Nuclear Theory·nucl-th

Tuesday·May 7, 2019

13 papers—6 primary·7 cross-listed

01
The Giant Pairing Vibration in Heavy Nuclei: Present Status and Future Studies
M. Assié🇫🇷 · C. H. Dasso🇪🇸 · R. J. Liotta🇸🇪 · A.O. Macchiavelli🇺🇸 · A. Vitturi🇮🇹
The Giant Pairing Vibration, a two-nucleon collective mode originating from the second shell above the Fermi surface, has long been predicted and expected to be strongly populated in two-nucleon transfer reactions with cross sections similar to those of the normal Pairing Vibration. Recent experiments have provided evidence for this mode in $^{14, 15}$ C but, despite sensitive studies, it has not been definitively identified either in Sn or Pb nuclei where pairing correlations are known to play a crucial role near their ground states. In this paper we review the basic theoretical concepts of this "elusive" state and the status of experimental searches in heavy nuclei. We discuss the hindrance effects due to Q-value mismatch and the use of weakly-bound projectiles as a way to overcome the limitations of the (p,t) and (t,p) reactions. We also discuss the role of the continuum and conclude with some possible future developments.
nucl-thnucl-ex1 citation
02
Production of a 4He_Lambda hypernucleus in the 4He(pi, K) reactions reexamined
Toru Harada🇯🇵 · Yoshiharu Hirabayashi🇯🇵
We investigate theoretically production cross sections of the $J^{π} =$ 0 $^{+}$ ground state of a $_{Λ}^{4}$ He hypernucleus in the $^{4}$ He( $π$ ,~ $K$ ) reaction with a distorted-wave impulse approximation using the optimal Fermi-averaged $π N \to K Λ$ $t$ matrix. We demonstrate the sensitivity of the production cross sections to the $Λ$ wavefunctions obtained from $3 N$ - $Λ$ potentials and to meson distorted waves in eikonal distortions. It is shown that the calculated laboratory cross sections of the 0 $^{+}$ ground state in $_{Λ}^{4}$ He amount to $d σ / d Ω_{lab} ≃$ 11 $μ$ b/sr at $p_{π} =$ 1.05 GeV/ $c$ in the $K$ forward direction because of an advantage of the use of the s-shell target nucleus such as $^{4}$ He. The importance of the recoil effects and the energy dependence of the $π N \to K Λ$ cross sections is also discussed.
nucl-thPRC(2019)·6 citations
03
Integer and half-integer channel spins for elastic scattering cross sections
A. S. Tkachenko · R. Ya. Kezerashvili · N. A. Burkova · S. B. Dubovichenko
We present the analytical expressions for the differential cross sections and independent partial amplitudes for elastic scattering of nuclear particles for channels with a spin value of 1/2, 1, 3/2, 2 and 5/2. The independent partial amplitudes are presented for arbitrary orbital angular momentum $l$ and taking into account spin-orbit splitting. The analytical expressions allow one to carry out full phase shift analyses using experimental data for differential cross sections for processes with channel spins 1/2, 1, 3/2, 2 and 5/2.
nucl-thNPA(2019)·1 citation
04
Effective lambda-proton and lambda-neutron potentials from subthreshold inverse scattering
Emile Meoto🇿🇦 · Mantile Lekala🇿🇦
Potentials are constructed for the lambda-nucleon interaction in the $^{1} S_{0}$ and $^{3} S_{1}$ channels. These potentials are recovered from scattering phases below the inelastic threshold through Gel'fand-Levitan-Marchenko theory. Experimental data with good statistics is not available for lambda-nucleon scattering. This leaves theoretical scattering phases as the only option through which the rigorous theory of quantum inverse scattering can be used in probing the lambda-nucleon force. Using rational-function interpolations on the theoretical scattering data, the kernels of the Gel'fand-Levitan-Marchenko integral equation become degenerate, resulting in a closed-form solution. The new potentials restored, which are shown to be unique through the Levinson theorem, bear the expected features of short-range repulsion and intermediate-range attraction. Charge symmetry breaking, which is perceptible in the scattering phases, is preserved in the new potentials. The lambda-nucleon force in the $^{1} S_{0}$ channel is observed to be stronger than in the $^{3} S_{1}$ channel, as expected. In addition, the potentials bear certain distinctive features whose effects on hypernuclear systems can be explored through Schrödinger calculations.
nucl-thJ.Phys.Comm.(2019)·5 citations
05
First principles electromagnetic responses in medium-mass nuclei
Johannes Simonis · Sonia Bacca · Gaute Hagen
We review the recent progress made in the computation of electromagnetic response functions in light and medium-mass nuclei using coupled-cluster theory. We show how a many-body formulation of the Lorentz integral transform method allows to calculate the photoabsorption cross sections of $^{16, 22}$ O and $^{40}$ Ca. Then, we discuss electromagnetic sum rules, with particular emphasis on the electric dipole polarizability, $α_{D}$ . By including triples corrections in coupled-cluster theory, we revisit $^{48}$ Ca, for which, beside the electric dipole polarizability, we had previously investigated the neutron and proton radii, as well as the size of the neutron-skin thickness [1]. We show that correlations among these observables still hold, albeit a better agreement with experiment is obtained for $α_{D}$ and the prediction of a small neutron-skin thickness is further corroborated.
nucl-thnucl-exEPJA(2019)·33 citations
06
Towards baryon-baryon scattering in manifestly Lorentz-invariant formulation of SU(3) baryon chiral perturbation theory
V. Baru🇩🇪 · E. Epelbaum🇩🇪 · J. Gegelia🇩🇪 · X.-L. Ren🇩🇪
We study baryon-baryon scattering by applying time-ordered perturbation theory to the manifestly Lorentz-invariant formulation of SU(3) baryon chiral perturbation theory. We derive the corresponding diagrammatic rules paying special attention to complications caused by momentum-dependent interactions and propagators of particles with non-zero spin. We define the effective potential as a sum of two-baryon irreducible contributions of time-ordered diagrams and derive a system of integral equations for the scattering amplitude, which provides a coupled-channel generalization of the Kadyshevsky equation. The obtained leading-order baryon-baryon potentials are perturbatively renormalizable, and the corresponding integral equations have unique solutions in all partial waves. We discuss the issue of additional finite subtractions required to improve the ultraviolet convergence of (finite) loop integrals on the example of nucleon-nucleon scattering in the $^{3} P_{0}$ partial wave. Assuming that corrections beyond leading order can be treated perturbatively, we obtain a fully renormalizable formalism which can be employed to study baryon-baryon scattering.
nucl-thhep-phPLB(2019)·29 citations

Affiliations

first authorsco-authorsvia INSPIRE

The Giant Pairing Vibration in Heavy Nuclei: Present Status and Future Studies

Production of a 4He_Lambda hypernucleus in the 4He(pi, K) reactions reexamined

Integer and half-integer channel spins for elastic scattering cross sections

Effective lambda-proton and lambda-neutron potentials from subthreshold inverse scattering

First principles electromagnetic responses in medium-mass nuclei

Towards baryon-baryon scattering in manifestly Lorentz-invariant formulation of SU(3) baryon chiral perturbation theory

Affiliations