One-boson Exchange Potentials Research Articles

Tribaryons with lattice QCD and one-boson exchange potentials

Tribaryons with lattice QCD and one-boson exchange potentials

Study of the Ground-State Energies of Some Nuclei Using Hybrid Model

The quark-quark (QQ) interaction as a perturbed term to the nucleon-nucleon interaction (NN) without any coupling between them is studied in a hybrid model. This model is used to calculate the ground-state energies of 2H1 and 4He2 nuclei. In a semirelativistic framework, this model is encouraged for light nuclei and the instanton-induced interaction by using the QQ potential and the NN interaction for a small scale around the hadron boundaries. This hybrid model depends on two theories, the one-boson exchange potential (OBEP) and the Cornell-dressed potential (CDP) for QQ. A small effect of quark-quark interaction is obtained on the values of the ground-state energies, around 6.7 and 1.2 percentage for 2H1 and 4He2, respectively nuclei.

The Ground-State Calculations for Some Nuclei by Mesonic Potential of Nucleon-Nucleon Interaction

The interaction of nucleon-nucleon (NN) has certain physical characteristics, indicated by nucleon, and meson degrees of freedom. The main purpose of this work is calculating the ground-state energies of 12H and 24He through the two-body system with the exchange of mesons (π, σ, and ω) that mediated between two nucleons. This paper investigates the NN interaction based on the quasirelativistic decoupled Dirac equation and self-consistent Hartree-Fock formulation. We construct a one-boson exchange potential (OBEP) model, where each nucleon is treated as a Dirac particle and acts as a source of pseudoscalar, scalar, and vector fields. The potential in the present work is analytically derived with two static functions of meson, the single-particle energy-dependent (SPED) and generalized Yukawa (GY) functions; the parameters used in meson functions are just published ones (mass, coupling constant, and cutoff parameters). The theoretical results are compared to other theoretical models and their corresponding experimental data; one can see that the SPED function gives more satisfied agreement than the GY function in the case of the considered nuclei.

Unitarily inequivalent vacua and long-range forces: Phenomenology with scalar boson mass-shift

We explore the impact of a sudden shift in the mass of a scalar boson field on long-range forces mediated by this field under the framework of unitarily inequivalent vacua. Since the search for new long-range forces is an active experimental area probing physics beyond the Standard Model, the consequence of a non-trivial vacuum state of a scalar boson on these experiments is elucidated. We show that while the mass shift affects the one-boson exchange potential, the Casimir force remains only dependent on the vacuum state.

Microscopic Calculation of the Optical Model Potential from One Boson Exchange Poten­tials

A new method for calculating the optical model potential from One Boson Exchange Potentials (OBEPs) is developed. The G-matrix is calculated by solving the Bethe-Goldstone equation in momentum space. Using vector brackets these G-matrix elements can be transformed from the center of mass representation into the laboratory system. This allows the evaluation of the (r-matrix interaction between nucleons in bound states and those in a plane-wave state. The lowest order contribution to the real part of the potential comes from the Hartree-Fock term, while the lowest order contribution to the imaginary part comes from the two-particle-one-hole (2p1h) diagram. Calculations for 16O and 40Ca have been carried out. Local approximations are obtained by describing the results for the central part in terms of a Woods-Saxon potential and those for the spin-orbit part in terms of the corresponding derivatives. The dependence of these potentials on energy and angular momentum is discussed. The parameters for these local approximations are in good agreement with empirical fits.

Charmed baryon\u2013nucleon interaction

We present a comparative study of the charmed baryon–nucleon interaction based on different theoretical approaches. For this purpose, we make use of (i) a constituent quark model tuned in the light-flavor baryon–baryon interaction and the hadron spectra, (ii) existing results in the literature based both on hadronic and quark-level descriptions, (iii) (2+1)-flavor lattice QCD results of the HAL QCD Collaboration at unphysical pion masses and their effective field theory extrapolation to the physical pion mass. There is a general qualitative agreement among the different available approaches to the charmed baryon–nucleon interaction. Different from hadronic models based on one-boson exchange potentials, quark-model based results point to soft interactions without two-body bound states. They also support a negligible channel coupling, due either to tensor forces or to transitions between different physical channels, Lambda _c N – Sigma _c N. Short-range gluon and quark-exchange dynamics generate a slightly larger repulsion in the ^1S_0 than in the ^3S_1Lambda _c N partial wave. A similar asymmetry between the attraction in the two S waves of the Lambda _c N interaction also appears in hadronic approaches. A comparative detailed study of Pauli suppressed partial waves, as the ^1S_0 (I=1/2) and ^3S_1 (I=3/2)Sigma _c N channels, would help to disentangle the short-range dynamics of two-baryon systems containing heavy flavors. The possible existence of charmed hypernuclei is discussed.

