Meson-baryon Coupling Constants Research Articles

Gravitational-Wave Instabilities in Rotating Compact Stars

It is generally accepted that the limit on the stable rotation of neutron stars is set by gravitational-radiation reaction (GRR) driven instabilities, which cause the stars to emit gravitational waves that carry angular momentum away from them. The instability modes are moderated by the shear viscosity and the bulk viscosity of neutron star matter. Among the GRR instabilities, the f-mode instability plays a historically predominant role. In this work, we determine the instability periods of this mode for three different relativistic models for the nuclear equation of state (EoS) named DD2, ACB4, and GM1L. The ACB4 model for the EoS accounts for a strong first-order phase transition that predicts a new branch of compact objects known as mass-twin stars. DD2 and GM1L are relativistic mean field (RMF) models that describe the meson-baryon coupling constants to be dependent on the local baryon number density. Our results show that the f-mode instability associated with m=2 sets the limit of stable rotation for cold neutron stars (T≲1010 K) with masses between 1M⊙ and 2M⊙. This mode is excited at rotation periods between 1 and 1.4 ms (∼20% to ∼40% higher than the Kepler periods of these stars). For cold hypothetical mass-twin compact stars with masses between 1.96M⊙ and 2.10M⊙, the m=2 instability sets in at rotational stellar periods between 0.8 and 1 millisecond (i.e., ∼25% to ∼30% above the Kepler period).

Extended-soft-core baryon-baryon model ESC16. I. Nucleon-nucleon scattering

Background: The Nijmegen extended-soft-core (ESC) model ESC16, as well as its predecessors ESC04--ESC08, describe the nucleon-nucleon ($NN$), hyperon-nucleon ($YN$), and hyperon-hyperon/nucleon ($YY/\mathrm{\ensuremath{\Xi}}\phantom{\rule{4pt}{0ex}}N$) interactions in a unified way using broken SU(3) symmetry. SU(3) symmetry serves to connect the $NN$ with the $YN$ and the $YY$ channels. In the spirit of the Yukawa approach to the nuclear force problem, the interactions are studied from the meson-exchange picture viewpoint, using generalized soft-core Yukawa functions. The meson exchanges are supplemented with diffractive contributions due to multiple-gluon exchanges. The extended-soft-core (ESC) meson-exchange interactions consist of local and nonlocal potentials due to (i) one-boson exchanges (OBE), which are the members of nonets of pseudoscalar, vector, scalar, and axial-vector mesons, (ii) diffractive exchanges, (iii) two-pseudoscalar exchange (PS-PS), and (iv) meson-pair exchange (MPE). The OBE and MPE vertices are regulated by Gaussian form factors producing potentials with a soft behavior near the origin. The assignment of the cutoff masses for the BBM vertices is dependent on the SU(3) classification of the exchanged mesons for OBE and a similar scheme for MPE.Purpose: The evolution of the ESC approach to the ESC16 model for the baryon-baryon (BB) interactions of the SU(3) flavor octet of baryons (N, $\mathrm{\ensuremath{\Lambda}}$, $\mathrm{\ensuremath{\Sigma}}$, and $\mathrm{\ensuremath{\Xi}}$) is described and presented. In this first of a series of papers, the $NN$ model and results are reported in detail.Methods: Important nonstandard ingredients in the OBE sector in the ESC models are (i) the axial-vector meson potentials, and (ii) a zero in the scalar- and axial-vector meson form factors. Furthermore, the strange scalar $\ensuremath{\kappa}$ meson is treated within the scheme of the Gell-Mann-Okubo mass relations, and like the $\ensuremath{\rho}$ and $\ensuremath{\epsilon}$ treated as a broad meson. The multiple-gluon exchanges are elaborated further by adding contributions due to odd number of gluon exchanges. A novel contribution is the incorporation of structural effects due to the quark core of the baryons. In establishing the parameters of the model a simultaneous fit to $NN$ and $YN$ channels has been performed. The meson-baryon coupling constants are calculated via SU(3) using the coupling constants of the $NN\ensuremath{\bigoplus}YN$ analysis as input. In ESC16 the couplings are kept completely SU(3) symmetric. About 25 physical coupling parameters and 8 cutoff and diffractive masses were searched.Results: In the fit to $NN$ and $YN$ many parameters are essentially fixed by the $NN$ data. A few, but severely constrained parameters, e.g., $F/(F+D)$ ratios, are left for determination of the $YN$ interactions and the $YY$ experimental indications. The simultaneous fit of the ESC models to the $NN$- and $YN$-scattering data with a single set of parameters has achieved excellent results for the $NN$ and $YN$ data, and for the $YY$ data in accordance with the experimental indications for $\mathrm{\ensuremath{\Lambda}}\mathrm{\ensuremath{\Lambda}}$ and $\mathrm{\ensuremath{\Xi}}N$. In the case of ESC16, the version discussed here, the achievements are: (i) For the selected 4313 $pp$ and $np$ scattering data with energies $0\ensuremath{\le}{T}_{\text{lab}}\ensuremath{\le}350\phantom{\rule{0.16em}{0ex}}\mathrm{MeV}$, the model reaches a fit having ${\ensuremath{\chi}}^{2}/{N}_{\text{data}}=1.10$. (ii) The deuteron binding energy and all the $NN$ scattering lengths are fitted very nicely. (iii) The $YN$ data are described very well with ${\ensuremath{\chi}}^{2}/{N}_{\text{data}}=1.04$, giving at the same time a description of the $\mathrm{\ensuremath{\Xi}}N$ cross sections in agreement with the experimental indications.Conclusions: The ESC approach leads to an excellent description of the $NN$ and $YN$ data, and for the scarce $YY$ data. The added innovations as well as the treatment of mass broken SU(3) make it possible to keep the meson coupling parameters and the $F/(F+D)$ ratios of the model qualitatively in accordance with the predictions of the $^{3}P_{0}$-dominated quark-antiquark pair creation (QPC) model. The information about estimates of (i) the $\mathrm{\ensuremath{\Lambda}}$- and $\mathrm{\ensuremath{\Sigma}}$-nuclear well-depth, and (ii) the $\mathrm{\ensuremath{\Lambda}}\mathrm{\ensuremath{\Lambda}}$ hypernuclei played an important role in the form of using constraints. In particular, the experimental indications for the $\mathrm{\ensuremath{\Lambda}}\mathrm{\ensuremath{\Lambda}}$-attraction and the $\mathrm{\ensuremath{\Sigma}}$-nuclear well-depth were directive.

