Nuclear Theory·nucl-th

Friday·May 31, 2019

9 papers—5 primary·4 cross-listed

01
Neutron-Star-Merger Equation of State
Veronica Dexheimer🇺🇸 · Constantinos Constantinou🇺🇸 · Elias R. Most🇩🇪 · L. Jens Papenfort🇩🇪 · Matthias Hanauske🇩🇪 · Stefan Schramm🇩🇪 · Horst Stoecker🇩🇪 · Luciano Rezzolla🇩🇪
In this work, we discuss the dense matter equation of state (EOS) for the extreme range of conditions encountered in neutron stars and their mergers. The calculation of the properties of such an EOS involves modeling different degrees of freedom (such as nuclei, nucleons, hyperons, and quarks), taking into account different symmetries, and including finite density and temperature effects in a thermodynamically consistent manner. We begin by addressing subnuclear matter consisting of nucleons and a small admixture of light nuclei in the context of the excluded volume approach. We then turn our attention to supranuclear homogeneous matter as described by the Chiral Mean Field (CMF) formalism. Finally, we present results from realistic neutron-star-merger simulations performed using the CMF model that predict signatures for deconfinement to quark matter in gravitational wave signals.
nucl-thastro-ph.HEastro-ph.SRUniverse(2019)·10 citations
02
Two-particle transfer processes as a signature of shape phase transition in Zirconium isotopes
J.A. Lay · A. Vitturi · L. Fortunato · Y. Tsunoda · T. Togashi · T. Otsuka
We explore two-particle transfer reactions as a unique probe of the occurence of shape coexistence in shape phase transitions. The (t,p) reactions to the ground state and to excited $0^{+}$ states are calculated for the isotope chain of even-even Zirconium isotopes starting from stable nuclei up to beyond current experimental limits. Two-particle spectroscopic factors derived from Monte Carlo Shell Model calculations are used, together with the sequential description of the two-particle transfer reaction mechanism. The calculation shows a clear signature for a shape phase transition between $^{98}$ Zr and $^{100}$ Zr, which displays coexistence of a deformed ground state with an excited spherical $0^{+}$ state. Furthermore, we show that there is a qualitative difference with respect to the case of a normal shape phase transition that can be discriminated with two-neutron transfer reactions.
nucl-thnucl-exPLB(2023)·8 citations
03
Effects of an induced three-body force in the incident channel of (d,p) reactions
M.J. Dinmore · N. K. Timofeyuk · J. S. Al-Khalili · R. C. Johnson
A widely accepted practice for treating deuteron breakup in $A (d, p) B$ reactions relies on solving a three-body $A + n + p$ Schrödinger equation with pairwise $A$ - $n$ , $A$ - $p$ and $n$ - $p$ interactions. However, it was shown in [Phys. Rev. C \textbf{89}, 024605 (2014)] that projection of the many-body $A + 2$ wave function into the three-body $A + n + p$ channel results in a complicated three-body operator that cannot be reduced to a sum of pairwise potentials. It contains explicit contributions from terms that include interactions between the neutron and proton via excitation of the target $A$ . Such terms are normally neglected. We estimate the first order contribution of these induced three-body terms and show that applying the adiabatic approximation to solving the $A + n + p$ model results in a simple modification of the two-body nucleon optical potentials. We illustrate the role of these terms for the case of $^{40}$ Ca( $d, p$ ) $^{41}$ Ca transfer reactions at incident deuteron energies of 11.8, 20 and 56 MeV, using several parameterisations of nonlocal optical potentials.
nucl-thPRC(2019)·12 citations
04
Towards Understanding Astrophysical Effects of Nuclear Symmetry Energy
Bao-An Li🇺🇸 · Plamen G. Krastev🇺🇸 · De-Hua Wen🇨🇳 · Nai-Bo Zhang🇨🇳
