Nuclear Theory·nucl-th

Monday·December 20, 2021

12 papers—7 primary·5 cross-listed

01
Locating the special point of hybrid neutron stars
Mateusz Cierniak🇵🇱 · David Blaschke🇵🇱
The special point is a feature unique to models of hybrid neutron stars. It represents a location on their mass--radius sequences that is insensitive to the phase transition density. We consider hybrid neutron stars with a core of deconfined quark matter that obeys a constant--sound--speed (CSS) equation of state model and provide a fit formula for the coordinates of the special point as functions of the squared sound speed ( $c_{s}^{2}$ ) and pressure scale ( $A$ ) parameters. Using the special point mass as a proxy for the maximum mass of the hybrid stars we derive limits for the CSS model parameters based on the recent NICER constraint on mass and radius of pulsar PSR J0740+6620, $0.36 < c_{s}^{2}_{min} < 0.43$ and $80 < A [MeV/fm^{3}] < 160$ . The upper limit for the maximum mass of hybrid stars depends on the upper limit for $c_{s}^{2}$ so that choosing $c_{s, ma x}^{2} = 0.6$ results in $M_{max} < 2.7 M_{⊙}$ , within the mass range of GW190814.
nucl-thastro-ph.HEhep-phEPJ Web Conf.(2022)·8 citations
02
Confining density functional approach for color superconducting quark matter and mesonic correlations
Oleksii Ivanytskyi🇵🇱 · David Blaschke🇵🇱 · Konstantin Maslov🇷🇺
We present a novel relativistic density-functional approach to modeling quark matter with a mechanism to mimic confinement. The quasiparticle treatment of quarks provides their suppression due to large quark selfenergy already at the mean-field level. We demonstrate that our approach is equivalent to a chiral quark model with medium-dependent couplings. The dynamical restoration of the chiral symmetry is ensured by construction of the density functional. Beyond the mean field, quark correlations in the pseudoscalar channel are described within the Gaussian approximation. This explicitly introduces pionic states into the model. Their contribution to the thermodynamics potential is analyzed within the Beth-Uhlenbeck framework. The modification of the meson mass spectrum in the vicinity of thee (de)confinement transition is interpreted as the Mott transition. Supplemented with the vector repulsion and diquark pairing the model is applied to construct a hybrid quark-hadron EoS of cold compact-star matter. We study the connection of such a hybrid EoS with the stellar mass-radius relation and tidal deformability. The model results are compared to various observational constraints including the NICER radius measurement of PSR J0740+6620 and the tidal deformability constraint from GW170817. The model is shown to be consistent with the constraints, still allowing for further improvement by adjusting the vector repulsion and diquark pairing couplings.
nucl-thhep-phEPJ Web Conf.(2022)·6 citations
03
Generator coordinate method for transition-state dynamics in nuclear fission
G.F. Bertsch · K. Hagino
Since its beginnings, fission theory has asumed that low-energy induced fission takes place through transition-state channels at the barrier tops. Neverthess, up to now there is no microscopic theory applicable to those conditions. We suggest that modern reaction theory is suitable for this purpose, and propose a methodology based on a configuration-interaction framework using the Generator Coordinate Method (GCM). Simple reaction-theoretic models are constructed with the Gaussian Overlap Approximation (GOA) to parameterize both the dynamics within the channels and their incoherent couplings to states outside the barrier. The physical characteristics of the channels examined here are their effective bandwidths and the quality of the coupling to compound-nucleus states as measured by the transmission factor $T$ . We also investigate the spacing of GCM states with respect to their degree of overlap. We find that a rather coarse mesh provides an acceptable accuracy for estimating the bandwidths and transmission factors. The common numerical stability problem in using the GCM is avoided due to the choice of meshes and the finite bandwidths of the channels. The bandwidths of the channels are largely controlled by the zero-point energy with respect to the collective coordinate in the GCM configurations.
nucl-thPRC(2022)·11 citations
04
Zr Isotopes as a region of intertwined quantum phase transitions
N. Gavrielov · A. Leviatan · F. Iachello