Meson–baryon coupling constants of the SU(3) baryons with flavor SU(3) symmetry breaking

We investigate the strong coupling constants for the baryon octet–octet, decuplet–octet, and decuplet–decuplet vertices with pseudoscalar mesons within a general framework of the chiral quark-soliton model, taking into account the effects of flavor SU(3) symmetry breaking to linear order in the expansion of the strange current quark mass. All relevant dynamical parameters are fixed by using the experimental data on hyperon semileptonic decays and the singlet axial-vector constant of the nucleon. The results of the strong coupling constants for the baryon octet and the pseudoscalar meson octet are compared with those determined from the Jülich–Bonn potential and the Nijmegen extended soft-core potential for hyperon–nucleon scattering. The results of the strong decay widths of the baryon decuplet are in good agreement with the experimental data. The effects of SUf(3) symmetry breaking are sizable on the η′ coupling constants. We predict also the strong coupling constants for the Ω baryons.

The relativistic chiral Lagrangian for decuplet and octet baryons at next-to-leading order

.A complete and minimal relativistic Lagrangian is constructed at next-to-leading order for SU(3) chiral perturbation theory in the presence of baryon octet and baryon decuplet states. The Lagrangian has 13 terms for the pure decuplet sector, 6 terms for the transition sector from baryon octet to decuplet and (as already known from the literature) 16 terms for the pure octet sector. The minimal field content of 25 of these terms is meson-baryon four-point interactions. 3 terms give rise to the mass splitting for baryon octet and decuplet states, respectively. 2 terms give rise to overall mass shifts. 4 terms provide anomalous magnetic moments and a decuplet-to-octet magnetic transition moment. 1 term leads to an axial vector transition moment. It is shown that meson-baryon three-point coupling constants come in at leading order whereas no additional one appears in the minimal Lagrangian at next-to-leading order. Those low-energy constants that give rise to mass splitting and magnetic moments, respectively, are determined. Predictions are provided for radiative decays of decuplet to octet baryons.