The properties of nuclear matter with lattice NN potential in relativistic Brueckner-Hartree-Fock theory.

We study the properties of nuclear matter with lattice nucleon-nucleon (NN) potential in the relativistic Brueckner-Hartree-Fock (RBHF) theory. To use this potential in such a microscopic many-body theory, we firstly have to construct a one-boson-exchange potential (OBEP) based on the latest lattice NN potential. Three mesons, pion, σ meson, and ω meson, are considered. Their coupling constants and cut-off momenta are determined by fitting the on-shell behaviors and phase shifts of the lattice force, respectively. Therefore, we obtain two parameter sets of the OBEP potential (named as LOBEP1 and LOBEP2) with these two fitting ways. We calculate the properties of symmetric and pure neutron matter with LOBEP1 and LOBEP2. In non-relativistic Brueckner-Hartree-Fock case, the binding energies of symmetric nuclear matter are around −3 and −5 MeV at saturation density, while it becomes −8 and −12 MeV in relativistic framework with 1S0, 3S1, and 3D1 channels using our two parameter sets. For the pure neutron matter, the equations of state in non-relativistic and relativistic cases are very similar due to only consideration 1S0 channel with isospin T = 1 case.

Scalar pseudo-Nambu-Goldstone boson in nuclei and dense nuclear matter

The notion that the scalar listed as $f_0 (500)$ in the particle data booklet is a pseudo-Nambu-Goldstone (NG) boson of spontaneously broken scale symmetry, explicitly broken by a small departure from an infrared fixed point, is explored in nuclear dynamics. That notion which puts the scalar -- that we shall identify as a "dilaton" -- on the same footing as the pseudo-scalar pseudo-NG bosons, i.e., octet $\pi$, while providing a simple explanation for the $\Delta I=1/2$ rule for kaon decay, generalizes the standard chiral perturbation theory (S$\chi$PT) to "scale chiral perturbation theory," denoted $\chi$PT$_\sigma$, with {\it one infrared mass scale for both symmetries}, with the $\sigma$ figuring as a chiral singlet NG mode in non-strange sector. Applied to nuclear dynamics, it is seen to provide possible answers to various hitherto unclarified nuclear phenomena such as the success of one-boson-exchange potentials (OBEP), the large cancellation of strongly attractive scalar potential by strongly repulsive vector potential in relativistic mean field theory of nuclear systems and in-medium QCD sum rules, the interplay of the dilaton and the vector meson $\omega$ in dense skyrmion matter, the BPS skyrmion structure of nuclei accounting for small binding energies of medium-heavy nuclei, and the suppression of hyperon degrees of freedom in compact-star matter.

Analysis of reaction cross sections of Ne and Mg isotopes at 240 MeV/u in the Dirac-Brueckner approach and Glauber model

Within a relativistic effective complex nucleon-nucleon interaction derived by solving the Dirac-Brueckner-Bethe-Goldstone equation, locally, starting from the one-boson-exchange potential (OBEP) as a bare NN interaction, the optical potentials and reaction cross sections of the 20-36Ne , 24-38Mg + 12C reactions, recently observed at 240MeV/u , are calculated. The proton and neutron density distributions of target and projectile are derived from Skyrme-Hartree-Fock calculations, employing SKRA and SKM* interactions. A comparison between the experimental data as well as recent theoretical calculations of Horiuchi et al. (Phys. Rev. C 86, 024614 (2012)) and Panda et al. (Mod. Phys. Lett. A 29, 1450013 (2014)) show that the data are well reproduced by the present relativistic calculations.

