Nuclear Theory·nucl-th

Tuesday·November 28, 2023

20 papers—7 primary·13 cross-listed

01
Uniform descriptions of pseudospin symmetries in bound and resonant states
Ting-Ting Sun · Zhi Pan Li
As a continuation of our previous work on the conservation and breaking of the pseudospin symmetry (PSS) in resonant states [Phys. Lett. B 847, 138320 (2023)}], in this work, the PSS in nuclear single-particle bound and resonant states are investigated uniformly within a relativistic framework by exploring the poles of the Green's function in spherical Woods-Saxon potentials. As the potential depths increase from zero to finite depths, the PS partners evolve from resonant states to bound states. In this progress,the PSS is broken gradually with energy, width, and density splittings. Specially, the energy and width splittings for the resonant and bound states are directly determined by the ratio of the pseudo spin-orbit potentials between the PS partners. Obvious threshold effect is observed for the energy splitting at a critical potential depth, with which the PS partners locate between the centrifugal barriers of PS partners. The differences in the density distributions of the lower component between the PS partners are manifested in the phase shift for the resonant states and amplitudes for bound states. Besides, the evolution of the phase shift as the potential depth is consistent with those for the width splitting.
nucl-thPLB(2024)·5 citations
02
Improved determination of the oscillator parameters in nuclei
Latsamy Xayavong · Yeunhwan Lim
The oscillator parameter in nuclei is refitted to reproduce the available charge radius data. As an important improvement, we include the Coulomb term evaluated within the assumption of a uniformly charged sphere, and take into account the symmetry effect induced by the difference between N and Z numbers in a straightforward manner using the conventional parameterization. The Coulomb interaction has repulsive effect, causing the wave functions to extend further toward the nucleus exterior, resulting in an effectively larger oscillator length parameter. The symmetry effect is attractive for protons in neutron-rich nuclei and for neutrons in proton-rich nuclei, and repulsive for the other cases. Therefore, three distinct oscillator parameters are determined: one for protons, one for neutrons, and one isospin-invariant version, which is obtained by subtracting the Coulomb and symmetry contributions. Additionally, we explore the direct fit of the harmonic oscillator wave functions to the eigenfunctions of the Hartree-Fock mean field using the Skyrme interaction. Generally, this method agrees well with the others for light nuclei, typically up to $^{40}$ Ca. Beyond this nucleus, however, the results begin to diverge over the orbits chosen for the fit. Only the parameters values obtained for the last occupied states agree remarkably well with the conventional ones throughout the mass range under consideration.
nucl-thnucl-ex0 citations
03
ANCs of the bound states of $^{16}$ O deduced from elastic $α$ - $^{12}$ C scattering data
Shung-Ichi Ando (Sunmoon Univ.)
Asymptotic normalization coefficients (ANCs) of the $0_{1}^{+}$ , $0_{2}^{+}$ , $1_{1}^{-}$ , $2_{1}^{+}$ , $3_{1}^{-}$ ( $l_{i t h}^{π}$ ) bound states of $^{16}$ O are deduced from the phase shift data of elastic $α$ - $^{12}$ C scattering at low energies. $S$ matrices of elastic $α$ - $^{12}$ C scattering are constructed within cluster effective field theory (EFT), in which both bound and resonant states of $^{16}$ O are considered. Parameters in the $S$ matrices are fitted to the precise phase shift data below the $p$ - $^{15}$ N breakup energy for the partial waves of $l = 0, 1, 2, 3, 4, 5, 6$ , and the ANCs are calculated by using the wave function normalization factors of $^{16}$ O propagators for $l = 0, 1, 2, 3$ . We review the values of ANCs, which are compared with other results in the literature, and discuss uncertainties of the ANCs obtained from the elastic $α$ - $^{12}$ C scattering data in cluster EFT.
nucl-thnucl-exFew Body Syst.(2024)·4 citations
04
Theories of Relativistic Dissipative Fluid Dynamics
Gabriel S. Rocha🇺🇸 · David Wagner🇩🇪 · Gabriel S. Denicol🇧🇷 · Jorge Noronha🇺🇸 · Dirk H. Rischke🇩🇪
Relativistic dissipative fluid dynamics finds widespread applications in high-energy nuclear physics and astrophysics. However, formulating a causal and stable theory of relativistic dissipative fluid dynamics is far from trivial; efforts to accomplish this reach back more than 50 years. In this review, we give an overview of the field and attempt a comparative assessment of (at least most of) the theories for relativistic dissipative fluid dynamics proposed until today and used in applications.
