S. G. Bondarenko, V. V. Burov, W-Y. Pauchy Hwang, E. P. Rogochaya
A new version of the separable kernel of the nucleon-nucleon interaction in the Bethe-Salpeter approach is presented. The phase shifts are fitted to recent experimental data for singlet and uncoupled triplet partial waves of the neutron-proton scattering with total angular momenta J=0,1. The results are compared with other model calculations.
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Within the framework of the improved quantum molecular dynamics model, the medium modifications on the free nucleon-nucleon elastic cross sections are investigated. By using various in-medium nucleon-nucleon elastic cross sections in the model, the nucleon-induced reactions on various targets are simulated, and the excitation functions of reaction cross sections in the energy range from 25 MeV to 1 GeV are calculated. By comparing the calculations with the experimental data, an isospin, density, and momentum-dependence medium correction factor on free nucleon-nucleon elastic cross sections is …
The lowest-order correction of the density dependence of in-medium nucleon-nucleon cross sections is obtained from geometrical considerations of Pauli-blocking effects. As a by-product, it is shown that the medium corrections imply an 1/E energy dependence of the density-dependent term.
The solution for the nucleon-nucleon T matrix in the framework of the covariant Bethe-Salpeter approach for a two spin-one-half particle system with a separable kernel of interaction is analyzed. The explicit analytical connection between parameters of the separable kernel and low energy scattering parameters, deuteron binding energy and phase shifts is established.Covariant separable kernels for positive-energy partial channels with total angular momentum J=0 (1S0+, 3P0+) and J=1 (3S1+-3D1+, 1P1+, 3P1+) are constructed by using obtained relations.
In the paper the covariant kernel of the nucleon-nucleon interaction of particles with scalar propagators is analyzed. The Bethe-Salpeter equation for the T matrix is considered in the rank- one separable kernel. The parameters of the kernel for the specific partial-wave channels explicitly connect with the observables { low energy scattering parameters and phase shifts, deuteron binding energy. Covariant separable kernels forthe partial-wave channels with total angular momentum J = 0 (1S0, 3P0) and J = 1 (3S1 -3D1, 1P1, 3P1) are constructed.
The influence of medium correction from an isospin dependent nucleon nucleon cross section on the fragmentation and nucleon emission in the intermediate energy heavy ion collisions was studied by using an isospin dependent quantum molecular dynamical model (IQMD). We found that the medium correction enhances the dependence of multiplicity of intermediate mass fragment $N_{imf}$ and the number of nucleon emission $N_{n}$ on the isospin effect of the nucleon nucleon cross section,while the momentum dependent interaction (MDI) produces also an important role for enhancing the influence of the med…
Based on an isospin dependent quantum molecular dynamics model we studied the influence of a medium correction of an isospin dependent nucleon nucleon cross section on the fragmentation at the intermediate energy heavy ion collisions. We found that the medium correction from an isospin dependent nucleon nucleon cross section increases the dependence of the fragmentation on the isospin effect of in-medium nucleon nucleon cross section, at the same time, the momentum dependent interaction (MDI) produces also an important role for enhancing the influence of the medium correction on the isospin ef…
The dispersion relations for nucleon-nucleon (NN) T-matrix in the framework of Bethe-Salpeter equation for two spin one-half particle system and with separable kernel of interaction are considered in the paper. The developed expressions are applied for construction of the separable kernel of interaction for S partial-waves in singlet and triplet channels. We calculate the low energy scattering parameters and the phase shifts and also the deuteron binding energy with the separable interaction. The approach can be easily extended to higher partial-waves for NN-scattering and other reactions (ant…
We derive in-medium nucleon-nucleon (NN) cross sections in a microscopic model. Our calculations are based upon the Bonn NN potential and the Dirac-Brueckner approach for nuclear matter. We consider energies up to 300 MeV (in the laboratory frame) and densities up to twice nuclear matter density. Our results deviate substantially from cross section parametrizations that are commonly used in the nuclear medium.
We present a formalism to solve the Bethe-Goldstone scattering equation without the use of partial wave expansion which is alternative to the one we developed in a previous work. The present approach is more suitable for the calculation of in-medium nucleon-nucleon cross sections, which are the focal point of this paper. The impact of removing the spherical approximation on the angle and energy dependence of, particularly, in-medium proton-proton and proton-neutron differential cross sections is discussed along with its potential implication.
