Nuclear Theory·nucl-th

Tuesday·July 18, 2017

9 papers—3 primary·6 cross-listed

01
Symmetry energies for $A = 24$ and $48$ and the USD and KB3 shell model Hamiltonians
A. Kingan · K. Neergård · L. Zamick
Calculations in the sd and pf shells reported some time ago by Satuła\etal\ [Phys.~Lett.~B~407, 103 (1997)] are redone for an extended analysis of the results. As in the original work, we do calculations for one mass number in each shell and consider in each case the sequence of lowest energies for isospins 0, 2, and 4, briefly the symmetry spectrum. Following further the original work we study how this spectrum changes when parts of the two-nucleon interaction are turned off. The variation of its width is explored in detail. A differential combination $ϵ_{W}$ of the three energies was taken in the original work as a measure of the so-called Wigner term in semi-empirical mass formulas, and it was found to decrease drastically when the two-nucleon interaction in the channel of zero isospin is turned off. Our analysis shows that the width of the symmetry spectrum experiences an equally drastic decrease, which can be explained qualitatively in terms of schematic approximations. We therefore suggest that the decrease of $ϵ_{W}$ be seen mainly as a side effect of a narrowing of the symmetry spectrum rather than an independent manifestation of the two-nucleon interaction in the channel of zero isospin.
nucl-thPRC(2017)·2 citations
02
The "Folk Theorem" on Effective Field Theory: How Does It Fare in Nuclear Physics?
Mannque Rho🇫🇷
This is a brief history of what I consider as very important, some of which truly seminal, contributions made by young Korean nuclear theorists, mostly graduate students working on PhD thesis in 1990's and early 2000's, to nuclear effective field theory, nowadays heralded as the first-principle approach to nuclear physics. The theoretical framework employed is an effective field theory anchored on a scale-invariant hidden local symmetric Lagrangian constructed along the line of Weinberg's "Folk Theorem" on effective field theory. The problems addressed are the high-precision calculations on the thermal $n p$ capture, the solar $pp$ fusion process, the solar $h e p$ process -- John Bahcall's challenge to nuclear theorists -- and the quenching of $g_{A}$ in giant Gamow-Teller resonances and the whopping enhancement of first-forbidden beta transitions in astrophysical processes. Extending adventurously the strategy to a wild uncharted domain in which a systematic implementation of the "theorem" is far from obvious, the same effective Lagrangian is applied to the structure of compact stars. A surprising result on the properties of massive stars, totally different from what has been obtained up to day in the literature, is predicted, such as the precocious onset of conformal sound velocity together with the possible emergence of hidden symmetries such as scale symmetry and hidden local symmetry.
nucl-thastro-ph.SRhep-phJ.Korean Phys.Soc.(2017)·2 citations
03
Anderson-Bogoliubov phonon in inner crust of neutron stars: Dipole excitation in spherical Wigner-Seitz cell
Tsunenori Inakura · Masayuki Matsuo
Background: The Anderson-Bogoliubov (AB) phonon, called also the superfluid phonon, has attracted attentions since it may influence the thermal conductivity and other properties of inner crust of neutron stars. However, there are limited number of microscopic studies of the AB phonon where the presence of clusters is explicitly taken into account.\\ Purpose: We intend to clarify how the presence of clusters affects the AB phonon in order to obtain microscopic information relevant to the coupling between the AB phonon and the lattice phonon. \\ Methods: The Hartree-Fock-Bogoliubov model and the quasiparticle random-phase approximation formulated in a spherical Wigner-Seitz cell are adopted to describe neutron superfluidity and associated collective excitations. We perform systematic numerical calculations for dipole excitation by varying the neutron chemical potential and the number of protons in a cell. \\ Results:The model predicts systematic emergence of the dipole AB phonon mode, which however exhibits strong suppression of phonon amplitude inside the cluster. We find also that the phonon amplitude around the cluster surface varies as the neutron density. At higher neutron densities the AB phonon mode exhibits behaviour similar to the pygmy dipole resonance in neutron-rich nuclei.\\ Conclusions: The dipole AB phonon mode does not penetrate into the clusters. This suggests that the coupling between the AB phonon and the lattice phonon may be weak.
nucl-thPRC(2017)·8 citations
04
Chiral symmetry and the properties of hadrons in the Generalised Nambu-Jona-Lasinio model
Yu.S. Kalashnikova🇷🇺 · A.V. Nefediev🇷🇺 · J.E.F.T. Ribeiro🇵🇹
Various aspects of the Generalised Nambu-Jona-Lasinio model for QCD in four dimensions are reviewed. The properties of mesonic excitations are discussed in detail, with special attention paid to the chiral pion. The spontaneous chiral symmetry breaking in the vacuum and the effective chiral symmetry restoration in the spectrum of highly excited mesons and baryons are described microscopically.
↳ hep-phhep-lathep-thnucl-thPhys.Usp.(2017)·6 citations
05
From hadrons to quarks in neutron stars: a review
Gordon Baym🇯🇵 · Tetsuo Hatsuda🇯🇵 · Toru Kojo🇺🇸 · Philip D. Powell🇺🇸 · Yifan Song🇺🇸 · Tatsuyuki Takatsuka🇯🇵