Charged ρ-meson condensation in neutron stars

We extend relativistic mean-field models with hadron masses and meson–baryon coupling constants dependent on the scalar field σ, including hyperons and Δ(1232) baryons, to incorporate a possibility of the charged ρ meson condensation in neutron star matter. The influence of the ρ− condensation on the equation of state proves to be strongly model dependent. In our models of one type (KVORcut-based ones) the ρ− condensation arises by a second-order phase transition above a critical density and the maximum value of the neutron star mass diminishes only slightly. The matter composition changes more significantly. In our models of other type (MKVOR*-based ones), if the system is considered at fixed density, the ρ− condensation arises by a second-order phase transition at the baryon density n=nc,ρ(II) and at a slightly higher density n=nc,ρ(I) there occurs a first-order phase transition. In a neutron star matter starting with a density n<nc,ρ(II) there appears a region of a mixed phase, or the system is described by Maxwell construction, that results in a substantial decrease of the value of the maximum neutron star mass. Nevertheless in the models under consideration the observational constraint on the maximum neutron star mass is fulfilled. Besides, in MKVOR*-based models the appearance of the ρ− condensate is accompanied by a strong rearrangement of the matter composition. Dependence of the results on a choice of the ρ meson scaling functions for the effective ρ meson mass and coupling constants is also investigated.

Delta isobars in relativistic mean-field models with σ-scaled hadron masses and couplings

We extend the relativistic mean-field models with hadron masses and meson–baryon coupling constants dependent on the scalar σ field, studied previously to incorporate Δ(1232) baryons. Available empirical information is analyzed to put constraints on the couplings of Δs with meson fields. Conditions for the appearance of Δs are studied. We demonstrate that with inclusion of the Δs our equations of state continue to fulfill majority of known empirical constraints including the pressure-density constraint from heavy-ion collisions, the constraint on the maximum mass of the neutron stars, the direct Urca and the gravitational-baryon mass ratio constraints.

Some New Features in the Pseudoscalar Meson and Vector Meson Photoproductions

We investigate the role of the t-channel meson exchange in various photoproduction processes to discuss features of the respective production mechanism. For the less model-dependent analysis we work with the t-channel meson pole reggeized in the Born approximation amplitude. With the meson–baryon coupling constants chosen consistently with symmetry prediction we show that the Reggeized pole model could reproduce the experimental data to a good degree in the lower energy region. Numerical consequences show the significance of the tensor meson exchange in the γp → K+Λ, the dominance of the pseudoscalar meson exchange in the πΔ (and KΣ*) processes, and the sizable role of the vector-meson magnetic moment in the charged ρ (and K*) photoproductions, respectively. These new features from the present analyses could provide a useful guide for future study of the N* resonances in the low energy region.

Hyperons and nuclear symmetry energy in neutron star matter

In this work, masses and radii of neutron stars are considered to investigate the effect of nuclear symmetry energy on astrophysical observables. A relativistic mean-field model with density-dependent meson-baryon coupling constants is employed in describing the equation of state of dense nuclear matter, and the density dependencies of the symmetry energies are quoted from the recent phenomenological formulas obtained from heavy-ion data at subnuclear saturation densities. Since hyperons can take part in the $\ensuremath{\beta}$-equilibrium of the dense matter inside neutron stars, we include hyperons in our estimation and their roles are discussed in combination with that of the nuclear symmetry energy.

