. We have also studied the dependence of the widths on the N-N and Lambda-N short range correlations. Using reasonable values for the parameters that control these correlations, as well as realistic nuclear densities and Lambda wave functions, we reproduce, for the first time, the experimental non-mesonic widths in a wide range of mass numbers (from medium to heavy hypernuclei).
The binding energies of baryonic systems with quantum number charm or beauty and neutron excess (or large isospin) are estimated within the bound state version of the chiral topological soliton model. The procedure of the skyrmion rescaling is applied which is of importance for large enough flavor excitation energies (for heavy flavors). Inclusion of the flavor excitation energies into the minimization of the total mass of the baryonic state naturally leads to its decrease, and this effect increases with increasing flavor mass. Our results concerning the binding energies turned out to be partl…
We investigate the existence of bound $Ξ$ \break states in systems with $A=4-7$ baryons using the Jacobi NCSM approach in combination with chiral NN and $Ξ$N interactions. We find three shallow bound states for the NNN$Ξ$ system (with $(J^π,T)=(1^+,0)$, $(0^+,1)$ and $(1^+,1)$) with quite similar binding energies. The $^5_Ξ\mathrm{H}(\frac{1}{2}^+,\frac{1}{2})$ and $^7_Ξ\mathrm{H}(\frac{1}{2}^+,\frac{3}{2})$ hypernuclei are also clearly bound with respect to the thresholds $^4\mathrm{He} + Ξ$ and $^6\mathrm{He} +Ξ$, respectively. The binding of all these $Ξ$ systems is predominantly due to the…
The Lambda decay rates in nuclei has been calculated in ref. 1 using the Propagator Method in Local Density Approximation. We have studied the dependence of the widths (including the one for the two-body induced process Lambda NN -> NNN) on the N-N and Lambda-N short range correlations. Using a reasonable parametrization of these correlations, as well as realistic nuclear densities and Lambda wave functions, we reproduce, for the first time, the experimental non-mesonic widths from medium to heavy hypernuclei.
We fit the $^1 S_0 ΛΛ$ interaction in the nuclear medium to the masses of the experimentally known double-$Λ$ hypernuclei: $^{\phantom{6}6}_{ΛΛ}$He, $^{10}_{ΛΛ}$Be and $^{13}_{ΛΛ}$B. We derive this effective interaction from OBE Jülich $ΛΛ$-type potentials and using both Hartree-Fock and variational approaches. We find that the inclusion of $ΛΛ$ correlations in the variational scheme leads to significant differences and a better understanding of the dynamical features of the system. We investigate the sensitivity of the binding energies and the mesonic decay widths of the above double-$Λ$ hype…
We investigate $S=-1$ and $-2$ hypernuclei with $A=4-8$ employing the Jacobi-NCSM approach and in combination with baryon-baryon interactions derived within the frame work of chiral effective field theory. The employed interactions are transformed using the similarity renormalization group (SRG) so that the low- and high-momentum states are decoupled, and, thereby,convergence of the binding energies with respect to model space can be significantly speeded up. Such an evolution is however only approximately unitary when the so-called SRG induced higher-body forces are omitted. We first explore …
We generalize the Jacobi no-core shell model (J-NCSM) to study double-strangeness hypernuclei. All particle conversions in the strangeness $S=-1,-2$ sectors are explicitly taken into account. In two-body space, such transitions may lead to the coupling between states of identical particles and of non-identical ones. Therefore, a careful consideration is required when determining the combinatorial factors that connect the many-body potential matrix elements and the free-space two-body potentials. Using second quantization, we systematically derive the combinatorial factors in question for $S=0,…
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 …
The binding energies of neutron rich strangeness $S=-1$ hypernuclei are estimated in the chiral soliton approach using the bound state rigid oscillator version of the SU(3) quantization model. Additional binding of strange hypernuclei in comparison with nonstrange neutron rich nuclei takes place at not large values of atomic (baryon) numbers, $A=B\leq\sim 10$. This effect becomes stronger with increasing isospin of nuclides, and for "nuclear variant" of the model with rescaled Skyrme constant $e$. Total binding energies of (Lambda)He-8 and recently discovered (Lambda)H-6 satisfactorily agree w…
A model based on chiral SU(3)-symmetry in nonlinear realisation is used for the investigation of nuclei, superheavy nuclei, hypernuclei and multistrange nuclear objects (so called MEMOs). The model works very well in the case of nuclei and hypernuclei with one Lambda-particle and rules out MEMOs. Basic observables which are known for nuclei and hypernuclei are reproduced satisfactorily. The model predicts Z=120 and N=172, 184 and 198 as the next shell closures in the region of superheavy nuclei. The calculations have been performed in self-consistent relativistic mean field approximation assum…
The identification of flavored multiskyrmions with the ground states of known hypernuclei is successful for several of them, e.g. for isodoublet H(Lambda) - He(Lambda), A=4, isoscalars He(Lambda) (A=5) and Li(Lambda) (A=7). In other cases agreement is not so good, but the behaviour of the binding energy with increasing baryon number is in qualitative agreement with data. Charmed or beauty hypernuclei within this approach are predicted to be bound stronger than strange hypernuclei. This conclusion is stable against variation of poorly known heavy flavor decay constants.
