Nuclear Theory·nucl-th

Wednesday·June 12, 2024

9 papers—7 primary·2 cross-listed

01
Uncertainty quantification for $μ \to e$ conversion in nuclei: charge distributions
Frederic Noël🇨🇭 · Martin Hoferichter🇨🇭
Predicting the rate for $μ \to e$ conversion in nuclei for a given set of effective operators mediating the violation of lepton flavor symmetry crucially depends on hadronic and nuclear matrix elements. In particular, the uncertainties inherent in this non-perturbative input limit the discriminating power that can be achieved among operators by studying different target isotopes. In order to quantify the associated uncertainties, as a first step, we go back to nuclear charge densities and propagate the uncertainties from electron scattering data for a range of isotopes relevant for $μ \to e$ conversion in nuclei, including $^{40, 48}$ Ca, $^{48, 50}$ Ti, and $^{27}$ Al. We provide as central results Fourier-Bessel expansions of the corresponding charge distributions with complete covariance matrices, accounting for Coulomb-distortion effects in a self-consistent manner throughout the calculation. As an application, we evaluate the overlap integrals for $μ \to e$ conversion mediated by dipole operators. In combination with modern ab-initio methods, our results will allow for the evaluation of general $μ \to e$ conversion rates with quantified uncertainties.
nucl-thhep-exhep-phnucl-exJHEP(2024)·13 citations
02
Time-dependent Relativistic Hartree-Fock model with spherical symmetry
Jing Geng · Zhi Heng Wang · Peng Wei Zhao · Yi Fei Niu · Haozhao Liang · Wen Hui Long
This work establishes the time-dependent relativistic Hartree-Fock (TD-RHF) model with spherical symmetry for the first time. The time-dependent integro-differential Dirac equations are solved by expanding Dirac spinors on the spherical Dirac Woods-Saxon (DWS) basis. The numerical verification demonstrates the high conservation qualities for both the total binding energy and the particle number, as well as the time-reversal invariance of the system, which ensures the precision and reliability of the newly developed TD-RHF model. Subsequently, the isoscalar giant monopole resonance (ISGMR) mode of $^{208}$ Pb is investigated using the RHF Lagrangian PKO1. The constrained energy of the ISGMR calculated by PKO1 is found to be in close agreement with the experimental data, and the strength function is similar to the results given by the relativistic Hartree-Fock plus random phase approximation. Based on the advantage of the TD-RHF model in avoiding complicated calculations of the residual interactions, the ISGMR mode of $^{208}$ Pb is calculated by twelve relativistic effective Lagrangians. The results indicate that the value of the incompressibility of nuclear matter $K_{\infty}$ constrained by relativistic effective Lagrangians is in the range of $237 \sim 246$ MeV, which is lower than the previous investigations based on the relativistic models.
nucl-thPRC(2025)·5 citations
03
Relativistic Hartree-Fock model for axial-symmetric nuclei with quadruple and octupole deformations
Yong Peng · Jing Geng · Wen Hui Long
\textbf{Background:} The initial observation of a negative-parity state in proximity to the ground state in the 1950s marked the advent of extensive research into octupole deformed nuclei. Since then, the physics of octupole deformed nuclei has consistently held a special interest within the field of nuclear physics. In the present era, with the advent of sophisticated radioactive ion beam (RIB) facilities and advanced detectors, coupled with the remarkable capabilities of high-performance computing, extensive and intensive explorations are being conducted from both experimental and theoretical perspectives to elucidate the physics of octupole deformed nuclei. \textbf{Results:} This work establishes the OD-RHF model, which provides a reliable tool for studying octupole nuclei over a fairly wide range. The reliability of the newly developed OD-RHF model is illustrated by taking the octupole nucleus $^{144}$ Ba as an example. Furthermore, the octupole deformation effects in $^{144}$ Ba is verified by using the RHF Lagrangians PKO $i$ ( $i = 1, 2, 3$ ) and the RMF one DD-ME2. The intrusion of the neutron $1 i_{13/2}$ and proton $1 h_{11/2}$ components is demonstrated to play an essential role in determining the notable octupole deformation of $^{144}$ Ba using PKO $i$ ( $i = 1, 2, 3$ ) and DD-ME2. It is indicated that the Fock terms play an important role in stabilizing the octupole deformation. More specifically, due to the repulsive tensor coupling between the intrude components and the core of $^{144}$ Ba, the tensor force component carried by the $π$ -PV coupling, that contributes only via the Fock terms, plays an opposing role in the formation of the octupole deformation of $^{144}$ Ba.