The zirconium isotopes with $A =$ 92 $-$ 110 have one of the most complicated evolution of structure in the nuclear chart. In order to understand the structural evolution of these isotopes, we carry a detailed calculation in a definite symmetry-based framework, the interacting boson model with configuration mixing (IBM-CM). We compare our calculation to a large range of experimental data, such as energy levels, two neutron separation energies, $E 2$ and $E 0$ transition rates, isotope shifts and magnetic moments. The structural evolution of the low lying spectra of these isotopes is explained using the notion of intertwined quantum phase transitions (IQPTs), for which a QPT involving a crossing of two configurations (Type II) is accompanied by a QPT involving a shape evolution of each configuration separately (Type I). In our study, we find the occurrence of Type I QPT within the intruder configuration, changing from weakly deformed to prolate deformed and finally to $γ$ -unstable, associated with the U(5), SU(3) and SO(6) dynamical symmetry limits of the IBM, respectively. Alongside the Type I QPT, we also find the occurrence of Type II QPT between the normal and intruder configurations, where both Types I and II have a critical-point near $A \approx 100$ . The good agreement of our calculation with the vast empirical data along the chain of isotopes demonstrates the relevance of IQPTs to the zirconium isotopes, and can serve as a case study to set path for new investigations of IQPTs in other nuclei and other physical systems.
nucl-thPRC(2022)·41 citations
05
Nuclear transparency of the charged hadron produced in the inclusive electronuclear reaction
Swapan Das🇮🇳
The nuclear transparency of the charged hadron produced in the inclusive $(e, e^{'})$ reaction on the nucleus has been calculated using Glauber model for the nuclear reaction. The color transparency (CT) of the produced hadron and the short-range correlation (SRC) of the nucleons in the nucleus have been incorporated in the Glauber model to investigate their effects on the nuclear transparency of the hadron. The calculated nuclear transparencies for the proton and pion are compared with the data.
nucl-thPRC(2022)·6 citations
06
Nuclear level densities away from line of $β$ -stability
T. Ghosh · B. Maheshwari · Sangeeta · G. Saxena · B. K. Agrawal
The variation of total nuclear level densities (NLDs) and level density parameters with proton number $(Z)$ are studied around the $β$ -stable isotope, $Z_{0}$ , for a given mass number. We perform our analysis for a mass range $A = 40$ to 180 using the NLDs from popularly used databases obtained with the single-particle energies from two different microsopic mass-models. These NLDs which include microscopic structural effects such as collective enhancement, pairing and shell corrections, do not exhibit inverted parabolic trend with a strong peak at $Z_{0}$ as predicted earlier. We also compute the NLDs using the single-particle energies from macroscopic-microscopic mass-model. Once the collective and pairing effects are ignored, the inverted parabolic trends of NLDs and the corresponding level density parameters become somewhat visible. Nevertheless, the factor that governs the $(Z - Z_{0})$ dependence of the level density parameter, leading to the inverted parabolic trend, is found to be smaller by an order of magnitude. We further find that the $(Z - Z_{0})$ dependence of NLDs is quite sensitive to the shell effects.
nucl-thJ.Phys.G(2022)·2 citations
07
Gamows alpha decay theory revisited
K. D. Krori · Samrat Dey
G. Gamow's alpha-decay theory (1928), although successful, has a wrong phenomenological argument that an alpha-particle inside a radioactive nucleus moves back and forth through the dense mass of nucleons (retaining its identity) a number of times before it comes out. This short paper seeks to get over this shortcoming by deriving principally the Gamow's theory through a slightly alternative approach by avoiding the problematic touching frequency in the original theory.
nucl-thReson.(2024)·0 citations
08
Concerning pion parton distributions
Z.-F. Cui🇨🇳 · M. Ding🇩🇪 · J. M. Morgado🇪🇸 · K. Raya🇪🇸 · D. Binosi🇮🇹 · L. Chang🇨🇳 · J. Papavassiliou🇪🇸 · C. D. Roberts🇨🇳 · J. Rodríguez-Quintero🇪🇸 · S. M. Schmidt🇩🇪
Analyses of the pion valence-quark distribution function (DF), $u^{π} (x; ζ)$ , which explicitly incorporate the behaviour of the pion wave function prescribed by quantum chromodynamics (QCD), predict $u^{π} (x ≃ 1; ζ) \sim (1 - x)^{β (ζ)}$ , $β (ζ ≳ m_{p}) > 2$ , where $m_{p}$ is the proton mass. Nevertheless, more than forty years after the first experiment to collect data suitable for extracting the $x ≃ 1$ behaviour of $u^{π}$ , the empirical status remains uncertain because some methods used to fit existing data return a result for $u^{π}$ that violates this constraint. Such disagreement entails one of the following conclusions: the analysis concerned is incomplete; not all data being considered are a true expression of qualities intrinsic to the pion; or QCD, as it is currently understood, is not the theory of strong interactions. New, precise data are necessary before a final conclusion is possible. In developing these positions, we exploit a single proposition, viz. there is an effective charge which defines an evolution scheme for parton DFs that is all-orders exact. This proposition has numerous corollaries, which can be used to test the character of any DF, whether fitted or calculated.
↳ hep-phhep-exhep-latnucl-ex+1EPJA(2022)·57 citations
09
Alpha-alpha scattering in the Multiverse
Serdar Elhatisari🇹🇷 · Timo A. Lähde🇩🇪 · Dean Lee🇺🇸 · Ulf-G. Meißner🇩🇪 · Thomas Vonk🇩🇪