The effects of the symmetry potential and the isospin dependent in-medium nucleon-nucleon (NN) cross section on the number of proton(neutron) emissions N$_p(N_n$) are studied respectively within an isospin-dependent quantum molecular dynamics (IQMD) model. The isospin dependent in-medium NN cross section is found to have a strong influence on N$_p(N_n$) but N$_p(N_n$) is not sensitive to the symmetry potential for the neutron-deficient colliding system at relatively high energies.We propose to make use of the N$_p(N_n$) as a probe to extract information on the isospin dependent in-medium NN cr…
The in-medium nucleon-nucleon cross section is calculated starting from the thermodynamic T-matrix at finite temperatures. The corresponding Bethe-Salpeter-equation is solved using a separable representation of the Paris nucleon-nucleon-potential. The energy-dependent in-medium N-N cross section at a given density shows a strong temperature dependence. Especially at low temperatures and low total momenta, the in-medium cross section is strongly modified by in-medium effects. In particular, with decreasing temperature an enhancement near the Fermi energy is observed. This enhancement can be dis…
We present updated predictions of effective elastic nucleon-nucleon cross sections intended for use in nucleus-nucleus reactions. A novel characteristic of the present approach combines all microscopic medium effects included in the Dirac-Brueckner-Hartree-Fock G-matrix with a Pauli blocking mechanism which is more appropriate for applications in ion-ion reaction models as compared to a previous approach. The effective in-medium cross section is found to be quite sensitive to the description of Pauli blocking in the final configurations.
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…
Several observables of unbound nucleons which are to some extent sensitive to the medium modifications of nucleon-nucleon elastic cross sections in neutron-rich intermediate energy heavy ion collisions are investigated. The splitting effect of neutron and proton effective masses on cross sections is discussed. It is found that the transverse flow as a function of rapidity, the $Q_{zz}$ as a function of momentum, and the ratio of halfwidths of the transverse to that of longitudinal rapidity distribution $R_{t/l}$ are very sensitive to the medium modifications of the cross sections. The transver…
Using an isospin-dependent quantum molecular dynamics, nuclear stopping in intermediate heavy ion collisions has been studied. The calculation has been done for colliding systems with different neutron-proton ratios in beam energy ranging from 15MeV/u to 150MeV/u. It is found that, in the energy region from above Fermi energy to 150MeV/u, nuclear stopping is very sensitive to the isospin dependence of in-medium nucleon-nucleon cross section, but insensitive to symmetry potential. From this investigation, we propose that nuclear stopping can be used as a new probe to extract the information on …
The properties of nucleon-nucleon scattering inside dense nuclear matter are investigated. We use the relativistic Brueckner-Hartree-Fock model to determine on-shell and half off-shell in-medium transition amplitudes and cross sections. At finite densities the on-shell cross sections are generally suppressed. This reduction is, however, less pronounced than found in previous works. In the case that the outgoing momenta are allowed to be off energy shell the amplitudes show a strong variation with momentum. This description allows to determine in-medium cross sections beyond the quasi-particle …
We analyze the effects of an in-medium broadening of nucleon resonances on the exclusive photoproduction of mesons on nuclei as well as on the total photoabsorption cross sections in a transport calculation. We show that the resonance widths observed in semi-inclusive photoproduction on nuclei are insensitive to an in-medium broadening of nucleon resonances. This is due to a simple effect: the sizeable width of the nuclear surface and Fermi motion.