nucl-thhep-phhep-thphysics.flu-dynEntropy(2024)·77 citations
05
Corrections to Landau Fermi-liquid fixed-point approximation in nonlinear bosonized theory: Application to $g_{A}^{L}$ in nuclei
Long-Qi Shao🇨🇳 · Mannque Rho🇫🇷
We calculated in nonlinear bosonized theory $1/ N ˉ$ corrections to the Landau Fermi-liquid fixed-point (FLFP) axial-vector coupling constant in nuclear matter $g_{A}^{L} \approx 1$ to which the Landau parameter $F_{1}^{ω}$ predominantly contributes. We obtain the correction to $F_{1}^{ω}$ to calculate the correction $δ g_{A}^{L}$ to the axial-vector coupling constant $g_{A}^{L}$ at the nuclear saturation density. It comes out to be extremely small, $δ g_{A}^{L} \sim O (1 0^{- 4})$ . We discuss how the "dilaton-limit fixed-point (DLFP)" result $g_{A} = 1$ can be preserved from finite nuclei to high densities relevant to massive neutron stars and its possible impact on $0 ν β β$ decay processes involved in going beyond the Standard Model.
nucl-thhep-phPRC(2024)·6 citations
06
Multireference covariant density-functional theory for the low-lying states of odd-mass nuclei
E. F. Zhou · X. Y. Wu · J. M. Yao
We extend multireference covariant density-functional theory (MR-CDFT) based on a relativistic point-coupling energy functional to describe the low-lying states of odd-mass nuclei. The nuclear wave function is constructed as a superposition of quadrupole-octupole deformed mean-field configurations, with projection onto angular momentum, particle numbers, and parity within the framework of the generator coordinate method. Using $^{25}$ Mg as an example, we calculate the energy spectrum, electric multipole, and magnetic dipole transition strengths based on three different schemes for the mean-field configurations of odd-mass nuclei. We find that the low-energy structure of $^{25}$ Mg is reasonably reproduced in all three schemes. In particular, the effect of octupole correlation is illustrated in the application to the low-lying parity doublets of $^{21}$ Ne. This work demonstrates the success of the MR-CDFT for the low-lying states of odd-mass nuclei with possible strong quadruple-octupole correlations.
nucl-thPRC(2024)·17 citations
07
Effects of hyperon potentials and symmetry energy in quark deconfinement
Rajesh Kumar🇺🇸 · Krishna Aryal🇺🇸 · Alexander Clevinger🇺🇸 · Veronica Dexheimer🇺🇸
In this letter we discuss how the results of recent nuclear experiments that correspond to measurements at low densities can affect the equation of state at large densities and temperatures, changing the particle composition and ultimately influencing deconfinement to quark matter. In particular, saturation values of the hyperon potentials affect the hyperon content, while the symmetry energy at saturation directly regulates how the stiffness of the equation of state changes with isospin. We make use of a chiral model that describes nucleons, hyperons, and quarks to show how astrophysical conditions, such as the ones in neutron stars, present the ideal ground to study the effects of these two quantities in dense matter. In this case, for small charge fraction/ large isospin asymmetry, the couplings that reproduce different symmetry energy slopes can significantly modify deconfinement, with quantitative changes in the critical chemical potential depending on the deconfining potential. On the other hand, different values of the parameter that controls the hyperon potentials (kept within a range close to experimental data) do not affect deconfinement significantly.
nucl-thastro-ph.HEastro-ph.SRPLB(2024)·6 citations
08
Pion and kaon electromagnetic and gravitational form factors
Yin-Zhen Xu🇪🇸 · Minghui Ding🇩🇪 · Khépani Raya🇪🇸 · Craig D. Roberts🇨🇳 · José Rodríguez-Quintero🇪🇸 · Sebastian M. Schmidt🇩🇪
A unified set of predictions for pion and kaon elastic electromagnetic and gravitational form factors is obtained using a symmetry-preserving truncation of each relevant quantum field equation. A key part of the study is a description of salient aspects of the dressed graviton + quark vertices. The calculations reveal that each meson's mass radius is smaller than its charge radius, matching available empirical inferences; and meson core pressures are commensurate with those in neutron stars. The analysis described herein paves the way for a direct calculation of nucleon gravitational form factors.