Determining the Equation of State (EOS) of dense neutron-rich nuclear matter is a shared goal of both nuclear physics and astrophysics. Except possible phase transitions, the density dependence of nuclear symmetry \esym is the most uncertain part of the EOS of neutron-rich nucleonic matter especially at supra-saturation densities. Much progresses have been made in recent years in predicting the symmetry energy and understanding why it is still very uncertain using various microscopic nuclear many-body theories and phenomenological models. Simultaneously, significant progresses have also been made in probing the symmetry energy in both terrestrial nuclear laboratories and astrophysical observatories. In light of the GW170817 event as well as ongoing or planned nuclear experiments and astrophysical observations probing the EOS of dense neutron-rich matter, we review recent progresses and identify new challenges to the best knowledge we have on several selected topics critical for understanding astrophysical effects of the nuclear symmetry energy.
nucl-thastro-ph.HEgr-qcnucl-exEPJA(2019)·218 citations
05
Possibility of $ρ$ Meson Condensation in Neutron Star: Unified Approach of Chiral SU(3) Model and QCD Sum Rules
Shivam🇮🇳 · Arvind Kumar🇮🇳
In the present work the conjunction of chiral SU(3) model with QCD sum rules is employed to explore the possibility of $ρ$ meson condensation in neutron stars. The quark and gluon condensates in terms of which the in-medium masses of $ρ$ mesons can be expressed are calculated using the chiral SU(3) model in the charge neutral matter which is relevant for neutron stars. It is observed that condition of $ρ$ meson condensation is satisfied for the density of about 7 $ρ_{0}$ , where $ρ_{0}$ is the nuclear saturation density. In the end, a brief qualitative discussion of the magnetic field is also involved to check out for the further possibility of $ρ$ meson condensation.
nucl-thEur.Phys.J.Plus(2019)·4 citations
06
Extensive/nonextensive statistics for $p_{T}$ distributions of various charged particles produced in p+p and A+A collisions in a wide range of energies
Abdel Nasser Tawfik (Nile U., ECTP and Johann Wolfgang Goethe-Universitat)🇪🇬 · Hayam Yassin🇪🇬 · Eman R. Abo Elyazeed (Ain Shams U., Cairo)🇪🇬
We present a systematic study for the statistical fits of the transverse momentum distributions of charged pions, Kaons and protons produced at energies ranging between 7.7 and 2670 GeV to the extensive Boltzmann-Gibbs (BG) and the nonextensive statistics (Tsallis as a special type and the generic axiomatic nonextensive approach). We also present a comprehensive review on various experimental parametrizations proposed to fit the transverse momentum distributions of these produced particles. The inconsistency that the BG approach is to be utilized in characterizing the chemical freezeout, while the Tsallis approach in determining the kinetic freezeout is elaborated. The resulting energy dependence of the different fit parameters largely varies with the particle species and the degree of (non)extensivity. This manifests that the Tsallis nonextensive approach seems to work well for p+p rather than for A+A collisions. Drawing a complete picture of the utilization of Tsallis statistics in modeling the transverse momentum distributions of several charged particle produced at a wide range of energies and accordingly either disprove or though confirm the relevant works are main advantages of this review. We propose analytical expressions for the dependence of the fit parameters obtained on the size of the colliding system, the energy, as well as the types of the statistical approach applied. We conclude that the statistical dependence of the various fit parameters, especially between Boltzmann and Tsallis approaches could be understood that the statistical analysis ad hoc is biased to the corresponding degree of extensivity (Boltzmann) or nonextensivity (Tsallis). Alternatively, the empirical parameterizations, the other models, and the generic (non)extensive approach seem to relax this biasness.
↳ hep-phnucl-thUkr.J.Phys.(2022)·15 citations
07
Almost-Entirely Empirical Estimation for Chemical Potential
Abdel Nasser Tawfik (Nile U., ECTP and Johann Wolfgang Goethe-Universitat)🇩🇪 · Magda Abdel Wahab🇪🇬 · Hayam Yassin (Ain Shams U., Cairo)🇪🇬 · Hadeer Nasr El Din (Modern Academy for Engineering, Cairo)🇪🇬
