Hyperon-nucleon Interaction Research Articles

EffectiveΛNpotential from relativistic Brueckner-Hartree-Fock theory

The effective $\ensuremath{\Lambda}N$ potentials are derived from one-boson-exchange hyperon-nucleon interaction such as Juelich potentials, Juelich94a (Jul94) and Juelich05 (Jul05), within the relativistic Brueckner-Hartree-Fock theory. The Jul94 effective $\ensuremath{\Lambda}N$ potential ${U}_{\ensuremath{\Lambda}}$ (${p}_{\ensuremath{\Lambda}}$) with ${p}_{\ensuremath{\Lambda}}=0$ is $\ensuremath{-}27.63$ MeV at the nuclear saturation density, which is in good agreement with the observed data, whereas for the Jul05 effective $\ensuremath{\Lambda}N$ potential, ${U}_{\ensuremath{\Lambda}}$ is $\ensuremath{-}47.85$ MeV, which is bound more than the observed data. We then compare the effective $\ensuremath{\Lambda}N$ potential energies obtained in nonrelativistic and relativistic frameworks. With the $\ensuremath{\Lambda}$ momentum ${p}_{\ensuremath{\Lambda}}$ increasing, the relativistic effect becomes obvious and provides more repulsive contribution. We also derive the scalar and vector potentials of the $\ensuremath{\Lambda}$ hyperon from the effective $\ensuremath{\Lambda}N$ potential in the relativistic framework. With these potentials, the coupling constants between mesons and the $\ensuremath{\Lambda}$ hyperon are determined for each density in the framework of relativistic mean-field theory. Finally, we calculate the $\ensuremath{\Lambda}$ single-particle energies of hypernuclei with these density-dependent coupling constants in the relativistic mean-field theory. We find that the single $\ensuremath{\Lambda}$ binding energies of $\ensuremath{\Lambda}$ hypernuclei from $_{\ensuremath{\Lambda}}^{16}\mathrm{O}$ to $_{\ensuremath{\Lambda}}^{208}\mathrm{Pb}$ by using the Jul94 potential compare well with the experimental data.

Nuclear territory predicted with a newly developed hyperon-nucleon interaction

The boundary of the nuclear chart is studied in the relativistic continuum Hartree-Bogoliubov theory with a newly developed effective \( \Lambda\)-nucleon interaction PK1-Y1. Compared with the linear prediction from the generalized mass formula, the neutron drip line is shifted outwards in light single-\( \Lambda\) hypernuclei and exhibits a pronounced shell structure in the heavy-mass region. The existence of a neutron magic number at \( N = 184\) is suggested. Systematic trend in the heavier region shows a very weak \( \Lambda\Lambda\) interaction. With \( \sigma^{*}\) , \( \phi\) mesons and \( \omega\Lambda\Lambda\) tensor coupling, the bond energy of Lambdas is sharply reduced.

Accurate determination of the interaction betweenΛhyperons and nucleons from auxiliary field diffusion Monte Carlo calculations

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 $\Lambda$ and $\Lambda\Lambda$ hypernuclei up to $A=91$. We investigate the contribution of two- and three-body $\Lambda$-nucleon forces to the $\Lambda$ binding energy. Ground state energies are computed solving the Schr\"odinger equation for non-relativistic baryons by means of the auxiliary field diffusion Monte Carlo algorithm extended to the hypernuclear sector. We show that a simple adjustment of the parameters of the $\Lambda NN$ three-body force yields a very good agreement with available experimental data over a wide range of hypernuclear masses. In some cases no experiments have been performed yet, and we give new predictions. The newly fitted $\Lambda NN$ force properly describes the physics of medium-heavy $\Lambda$ hypernuclei, correctly reproducing the saturation property of the hyperon separation energy.

Chiral effective field theory description of the hyperon-nucleon interaction at next-to-leading order

In this proceeding results for hyperon-nucleon interactions calculated at next-to-leading order (i.e. one-loop order) in SU(3) chiral effective field theory are presented. The potentials include contributions from one- and two-meson exchange, and four-baryon contact terms provided by the SU(3) chiral Lagrangian. SU(3) flavor symmetry is imposed for the low-energy constants, while explicit SU(3) symmetry breaking is included only through the physical pseudoscalar-meson and baryon masses. Calculations have been performed for hyperon-nucleon scattering cross sections using a regularized Lippmann-Schwinger equation. A good description of the available data is achieved, comparable to modern phenomenological hyperon-nucleon interaction models. These results provide a new basis for studies of hypernuclei or hyperons in nuclear matter.

Few-nucleon system dynamics in medium energy domain

Nucleon-nucleon interactions and hyperon nucleon interactions are study in three body final state with one being a meson. In addition to final state parameters possible resonances in the two baryon states are of interest.

