Nuclear Theory·nucl-th

Tuesday·August 29, 2023

21 papers—12 primary·9 cross-listed

01
Core destruction in knockout reactions
C.A. Bertulani
A model is presented to calculate projectile core destruction in knockout reactions. It incorporates physics arguments similar to the formulation of the state of the art theory to calculate stripping and diffraction dissociation cross sections in heavy ion collisions with bombarding energies around 100 MeV/nucleon and larger. It is shown that secondary collisions between the incoming and struck nucleons and the projectile core decrease the core survival probability by as much as 9.5\%. However, no clear evidence is found for reduction of the cross section with increasing binding energy of the removed nucleon.
nucl-thnucl-exPLB(2023)·11 citations
02
Ab initio investigation of the $^{7}$ Li( $p, e^{+} e^{-}$ ) $^{8}$ Be process and the X17 boson
P. Gysbers🇨🇦 · P. Navratil🇨🇦 · K. Kravvaris🇺🇸 · G. Hupin🇫🇷 · S. Quaglioni🇺🇸
Observations of anomalies in the electron-positron angular correlations in high-energy decays in $^{4}$ He, $^{8}$ Be, and $^{12}$ C have been reported recently by the ATOMKI collaboration. These could be explained by the creation and subsequent decay of a new boson with a mass of $\sim 17$ MeV. Theoretical understanding of pair creation in the proton capture reactions used in these experiments is important for the interpretation of the anomalies. We apply the ab initio No-Core Shell Model with Continuum (NCSMC) to the proton capture on $^{7}$ Li. The NCSMC describes both bound and unbound states in light nuclei in a unified way with chiral two- and three-nucleon interactions as the only input. We investigate the structure of $^{8}$ Be, the $p +^{7}$ Li elastic scattering, the $^{7}$ Li( $p, γ$ ) $^{8}$ Be cross section and the internal pair creation $^{7}$ Li( $p, e^{+} e^{-}$ ) $^{8}$ Be. We discuss the impact of a proper treatment of the initial scattering state on the electron-positron angular correlation spectrum and compare our results to available ATOMKI data sets. Finally, we calculate $^{7}$ Li( $p, X$ ) $^{8}$ Be cross sections for several proposed models of the hypothetical X17 particle.
nucl-thhep-phnucl-exPRC(2024)·11 citations
03
Charged-current quasielastic neutrino scattering from $^{12}$ C in an extended superscaling model with two-nucleon emission
V. L. Martinez-Consentino🇪🇸 · J.E. Amaro🇪🇸
The quasielastic cross-section of charged-current neutrino and antineutrino scattering on $^{12}$ C is calculated using an improved superscaling model with relativistic effective mass. Our model encompasses two-particle emission induced by neutrinos, which we distinguish into two contributions. The first contribution arises from meson-exchange currents, and its calculation is performed at a microscopic level. The second contribution is phenomenological and extracted from the high-energy tail of the scaling function, assumed to be produced by 2p2h mechanisms where the one-body current plays a role, such as short-range correlations and interferences with MEC, final-state interaction, etc. The model explicitly includes the modification of the relativistic effective mass of the nucleon within the relativistic mean field model of nuclear matter. The meson exchange currents are also consistently calculated within the same model. With this model, we present predictions for the neutrino and antineutrino cross sections of $^{12}$ C that have been measured in accelerator experiments.
nucl-thhep-phPRD(2023)·13 citations
04
Establishing connection between neutron star properties and nuclear matter parameters through a comprehensive multivariate analysis
N. K. Patra🇦🇲 · Prafulla Saxena🇮🇳 · B. K. Agrawal🇦🇲 · T. K. Jha🇦🇲
We have attempted to mitigate the challenge of connecting the neutron star (NS) properties with the nuclear matter parameters that describe equations of state (EoSs). The efforts to correlate various neutron star properties with individual nuclear matter parameters have been inconclusive. A Principal Component Analysis is employed as a tool to uncover the connection between multiple nuclear matter parameters and the tidal deformability as well as the radius of neutron stars within the mass range of $1.2 - 1.8 M_{⊙}$ . The essential EOSs for neutron star matter at low densities have been derived using both uncorrelated uniform distributions and minimally constrained joint posterior distributions of nuclear matter parameters. For higher densities ( $ρ > 0.32$ fm $^{- 3}$ ), the EOSs have been established through a suitable parameterization of the speed of sound, which consistently maintains causality and gradually approaches the conformal limit. Our analysis reveals that in order to account for over 90\% of the variability in NS properties, it is crucial to consider two or more principal components, emphasizing the significance of employing multivariate analysis. To explain the variability in tidal deformability needs a greater number of principal components compared to those for the radius at a given NS mass. The contributions from iso-vector nuclear matter parameters to the tidal deformability and radius of NS decrease by $\sim$ 25\% with the increase in mass of NS from 1.2 $M_{⊙}$ to 1.8 $M_{⊙}$ .