We present an evaluation of the non-mesonic decay widths for Lambda-hypernuclei (Lambda N --> NN, Lambda NN --> NNN) within the framework of the polarization propagator method. The full Lambda self-energy is evaluated microscopically in nuclear matter by using the functional approach, which supplies a theoretically well grounded approximation scheme for the classification of the relevant diagrams, according to the prescriptions of the bosonic loop expansion. We employ average Fermi momenta, suitably adapted to different mass number regions (medium-light, medium and heavy hypernuclei). Moreover…
The most recent development of the quark-meson coupling (QMC) model, in which the effect of the mean scalar field in-medium on the hyperfine interaction is also included self-consistently, is used to compute the properties of finite hypernuclei. The calculations for $Λ$ and $Ξ$ hypernuclei are of comparable quality to earlier QMC results without the additional parameter needed there. Even more significantly, the additional repulsion associated with the increased hyperfine interaction in-medium completely changes the predictions for $Σ$ hypernuclei. Whereas in the earlier work they were bound b…
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…
New experimental data on medium to heavy single Lambda hypernuclei revealed a much larger spin-orbit splitting than observed in older measurements of light hypernuclei. Taking into account particle threshold effects and the density-dependence of in-medium coupling constants the apparent suppression of spin-orbit strength in light hypernuclei as well as the spin-orbit structure observed in medium to heavy nuclei are explained in a unified manner within the density dependent relativistic hadron field theory. It is concluded that the most valuable information on the Lambda spin-orbit dynamics in …
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.
The density dependent relativistic hadron (DDRH) theory is introduced as an effective field theory for nuclei and hypernuclei. A Dirac-Brueckner approach to in-medium nucleon-hyperon interactions is presented. Density dependent meson-baryon vertices are determined from DBHF self-energies in infinite matter. Scaling laws for hyperon vertices are derived from a diagrammatic analysis of self-energies. In a local density approximation the DB vertices are applied in relativistic DDRH Hartree calculations to finite hypernuclei. Lambda single particle spectra and spin-orbit splittings are described r…
The non-mesonic weak decay of $Λ$--hypernuclei is studied within a one-meson-exchange potential supplemented by a chirally motivated two-pion-exchange mechanism. The effects of final state interactions on the outgoing nucleons are also taken into account. In view of the severe discrepancies between theoretical expectations and experimental data, particular attention is payed to the asymmetry of the protons emitted by polarized hypernuclei. The one-meson-exchange model describes the non-mesonic rates and the neutron-to-proton ratio satisfactorily but predicts a too large and negative asymmetry …
Recent experiments have presented more accurate data on the $ΛΛ$-binding energies of a few $ΛΛ$- hypernuclei. This is important as the $ΛΛ$- bond energies ($ΔB_{ΛΛ}$) of double-$Λ$ hypernuclei provide a measure of the in-medium strength of the $ΛΛ$ interaction. A mass formula, optimized with the newly available $ΛΛ$ binding energy data, is used to estimate the binding energy and bond energy over a wide range of hypernuclei. The $ΔB_{ΛΛ}$ values calculated with this mass formula are in good agreement with the experimental data, predictions of the quark mean-field (QMF) model and the relativisti…
We present the first ab initio calculations for p-shell single-Lambda hypernuclei. For the solution of the many-baryon problem, we develop two variants of the no-core shell model with explicit $Λ$ and $Σ^+$, $Σ^0$, $Σ^-$ hyperons including $Λ$-$Σ$ conversion, optionally supplemented by a similarity renormalization group transformation to accelerate model-space convergence. In addition to state-of-the-art chiral two- and three-nucleon interactions, we use leading-order chiral hyperon-nucleon interactions and a recent meson-exchange hyperon-nucleon interaction. We validate the approach for s-she…
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…
This reports our recent studies on changes in properties of heavy hadrons containing at least a charm or a bottom quark in nuclear matter, and that the results for the $Λ^+_c$ and $Λ_b$ hypernuclei are studied quantitatively. Comparisons are made with the results for the $Λ$ hypernuclei studied previously in the same approach. It is shown that although the scalar and vector potentials for the $Λ$, $Λ_c^+$ and $Λ_b$ in the hypernuclei multiplet with the same baryon numbers are quite similar, the wave functions obtained, e.g., for $1s_{1/2}$ state, are very different. The $Λ^+_c$ probability den…
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 present results of hypernuclei calculated in the latest quark-meson coupling (QMC) model, where the effect of the mean scalar field in-medium on the one-gluon exchange hyperfine interaction, is also included self-consistently. The extra repulsion associated with this increased hyperfine interaction in-medium completely changes the predictions for Σ hypernuclei. Whereas in the earlier version of QMC they were bound by an amount similar to Λ hypernuclei, they are unbound in the latest version of QMC, in qualitative agreement with the experimental absence of such states.
