Nuclear Theory·nucl-th

Friday·June 25, 2021

10 papers—5 primary·5 cross-listed

01
On the calculation of neutron sources generating steady prescribed power distributions in subcritical systems using multigroup X,Y-geometry discrete ordinates models
Leonardo · R. C. Moraes · Hermes Alves Filho · Ricardo C. Barros
In this paper a methodology is described to estimate multigroup neutron source distributions which must be added into a subcritical system to drive it to a steady state prescribed power distribution. This work has been motivated by the principle of operation of the ADS (Accelerator Driven System) reactors, which have subcritical cores stabilized by the action of external sources. We use the energy multigroup two-dimensional neutron transport equation in the discrete ordinates formulation (SN) and the equation which is adjoint to it, whose solution is interpreted here as a distribution measuring the importance of the angular flux of neutrons to a linear functional. These equations are correlated through a reciprocity relation, leading to a relationship between the interior sources of neutrons and the power produced by unit length of height of the domain. A coarse-mesh numerical method of the spectral nodal class, referred to as adjoint response matrix constant-nodal method, is applied to numerically solve the adjoint SN equations. Numerical experiments are performed to analyze the accuracy of the present methodology so as to illustrate its potential practical applications.
nucl-thcs.CE0 citations
02
Relativistic kinetic approach to light nuclei production in high-energy nuclear collisions
Kai-Jia Sun🇺🇸 · Rui Wang🇨🇳 · Che Ming Ko🇺🇸 · Yu-Gang Ma🇨🇳 · Chun Shen🇺🇸
Understanding the production mechanism of light (anti-)nuclei in high-energy nuclear collisions and cosmic rays has been a long-standing problem in nuclear physics. In the present study, we develop a stochastic method to solve the relativistic kinetic equations for light nuclei production from many-body reactions with the inclusion of their finite sizes. The present approach gives an excellent description of the deuteron and helium-3 data from central Au+Au (Pb+Pb) collisions at $s_{NN}$ $=$ $200 GeV$ ( $2.76 TeV$ ). It can also naturally explain their suppressed production in $pp$ collisions at 7 TeV as a result of their finite sizes.
nucl-thhep-ph30 citations
03
Electroweak Physics: Summary
Rupa Chatterjee🇮🇳
Electroweak probes are potential tool to study the properties of the hot and dense strongly interacting matter produced in relativistic nuclear collisions due to their unique nature. A selection of the new experimental analysis and results from theory calculations on electromagnetic and weak probes presented at the Hard Probes 2020 are discussed in this contribution.
nucl-thnucl-exPoS(2021)·3 citations
04
Tidal Deformability of Quark Stars with Repulsive Interactions
M. B. Albino🇧🇷 · R. Fariello🇧🇷 · F. S. Navarra🇧🇷
In an early work, we applied a QCD-based equation of state to the study of the stellar structure of self-bound strange stars, obtaining sequences with maximum masses larger than two solar masses and radii ranging from 8 to 12 Km. In this work, we update the previous calculations and compare them with the most recent data, including the very recent determination of the mass and radius of the massive pulsar PSR J0740+6620 performed by the NICER and XMM-Newton Collaborations. Our equation of state is similar to the MIT bag model one, but it includes repulsive interactions, which turn out to be essential to reproduce the accumulated experimental information. We find that our EOS is still compatible with all astrophysical observations but the parameter window is now narrower.
nucl-thPRD(2021)·24 citations
05
Study of fusion reactions of light nuclei at low energies using complex nucleon-nucleus potential function
Md. A. Khan · S. H. Mondal · M. Alam · M. Hasan
Nuclear fusion reactions, at energies, far below the Coulomb barrier play a significant role in the synthesis of light elements in the primordial nucleosynthesis as well as in the interior of compact stellar objects. Many different kinds of nuclear reactions are occurring simultaneously inside the stellar core depending upon the density and temperature conditions of the nuclear plasma along with other relevant parameters of these stars. Nuclear fusion reactions in the energy range ( $E \sim$ 1 eV to few keV) can be explained successfully by quantum mechanical tunneling through the mutual Coulomb barrier of interacting nuclei. The measurement of the cross-sections at extremely low energy is quite difficult because of the larger width of the Coulomb barrier, which results in a very small value of the reaction cross-section. Hence, any improvement in the data on astrophysical S-factors for the light nuclei fusion may give a better picture of the elemental abundance in nucleosynthesis. In this work, we have theoretically investigated the energy dependence of fusion cross-sections and astrophysical S-factors for fusion reaction of light nuclei like D-D and p- $^{11}$ B using complex Gaussian nuclear potential with adjustable depth and range parameters plus the mutual Coulomb interaction of the interacting nuclei. Numerical computation of the observables is done in the framework of the selective resonant tunneling model approach. The results of our calculation are compared with those found in the literature.
nucl-thBulg.J.Phys.(2023)·1 citation
06
Higher-order corrections to exclusive heavy vector meson production
Tuomas Lappi🇫🇮 · Heikki Mäntysaari🇫🇮 · Jani Penttala🇫🇮
We present results for higher-order corrections to exclusive $J / ψ$ production. This includes the first relativistic correction of order $v^{2}$ in quark velocity, and next-to-leading order corrections in $α_{s}$ for longitudinally polarized production. The relativistic corrections are found to be important for a good description of the HERA data, especially at small values of the photon virtuality. The next-to-leading order results for longitudinal production are evaluated numerically. We also demonstrate how the vector meson production provides complementary information to the structure functions for extracting the initial condition for the small- $x$ evolution of the dipole-proton scattering amplitude.