↳ hep-phhep-exhep-latnucl-ex+1EPJC(2024)·60 citations
09
Spin polarization and spin alignment from quantum kinetic theory with self-energy corrections
Shuo Fang🇨🇳 · Shi Pu🇨🇳 · Di-Lun Yang🇹🇼
We derive the quantum kinetic theory for massive fermions with collision terms and self-energy corrections based on quantum field theory. We adopt an effective power counting scheme with $ℏ$ expansion to obtain the leading-order perturbative solutions of the vector and axial Wigner functions and the corresponding kinetic equations. We observe that both the onshell relation and the structure of Wigner functions, along with the kinetic equations, are modified due to the presence of self-energies and their space-time gradients. We further apply our formalism to investigate the spin polarization phenomena in relativistic heavy ion collisions and derive the modification to the spin polarization spectrum of massive quarks. We find that the gradient of vector self-energy plays a similar role to the background electromagnetic fields, which induces a more dominant contribution than the collisional effects by a naive power counting in the gradient expansion and weak coupling. Our findings could further modify the spin polarization of strange quarks and spin alignment of $ϕ$ mesons beyond local thermal equilibrium.
↳ hep-phhep-thnucl-thPRD(2024)·38 citations
10
Speed of sound exceeding the conformal bound in dense 2-color QCD
Etsuko Itou🇯🇵 · Kei Iida🇯🇵
We review recent works on the Monte Carlo simulations of dense two-color QCD (QC $_{2}$ D) by focusing on the phase diagram, the equation of state, and the sound velocity at nonzero quark chemical potential. A possible upper bound of the sound velocity is known as the conformal bound, namely, $c_{s}^{2} / c^{2} \leq 1/3$ . The sound velocity is below the bound at least in the case of finite-temperature QCD. However, our recent work~\cite{Iida:2022hyy} shows the breaking of this bound in dense QC $_{2}$ D. This phenomenon was previously unknown from any lattice calculations. We also discuss recent related works including lattice studies on QCD at nonzero isospin chemical potential, some effective model analyses, and an analysis based on recent neutron star observations. These works also suggest the breaking of the conformal bound.
↳ hep-lathep-phhep-thnucl-thPoS(2024)·5 citations
11
Universal relations for compact stars with exotic degrees of freedom
Anil Kumar · Manoj Kumar Ghosh · Pratik Thakur · Vivek Baruah Thapa · Monika Sinha
The nature of the highly dense matter inside the supernova remnant compact star is not constrained by terrestrial experiments and hence modeled phenomenologically to accommodate the astrophysical observations from compact stars. The observable properties of the compact stars are highly sensitive to the microscopic model of highly dense matter. However, some universal relations exist between some macroscopic properties of compact stars independent of the matter model. We study the universal relation including the stars containing exotic degrees of freedom such as heavier strange and non-strange baryons, strange quark matter in normal and superconducting phases, etc. We examine the universal relations for quantities moment of inertia - tidal love number - quadrupole moment. We also study the correlation of non-radial f-mode and p-mode frequencies with stellar properties. We find the f-mode frequency observes the universal relation with dimensionless tidal deformability but the p-mode frequency does not show a good correlation with stellar properties. The p-mode frequency is sensitive to the composition of the matter. We find that universal relation is also applicable for stars with exotic matter in the core of the star with several models of exotic matter.
↳ astro-ph.HEhep-phnucl-thEPJC(2024)·16 citations
12
New configuration set of HAL QCD collaboration
Etsuko Itou for HAL QCD collaboration🇯🇵
We give a brief report on the basic properties and cutoff scale of our new configuration set (HAL-Conf-2023). We generated 8,000 trajectories of the gauge configurations on $9 6^{4}$ lattices with the same lattice parameters as the PACS collaboration \cite{Ishikawa:2018jee, PACS:2019ofv}. The topological distribution, the PCAC masses, and decay constants for pseudo-scalar mesons are studied. As for the scale setting, we utilize the $Ω$ baryon mass as a reference scale and carefully investigate the operator dependence of the correlation function. As a result, we obtain $a^{- 1} = 2338.8 (1.5)_{- 3.3}^{+ 0.2} [MeV]$ as a lattice cutoff. Our hadron spectra in the physical unit reproduce well the experimental results.
↳ hep-latnucl-thPoS(2024)·2 citations
13
Overview of the experimental quest for the giant pairing vibration
M. Assié🇫🇷
The search for the giant pairing vibration (GPV) has a long standing history since the 1970's when it was predicted. First experimental measurements focused on (p,t) transfer reactions in the heavy nuclei and did not show convincing evidence. The discovery of a signal compatible with the GPV in the light carbon isotopes has renewed the interest for the GPV. It triggered new theoretical models showing that the GPV in the heavy nuclei might be too wide or too melted to be observed and triggered new experiments with radioactive probes based on ( $^{6}$ He, $^{4}$ He) transfer.