Auxiliary Field Diffusion Monte Carlo (AFDMC) calculations have been employed to revise the interaction between $Λ$-hyperons and nucleons in hypernuclei. The scheme used to describe the interaction, inspired by the phenomenological Argonne-Urbana forces, is the $ΛN+ΛNN$ potential firstly introduced by Bodmer, Usmani et al.. Within this framework, we performed calculations on light and medium mass hypernuclei in order to assess the extent of the repulsive contribution of the three-body part. By tuning this contribution in order to reproduce the $Λ$ separation energy in $^5_Λ$He and $^{17}_{~Λ}$…
We take an approach to the Lambda non-mesonic weak decay in nuclei based on the exchange of mesons. 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 (sigma-like exchange), or uncorrelated (box diagrams). Extra effects of omega exchange in the scalar-isoscalar channel are also considered. Constraints of chiral dynamics are used to generate these exchanges. A drastic reduction of the OPE results for the Gamma_n/Gamma_p ratio is obtained and the new results are compatible with all prese…
The $Λ$ separation energies in the mirror hypernuclei ${_Λ^4}{\rm H}-{_Λ^4}{\rm He}$ exhibit large charge symmetry breaking (CSB). Analyzing this CSB within pionless effective field theory while using partially conserved baryon-baryon SU(3) flavor symmetry, we deduce a $Λ-Σ^0$ induced in-medium admixture amplitude ${\cal A}_{I=1}\approx 1.5\%$ in the dominantly isospin $I=0$ $Λ$ hyperon. Our results confirm the free-space value ${\cal A}^{(0)}_{I=1}$ inferred directly within the SU(3) baryon octet by Dalitz and von-Hippel in 1964 and reaffirmed in a recent QCD+QED lattice calculation. Furtherm…
We investigate the weak kaon-nucleon (NNK) S-wave and P-wave interactions using heavy baryon chiral perturbation theory. The leading 1-loop SU(3) breaking contributions to the $ppK$, $pnK$, and $nnK$ couplings are computed. We find that they suppress all NNK amplitudes by $30\%$ to $50\%$. The ratio of neutron-induced to proton-induced hypernuclear decay widths is sensitive to such reductions. It has been argued that the discrepancy between the predicted and observed P-wave amplitudes in $Δs=1$ hyperon decay results from an accidental cancellation between tree-level amplitudes, and is not a fu…
The dynamics of exotic hypernuclei in heavy-ion collisions has been investigated thoroughly with a microscopic transport model. All possible channels on hyperon ($Λ$, $Σ$ and $Ξ$) production near threshold energies are implemented in the transport model. The light complex fragments (Z$\leq$2) are constructed with the Wigner-function method. The classical phase-space coalescence is used for recognizing heavy nuclear and hyperfragments and the statistical model is taken for describing the decay process. The nuclear fragmentation reactions of the available experimental data from the ALADIN collab…
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 inclu…
We calculate hyperon-nucleon and hyperon-hyperon interactions at next-to-leading order in SU(3) baryon chiral perturbation theory extending earlier work by the Bonn-Juelich group. The constructed potentials in momentum space include all one- and two-meson exchange terms generated by the SU(3) chiral Lagrangian. Effects from intermediate decuplet baryons are considered as well. These chiral baryon-baryon potentials, together with appropriate contact terms, provide a new basis for systematic studies of hyperon-nucleon scattering and light hypernuclei.