nucl-thastro-ph.HEgr-qchep-phPRD(2023)·14 citations
05
Quark-hadron pasta phase in neutron stars: the role of medium-dependent surface and curvature tensions
Mauro Mariani🇦🇷 · Germán Lugones🇧🇷
We investigate the properties of the hadron-quark mixed phase, often termed the \textit{pasta} phase, expected to exist in the cores of massive neutron stars. To construct the equations of state (EoS), we combine an analytical representation based on the APR EoS for hadronic matter with the MIT bag model featuring vector interactions for quark matter. For modeling the mixed phase, we utilize the compressible liquid drop model that consistently accounts for finite-size and Coulomb effects. Unlike most previous analyses that treated surface tension as a constant free parameter and neglected curvature tension, we employ microphysical calculations using the multiple reflection expansion formalism to determine these parameters, while also ensuring their self-consistency with the EoS. We construct an extensive set of mixed hybrid EoSs by varying model parameters, solve the stellar structure equations to obtain neutron star mass-radius relationships, and select the models that satisfy current astrophysical constraints. Our findings closely align with calculations using a constant surface tension in terms of EoS stiffness and resulting stellar structure. However, they reveal significant differences in the types of geometric structures and their prevalence ranges within the mixed phase. Specifically, curvature effects enhance the emergence of tubes and bubbles at high densities despite the large value of surface tension, while suppressing the existence of drops and rods at low densities.
nucl-thastro-ph.HEhep-phPRD(2024)·16 citations
06
Momentum dependence of $ϕ$ meson's spin alignment
Xin-Li Sheng🇮🇹 · Shi Pu🇨🇳 · Qun Wang🇨🇳
We study the rapidity and azimuthal angle dependences of the global spin alignment $ρ_{00}$ for $ϕ$ mesons with respect to the reaction plane in Au+Au collisions at RHIC by the relativistic coalescence model in the spin transport theory. The global spin alignment of $ϕ$ mesons arises from local fluctuations of strong force fields whose values are extracted from the STAR's data. The calculated results show that $ρ_{00} < 1/3$ at the rapidity $Y = 0$ , and then it increases with rapidity and becomes $ρ_{00} > 1/3$ at $Y = 1$ . Such a rapidity dependence is dominated by the relative motion of the $ϕ$ meson in the bulk matter. We also give prediction for the azimuthal angle dependence of $ρ_{00}$ at different rapidities.
nucl-thhep-phPRC(2023)·47 citations
07
Production of various elements in ultraperipheral $^{208}$ Pb- $^{208}$ Pb collisions at the LHC
U.A. Dmitrieva🇷🇺 · I.A. Pshenichnov🇷🇺
As predicted by theory and confirmed by measurements, one, two or three neutrons are emitted frequently in ultraperipheral collisions (UPCs) of heavy relativistic nuclei, in particular, $^{208}$ Pb. The exchange of low-energy Weizsäcker--Williams photons dominates in such interactions. This leads to the excitation and decay of Giant Dipole Resonances (GDR) in colliding nuclei below the proton emission threshold. Less is known about the electromagnetic dissociation of $^{208}$ Pb induced by energetic photons leading to violent fragmentation of $^{208}$ Pb. The UPCs of lead nuclei at the LHC were modelled with Relativistic ELectromagnetic Dissociation (RELDIS) model to evaluate the contribution of photonuclear reactions in the domain of quasideuteron absorption and at higher photon energies. It was demonstrated that due to the presence of a single heavy residue in the final state mostly accompanied by free protons and neutrons, the cross sections of the production of specific elements can be well approximated by the proton emission cross sections, which can be measured in the ALICE experiment at the LHC.
nucl-thnucl-exPhys.Part.Nucl.Lett.(2023)·3 citations
08
Bayesian analysis of a relativistic hadronic model constrained by recent astrophysical observations
B. A. de Moura S.🇧🇷 · C. H. Lenzi🇧🇷 · O. Lourenço🇧🇷 · M. Dutra🇧🇷
We use Bayesian analysis in order to constrain the equation of state for nuclear matter from astrophysical data related to the recent measurements from the NICER mission, LIGO/Virgo collaboration, and probability distributions of mass and radius from other 12 sources, including thermonuclear busters, and quiescent low-mass X-ray binaries. For this purpose, we base our study on a relativistic hadronic mean field model including an $ω - ρ$ interaction. Our results indicate optimal ranges for some bulk parameters at the saturation density, namely, effective mass, incompressibility, and symmetry energy slope ( $L_{0}$ ). For instance, we find $L_{0} = 50.7 9_{- 9.24}^{+ 15.16}$ MeV (Case 1) and $L_{0} = 75.0 6_{- 4.43}^{+ 8.43}$ MeV (Case 2) in a $68%$ confidence interval for the 2 cases analyzed (different input ranges for $L_{0}$ related to the PREX-II data). The respective parametrizations are in agreement with important nuclear matter constraints, as well as observational neutron star data, such as the dimensionless tidal deformability of the GW170817 event. From the mass-radius curves obtained from these best parametrizations, we also find the ranges of $11.97 \mbox k m ⩽ R_{1.4} ⩽ 12.73 \mbox k m$ (Case 1) and $12.34 \mbox k m ⩽ R_{1.4} ⩽ 13.06 \mbox k m$ (Case 2) for the radius of the $1.4 M_{⊙}$ neutron star.