We review the equation of state of matter in neutron stars from the solid crust through the liquid nuclear matter interior to the quark regime at higher densities. We focus in detail on the question of how quark matter appears in neutron stars, and how it affects the equation of state. After discussing the crust and liquid nuclear matter in the core we briefly review aspects of microscopic quark physics relevant to neutron stars, and quark models of dense matter based on the Nambu--Jona-Lasinio framework, in which gluonic processes are replaced by effective quark interactions. We turn then to describing equations of state useful for interpretation of both electromagnetic and gravitational observations, reviewing the emerging picture of hadron-quark continuity in which hadronic matter turns relatively smoothly, with at most only a weak first order transition, into quark matter with increasing density. We review construction of unified equations of state that interpolate between the reasonably well understood nuclear matter regime at low densities and the quark matter regime at higher densities. The utility of such interpolations is driven by the present inability to calculate the dense matter equation of state in QCD from first principles. As we review, the parameters of effective quark models -- which have direct relevance to the more general structure of the QCD phase diagram of dense and hot matter -- are constrained by neutron star mass and radii measurements, in particular favoring large repulsive density-density and attractive diquark pairing interactions. We describe the structure of neutron stars constructed from the unified equations of states with crossover. Lastly we present the current equations of state -- called "QHC18" for quark-hadron crossover -- in a parametrized form practical for neutron star modeling.
↳ astro-ph.HEhep-phnucl-exnucl-thRept.Prog.Phys.(2018)·957 citations
06
Dihadron fragmentation functions in the quark-jet model: Longitudinally polarized quarks
Hrayr H. Matevosyan🇦🇺 · Aram Kotzinian🇮🇹 · Anthony W. Thomas🇦🇺
We study the dihadron fragmentation functions (DiFF) of longitudinally polarized quarks into pion pairs. The quark-jet framework is used to model the sequential hadronization of a polarized quark into hadrons, where the polarization transfer to the remnant quark in each hadron emission step is calculated using the spin density matrix formalism. Using Monte Carlo (MC) simulations of the hadronization process, we find a nonvanishing helicity dependent DiFF, $G_{1}^{⊥}$ , which is also related to the longitudinal jet handedness. A method is developed for extracting the angular moments of this DiFF, which enter the expressions for the azimuthal asymmetries for an electron-positron annihilation process into two pairs of hadrons from back-to-back jets and the dihadron production in semi-inclusive deep inelastic scattering. Finally, we derive explicit integral expressions for DiFFs where only two hadrons are emitted by a quark and use them to validate our MC results for both unpolarized and helicity dependent DiFFs.
↳ hep-phnucl-thPRD(2017)·23 citations
07
Drag Force on Heavy Quarks and Spatial String Tension
Oleg Andreev🇷🇺
Heavy quark transport coefficients in a strongly coupled Quark-Gluon Plasma can be evaluated using a gauge/string duality and lattice QCD. Via this duality, one can argue that for low momenta the drag coefficient for heavy quarks is proportional to the spatial string tension. Such a tension is well studied on the lattice that allows one to straightforwardly make non-perturbative estimates of the heavy quark diffusion coefficients near the critical point. The obtained results are consistent with those in the literature.
↳ hep-phhep-lathep-thnucl-thMod.Phys.Lett.A(2018)·29 citations
08
Parity doubling of baryons in a chiral approach with three flavors
Chihiro Sasaki🇵🇱
We formulate a set of mass relations for the baryon octet and decuplet with positive and negative parity in terms of the order parameter of QCD chiral symmetry. The Gell-Mann--Okubo mass formula and Gell-Mann's equal spacing rule hold manifestly in this approach. Thermal masses of the baryons are calculated in the mean field approximation for various pion masses, and the results are compared with the recent lattice studies. A general trend of the nucleon, $Δ$ and $Ω$ parity-doublers seen in the available lattice data can be understood qualitatively. Expected mass modifications of other strange baryons are also given with the physical and heavier pion masses.
↳ hep-phnucl-thNPA(2018)·28 citations
09
Strange Hadron Spectroscopy with a Secondary KL Beam at GlueX
M.J. Amaryan (ODU) · M. Bashkanov (Edinburgh U.) · J. Ritman (Ruhr-U.) · J.R. Stevens (W&M) · I. Strakovsky (GWU) · GlueX Collaboration
We propose to create a secondary beam of neutral kaons in Hall D at Jefferson Lab to be used with the GlueX experimental setup for strange hadron spectroscopy. A flux on the order of 3 x 10^4 KL/s will allow a broad range of measurements to be made by improving the statistics of previous data obtained on hydrogen targets by three orders of magnitude. Use of a deuteron target will provide first measurements on the neutron which is {\it terra incognita}. The experiment will measure both differential cross sections and self-analyzed polarizations of the produced {\Lambda}, {\Sigma}, {\Xi}, and {\Omega} hyperons using the GlueX detector at the Jefferson Lab Hall D. The measurements will span c.m. cos{\theta} from -0.95 to 0.95 in the c.m. range above W = 1490 MeV and up to 3500 MeV. These new GlueX data will greatly constrain partial-wave analyses and reduce model-dependent uncertainties in the extraction of strange resonance properties (including pole positions), and provide a new benchmark for comparisons with QCD-inspired models and lattice QCD calculations. The proposed facility will also have an impact in the strange meson sector by providing measurements of the final-state K{\pi} system from threshold up to 2 GeV invariant mass to establish and improve on the pole positions and widths of all K*(K{\pi}) P-wave states as well as for the S-wave scalar meson {\kappa}(800).
↳ hep-exhep-phnucl-exnucl-th18 citations

Affiliations

first authorsco-authorsvia INSPIRE