Numerical solution of relativistic problems on bound states of systems of two spinless particles

Numerical solutions of the equations of quantum field theory describing bound s-states of systems of two scalar particles have been found for the following three cases: a one-boson exchange potential, a superposition of such potentials, and also the Coulomb potential in the relativistic configuration representation. On the basis of these solutions, the elastic scattering form factors and decay constants for decay of a two-particle system into two photons have been obtained. It is shown that the number of zeros of the elastic form factors coincides with the number of zeros of the wave functions and is equal to the quantum number of the state of the system minus one. The obtained energy spectra and decay constants are compared with the experimentally measured values for positronium.

Role of Form Factor in Relativistic Hartree-Fock Approach for Finite Nuclei

We study the role of the form factor in meson exchange interactions within the relativistic Hartree-Fock (RHF) approach. We calculate finite nuclei properties with different cutoff parameters in σ and ω exchange interactions, and find that the results are quite sensitive to the choice of the cutoff parameters. It is essential to include the form factors in the one-bosonexchange potential (OBEP) model, also the form factor can change the single-particle spectra of nuclei. We discuss the different treatment of the π-pseudovector coupling and ρ-tensor coupling in the RHF model. It is found that the results with the form factors are different from those without the form factors and with the δ-function pieces, while the removal of the δ-function pieces can dramatically alter the contributions from π and ρ exchanges. Subject Index: 211, 212

Muon capture in deuterium

Model dependence of the capture rates of the negative muon capture in deuterium is studied starting from potential models and the weak two-body meson exchange currents constructed in the tree approximation and also from an effective field theory. The tree one-boson exchange currents are derived from the hard pion chiral Lagrangians of the N Δ π ρ ω a 1 system. If constructed in conjunction with the one-boson exchange potentials, the capture rates can be calculated consistently. On the other hand, the effective field theory currents, constructed within the heavy baryon chiral perturbation theory, contain a low energy constant d ˆ R that cannot be extracted from data at the one-particle level nor determined from the first principles. Comparative analysis of the results for the doublet transition rate allows us to extract the constant d ˆ R .

Wigner symmetry, largeNc, and renormalized one-boson exchange potentials

Wigner symmetry in nuclear physics provides a unique example of a nonperturbative medium and long distance symmetry, a symmetry strongly broken at short distances. We analyze the consequences of such a concept within the framework of one-boson exchange potentials in $\mathit{NN}$ scattering and keeping the leading ${N}_{c}$ contributions. Phenomenologically successful relations between singlet ${}^{1}{S}_{0}$ and triplet ${}^{3}{S}_{1}$ scattering phase shifts are provided in the entire elastic region. We establish symmetry breaking relations among noncentral phase shifts which are successfully fulfilled by even-$L$ partial waves and strongly violated by odd-$L$ partial waves, in full agreement with large ${N}_{c}$ requirements.

New One-Boson-Exchange Potential functions

A new one-boson-exchange potential (OBEP) is derived by fitting the oscillator matrix elements of the sum of the OBEP functions to those of the matrix elements derived by the lowest order constrained variational (LOCV) technique. The results give a reasonable fit to the OBEP model. Journal of the Nigerian Association of Mathematical Physics Vol. 10 2006: pp. 5-10

Weak axial nuclear heavy meson exchange currents and interactions of solar neutrinos with deuterons

Starting from the axial heavy meson exchange currents, constructed earlier in conjunction with the Bethe–Salpeter equation, we first present the axial ρ-, ω- and a 1 -meson exchange Feynman amplitudes that satisfy the partial conservation of the axial current. Employing these amplitudes, we derive the corresponding weak axial heavy meson exchange currents in the leading order in the 1 / M expansion ( M is the nucleon mass), suitable for the nuclear physics calculations beyond the threshold energies and with wave functions obtained by solving the Schrödinger equation with one-boson exchange potentials. The constructed currents obey the nuclear form of the partial conservation of the axial current. We apply the space component of these currents in calculations of the cross sections for the disintegration of deuterons by low energy (anti)neutrinos. The deuteron and the final state nucleon–nucleon wave functions are derived (i) from a variant of the OBEPQB potential, and (ii) from the Nijmegen 93 and Nijmegen I nucleon–nucleon interaction. The extracted values of the constant L 1 , A , entering the axial exchange currents of the pionless effective field theory, are in a reasonable agreement with its value predicted by the dimensional analysis.