Doubly strange system physics with antiprotons at PANDA

The study of the doubly strange hyper-systems represents a step forward in understanding the unexplored world of the strange matter in the frame of a better knowledge of the hyperon-nucleon and hyperon-nucleus interaction. The production of double hyper-systems, up to now, have been based on the use of kaon beams through a double strangeness exchange reaction. A new technique has been designed by the PANDA Collaboration, which will use the antiprotons at 3 GeV/c of the HESR facility at FAIR to create doubly strange hyperons and drive them into nuclear targets. This technique requires the use of 2 targets, located inside and outside the beam pipe. In spite of the constraints arising from the presence of a solid target inside an antiproton ring, the technique looks promising in terms of rate of hyperons and hyper-nuclei produced. After a review of the physics items that will be investigated in the hyper-nuclear section of PANDA experiment, the characteristics of the antiprotons facility, the results of the feasibility study of the 2-target technique, the design of the hyper-nuclear set-up in PANDA and the expected rates of the double hyper-nuclei will be presented.

Shape evolution of Ne isotopes and Ne hypernuclei: The interplay of pairing and tensor interactions

We study tensor and pairing effects on the quadruple deformation of neon isotopes based on a deformed Skyrme-Hartree-Fock model with BCS approximation for the pairing channel. We extend the Skyrme-Hartree-Fock formalism for the description of hypernuclei adopting the recently-proposed ESC08b hyperon-nucleon interaction. It is found that the interplay of pairing and tensor interactions is crucial to derive the deformations in several neon isotopes. Especially, the shapes of 26,30Ne are studied in details in comparisons with experimentally observed shapes. Furthermore the deformations of the hypernuclei are compared with the corresponding neon isotopic cores in the presence of tensor force. We find the same shapes with somewhat smaller deformations for single Λ-hypernuclei compared with their core deformations.

Microscopic investigation of the structure characteristics and wave functions of the five-body hypernucleusHeλ5

The Parentage Scheme of Summarization to the N-body symmetrized basis construction (1), necessary for the description of the structural characteristics and decay reactions of the hypernuclear and nuclear systems with arbitrary amount of particles, is applied to the solution of five-body problem in hypernuclear physics. Hypernucleus �� � � as a system of four nucleons and one hyperon is investigated by the use of the Hyperspherical Function Method in momentum space. The dependence of the structure characteristics and wave functions on the types of nucleon-nucleon and hyperon-nucleon interaction potentials is studied. Mean square�� � − � � �and�� − � distances and the binding energies for the �� and ��� � � are obtained.

Hyperon–Nucleon Interaction in Chiral Effective Field Theory

Results from an ongoing study of the hyperon-nucleon system within chiral effective field theory are reported. The investigation is based on the scheme proposed by Weinberg which has been applied rather successfully to the nucleon-nucleon interaction in the past. First results for the hyperon-nucleon interaction at next-to-leading order are presented and discussed.

Hyperon–nucleon interaction at next-to-leading order in chiral effective field theory

Results for the ΛN and ΣN interactions obtained at next-to-leading order in chiral effective field theory are reported. At the order considered there are contributions from one- and two-pseudoscalar-meson exchange diagrams and from four-baryon contact terms without and with two derivatives. SU(3) flavor symmetry is imposed for constructing the hyperon–nucleon interaction, however, the explicit SU(3) symmetry breaking by the physical masses of the pseudoscalar mesons (π, K, η) and of the involved baryons is taken into account. An excellent description of the hyperon–nucleon system can be achieved at next-to-leading order. It is on the same level of quality as the one obtained by the most advanced phenomenological hyperon–nucleon interaction models.

Selected Topics in Spectroscopy of -Hypernuclei and Hyperon-Nucleon Interactions

Selected Topics in Spectroscopy of -Hypernuclei and Hyperon-Nucleon Interactions

Hyperon-Meson Vertices and Hyperon-Nucleon Interactions on Quark Model

In this paper, we introduce two parts of work: the hyperon-meson vertex structure from the one-gluon-exchange quark-antiquark pair creation model and the hyperon-nucleon interactions on a modified quark potential model. For both parts some significant results have been obtained.

Weak Hyperon-Nucleon Interaction in a Quark Model and Application to the pn -> p Scattering

Weak Hyperon-Nucleon Interaction in a Quark Model and Application to the pn -> p Scattering

The Baryon-Baryon Interaction in a Quark Model with Quark - Antiquark Excitations

The flavor symmetry aspect of the hyperon-nucleon interaction is investigated in a quark model in which the (qq̄) excitations inherent in the quark-gluon interaction are explicitly incorporated into the model space. It is shown that the long range part of the hyperon-nucleon interaction generated from the (3q)-(3q) to (3q)-(3q)(qq̄) coupling kernels has similar flavor dependence to that of the SU3 OBEP, where the SU3 parameters of the coupling constants are usually selected around the SU6 values. The flavor-SU3 symmetry breaking effect is also discussed in the single baryon problem ; results are given for the baryon-meson coupling constants, the ground state baryon spectrum, and the magnetic moments of the octet baryons.