Based on statistical thermal approaches, the transverse momentum distribution of the well-identified produced particles, $π^{+}$ , $π^{-}$ , $K^{+}$ , $K^{-}$ , $p$ , $p ˉ$ , is studied. From the partition function of grand-canonical ensemble, we propose a generic expression for the dependence of the full chemical potential $μ$ on rapidity $y$ . Then, by fitting this expression with the experimental results of most central $p_{⊥}$ and $d^{2} N /2 π p_{⊥} d p_{⊥} d y$ , at $7.7$ , $11.5$ , $19.6$ , $27$ , $39$ , $130$ , $200$ GeV, we introduce a generic expression for the rapidity dependence of $μ$ , at different energies and particle types, $μ = a + b y^{2}$ . The resulting energy dependence reads $s_{NN} = c [(μ - a) / b]^{d /2}$ . As a validation check, the proposed approach reproduces, excellently, the rapidity spectra measured at different energies.
↳ hep-phnucl-thJ.Exp.Theor.Phys.(2020)·3 citations
08
Analytic crystals of solitons in the four dimensional gauged non-linear sigma model
Fabrizio Canfora🇨🇱 · Seung Hun Oh🇰🇷 · Aldo Vera🇨🇱
The first analytic topologically non-trivial solutions in the (3+1)-dimensional gauged non-linear sigma model representing multi-solitons at finite volume with manifest ordered structures generating their own electromagnetic field are presented. The complete set of seven coupled non-linear field equations of the gauged non-linear sigma model together with the corresponding Maxwell equations are reduced in a self-consistent way to just one linear Schrodinger-like equation in two dimensions. The corresponding two dimensional periodic potential can be computed explicitly in terms of the solitons profile. The present construction keeps alive the topological charge of the gauged solitons. Both the energy density and the topological charge density are periodic and the positions of their peaks show a crystalline order. These solitons describe configurations in which (most of) the topological charge and total energy are concentrated within three-dimensional tube-shaped regions. The electric and magnetic fields vanish in the center of the tubes and take their maximum values on their surface while the electromagnetic current is contained within these tube-shaped regions. Electromagnetic perturbations of these families of gauged solitons are shortly discussed.
↳ hep-thhep-phnucl-thEPJC(2019)·37 citations
09
Dispersion relations for $γ^{*} γ^{*} \to π π$ : helicity amplitudes, subtractions, and anomalous thresholds
Martin Hoferichter🇺🇸 · Peter Stoffer🇺🇸
We present a comprehensive analysis of the dispersion relations for the doubly-virtual process $γ^{*} γ^{*} \to π π$ . Starting from the Bardeen-Tung-Tarrach amplitudes, we first derive the kernel functions that define the system of Roy-Steiner equations for the partial-wave helicity amplitudes. We then formulate the solution of these partial-wave dispersion relations in terms of Omnès functions, with special attention paid to the role of subtraction constants as critical for the application to hadronic light-by-light scattering. In particular, we explain for the first time why for some amplitudes the standard Muskhelishvili-Omnès solution applies, while for others a modified approach based on their left-hand cut is required unless subtractions are introduced. In the doubly-virtual case, the analytic structure of the vector-resonance partial waves then gives rise to anomalous thresholds, even for space-like virtualities. We develop a strategy to account for these effects in the numerical solution, illustrated in terms of the $D$ -waves in $γ^{*} γ^{*} \to π π$ , which allows us to predict the doubly-virtual responses of the $f_{2} (1270)$ resonance. In general, our results form the basis for the incorporation of two-meson intermediate states into hadronic light-by-light scattering beyond the $S$ -wave contribution.
↳ hep-phhep-exnucl-thJHEP(2019)·88 citations

Affiliations

first authorsco-authorsvia INSPIRE