↳ nucl-exnucl-thNuovo Cim.C(2024)·0 citations
14
Prospects of identifying the presence of Strange Stars using Gravitational Waves from binary systems
Bikram Keshari Pradhan🇮🇳 · Swarnim Shirke🇮🇳 · Debarati Chatterjee🇮🇳
The existence of self-bound strange stars is a long-standing mystery in astrophysics. Future astrophysical data, even with improved precision, may not allow us to discriminate them from neutron stars, given the uncertainties in observational and theoretical modeling. In this work, we propose a unique strategy to distinguish strange stars from neutron stars using gravitational waves from binary compact star systems. We demonstrate that empirical relations connecting f-mode frequencies with tidal deformation are distinct for the two classes of compact objects, irrespective of their equations of state. Therefore simultaneous measurement of f-mode frequency and tidal deformability from the inspiral phase of compact binary mergers with the next-generation detectors can provide smoking gun evidence for the presence of strange stars. This would have crucial implications not only in gravitational wave physics but multidisciplinary fields such as nuclear and high energy physics.
↳ gr-qcastro-ph.HEhep-thnucl-th3 citations
15
Impact of shell model interactions on nuclear responses to WIMP elastic scattering
Raghda Abdel Khaleq🇦🇺 · Giorgio Busoni🇦🇺 · Cedric Simenel🇦🇺 · Andrew E. Stuchbery
Background: Nuclear recoil from scattering with weakly interacting massive particles (WIMPs) is a signature searched for in direct detection of dark matter. The underlying WIMP-nucleon interactions could be spin and/or orbital angular momentum (in)dependent. Evaluation of nuclear recoil rates through these interactions requires accounting for nuclear structure, e.g., through shell model calculations. Purpose: To evaluate nuclear response functions induced by these interactions for $^{19}$ F, $^{23}$ Na, $^{28, 29, 30}$ Si, $^{40}$ Ar, $^{70, 72, 73, 74, 76}$ Ge, $^{127}$ I, and $^{128, 129, 130, 131, 132, 134, 136}$ Xe nuclei that are relevant to current direct detection experiments, and to estimate their sensitivity to shell model interactions. Methods: Shell model calculations are performed with the NuShellX solver. Nuclear response functions from non-relativistic effective field theory (NREFT) are evaluated and integrated over transferred momentum for quantitative comparisons. Results: Although the standard spin independent response is barely sensitive to the structure of the nuclei, large variations with the shell model interaction are often observed for the other channels. Conclusions: Significant uncertainties may arise from the nuclear components of WIMP-nucleus scattering amplitudes due to nuclear structure theory and modelling. These uncertainties should be accounted for in analyses of direct detection experiments.
↳ hep-phnucl-thPRD(2024)·7 citations
16
Chiral hydrodynamics of expanding systems
Nora Weickgenannt🇫🇷 · Jean-Paul Blaizot🇫🇷
We obtain equations of motion for the boost-invariant expansion of a system of chiral particles. Our analysis is based on the Boltzmann equation for left- and right-handed massless particles in the relaxation time approximation. We assume Bjorken symmetry, but allow for parity breaking. We generalize the relaxation time approximation to take into account the so-called side-jump effect, but we show that the ensuing correction happens to vanish for Bjorken symmetry. After expressing the conserved currents in terms of chiral moments, we derive equations of motion for these moments from the Boltzmann equation. After a suitable truncation, these equations allow us to study the transition from the early-time collisionless regime to the hydrodynamic regime at late time, where the parity-violating chiral moments decay exponentially. The truncation that we use for the parity-violating moments is shown to be identical to Israel-Stewart's 14-moment approximation. Our final set of equations can be used to calculate the energy-momentum tensor, vector-, and axial-vector currents with chiral degrees of freedom for possible applications in heavy-ion collisions.
↳ hep-phnucl-thPRD(2024)·23 citations
17
Extraction of the microscopic properties of quasi-particles using deep neural networks
Olga Soloveva🇩🇪 · Andrea Palermo🇺🇸 · Elena Bratkovskaya🇩🇪
We use deep neural networks (DNN) to obtain the microscopic characteristics of partons in terms of dynamical degrees of freedom on the basis of an off-shell quasiparticle description. We aim to infer masses and widths of quasi-gluons, up/down, and strange quarks using constraints on the macroscopic thermodynamic observables obtained by the first-principles calculations lattice QCD. In this work, we use 3 independent dimensionless thermodynamic observables from lQCD for minimization. First, we train our DNN using the DQPM (Dynamical QuasiParticle Model) Ansatz for the masses and widths. Furthermore, we use the DNN capabilities to generalize this Ansatz, to evaluate which quasiparticle characteristics are desirable to describe different thermodynamic functions simultaneously. To evaluate consistently the microscopic properties obtained by the DNN in the case of off-shell quarks and gluons, we compute transport coefficients using the spectral function within Kubo-Zubarev formalism in different setups. In particular, we make a comprehensive comparison in the case of the dimensionless ratios of shear viscosity over entropy density $η / s$ and electric conductivity over temperature $σ_{Q} / T$ , which provide additional constraints for the parameter generalization of the considered models.