Baryon-Baryon Interactions

We review the Nijmegen extended-soft-core (ESC) models for the baryon-baryon (BB) interactions of the SU(3) flavor-octet of baryons (N, Lambda Sigma and Xi). The interactions are basically studied from the meson-exchange point of view, in the spiri t of the Yukawa-approach to the nuclear force problem [H. Yukawa, 'On the interaction of Elementary Particles I' Proceedings of the Physico-Mathematical Society of Japan 17 (1935), 48], using generalized soft-core Yukawa-functions. These interactions are supplemented with (i) multiple-gluon-exchange, and (ii) structural effects due to the quark-core of the baryons. We present in some detail the most recent extended-soft-core model, henceforth referred to as ESC08, which is the most complete, sophisticated , and successful interaction-model. Furthermore, we discuss briefly its predecessor the ESC04-model [Th. A. Rijken and Y. Yamamoto, Phys. Rev. C 73 (2006), 044007, Th. A. Rijken and Y. Yamamoto, Phys. Rev. C 73 (2006), 044008, Th. A. Rijken and Y. Yamamot o, nucl-th/0608074]. For the soft-core one-boson-exchange (OBE) models we refer to the literature [Th. A. Rijken, in Proceedings of the International Conference on Few-Body Problems in Nuclear and Particle Physics, Quebec, 1974, ed. R. J. Slobodrian, B. C uec and R. Ramavataram (Presses Universite Laval, Quebec, 1975), p. 136, Th. A. Rijken, Ph. D. thesis, University of Nijmegen, 1975, M. M. Nagels, Th. A. Rijken and J. J. de Swart, Phys. Rev. D 17 (1978), 768, P. M. M. Maessen, Th. A. Rijken and J. J. de Swart, Phys. Rev. C 40 (1989), 2226, Th. A. Rijken, V. G. J. Stoks and Y. Yamamoto, Phys. Rev. C 59 (1999), 21, V. G. J. Stoks and Th. A. Rijken, Phys. Rev. C 59 (1999), 3009]. All ingredients of these latter models are also part of ESC08, and so a descri ption of ESC08 comprises all models so far in principle. The extended-soft-core (ESC) interactions consist of local- and non-local-potentials due to (i) one-boson-exchanges (OBE), which are the members of nonets of pseudo-scalar-, vector-, scalar-, and ax ial-mesons, (ii) diffractive (i.e. multiple-gluon) exchanges, (iii) two pseudo-scalar exchange (PS-PS), and (iv) meson-pair-exchange (MPE). The OBE- and pair-vertices are regulated by gaussian form factors producing potentials with a soft behavior near th e origin. The assignment of the cutoff masses for the BBM-vertices is dependent on the SU(3)-classification of the exchanged mesons for OBE, and a similar scheme for MPE. The ESC-models ESC04 and ESC08 describe the nucleon-nucleon (NN), hyperon-nucleon (Y N), and hyperon-hyperon (YY) interactions in a unified way using broken SU(3)-symmetry. Novel ingredients in the OBE-sector in the ESC-models are the inclusion of (i) the axial-vector meson potentials, (ii) a zero in the scalar- and axial-vector meson for m factors. These innovations made it possible for the first time to keep the meson coupling parameters of the model qualitatively in accordance with the predictions of the (3)P0 quark-antiquark creation (QPC) model. This is also the case for the F/(F+D)-r atios. Furthermore, the introduction of the zero helped to avoid the occurrence of unwanted bound states in LambdaN. Broken SU(3)-symmetry serves to connect the NN and the YN channels, which leaves after fitting NN only a few free parameters for the deter mination of the YN-interactions. In particular, the meson-baryon coupling constants are calculated via SU(3) using the coupling constants of the NN+YN-analysis as input. In ESC04 medium strong flavor-symmetry-breaking (FSB) of the coupling constants was i nvestigated, using the (3)P0-model with a Gell-Mann-Okubo hypercharge breaking for the BBM-coupling. In ESC08 the couplings are kept SU(3)-symmetric. The charge-symmetry-breaking (CSB) in the Lambdap and Lambdan channels, which is an SU(2) isospin breakin g, is included in the OBE-, TME-, and MPE-potentials. In ESC04 and ESC08 simultaneous fits to the NN- and the YN- scattering data have been achieved, using different options for the ESC-model. In particularly in ESC08 with single-sets of parameters excell ent fits were obtained for the NN- and YN-data. For example, in the case of ESC08a' we have: (i) For the selected 4233 NN-data with energies 0 Tlab Ndata = 1.094. (ii) For the usual set of 35 YN-data and 3 Sigma+p cross-sections from a recent KEK-experime nt E289 [H. Kanda et al., AIP Conf. Proc. 842 (2006), 501, H. Kanda, Measurement of the cross sections of Sigma(=)p elastic scattering, Ph. D. thesis, Department of Physics, Faculty of Science, Kyoto University, March 2007] the fit has chi(2)/YNdata appro x.0.83. (iii) For YY there is a weak LambdaLambda-interaction, which successfully matches with the Nagara-event [H. Takahashi et al., Phys. Rev. Lett. 87 (2001), 212502]. (iv) The nuclear Sigma and Xi well-dephts satisfy USigma > 0 and UXi The predictions for the S = -2 (LambdaLambda XiN, LambdaSigma SigmaSigma)-channels are the occurrences of an S = -2 bound states in the XiN((3)S1-(3)D1, I = 0,1)-channels.