↳ hep-phnucl-thSciPost Phys.Proc.(2022)·8 citations
07
Influence of the crust on the neutron star macrophysical quantities and universal relations
Lami Suleiman🇵🇱 · Morgane Fortin🇵🇱 · Julian Leszek Zdunik🇵🇱 · Pawel Haensel🇵🇱
Measurements of neutron-star macrophysical properties thanks to multimessenger observations offer the possibility to constrain the properties of nuclear matter. Indeed cold and dense matter as found inside neutron stars, in particular in their core, is not accessible to terrestrial laboratories.We investigate the consequences of using equations of state that employ models for the core and the crust that are not calculated consistently on the neutron-star macrophysical properties, on some of the so-called universal relations and on the constraints obtained from gravitational-wave observations. We use various treatments found in the literature to connect together nonconsistent core and crust equations of state. We then compute the mass, the radius, the tidal deformability, and the moment of inertia for each model. Finally, we assess the discrepancies in the neutron-star macrophysical properties obtained when consistent models for the whole star and nonconsistent ones are employed. The use of crust models nonconsistent with the core introduces an error on the macrophysical parameters which can be as large as the estimated accuracy of current and next generation telescopes. The precision of some of the universal relations reported in the literature is found to be overestimated. We confirm that the equation of the crust has limited influence on the macrophysical properties. The discrepancy between results obtained for a fully consistent equation of state and a nonconsistent one can be reduced if one connects the core and the crust models at baryon densities around 0.08-0.1 fm $^{- 3}$ . The equation of the crust cannot be probed with current multimessenger observations and near-future ones.
↳ astro-ph.HEnucl-thPRC(2021)·51 citations
08
Unitary $p$ -wave Fermi gas in one dimension
Hiroyuki Tajima · Shoichiro Tsutsui · Takahiro M. Doi · Kei Iida
We elucidate universal many-body properties of a one-dimensional, two-component ultracold Fermi gas near the $p$ -wave Feshbach resonance. The low-energy scattering in this system can be characterized by two parameters, that is, $p$ -wave scattering length and effective range. At the unitarity limit where the $p$ -wave scattering length diverges and the effective range is reduced to zero without conflicting with the causality bound, the system obeys universal thermodynamics as observed in a unitary Fermi gas with contact $s$ -wave interaction in three dimensions. It is in contrast to a Fermi gas with the $p$ -wave resonance in three dimensions in which the effective range is inevitably finite. We present the universal equation of state in this unitary $p$ -wave Fermi gas within the many-body $T$ -matrix approach as well as the virial expansion method. Moreover, we examine the single-particle spectral function in the high-density regime where the virial expansion is no longer valid. On the basis of the Hartree-like self-energy shift at the divergent scattering length, we conjecture that the equivalence of the Bertsch parameter across spatial dimensions holds even for a one-dimensional unitary $p$ -wave Fermi gas.
↳ cond-mat.quant-gascond-mat.str-elcond-mat.supr-connucl-thPRA(2021)·10 citations
09
On the Application of the Analytical Discrete Ordinates Method to the Solution of Nonclassical Transport Problems in Slab Geometry
Leonardo R. C. Moraes · Liliane B. Barichello · Ricardo C. Barros · Richard Vasques
In this work we investigate the use of the Analytical Discrete Ordinates (ADO) method when solving the spectral approximation of the nonclassical transport equation. The spectral approximation is a recently developed method based on the representation of the nonclassical angular flux as a series of Laguerre polynomials. This representation generates, as outcome, a system of equations that have the form of classical transport equations and can therefore be solved by current deterministic algorithms. Thus, the investigation of efficient approaches to solve the nonclassical transport equation is of interest and shall be pursued. This is the case of the ADO method which has been successfully used to solve a wide class of problems in the general area of particle transport. Numerical results are presented for two nonclassical test problems in slab geometry. These nonclassical transport problems are chosen in such way that their solution exactly reproduces the solution of the classical diffusion problem. Very accurate results are obtained for both test problems. However, the use of high precision arithmetic is sometimes required as illustrated in the second test problem. Limitations of the spectral approximation are also analyzed and discussed.
↳ physics.comp-phnucl-thJ.Comput.Phys.(2022)·1 citation
10
Short-distance constraints for the longitudinal component of the hadronic light-by-light amplitude: an update
Gilberto Colangelo🇨🇭 · Franziska Hagelstein🇨🇭 · Martin Hoferichter🇨🇭 · Laetitia Laub🇨🇭 · Peter Stoffer🇦🇹
We reassess the impact of short-distance constraints for the longitudinal component of the hadronic light-by-light amplitude on the anomalous magnetic moment of the muon, $a_{μ} = (g - 2)_{μ} /2$ , by comparing different solutions that have recently appeared in the literature. In particular, we analyze the relevance of the exact axial anomaly and its impact on $a_{μ}$ and conclude that it remains rather limited. We show that all recently proposed solutions agree well within uncertainties on the numerical estimate of the impact of short-distance constraints on $a_{μ}$ , despite differences in the concrete implementation. We also take into account the recently calculated perturbative corrections to the massless quark loop to update our estimate and outline the path towards future improvements.
↳ hep-phhep-latnucl-thEPJC(2021)·73 citations

Affiliations

first authorsco-authorsvia INSPIRE