Nonlocality in the nucleon-nucleon interaction and nuclear matter saturation

We study the possible relationship between the saturation properties of nuclear matter and the inclusion of non-locality in the nucleon-nucleon interaction. To this purpose we compute the saturation curve of nuclear matter within the Bethe-Brueckner-Goldstone theory using a recently proposed realistic non-local potential, and compare it with the corresponding curves obtained with a purely local realistic interaction (Argonne v$_{18}$) and the most recent version of the one-boson exchange potential (CD Bonn). We find that the inclusion of non-locality in the two-nucleon bare interaction strongly affects saturation, but it is unable to provide a consistent description of few-body nuclear systems and nuclear matter.

Quark-Model Baryon-Baryon Interaction and Its Applications to Hypernuclei

The quark-model baryon-baryon interaction fss2, proposed by the Kyoto-Niigata group, is a unified model for the complete baryon octet (B_8=N, Lambda, Sigma and Xi), which is formulated in a framework of the (3q)-(3q) resonating-group method (RGM) using the spin-flavor SU_6 quark-model wave functions and effective meson-exchange potentials at the quark level. Model parameters are determined to reproduce properties of the nucleon-nucleon system and the low-energy cross section data for the hyperon-nucleon scattering. Due to the several improvements including the introduction of vector-meson exchange potentials, fss2 has achieved very accurate description of the NN and YN interactions, comparable to various one-boson exchange potentials. We review the essential features of fss2 and our previous model FSS, and their predictions to few-body systems in confrontation with the available experimental data. Some characteristic features of the B_8 B_8 interactions with the higher strangeness, S=-2, -3, -4, predicted by fss2 are discussed. These quark-model interactions are now applied to realistic calculations of few-body systems in a new three-cluster Faddeev formalism which uses two-cluster RGM kernels. As for the few-body systems, we discuss the three-nucleon bound states, the Lambda NN-Sigma NN system for the hypertriton, the alpha alpha Lambda system for 9Be Lambda, and the Lambda Lambda alpha system for 6He Lambda Lambda.

What does the free space Lambda Lambda interaction predict for Lambda Lambda hypernuclei?

Data on LambdaLambda hypernuclei provide a unique method to learn details about the strangeness S = -2 sector of the baryon-baryon interaction. From the free space Bonn-Jülich potentials, determined from data on baryon-baryon scattering in the S = 0,-1 channels, we construct an interaction in the S = -2 sector to describe the experimentally known LambdaLambda hypernuclei. After including short-range (Jastrow) and RPA correlations, we find masses for these LambdaLambda hypernuclei in a reasonable agreement with data, taking into account theoretical and experimental uncertainties. Thus, we provide a natural extension, at low energies, of the Bonn-Jülich one-boson exchange potentials to the S = -2 channel.

N and OBEP and --Nucleus Bound States

One-boson-exchange potentials (OBEP) for ΞN and ΞΞ systems are derived in extension from the NN OBEP of Ueda, Riewe and Green in the framework of SU(3) invariance with effective nonet mesons in addition to the effective SU(3)-violating σ meson. The ΞN OBEP is applied to Ξ−-nucleus bound states. The SU(3) parameters that were determined in fitting the ΛN system are used. Only the coupling constant gΞΞσ is newly adjustable. This is determined so as to reproduce the energies of Ξ−-12C bound states. With the best value, we predict the scattering and bound states for ΞN and ΞΞ systems. In particular, we predict a Ξ -B bound state in agreement with the experimental results of the E885 collaboration.

An SU(3) Symmetric One-Boson-Exchange Potential between Two Octet Baryons

The SU(3) symmetric one-boson-exchange potential (OBEP) with a Gaussian soft core is proposed for interactions between two octet baryons. In this potential model, the breaking of the SU(3) symmetry is introduced by using the physical masses for the baryons and mesons. In the outer region (r ≥ 1fm), the OBEP works very well. In the core region (r ≤ 1fm), SU(3) symmetric Gaussian cores are introduced to guarantee the coexistence of the mechanisms of the meson exchange and the core, and the Gaussian cutoff function is multiplied to the OBEP. There are 22 free parameters, which consist of 11 SU(3) parameters for nonet mesons (g1, g8, gF/(gF+gD)= α,θ : each mesons) and 11 core parameters (core strength, core range). These parameters are determined via SU(3) relations by the method of χ2-fitting to reproduce the NN phase shifts and YN data. The fitting is quite satisfactory on the whole. Therefore, this OBEP is applicable to the calculation of nuclear and hyper-nuclear structures.