nucl-thCPC(2025)·3 citations
04
Bayesian inference of nuclear incompressibility from collective flow in mid-central Au+Au collisions at 400--1500 MeV/nucleon
J. M. Wang🇨🇳 · X. G. Deng🇨🇳 · W. J. Xie🇨🇳 · B. A. Li🇺🇸 · Y. G. Ma🇨🇳
The incompressibility $K$ of symmetric nuclear matter (SNM) is determined through a Bayesian analysis of collective flow data from Au + Au collisions at beam energies $E = 400 - 1500$ MeV/nucleon. This analysis utilizes a Gaussian process (GP) emulator applied to the isospin-dependent quantum molecular dynamics (IQMD) model for heavy-ion collisions, both with and without incorporating the momentum dependence of the single-nucleon potentials. Specifically, the inferred incompressibility values are $K = 188. 9_{- 4.5}^{+ 2.9}$ MeV and $256. 1_{- 8.7}^{+ 8.2}$ MeV at $E = 400$ MeV/nucleon, respectively, at the 68\% confidence level using rapidity and transverse velocity dependence of proton elliptic flow data, with and without consideration of the momentum dependence. When the transverse momentum dependence of proton-like directed flow data is included, the inferred incompressibility values become $K = 222. 3_{- 9.9}^{+ 9.0}$ MeV and $K = 285. 5_{- 7.3}^{+ 6.7}$ MeV, respectively. Furthermore, we found that the value of $K$ derived from observables of proton elliptic flow increases with beam energy. This indicates that the equation of state (EoS) of nuclear matter hardens at higher densities and temperatures in reactions with higher beam energies.
nucl-thnucl-exCPC(2025)·13 citations
05
Superscaling analysis of inclusive electron and (anti)neutrino scattering within the coherent density fluctuation model
M. V. Ivanov🇧🇬 · A. N. Antonov🇧🇬
The experimental data from quasielastic electron and (anti)neutrino scattering on $^{12}$ C are reanalyzed in terms of a new scaling variable $ψ^{*}$ suggested by the interacting relativistic Fermi gas with scalar and vector interactions, which is known to generate a relativistic effective mass for the interacting nucleons. We construct a new scaling function $f^{QE} (ψ^{*})$ for the inclusive lepton scattering from nuclei within the coherent density fluctuation model (CDFM). The latter is a natural extension of the relativistic Fermi gas model to finite nuclei. In this work, on the basis of the scaling function obtained within CDFM with a relativistic effective mass $m_{N}^{*} = 0.8 m_{N}$ , we calculate and compare the theoretical predictions with a large set of experimental data for inclusive ( $e, e^{'}$ ) and (anti)neutrino cross sections. The model also includes the contribution of weak two-body currents in the two-particle two-hole sector, evaluated within a fully relativistic Fermi gas. Good agreement with experimental data is found over the whole range of electron and (anti)neutrino energies.
nucl-thPRC(2024)·9 citations
06
Impact of the nuclear equation of state on the formation of twin stars
Nai-Bo Zhang🇨🇳 · Bao-An Li🇺🇸
Twin stars-two stable neutron stars (NSs) with the same mass but different radii have long been proposed to appear as a consequence of a possible first-order phase transition in NS matter. Within a meta-model for the EOS of hybrid stars, we revisit the viability of twin stars and its dependence on numerous parameters characterizing the EOS of nuclear matter, quark matter, and the phase transition between them. While essentially no experimental constraint exists for the last two, parameters characterizing the EOS of neutron-rich nucleonic matter have been constrained within various ranges by terrestrial experiments and astrophysical observations. Within these ranges, the impact of nuclear EOS and crust-core transition density on the formation of twin stars is studied. It is found that the symmetry energy of neutron-rich nucleonic matter notably influences the formation of twin stars, particularly through its slope $L$ and curvature $K_{sym}$ . Conversely, varying the EOS of symmetric nuclear matter within their currently known uncertainty ranges shows minimal influence on the formation of twin stars.