Excitations of the Roper resonances

We present a method that incorporates solutions of a broad class of quark models into the coupled-channel formalism for the K matrix. The method is applied to the calculation of the P11 and P33 scattering amplitudes in the region of the N(1440) and Δ(1600) resonances. Solving the Lippmann-Schwinger equation for the K matrix we find a strong enhancement of the bare quark-model meson-baryon coupling constants consistent with the values used in effective Lagrangian approaches.

Recent soft-core baryon–baryon interactions

Recent results obtained with the extended-soft-core (ESC) interactions are presented. In a unified manner the ESC-model describes nucleon–nucleon (NN), hyperon–nucleon (YN), and hyperon–hyperon (YY), using (broken) SUF(3)-symmetry. In the ESC approach to baryon–baryon (BB) the dynamics is derived from (i) one-boson-exchanges (OBE), (ii) two-meson-exchanges (TME), and (iii) meson-pair-exchanges (MPE). Special features are the inclusion of the axial-vector meson potentials, and a zero in the scalar-meson form-factors. With these ingredients a rather flexible dynamical framework is constructed. Namely, it appeared feasible to keep the parameters of the model rather close to the predictions of the P03 quark-pair-creation model (QPC). This is the case for the meson–baryon coupling constants and the F/(F+D)-ratios as well. The NN, YN, and YY results for this model are rather promising. Here, we report on a recently obtained version, called ESC04. Also, we present the first results with the next version, called ESC06, where we explore the inclusion of the second nonets for the pseudoscalar, vector, and scalar mesons, which have masses approximately in the interval 1GeV⩽M⩽1.5GeV. In the qq¯-picture these mesons are the radially excited states, with principal quantum number N=2, of the low lying meson nonets for M⩽1 GeV. This improves the Σ-well-depth considerably.

Extended-soft-core baryon-baryon model. II. Hyperon-nucleon interaction

The YN results are presented from the extended soft-core (ESC) interactions. They consist of local and nonlocal potentials because of (i) one-boson exchanges (OBE), which are the members of nonets of pseudoscalar, vector, scalar, and axial mesons; (ii) diffractive exchanges; (iii) two-pseudoscalar exchange; and (iv) meson-pair exchange (MPE). Both the OBE and pair vertices are regulated by Gaussian form factors producing potentials with a soft behavior near the origin. The assignment of the cutoff masses for the baryon-baryon-meson (BBM) vertices is dependent on the SU(3) classification of the exchanged mesons for OBE and a similar scheme for MPE. The particular version of the ESC model, called ESC04 [T. A. Rijken, Phys. Rev. C 73, 044007 (2006)], describes nucleon-nucleon (NN) and hyperon-nucleon (YN) interactions in a unified way using broken SU(3) symmetry. Novel ingredients are the inclusion of (i) the axial-vector meson potentials and (ii) a zero in the scalar- and axial-vector meson form factors. These innovations made it possible for the first time to keep the parameters of the model close to the predictions of the ${}^{3}{P}_{0}$ quark-antiquark creation model. This is also the case for the $F/(F+D)$ ratios. Furthermore, the introduction of the zero helped to avoid the occurrence of unwanted bound states. Broken SU(3) symmetry serves to connect the NN and the YN channels, which leaves after fitting NN only a few free parameters for the determination of the YN interactions. In particular, the meson-baryon coupling constants are calculated via SU(3) using the coupling constants of the NN analysis as input. Here, as a novel feature, medium-strong flavor-symmetry breaking (FSB) of the coupling constants was allowed, using the ${}^{3}{P}_{0}$ model with a Gell-Mann-Okubo hypercharge breaking for the BBM coupling. Very good fits for ESC model with and without FSB were obtained. The charge-symmetry breaking in the $\ensuremath{\Lambda}p$ and $\ensuremath{\Lambda}n$ channels, which is an SU(2) isospin breaking, is included in the OBE, TME, and MPE potentials. Simultaneous fits to the NN- and the YN-scattering data are described, using different options for the ESC model. For the selected 4233 NN data with energies $0\ensuremath{\le}{T}_{\mathrm{lab}}\ensuremath{\le}350$ MeV, a ${\ensuremath{\chi}}^{2}/{N}_{\mathrm{data}}=1.22$ was typically reached. For the usual set of 35 YN data and 3 ${\ensuremath{\Sigma}}^{+}p$ cross sections from a recent KEK experiment E289 ${\ensuremath{\chi}}^{2}/{\mathit{YN}}_{\mathrm{data}}\ensuremath{\approx}0.63$ was obtained. In particular, we were able to fit the precise experimental datum ${r}_{R}=0.468\ifmmode\pm\else\textpm\fi{}0.010$ for the inelastic capture ratio at rest rather well. The four versions (a,b,c, and d) of ESC04 presented in this article, give different results for hypernuclei. The reported G-matrix calculations are performed for YN ($\ensuremath{\Lambda}N,\ensuremath{\Sigma}N,\ensuremath{\Xi}N$) pairs in nuclear matter. The obtained well depths (${U}_{\ensuremath{\Lambda}},{U}_{\ensuremath{\Sigma}},{U}_{\ensuremath{\Xi}}$) reveal distinct features of ESC04a--d. The $\ensuremath{\Lambda}\ensuremath{\Lambda}$ interactions are demonstrated to be consistent with the observed data of ${}_{\ensuremath{\Lambda}\ensuremath{\Lambda}}^{6}$He. The possible three-body effects are investigated by considering phenomenologically the changes of the vector-meson masses.