Electro-Production of Light Lambda Hypernuclei

Through the study of light hypernuclei, we can learn about hyperon nucleon interaction. The hypernuclear spectroscopy with electron beams is one of most powerful methods to study detailed structure of light hypernuclei thanks to its high energy resolution. With a decade of efforts at Jefferson Lab, the spectroscopy of Λ hypernuclei with an electron beam is now established. Observation of \({_{\Lambda}^{7}}\) He which gave the last missing binding energy of the A = 7, T = 1 iso-triplet hypernuclei provides an important experimental input for the charge symmetry breaking (CSB) effect of the ΛN interaction. Further study about A = 4 hypernuclear iso-doublet, \({_{\Lambda}^{4}}\) H and \({_{\Lambda}^{4}}\) He, is necessary and such experiments are now planned.

Effects of the two-body and three-body hyperon-nucleon interactions inΛhypernuclei

Background: The calculation of the hyperon binding energy in hypernuclei is crucial to understanding the interaction between hyperons and nucleons. Purpose: We assess the relative importance of two- and three-body hyperon-nucleon force by studying the effect of the hyperon-nucleon-nucleon interaction in closed shell \Lambda-hypernuclei from A=5 to 91. Methods: The \Lambda-binding energy has been calculated using the auxiliary field diffusion Monte Carlo method for the first time, to study light and heavy hypernuclei within the same model. Results: Our results show that including a three-body component in the hyperon-nucleon interaction leads to a saturation of the \Lambda-binding energy remarkably close to the experimental data. In contrast, the two-body force alone gives an unphysical limit for the binding energy. Conclusions: The repulsive contribution of the three-body hyperon-nucleon-nucleon force is essential to reproduce, even qualitatively, the binding energy of the hypernuclei in the mass range considered.

Light hypernuclei based on chiral and phenomenological interactions

Abstract We present binding energies and properties of wave functions for the light hypernuclei H Λ 3 , H Λ 4 , and He Λ 4 based on realistic hyperon–nucleon and nucleon–nucleon interactions including Λ – Σ conversion. For the solution, the non-relativistic Schrodinger equation is rewritten into Faddeev or Yakubovsky equations which are solved in momentum space. The accuracy of the numerical calculations is discussed. Based on first leading and next-to-leading order chiral interactions, we discuss the possibility to constrain the hyperon–nucleon interactions by hypernuclear binding energies. Finally, we predict the charge-symmetry breaking of the Λ separation energies of H Λ 4 / He Λ 4 .

Maximum mass of neutron stars and strange neutron-star cores

Recent measurement of mass of PSR J1614-2230 rules out most of existing models of equation of state (EOS) of dense matter with high-density softening due to hyperonization, based on the recent hyperon-nucleon and hyperon-hyperon interactions, leading to a "hyperon puzzle". We study a specific solution of "hyperon puzzle", consisting in replacing a too soft hyperon core by a sufficiently stiff quark core. We construct an analytic approximation fitting very well modern EOSs of 2SC and CFL color superconducting phases of quark matter. This allows us for simulating continua of sequences of first-order phase transitions from hadronic matter to the 2SC, and then to the CFL state of color superconducting quark matter. We obtain constraints in the parameter space of the EOS of superconducting quark cores, resulting from M_max> 2 M_sol. We also derive constraints that would result from significantly higher measured masses. For 2.4 M_sol required stiffness of the CFL quark core should have been close to the causality limit, the density jump at the phase transition being very small. Condition M_max > 2 M_sol puts strong constraints on the EOSs of the 2SC and CFL phases of quark matter. Density jumps at the phase transitions have to be sufficiently small and sound speeds in quark matter - sufficiently large. A strict condition of thermodynamic stability of quark phase results in the maximum mass of hybrid stars similar to that of purely baryon stars. Therefore, to get M_max>2 M_sol for stable hybrid stars, both sufficiently strong additional hyperon repulsion at high density baryon matter and a sufficiently stiff EOS of quark matter would be needed. However, it is likely that the high density instability of quark matter (reconfinement) indicates actually the inadequacy of the point-particle model of baryons in dense matter at very high densities.

Recent Results from CLAS on Baryon Structure and Interactions

The understanding of baryon structure and interactions from Quantum Chromodynamics is one of the main objectives of modern hadron physics. Of particular interest is the regime of confinement where perturbative methods are not applicable to derive testable predictions. Understanding the transition from hadronic to partonic degrees of freedom, the hyperon-nucleon interaction, and nuclei in terms of quarks and gluons are some of the key problems. Here we present results of photoproduction experiments on light nuclear targets from Jefferson Lab Hall B. Our observation of onset of dimensional scaling in the cross section of two-body photodisintegration of 3He at energy and momentum transfer well below 1 GeV suggests that quarks and gluons may be relevant degrees of freedom for the description of nuclear dynamics at energies lower than previously considered. Our program to study lambda-nucleon scattering via a large set of polarization observables for final-state interactions in exclusive hyperon photoproduction off the deuteron has produced preliminary results for single-polarization observables. The beam-spin asymmetry shows interesting features at large lambda polar angles and large kaon momenta.

SU(3) chiral dynamics and baryon–baryon interactions

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.