We apply the subtracted kernel method (SKM), a renormalization approach based on recursive multiple subtractions performed in the kernel of the scattering equation, to the chiral nucleon-nucleon (NN) interactions up to next-to-next-to-leading-order (NNLO). We evaluate the phase-shifts in the 1S0 channel at each order in Weinberg's power counting scheme and in a modified power counting scheme which yields a systematic power-law improvement. We also explicitly demonstrate that the SKM procedure is renormalization group invariant under the change of the subtraction scale through a non-relativisti…
Methods based on Wilson's renormalization group have been successfully applied in the context of nuclear physics to analyze the scale dependence of effective nucleon-nucleon ($NN$) potentials, as well as to consistently integrate out the high-momentum components of phenomenological high-precision $NN$ potentials in order to derive phase-shift equivalent softer forms, the so called $V_{low-k}$ potentials. An alternative renormalization group approach that has been applied in this context is the Similarity Renormalization Group (SRG), which is based on a series of continuous unitary transformati…
We compute the binding energies, radii, and densities for selected medium-mass nuclei within coupled-cluster theory and employ the "bare" chiral nucleon-nucleon interaction at order N3LO. We find rather well-converged results in model spaces consisting of 15 oscillator shells, and the doubly magic nuclei 40Ca, 48Ca, and the exotic 48Ni are underbound by about 1 MeV per nucleon within the CCSD approximation. The binding-energy difference between the mirror nuclei 48Ca and 48Ni is close to theoretical mass table evaluations. Our computation of the one-body density matrices and the corresponding …
A systematic study of the in-medium correction factor ($F$) on nucleon-nucleon elastic cross section is performed within the Ultra-relativistic Quantum Molecular Dynamics (UrQMD) model. The effects of the beam energy dependence of $F$ on the directed, elliptic flow and nuclear stopping in $^{197}$Au+$^{197}$Au collisions with energy ranging from $0.09$ to $0.8A$ GeV are explored. It is found that the directed, elliptic flow and nuclear stopping at relatively low energies are very sensitive to $F$, and the sensitivity gradually weakens with increasing beam energy. The beam energy dependent in-m…
We investigate the kinetic freeze out scenario of a nucleon gas through a finite layer. The in-medium mass modification of nucleons and it's impact on the freeze out process is studied. A considerable modification of the thermodynamical parameters temperature, flow-velocity, energy density and particle density has been found in comparison with evaluations which use a constant vacuum nucleon mass.
Using a more reasonable separate density-dependent scenario instead of the total density-dependent scenario for in-medium $nn$, $pp$ and $np$ interactions, we examine effects of differences of in-medium nucleon-nucleon interactions in two density-dependent scenarios on isospin-sensitive observables in central $^{197}$Au+$^{197}$Au collisions at 400 MeV/nucleon. Moreover, to more physically detect the differences between the nucleon-nucleon interactions in two density-dependent scenarios, we also map the nucleon-nucleon interaction in the separate density-dependent scenario into that in the tot…
In-medium nucleon-nucleon cross sections from relativistic ab initio calculations
本文通过相对论性从头计算方法，研究了介子中核子-核子散射截面的动量、密度和异ospin依赖性，为多参数依赖性的总散射截面参数化研究提供了基础。
We study the modification of the nucleon axial form factor in nuclear matter. The internal quark substructure of the nucleon is self-consistently described by the quark meson coupling model. We find that the axial form factor of the bound nucleon is quenched considerably from that of the free nucleon. The axial vector coupling constant is reduced by roughly 10% at normal nuclear matter density and the axial form factor varies within 8% for moderate momentum transfer.
Mechanical properties of the nucleon in the chiral confining model. II -- in-medium evolution of the nucleon properties
在手征禁闭模型框架下，通过冯·劳厄稳定性条件确定介质中核子试验态，研究标量场对复合核子的响应以及禁闭和手征对称性破缺对核子质量演化的作用，并分析核子内部能量密度和压力分布的变化。
The three--nucleon scattering problem in a nuclear medium is considered within the Faddeev technique. In particular the deuteron break--up cross section that governs the formation and the break--up reactions of deuterons (NNN <-> Nd) in a nuclear environment is calculated at finite temperatures and densities. A significant enhancement of the in--medium break--up cross section with increasing density has been found.
After reviewing our microscopic approach to nuclear and neutron-rich matter, we focus on how nucleon-nucleon scattering is impacted by the presence of a dense hadronic medium, with special emphasis on the case where neutron and proton densities are different. We discuss in detail medium and isospin asymmetry effects on the total elastic cross section and the mean free path of a neutron or a proton in isospin-asymmetric nuclear matter. We point out that in-medium cross sections play an important role in heavy-ion simulations aimed at extracting constraints on the symmetry potential. We argue th…
We study the isospin effects of the mean field and two-body collision on the nucleon emissions at the intermediate energy heavy ion collisions by using an isospin dependent transport theory. The calculated results show that the nucleon emission number $N_{n}$ depends sensitively the isospin effect of nucleon nucleon cross section and weakly on the isospin dependent mean field for neutron-poor system in higher beam energy region . In particular, the correlation between the medium correction of two-body collision and the momentum dependent interaction enhances the dependence of nucleon emission …
The momentum dependence of the medium modifications on nucleon-nucleon elastic cross sections is discussed with microscopic transport theories and numerically investigated with an updated UrQMD microscopic transport model. The semi-peripheral Au+Au reaction at beam energy $E_b=400A$ MeV is adopted as an example. It is found that the uncertainties of the momentum dependence on medium modifications of cross sections influence the yields of free nucleons and their collective flows as functions of their transverse momentum and rapidity. Among these observables, the elliptic flow is sensitively dep…
Talk given at the "International Workshop on (e,e'p) Processes", July 2-6, 2017, Bled, Slovenia. Various many-body calculations are compared and the results provided by the Normalization Conserving Linked Cluster Expansion with realistic NN interactions are reviewed and analyzed in detail, as far as ground state energies, momentum distributions and spectral functions of few-nucleon system and complex nuclei are concerned.