Recent soft-core baryon–baryon interactions

We present recent results obtained with the extended soft-core (ESC) interactions. This ESC-model, henceforth called ESC03, describes nucleon–nucleon ( NN), hyperon–nucleon ( YN), and hyperon–hyperon ( YY), in a unified manner using (broken) SU f ( 3 ) -symmetry. Novel ingredients are the inclusion of (i) the axial-vector meson potentials, (ii) a zero in the scalar-meson form-factors. With these innovations, it proved possible for the first time to keep the parameters of the model closely to the predictions of the P 0 3 quark-pair-creation model (QPC). This is the case for the meson–baryon coupling constants and F / ( F + D ) -ratio's as well. Also, the YN and YY results for this model are rather excellent.

Density dependent hadron field theory for neutron stars with antikaon condensates

We investigate ${K}^{\ensuremath{-}}$ and ${K}^{0}$ condensation in \ensuremath{\beta}-equilibrated hyperonic matter within a density dependent hadron field theoretical model. In this model, baryon-baryon and (anti)kaon-baryon interactions are mediated by the exchange of mesons. Density dependent meson-baryon coupling constants are obtained from microscopic Dirac-Brueckner calculations using Groningen and Bonn A nucleon-nucleon potentials. It is found that the threshold of antikaon condensation is not only sensitive to the equation of state but also to antikaon optical potential depth. Only for large values of antikaon optical potential depth does ${K}^{\ensuremath{-}}$ condensation set in even in the presence of negatively charged hyperons. The threshold of ${K}^{0}$ condensation is always reached after ${K}^{\ensuremath{-}}$ condensation. Antikaon condensation makes the equation of state softer thus resulting in smaller maximum mass stars compared with the case without any condensate.

Meson-baryon couplings and theF/Dratio in light cone QCD

Using the general form of the baryon currents, we calculate the meson-baryon coupling constants and the F/D ratio within the framework of light cone QCD sum rules in the SU(3) flavor symmetry limit. The dependence of the results on the Dirac structure and on the free parameter (b) appearing in the general baryon current is considered. Comparison of our results on F/D ratio with the existing results is presented.

Comment on “Charge-Symmetry-Breaking Potentials from Isospin-Violating Meson-Baryon Coupling Constants”

A Comment on the Letter by S. Gardner, C. J. Horowitz, J. Piekarewicz, Phys. Rev. Lett. 75, 2462 (1995). The authors of the Letter offer a Reply.