The dynamics of light hypernuclei and nuclear clusters produced in $^{197}$Au+$^{197}$Au collisions has been investigated thoroughly with a microscopic transport model. All possible channels of hyperon production and transportation of hyperons in nuclear medium are implemented into the model. The light complex fragments are recognized with the Wigner density approach at the stage of freeze out in nuclear collisions. The isospin diffusion in the collisions is responsible for the neutron-rich cluster formation. The collective flows of nuclear clusters are consistent with the experimental data fr…
The nonmesonic weak decay of $Λ$ hypernuclei is studied in a shell model framework. A complete strangeness-changing weak $ΛN \to NN$ transition potential, based on one boson exchange, is constructed by including the exchange of the pseudoscalar mesons $π$, K, $η$ as well as the vector mesons $ρ, ω$, and K$^*$, whose weak coupling constants are obtained from soft meson theorems and SU(6)$_w$. General expressions for nucleons in arbitrary shells are obtained. The transition matrix elements include realistic $Λ$N short-range correlations and NN final state interactions based on the Nijmegen baryo…
A novel comparison between the data and the theory is proposed for the nonmesonic (NM) weak decay of hypernuclei. Instead of confronting the primary decay rates, as is usually done, we focus attention on the effective decay rates that are straightforwardly related with the number of emitted particles. Proton kinetic energy spectra of $^5_Λ$He, $^7_Λ$Li, $^9_Λ$Be, $^{11}_Λ$B, $^{12}_Λ$C, $^{13}_Λ$C, $^{15}_Λ$N and $^{16}_Λ$O, measured by FINUDA, are evaluated theoretically. The Independent Particle Shell Model (IPSM) is used as the nuclear structure framework, while the dynamics is described by…
We perform a study of infinite hadronic matter, finite nuclei and hypernuclei with an improved method of calculating the effective baryon mass. A detailed study of the predictions of the model is made in comparison with the available data and the level of agreement is generally very good. Comparison with an earlier treatment shows relatively minor differences at or below normal nuclear matter density, while at high density the improved calculation is quite different. In particular, we find no phase transition corresponding to chiral symmetry restoration in high density nuclear matter.
The Jülich-Bonn group aims at an extensive study of the baryon-baryon ($BB$) interaction involving strange baryons ($Λ$, $Σ$, $Ξ$) within SU(3) chiral effective field theory. An overview of achievements and new developments over the past few years is provided. The topics covered are: 1) Derivation of the leading charge-symmetry breaking (CSB) interaction for the $ΛN$ system and its application in a study of CSB effects in $A$=$4$ $Λ$-hypernuclei. 2) Updated results for the $ΞN$ interaction at NLO and predictions for $Ξ^- p$ correlation functions. 3) Extension of the $ΛN$-$ΣN$ interaction to ne…
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…
The interaction between hyperons and nucleons has a wide range of applications in strangeness nuclear physics and is a topic of continuing great interest. These interactions are not only important for hyperon-nucleon scattering but also essential as basic input to studies of hyperon-nuclear few- and many-body systems including hypernuclei and neutron star matter. We review the systematic derivation and construction of such baryonic forces from the symmetries of quantum chromodynamics within non-relativistic SU(3) chiral effective field theory. Several applications of the resulting potentials a…
In this proceeding we summarize results for baryonic contact terms derived within SU(3) chiral effective field theory. The four-baryon contact terms, necessary for the description of the hyperon-nucleon interaction, include SU(3) symmetric and explicit chiral symmetry breaking terms. They also include four-baryon contact terms involving pseudoscalar mesons, which become important for three-body forces. Furthermore we derive the leading order six-baryon contact terms in the non-relativistic limit and study their contribution to the $ΛNN$ three-body contact interaction. These results could play …
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…
We report on ab-initio NCSM calculations of the A=4 mirror Lambda hypernuclei Lambda-4H and Lambda-4He, using the Bonn-Juelich LO chiral EFT YN potentials plus a CSB Lambda0--Sigma0 mixing vertex. In addition to reproducing rather well the 0+ (g.s.) and 1+ (exc.) binding energies, these four-body calculations demonstrate for the first time that the observed CSB splitting of mirror levels, reaching hundreds of keV for 0+ (g.s.), can be reproduced using realistic theoretical interaction models, although with a non-negligible momentum cutoff dependence. Our results are discussed in relation to re…
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 …
In this talk a brief review of several problems involving systems with strangeness is made. In the first place one shows how the $Λ(1405)$, $Λ(1670)$ and $Σ(1620)$ states, for $S = -1$, and the $Ξ(1620)$ for $S= -2$ are generated dynamically in the context of unitarized chiral perturbation theory. The results for the $\bar{K}N$ interaction are then used to evaluate the $K^- d$ scattering length. Results obtained for the kaon selfenergy in a nuclear medium within this approach, with application to $K^-$ atoms, are also mentioned. Finally a few words are said about recent developments in the wea…