↳ hep-phnucl-thPRC(2024)·10 citations
18
Neutron stars in accreting systems -- signatures of the QCD phase transition
Noshad Khosravi Largani🇵🇱 · Tobias Fischer🇵🇱 · Shota Shibagaki🇵🇱 · Pablo Cerdá-Durán🇪🇸 · Alejandro Torres-Forné🇪🇸
Neutron stars (NS) that are born in binary systems with a main-sequence star companion can experience mass transfer, resulting in the accumulation of material at the surface of the NS. This, in turn, leads to the continuous growth of the NS mass and the associated steepening of the gravitational potential. Supposing the central density surpasses the onset for the phase transition from nuclear, generally hadronic matter to deconfined quark-gluon plasma, which is a quantity currently constrained solely from an upper limit by asymptotic freedom in quantum chromodynamics (QCD), the system may experience a dynamic response due to the appearance of additional degrees of freedom in the equation of state (EOS). This dynamical response might give rise to a rapid softening of the EOS during the transition in the hadron-quark matter co-existence region. While this phenomenon has long been studied in the context of hydrostatic configurations, the dynamical implications of this problem are still incompletely understood. It is the purpose of the present paper to simulate the dynamics of NSs with previously accreted envelopes caused by the presence of a first-order QCD phase transition. Therefore, we employed the neutrino radiation hydrodynamics treatment based on the fully general relativistic approach in spherical symmetry, implementing a three-flavor Boltzmann neutrino transport and a microscopic model EOS that contains a first-order hadron-quark phase transition. The associated neutrino signal shows a sudden rise in the neutrino fluxes and average energies, becoming observable for the present generation of neutrino detectors for a galactic event, and a gravitational wave mode analysis revealed the behaviors of the dominant $f$ mode and the first and the second gravity $g$ modes that are excited during the NS evolution across the QCD phase transition.
↳ astro-ph.HEnucl-thAstron.Astrophys.(2024)·9 citations
19
Energy loss of a fast moving parton in Gribov-Zwanziger plasma
Manas Debnath🇮🇳 · Ritesh Ghosh🇺🇸 · Mohammad Yousuf Jamal🇮🇳 · Manu Kurian🇺🇸 · Jai Prakash🇮🇳
The Gribov-Zwanziger prescription applied within Yang-Mills theory is demonstrated to be an efficient method for refining the theory's infrared dynamics. We study the collisional energy loss experienced by a high-energetic test parton as it traverses through the Grivov plasma at finite temperature. To achieve this, we employ a semi-classical approach that considers the parton's energy loss while accounting for the back-reaction induced by the polarization effects due to its motion in the medium. The polarization tensor of the medium is estimated within a non-perturbative resummation considering the Gribov-Zwanziger approach. The modification of the gluon and ghost loops due to the presence of the Gribov parameter plays a vital role in our estimation. We observe that the non-perturbative interactions have a sizable effect on the parton energy loss. Further, we discuss the implications of our findings in the context of relativistic heavy-ion collisions.
↳ hep-phnucl-thPRD(2024)·16 citations
20
A solution for infinite variance problem of fermionic observables
Hyunwoo Oh🇺🇸 · Andrei Alexandru🇺🇸 · Paulo F. Bedaque🇺🇸 · Andrea Carosso🇺🇸
Fermionic Monte Carlo calculations with continuous auxiliary fields often encounter infinite variance problem from fermionic observables. This issue renders the estimation of observables unreliable, even with an infinite number of samples. In this work, we show that the infinite variance problem stems from the fermionic determinant. Also, we propose an approach to address this problem by employing a reweighting method that utilizes the distribution from an extra time-slice. Two strategies to compute the reweighting factor are explored: one involves truncating and analytically calculating the reweighting factor, while the other employs a secondary Monte Carlo estimation. With Hubbard model as a testbed, we demonstrate that utilizing the sub-Monte Carlo estimation, coupled with an unbiased estimator, offers a solution that effectively mitigates the infinite variance problem at a minimal additional cost.
↳ hep-latcond-mat.str-elnucl-thPoS(2024)·0 citations

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