nucl-thastro-ph.HEMNRAS(2023)·6 citations
09
Charm balance function in relativistic heavy-ion collisions
Tribhuban Parida🇮🇳 · Piotr Bozek🇵🇱 · Sandeep Chatterjee🇮🇳
We calculate the balance function for charm in relativistic heavy-ion collisions. The distribution of pairs of charm-anticharm quarks produced in hard processes in the early stages of the nucleus-nucleus collision evolves in the dense fireball formed in the collision. The evolution of the dense matter is described using a relativistic viscous hydrodynamic model and the quark diffusion with a Langevin equation. The evolution of the charm quark balance function from the formation of the charm-anticharm pair up to the freeze-out traces the partial thermalization of the heavy quarks in the dense matter. For the balance function in azimuthal angle we reproduce the collimation effect due to the transverse flow. The evolution in rapidity shows the thermalization of the longitudinal velocity of the quark in the fluid. We provide predictions for the one and two-dimensional balance functions for $D^{0}$ - $D^{0} ˉ$ mesons produced in ultarelativistic Pb+Pb collisions at $s_{N N} = 5.02$ TeV. The shape of the charm balance function in relative rapidity is sensitive to the rescattering of heavy quarks in the early stages of the collision, while the shape of the balance function in azimuthal angle is sensitive to the rescattering in the latter stages.
nucl-thhep-phnucl-exPRC(2024)·7 citations
10
New covariant density functionals of nuclear matter for compact star simulations
Jia Jie Li (SWU, Chongqing)🇨🇳 · Armen Sedrakian (FIAS, Frankfurt and U. Wroclaw)🇩🇪
We generate three families of extended covariant density functionals of nuclear matter that have varying slope of symmetry energy and skewness at nuclear saturation density, but otherwise share the same basic parameters (symmetry energy, compressibility, saturation parameters, etc.) with the standard DDME2, DD2, and MPE functionals. Tables of the parameters of these new density functionals are given, which can be straightforwardly used in DDME2, DD2, and MPE parameterization-based codes. Furthermore, we provide tables of a large number of equations of state (81 for each family) that can be used in astrophysical simulations to assess the impact of variations of not-well-known slope of symmetry energy and skewness of nuclear systems on the astrophysics of compact objects. We also provide tables of computed integral parameters (mass, radius, and tidal deformability) that can be used, e.g., for modeling gravitational waveforms. Finally, for the extended DDME2-based parameterization, we implement a first-order phase transition to quark matter to obtain a family of equations of state that accommodates a phase transition to quark matter. Analogous tables of the equations of state and integral parameters are provided for this case as well.
nucl-thastro-ph.HEhep-phApJ(2023)·21 citations
11
Renormalization of many-body effective field theory
Bing-Nan Lu🇨🇳 · Bao-Ge Deng🇨🇳
The renormalization of the effective field theories (EFTs) in many-body systems is the most pressing and challenging problem in modern nuclear ab initio calculation. For general non-relativistic EFTs, we prove that the renormalization group (RG) invariance can be achieved if and only if all single-particle momenta are regulated with a universal cutoff \Lambda. For a numerical demonstration, we construct a series of N^{2}LO chiral forces with \Lambda varying from 250 MeV to 400 MeV. With all low energy constants fixed in two- and three-nucleon systems, we reproduce the experimental binding energies of ^{4}He and ^{16}O nearly independently of \Lambda. In contrast, all recent nuclear EFT constructions regulate the relative momenta for Galilean invariance, thus inherently break the RG invariance. This explains the unpleasantly strong cutoff-dependences observed in recent ab initio calculations. Our method can also be used to build RG-invariant EFTs with non-perturbative interactions.
nucl-thcond-mat.quant-gashep-lat4 citations
12
Circumventing the odd particle-number sign problem in the shell model Monte Carlo
Y. Alhassid · P. Fanto · C. Özen
The shell model Monte Carlo (SMMC) method is a powerful method for calculating exactly (up to statistical errors) thermal observables and statistical properties of atomic nuclei. However, its application has been limited by a sign problem at low temperatures that arises from the projection onto odd particle number even for good-sign interactions. Here, we develop a technique - the partition function extrapolation method (PFEM) - to extract the ground-state energy of an odd-mass nucleus from the excitation partition function calculated at temperatures at which this sign problem is moderate. We validate the PFEM in heavy even-mass nuclei and systematically calculate ground-state energies for isotopic chains of heavy odd-mass nuclei. The PFEM can be extended to other finite-size quantum many-body systems.
nucl-thPRC(2024)·2 citations

Affiliations

first authorsco-authorsvia INSPIRE