Meson-baryon coupling constants from a chiral-invariant SU(3) Lagrangian and application to NN scattering

We present a chiral-invariant meson-baryon Lagrangian which describes the interactions of the baryon octet with the lowest-mass meson nonets. The nonlinear realization of the chiral symmetry generates pair-meson interaction vertices. The corresponding pair-meson coupling constants can all be expressed in terms of the meson-nucleon-nucleon pseudovector, scalar, and vector coupling constants, and their corresponding F (F + D) ratios, and for which empirical estimates are given. We show that it is possible to construct an NN potential of reasonable quality satisfying these theoretical and empirical constraints.

Charge-symmetry-breaking potentials from isospin-violating meson-baryon coupling constants.

We consider charge-symmetry violations in the nucleon-nucleon force that result from isospin-violating meson-baryon coupling constants. The isospin violations arise from the difference in the up and down constituent quark masses. We show that a class IV charge-symmetry-breaking potential exists in the resulting $\ensuremath{\omega}$ exchange contribution to the $\mathrm{NN}$ force. The magnitude of this contribution is consistent with that phenomenologically required by the measured difference of $n$ and $p$ analyzing powers in elastic $\stackrel{\ensuremath{\rightarrow}}{n}\ensuremath{-}\stackrel{\ensuremath{\rightarrow}}{p}$ scattering at 183 MeV.

Hyperon-nucleus scattering in Dirac phenomenology

Optical potentials for Λ and ϵ scattering off nuclei are developed based on a global nucleon-nucleus Dirac optical potential and the constituent-quark-model values of the meson-baryon coupling constants. The differential cross section and analyzing power are calculated for a few energies and nuclei. The tensor coupling has a large effect on the predictions for the analyzing power.

Soft-core baryon-baryon one-boson-exchange models. II. Hyperon-nucleon potential.

The results of the Nijmegen soft-core potential model are presented for the low-energy YN interactions. The YN version of the model is obtained by a straightforward extension of the NN model through the application of SU(3). The potentials are due to the dominant parts of the \ensuremath{\pi}, \ensuremath{\eta}, \ensuremath{\eta}', \ensuremath{\rho}, \ensuremath{\omega}, \ensuremath{\varphi}, \ensuremath{\delta}, \ensuremath{\varepsilon}, and ${S}^{\mathrm{*}}$ Regge trajectories. This gives the traditional one-boson-exchange potentials. In addition to these, the J=0 contributions from the tensor f,f',${A}_{2}$ and Pomeron trajectories are included in the potentials. The latter give potentials of the Gaussian type. Also the form factors from Regge poles are Gaussian, which guarantees that the potentials have a soft behavior near the origin. The multichannel Schr\odinger equation is solved in configuration space for the (partially) nonlocal potentials. We work on the particle basis and include the Coulomb interaction exactly.The meson-baryon coupling constants are calculated via SU(3), using the coupling constants of the NN analysis as input. Charge symmetry breaking in the \ensuremath{\Lambda}p and \ensuremath{\Lambda}n channels is included. An excellent description is achieved of the available low-energy data per degree of freedom (${\ensuremath{\chi}}^{2}$\ensuremath{\approxeq}0.58 for 35 YN data). In particular, we were able to fit the inelastic capture ratio at rest perfectly. We have ${r}_{R}$=0.471, where experimentally the average value is ${r}_{R}$=0.468\ifmmode\pm\else\textpm\fi{}0.010. The obtained values for the adjustable mixing angles and F/(F+D) ratios agree very well with the literature. We find ${\ensuremath{\alpha}}_{\mathrm{PV}=0.355}$ and ${\ensuremath{\alpha}}_{V}^{m}$=0.275. For the scalar-meson mixing angle we obtain ${\ensuremath{\theta}}_{s}$=40.895\ifmmode^\circ\else\textdegree\fi{}, which lies between the ideal mixing angles for the scalar ${q}^{2}$q\ifmmode\bar\else\textasciimacron\fi{} $^{2}$ and qq\ifmmode\bar\else\textasciimacron\fi{} states. In the \ensuremath{\Lambda}p system we find a cusp at the ${\ensuremath{\Sigma}}^{+}$n threshold, but there is on the second Riemann sheet no pole in the vicinity causing this cusp. The predictions of the total cross sections up to the pion production threshold are given and compared to the experimental data.