Nuclear Theory·nucl-th

Thursday·June 30, 2022

11 papers—5 primary·6 cross-listed

01
Isospin-symmetry implications for nuclear two-body distributions and short-range correlations
R. Weiss🇺🇸 · A. Lovato🇺🇸 · R. B. Wiringa🇺🇸
We study the implications of isospin symmetry in nuclear systems on two-body distributions and derive relations between different densities or momentum distributions of a given nucleus or of different nuclei in the same isospin multiplet. A connection between neutrinoless double beta decay transition of mirror nuclei and two-body densities is also obtained. The relations are numerically verified by means of quantum Monte Carlo calculations. We discuss the relevance of these results to the analysis of nuclear short-range correlations and also show that isospin symmetry allows us to extract information about the spectator nucleons when a short-range correlated pair is formed.
nucl-thnucl-exPRC(2022)·2 citations
02
Microscopic-macroscopic level densities for low excitation energies
A.G. Magner · A.I. Sanzhur · S.N. Fedotkin · A.I. Levon · U.V. Grygoriev · S. Shlomo
Level density $ρ (E, Q)$ is derived within the micro-macroscopic approximation (MMA) for a system of strongly interacting Fermi particles with the energy $E$ and additional integrals of motion $Q$ , in line with several topics of the universal and fruitful activity of A.S. Davydov. Within the extended Thomas Fermi and semiclassical periodic orbit theory beyond the Fermi-gas saddle-point method we obtain $ρ \propto I_{ν} (S) / S^{ν}$ , where $I_{ν} (S)$ is the modified Bessel function of the entropy $S$ . For small shell-structure contribution one finds $ν = κ /2 + 1$ , where $κ$ is the number of additional integrals of motion. This integer number is a dimension of $Q$ , $Q = {N, Z, ...}$ for the case of two-component atomic nuclei, where $N$ and $Z$ are the numbers of neutron and protons, respectively. For much larger shell structure contributions, one obtains, $ν = κ /2 + 2$ . The MMA level density $ρ$ reaches the well-known Fermi gas asymptote for large excitation energies, and the finite micro-canonical combinatoric limit for low excitation energies. The additional integrals of motion can be also the projection of the angular momentum of a nuclear system for nuclear rotations of deformed nuclei, number of excitons for collective dynamics, and so on. Fitting the MMA total level density, $ρ (E, Q)$ , for a set of the integrals of motion $Q = {N, Z}$ , to experimental data on a long nuclear isotope chain for low excitation energies, one obtains the results for the inverse level-density parameter $K$ , which differs significantly from those of neutron resonances, due to shell, isotopic asymmetry, and pairing effects.
nucl-thLow Temp.Phys.(2022)·3 citations
03
Investigating the coalescence-inspired sum rule for light nuclei and hypernuclei in heavy-ion collisions
Ashik Ikbal Sheikh🇺🇸
A data-driven idea is presented to test if light nuclei and hypernuclei obey the coalescence-inspired sum rule, i.e., to test if the flow of a light nucleus or hypernucleus is the summed flow of each of its constituents. Here, the mass difference and charge difference among the constituents of light nuclei and hypernuclei are treated appropriately. The idea is applied to the available data for $s_{N N} = 3$ GeV fixed-target Au+Au collisions at the Relativistic Heavy Ion Collider (RHIC), published by the STAR collaboration. It is found that the sum rule for light nuclei is approximately valid near mid-rapidity ( $- 0.3 < y < 0$ ), but there is a clear violation of the sum rule at large rapidity ( $y < - 0.3$ ). The Jet AA Microscopic Transport Model (JAM), with baryonic mean-field plus nucleon coalescence, generates a similar pattern as obtained from the experimental data. In the present approach, the rapidity dependence of directed flow of the hypernuclei $_{Λ}^{3} H$ and $_{Λ}^{4} H$ is predicted in a model-independent way for $s_{N N} = 3$ GeV Au+Au collisions, which will be explored by ongoing and future measurements from STAR.
nucl-thhep-exhep-phnucl-exPRC(2022)·2 citations
04
Quasi-bound state in the $K ˉ N N N$ system
N.V. Shevchenko🇨🇿
The paper is devoted to the $K ˉ N N N$ system, which is an exotic system consisting of an antikaon and three nucleons. Dynamically exact four-body Faddeev-type equations were solved and characteristics of the quasi-bound state in the system were evaluated. Three antikaon-nucleon and three nucleon-nucleon potentials were used, so the dependence of the four-body pole positions on the two-body interaction models was studied. The resulting binding energies $B_{K^{-} pp n}^{Chiral} \sim 30.5 - 34.5$ MeV obtained with chirally motivated and $B_{K^{-} pp n}^{SIDD} \sim 46.4 - 52.0$ MeV obtained with phenomenological antikaon-nucleon potentials are close to those obtained for the $K^{-} pp$ system with the same $K ˉ N$ and $N N$ potentials, while the four-body widths $Γ_{K^{-} pp n} \sim 38.2 - 50.9$ MeV are smaller.
nucl-thPRC(2022)·6 citations
05
Two-photon exchange in (muonic) deuterium at N3LO in pionless effective field theory
Vadim Lensky (JGU Mainz)🇩🇪 · Franziska Hagelstein (JGU Mainz and PSI Villigen)🇩🇪 · Vladimir Pascalutsa (JGU Mainz)🇩🇪
We present a study of the two-photon-exchange ( $2 γ$ -exchange) corrections to the $S$ -levels in muonic ( $μ$ D) and ordinary (D) deuterium within the pionless effective field theory (pionless EFT). Our calculation proceeds up to next-to-next-to-next-to-leading order (N3LO) in the pionless EFT expansion. The only unknown low-energy constant entering the calculation at this order corresponds to the coupling of a longitudinal photon to the nucleon-nucleon system. To minimise its correlation with the deuteron charge radius, it is extracted using the information about the hydrogen-deuterium isotope shift. We find the elastic $2 γ$ -exchange contribution in $μ$ D larger by several standard deviations than obtained in other recent calculations. This discrepancy ameliorates the mismatch between theory and experiment on the size of $2 γ$ -exchange effects, and is attributed to the properties of the deuteron elastic charge form factor parametrisation used to evaluate the elastic contribution. We identify a correlation between the deuteron charge and Friar radii, which can help one to judge how well a form factor parametrisation describes the low-virtuality properties of the deuteron. We also evaluate the higher-order $2 γ$ -exchange contributions in $μ$ D, generated by the single-nucleon structure and expected to be the most important terms beyond N3LO. The uncertainty of the theoretical result is dominated by the truncation of the pionless EFT series and is quantified using a Bayesian approach. The resulting extractions of the deuteron charge radius from the $μ$ D Lamb shift, the $2 S - 1 S$ transition in D, and the $2 S - 1 S$ hydrogen-deuterium isotope shift, with the respective $2 γ$ -exchange effects evaluated in a unified pionless EFT approach, are in perfect agreement.
nucl-thhep-phnucl-exphysics.atom-phEPJA(2022)·6 citations

Affiliations

first authorsco-authorsvia INSPIRE

Isospin-symmetry implications for nuclear two-body distributions and short-range correlations

Microscopic-macroscopic level densities for low excitation energies

Investigating the coalescence-inspired sum rule for light nuclei and hypernuclei in heavy-ion collisions

Quasi-bound state in the KˉNNN system

Two-photon exchange in (muonic) deuterium at N3LO in pionless effective field theory

Affiliations

Quasi-bound state in the $K ˉ N N N$ system