We study the in-medium modification of the isovector pi N amplitude using a non-linear representation of the sigma model but keeping the scalar degree of freedom. We check that our result does not depend on the representation. We discuss the connection with other approaches based on chiral perturbation theory.
We study the transverse flow throughout the mass range from $^{20}Ne+^{20}Ne$ to $^{131}Xe+^{131}Xe$ as a function of the impact parameter. We find that at smaller impact parameters the flow is negative while going through the impact parameter, transverse flow vanishes at a particular colliding geometry named GVF. We find that the mass dependence of GVF is insensitive to the equation of state and momentum dependent interactions whereas it is quite sensitive to the cross section. So it can act as a useful tool to pin down the nucleon nucleon cross section.
We analyze low-energy hyperon-nucleon scattering using an effective field theory in next-to-leading order. By fitting experimental cross sections for laboratory hyperon momenta below 200 MeV/c and using information from the hypertriton we determine twelve contact-interaction coefficients. Based on these we discuss the low-density expansion of hyperon mass shifts in the nuclear medium.
In-medium $ΛN$ interactions with leading order covariant chiral hyperon/nucleon-nucleon forces
本研究首次在相对论布鲁克纳-哈特里-福克框架下采用领头阶协变手征超子/核子-核子力研究介质内$\Lambda N$相互作用，可同时自洽描述实验截面与$\Lambda$单粒子势经验值，为相对论从头算超核物理提供新视角。
The study focuses on exploring the changes in the hyperon-baryon interaction at various nuclear densities. This approach starts by building a vacuum hyperon-nucleon interaction model based on Boson -Exchange maintaining SU(3) flavor symmetry. Bethe-Goldstone equation is then explored to investigate the medium properties over the bare interaction. A detailed investigation of the density dependence revealed clear changes in the low energy parameters with the variation of the medium density shown for different strangeness channels.
In-medium nucleon electromagnetic form factors are calculated in the quark meson coupling model. The form factors are typically found to be suppressed as the density increases. For example, at normal nuclear density and $Q^2 \sim 0.3 { GeV}^2$, the nucleon electric form factors are reduced by approximately 8% while the magnetic form factors are reduced by only 1 - 2%. These variations are consistent with current experimental limits but should be tested by more precise experiments in the near future.
We develop a new lattice Hamiltonian method for solving the Boltzmann-Uehling-Uhlenbeck (BUU) equation. Adopting the stochastic approach to treat the collision term and using the GPU parallel computing to carry out the calculations allows for a rather high accuracy in evaluating the collision term, especially its Pauli blocking, leading thus to a new level of precision in solving the BUU equation. Applying this lattice BUU method to study the width of giant dipole resonance (GDR) in nuclei, where the accurate treatment of the collision term is crucial, we find that the obtained GDR width of $^…
The problem of the near vanishing of the Gamow-Teller transition ($GT$) in the A=14 system between the lowest $J=0^+~ T=1$ and $J=1^+~ T=0$ states is revisited. The model space is extended from the valence space $(p^{-2})$ to the valence space plus all 2$\hbar ω$ excitations. The question is addressed as to what features of the effective nucleon-nucleon interaction in the medium are required to obtain the vanishing $GT$ strength in this extended space. It turns out that a combination of a realistic strength of the tensor force combined with a spin-orbit interaction which is enhanced as compare…
Elastic electron-helium-3 scattering is studied in the relativistic impulse approximation. The amplitudes for the three-nucleon system are obtained by solving the relativistic generalization of the Faddeev equations with a separable rank-one kernel of the nucleon-nucleon interaction. The contribution of partial-wave states with nonzero orbital moment of a nucleon pair is investigated. The static approximation and additional relativistic corrections for the 3He charge form factor are calculated for the momentum transfer squared up to 100 fm^-2. The contribution of the 3D1 partial-wave state and…
In-medium effects of nucleon-nucleon cross sections in heavy-ion collisions
基于Brueckner-Hartree-Fock微观截面，利用输运模型系统研究了核子-核子截面介质效应对核子和π介子观测量的影响，发现散射振幅、态密度和总动量依赖的贡献至关重要。
Based on the thermodynamic Green function approach two-nucleon correlations in nuclear matter at finite temperatures are revisited. To this end, we derive phase equivalent effective $r$-space potentials that include the effect of the Pauli blocking at a given temperature and density. These potentials enter into a Schrödinger equation that is the $r$-space representation of the Galitskii-Feynman equation for two nucleons. We explore the analytical structure of the equation in the complex $k$-plane by means of Jost functions. We find that despite the Mott effect the correlation with deuteron qua…