We investigate the phase shifts of low-energy alpha-alpha scattering under variations of the fundamental parameters of the Standard Model, namely the light quark mass, the electromagnetic fine-structure constant as well as the QCD theta-angle. As a first step, we recalculate alpha-alpha scattering in our Universe utilizing various improvements in the adiabatic projection method, which leads to an improved, parameter-free prediction of the S- and D-wave phase shifts for laboratory energies below 10 MeV. We find that positive shifts in the pion mass have a small effect on the S-wave phase shift, whereas lowering the pion mass adds some repulsion in the two-alpha system. The effect on the D-wave phase shift turns out to be more pronounced as signaled by the D-wave resonance parameters. Variations of the fine-structure constant have almost no effect on the low-energy alpha-alpha phase shifts. We further show that up-to-and-including next-to-leading order in the chiral expansion, variations of these phase shifts with respect to the QCD theta-angle can be expressed in terms of the theta-dependent pion mass.
↳ hep-thastro-ph.COhep-lathep-ph+1JHEP(2022)·17 citations
10
Thermal freeze-out parameters and pseudo-entropy from charged hadron spectra in high energy collisions
Xu-Hong Zhang🇨🇳 · Ya-Qin Gao🇨🇳 · Fu-Hu Liu🇨🇳 · Khusniddin K. Olimov🇺🇿
We collected the transverse momentum (mass) spectra of charged hadrons ( $π^{-}$ , $π^{+}$ , $K^{-}$ , $K^{+}$ , $p$ , and $p$ ) produced in collisions over a center-of-mass energy range from 2.70 to 200 GeV (per nucleon pair). The modified Tsallis--Pareto-type function (the TP-like function) with average transverse flow velocity is used to describe the contribution of participant or constituent quarks to transverse momentum of considered hadron. The experimental spectra of $π^{\mp}$ and $K^{\mp}$ (or $p$ and $p$ ) are fitted by the convolution of two (or three) TP-like functions due to the fact that two (or three) constituent quarks are regarded as two (or three) energy resources in the formation of considered hadron. From the reasonable fits to the spectra, the thermal freeze-out parameters are extracted, and the pseudo-entropy is newly defined and extracted. Some parameters quickly change in the energy range of less than 7.7 GeV, and slowly change in the energy range of greater than 7.7 GeV, indicating the variation of collision mechanism at around 7.7 GeV.
↳ hep-phhep-exnucl-exnucl-thAdv.High Energy Phys.(2022)·8 citations
11
A Bayesian analysis of the properties of hybrid stars with the NJL model
Antoine Pfaff🇫🇷 · Hubert Hansen🇫🇷 · Francesca Gulminelli🇫🇷
We implement a Bayesian analysis of the properties of non-rotating hybrid stars at equilibrium with quark matter cores, as described by the SU(3) Nambu--Jona-Lasinio (NJL) model. The hadronic phase is described by a unified metamodeling approach, with a prior parameter space covering the present uncertainties on nuclear matter properties with nucleonic degrees of freedom. The parameter space of the NJL model includes vector-isoscalar and vector-isovector couplings and, additionally, an effective bag constant for the quark pressure is introduced as a free parameter. The phase transition is assumed to be first order with charge neutral phases, following the Maxwell construction. Our Bayesian framework includes filters on the experimental and theoretical low-density nuclear physics knowledge (atomic masses, ab initio calculations of the EoS) and high density constraints from astrophysical observations (maximum mass of J0348+0432, binary tidal deformability of the GW170817 event). We find that microscopic vector interactions play an important role in quark matter in order to stiffen the equation of state sufficiently to reach high star masses, in agreement with previous studies. Even within a very large prior for both the hadronic phase and the quark phase and the important freedom brought by the effective bag constant, our posterior quark cores tend to be relatively small and only appear in very heavy stars ( $M ≳ 2 M_{⊙}$ ). Coincidentally, the inclusion of the nucleon-quark transition (deconfinement transition) only weakly affects the radii of compact stars, foreshadowing a very low observability of a possible phase transition using x-ray radii measurements.
↳ astro-ph.HEhep-phnucl-thPRC(2022)·26 citations
12
Proposed Lunar Measurements of $r$ -Process Radioisotopes to Distinguish Origin of Deep-sea 244Pu
Xilu Wang🇨🇳 · Adam M. Clark🇺🇸 · John Ellis🇬🇧 · Adrienne F. Ertel🇺🇸 · Brian D. Fields🇺🇸 · Brian J. Fry🇺🇸 · Zhenghai Liu🇺🇸 · Jesse A. Miller🇺🇸 · Rebecca Surman🇺🇸
244Pu has recently been discovered in deep-sea deposits spanning the past 10 Myr, a period that includes two 60Fe pulses from nearby supernovae. 244Pu is among the heaviest $r$ -process products, and we consider whether it was created in the supernovae, which is disfavored by nucleosynthesis simulations, or in an earlier kilonova event that seeded 244Pu in the nearby interstellar medium that was subsequently swept up by the supernova debris. We discuss how these possibilities can be probed by measuring 244Pu and other $r$ -process radioisotopes such as 129I and 182Hf, both in lunar regolith samples returned to Earth by missions such as Chang'e and Artemis, and in deep-sea deposits.
↳ astro-ph.HEhep-phnucl-exnucl-th+1Astrophysics(2023)·13 citations

Affiliations

first authorsco-authorsvia INSPIRE