nucl-thastro-ph.HEnucl-exEPJA(2025)·21 citations
07
Helium-4 gravitational form factors: exchange currents
Fangcheng He🇺🇸 · Ismail Zahed🇺🇸
We evaluate the leading exchange corrections to the Helium-4 gravitational form factors (GFFs) upto momenta of the order of the nucleon mass. We use both the K-harmonic method with simple pair nucleon potential, and a Jastrow trial function using the Argonne $v_{14}$ potential, to evaluate the Helium-4 GFFs. The exchange current contributions include the pair interaction, plus the seagull and the pion exchange interactions, modulo the recoil corrections. To estimate the off-shellness of the pion nucleon coupling in this momenta range, we discuss the results using either the pseudo-scalar (PS) or pseudo-vector (PV) pion-nucleon couplings. When the PV coupling is used, the pair diagram contribution is higher order in the non relativistic expansion. The results for the Helium-4 A-GFF are comparable to those given by the impulse approximation, especially for the PS coupling using both the K-Harmonic method and variational method. The exchange current contributions with the PS coupling for the charge form factor of Helium-4, yield better agreement with the existing data over a broad range of momenta, especially when the Argonne $v_{14}$ potential including the D-wave admixture is used.
nucl-thhep-phPRC(2024)·3 citations
08
Transient dynamics of quasinormal mode sums
Javier Carballo🇬🇧 · Benjamin Withers🇬🇧
Quasinormal modes of spacetimes with event horizons are typically governed by a non-normal operator. This gives rise to spectral instabilities, a topic of recent interest in the black hole pseudospectrum programme. In this work we show that non-normality leads to the existence of arbitrarily long-lived sums of short-lived quasinormal modes, corresponding to localising packets of energy near the future horizon. There exist sums of $M$ quasinormal modes whose lifetimes scale as $lo g M$ . This transient behaviour results from large cancellations between non-orthogonal quasinormal modes. We provide simple closed-form examples for a massive scalar field in the static patch of dS $_{d + 1}$ and the BTZ black hole. We also provide numerical examples for scalar perturbations of Schwarzschild-AdS $_{d + 1}$ , and gravitational perturbations of Schwarzschild in asymptotically flat spacetime, using hyperboloidal foliations. The existence of these perturbations is linked to certain properties of black hole pseudospectra. We comment on implications for thermalisation times in holographic plasmas.
↳ hep-thcond-mat.str-elgr-qcnucl-thJHEP(2024)·26 citations
09
Anomalous propagators and the particle-particle channel: Hedin's equations
Antoine Marie · Pina Romaniello · Pierre-François Loos
Hedin's equations provide an elegant route to compute the exact one-body Green's function (or propagator) via the self-consistent iteration of a set of non-linear equations. Its first-order approximation, known as $G W$ , corresponds to a resummation of ring diagrams and has shown to be extremely successful in physics and chemistry. Systematic improvement is possible, although challenging, via the introduction of vertex corrections. Considering anomalous propagators and an external pairing potential, we derive a new self-consistent set of closed equations equivalent to the famous Hedin equations but having as a first-order approximation the particle-particle (pp) $T$ -matrix approximation where one performs a resummation of the ladder diagrams. This pp version of Hedin's equations offers a way to go systematically beyond the $T$ -matrix approximation by accounting for low-order pp vertex corrections.
↳ physics.chem-phcond-mat.mtrl-scicond-mat.str-elnucl-thPRB(2024)·5 citations

Affiliations

first authorsco-authorsvia INSPIRE