The in-medium neutron-proton, proton-proton(neutron-neutron) scattering cross sections($σ_{np}^{*}$, $σ_{pp(nn)}^{*}$) are studied based on QHD-II type Lagrangian within the framework of the microscopic transport theory. The results demonstrate that, for free nucleon-nucleon scattering cross sections, the isospin dependence is dominantly caused by $ρ$ meson field. The medium correction of nucleon-nucleon scattering cross sections is also isospin dependent, $σ_{np}^{*}$ depends on the baryon density weakly and $σ_{pp(nn)}^{*}$ depends on the baryon density significantly, which is due to the dif…
We derive density-dependent corrections to the in-medium nucleon-nucleon interaction from the leading-order chiral three-nucleon force. To this order there are six distinct one-loop diagrams contributing to the in-medium nucleon-nucleon scattering T-matrix. Analytic expressions are presented for each of these in both isospin-symmetric nuclear matter as well as nuclear matter with a small isospin asymmetry. The results are combined with the low-momentum nucleon-nucleon potential V(low-k) to obtain an effective density-dependent interaction suitable for nuclear structure calculations. The in-med…
Within the $σ-ω$ model of coupled nucleon-meson systems, a generalized relativistic Lenard--Balescu--equation is presented resulting from a relativistic random phase approximation (RRPA). This provides a systematic derivation of relativistic transport equations in the frame of nonequilibrium Green's function technique including medium effects as well as fluctuation effects. It contains all possible processes due to one meson exchange and special attention is kept to the off--shell character of the particles. As a new feature of many particle effects, processes are possible which can be interpr…
We show the first results for the elastic scattering of neutrons off oxygen and calcium isotopes obtained from ab initio optical potentials. The potential is derived using self consistent Green's function theory (SCGF) with the saturating chiral interaction NNLO$_{\textrm{sat}}$. Our calculations are compared to available scattering data and show that it is possible to reproduce low energy scattering observables in medium mass nuclei from first principles.
Based on the Isospin-dependent Boltzmann-Uehling-Uhlenbeck (IBUU) transport model, the in-medium nucleon-nucleon inelastic scattering ( which is dominated by pion production at low and intermediate energies) is explored. It is found that the in-medium modification of nucleon-nucleon inelastic scatterings appears to reduce the neutron to proton ratio n/p at higher kinetic energies. Although the in-medium modification of nucleon-nucleon inelastic scatterings, as expected, affects the value of $π^-/π^+$ ratio, considering a series of undetermined properties of delta resonance and $π$ in medium, t…
Within the $σ-ω$ model of coupled nucleon-meson systems, a generalized relativistic Lenard--Balescu--equation is presented resulting from a relativistic random phase approximation (RRPA). This provides a systematic derivation of relativistic transport equations in the frame of nonequilibrium Green's function technique including medium effects as well as flucuation effects. It contains all possible processes due to one meson exchange and special attention is kept to the off--shell character of the particles. As a new feature of many particle effects, processes are possible which can be interpre…
We investigate the asymptotic separation of the optical model potential for nucleon-nucleus scattering in momentum space, where the potential is split into a medium-independent term and another depending exclusively on the gradient of the density-dependent g matrix. This decomposition confines the medium sensitivity of the nucleon-nucleus coupling to the surface of the nucleus. We examine this feature in the context of proton-nucleus scattering at beam energies between 30 and 100 MeV and find that the pn coupling accounts for most of this sensitivity. Additionally, based on this general struct…
The calculation of the energy-, density-, and isospin-dependent $Δ$ production cross sections in nucleon-nucleon (NN) scattering $σ^*_{NN\rightarrow NΔ}$ has been performed within the framework of the relativistic BUU approach. The N$Δ$ cross sections are calculated in Born approximation taking into account the effective mass splitting of the nucleons and $Δ$s in asymmetric matter. Due to the different mass splitting for neutron, proton and differently charged $Δ$s, it is shown that, similar to the NN elastic ones, the reductions of N$Δ$ inelastic cross sections in isospin-asymmetric nuclear m…
The paper considers the electrodisintegration of the deuteron for kinematic conditions of the JLab experiment E-94-019. The calculations have been performed within the covariant Bethe-Salpeter approach with a separable kernel of nucleon-nucleon interactions. The results have been obtained using the relativistic plane wave impulse approximation and compared with experimental data and other models. The influence of nucleon electromagnetic form factors has been investigated.
The effective masses and sizes of N(939), $Δ(1232)$ and N(1440) in nuclear medium are calculated for a model in which quarks are subjected to a confinement force quenched by the scalar part of nuclear interactions. At the nuclear matter density, the nucleon swells by 50\% relative to the free nucleon. The masses of $Δ(1232)$ and N(1440) decrease in nuclear medium more than the nucleon, so that the pion requires less energy to excite them in nuclear medium than it does for a free nucleon.
It is found that the coupled piNNN-NNN system breaks into fragments in a nontrivial way. Assuming the particles as distinguishable, there are indeed four modes of fragmentation into two clusters, while in the standard three-body problem there are three possible two-cluster partitions and conversely the four-body problem has seven different possibilities. It is shown how to formulate the pion-three-nucleon collision problem through the integral-equation approach by taking into account the proper fragmentation of the system. The final result does not depend on the assumption of separability of t…
A model of a fluid of skyrmions coupled to a scalar and to the $ø$ meson mean fields is developed. The central and spin-orbit potentials of a skyrmion generated by the fields predict correct energy levels in selected closed shell nuclei. The effect of the meson fields on the properties of skyrmions in nuclei is investigated.
Few body methods are used in many particle physics to describe correlations, bound states, and reactions in strongly correlated quantum systems. Although this has already been recognized earlier, rigorous attempts to treat three-body collisions have only been done recently. In this talk I shall give examples and areas where few-body methods have been and might be of use in the future.
In-medium effects in photon excitation of the S$_{11}$ resonance from nucleon and its decay to $η$-meson using the RMF approach is studied. We examine the in-medium effects by varing the Dirac fields of the nucleon and the S$_{11}$ resonance separately. We obtained a conclusion that the Dirac fields of the nucleon, which reduces the nucleon effective mass, enlarge the width of S$_{11}$ resonance, and small Dirac-fields of the resonance shifts the peak position, and these combined effects can explain the in-medium properties observed in the experimental data for $^{12}$C($γ$,$η$) reaction.
We derive ab initio optical potentials from self-consistent Green's function (SCGF) theory and compute the elastic scattering of neutrons off oxygen and calcium isotopes. The comparison with scattering data is satisfactory at low scattering energies. The method is benchmarked against no-core shell model with continuum (NCSMC) calculations, showing that virtual excitations of the target are crucial to predict proper fragmentation and absorption at higher energies. This is a significant step toward deriving optical potentials for medium mass nuclei and complex many-body systems in general.
We use the recently proposed In-Medium Similarity Renormalization Group (IM-SRG) to carry out a systematic study of closed-shell nuclei up to $\nuc{Ni}{56}$, based on chiral two- plus three-nucleon interactions. We analyze the capabilities of the IM-SRG by comparing our results for the ground-state energy to Coupled Cluster calculations, as well as to quasi-exact results from the Importance-Truncated No-Core Shell Model. Using chiral two- plus three-nucleon Hamiltonians whose resolution scales are lowered by free-space SRG evolution, we obtain good agreement with experimental binding energies …
The mean free paths and in-medium scattering cross sections of energetic nucleons in neutron-rich nucleonic matter are investigated using the nucleon optical potential obtained within the relativistic impulse approximation with the empirical nucleon-nucleon scattering amplitudes and the nuclear densities obtained in the relativistic mean field model. It is found that the isospin-splitting of nucleon mean free paths, sensitive to the imaginary part of the symmetry potential, changes its sign at certain high kinetic energy. The in-medium nucleon-nucleon cross sections are analytically and numeri…
In the relativistic impulse approximation (RIA), we study symmetry potentials and in-medium nucleon-nucleon (NN) cross sections with the Nambu-Jona-Lasinio (NJL) model that features chiral symmetry. The chiral symmetry that plays a fundamental role in the nonperturbative physics in the strong interaction is anticipated to add restrictive effects on the symmetry potentials and in-medium NN cross sections. For comparison, we also perform the study with the usual relativistic mean-field (RMF) model. The numerical results with the NJL and RMF models are similar at saturation density and below, sin…
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