Nuclear Theory·nucl-th

Tuesday·March 13, 2018

15 papers—8 primary·7 cross-listed

01
Nucleon Quark Distribution Functions from the Dyson-Schwinger Equations
Kyle D. Bednar🇺🇸 · Ian C. Cloët🇺🇸 · Peter C. Tandy🇺🇸
We present results for the nucleon's leading-twist spin-independent valence parton distribution functions obtained from a theoretical framework based on the Dyson-Schwinger equations (DSEs) of QCD that previously gave an excellent description of nucleon electromagnetic form factors. We employ the rainbow-ladder truncation of the DSEs and utilize nucleon bound state amplitudes from the Poincaré-covariant Faddeev equation, where the dominant scalar and axial-vector quark-quark correlations are included. This DSE framework is used to numerically evaluate the first 20 moments of the valence $u$ and $d$ quark distribution functions, from which the $x$ -dependence of the distributions is found to be well constrained. We find good agreement with empirical parameterizations of experimental data and make the prediction that the $d / u$ ratio in the $x \to 1$ limit, invariant under scale evolution, takes the value $d / u \to 0.087 \pm 0.010$ . We find that this ratio is rather sensitive to the strength of axial-vector diquark correlations. However, contrary to a naive expectation, our result for the $d / u$ ratio in the $x \to 1$ limit does not vanish when only scalar diquark correlations are present, although it is an order of magnitude smaller than our $d / u$ result that also includes axial-vector diquarks. The valence quark distribution results are set in a broader context via a simple pion cloud model estimate of sea-quark light-cone momenta and gluon light-cone momentum.
nucl-thhep-phnucl-exPLB(2018)·21 citations
02
Competition between delta isobars and hyperons and properties of compact stars
Jia Jie Li (ITP, Frankfurt)🇩🇪 · Armen Sedrakian (FIAS)🇩🇪 · Fridolin Weber (SDSU)🇺🇸
The $Δ$ -isobar degrees of freedom are included in the covariant density functional (CDF) theory to study the equation of state (EoS) and composition of dense matter in compact stars. In addition to $Δ$ 's we include the full octet of baryons, which allows us to study the interplay between the onset of delta isobars and hyperonic degrees of freedom. Using both the Hartree and Hartree-Fock approximation we find that $Δ$ 's appear already at densities slightly above the saturation density of nuclear matter for a wide range of the meson- $Δ$ coupling constants. This delays the appearance of hyperons and significantly affects the gross properties of compact stars. Specifically, $Δ$ 's soften the EoS at low densities but stiffen it at high densities. This softening reduces the radius of a canonical $1.4 M_{⊙}$ star by up to 2~km for a reasonably attractive $Δ$ potential in matter, while the stiffening results in larger maximum masses of compact stars. We conclude that the hypernuclear CDF parametrizations that satisfy the 2 $M_{⊙}$ maximum mass constraint remain valid when $Δ$ isobars are included, with the important consequence that the resulting stellar radii are shifted toward lower values, which is in agreement with the analysis of neutron star radii.
nucl-thastro-ph.HEastro-ph.SRPLB(2018)·122 citations
03
Extraction of Heavy-Flavor Transport Coefficients in QCD Matter
R. Rapp🇺🇸 · P.B. Gossiaux🇫🇷 · A. Andronic🇩🇪 · R.Averbeck🇩🇪 · S.Masciocchi🇩🇪 · A. Beraudo🇮🇹 · E. Bratkovskaya🇩🇪 · P. Braun-Munzinger🇩🇪 · S. Cao🇺🇸 · A. Dainese🇮🇹 · S.K. Das🇨🇳 · M. Djordjevic🇷🇸 and 19 other authors
We report on broadly based systematic investigations of the modeling components for open heavy-flavor diffusion and energy loss in strongly interacting matter in their application to heavy-flavor observables in high-energy heavy-ion collisions, conducted within an EMMI Rapid Reaction Task Force framework. Initial spectra including cold-nuclear-matter effects, a wide variety of space-time evolution models, heavy-flavor transport coefficients, and hadronization mechanisms are scrutinized in an effort to quantify pertinent uncertainties in the calculations of nuclear modification factors and elliptic flow of open heavy-flavor particles in nuclear collisions. We develop procedures for error assessments and criteria for common model components to improve quantitative estimates for the (low-momentum) heavy-flavor diffusion coefficient as a long-wavelength characteristic of QCD matter as a function of temperature, and for energy loss coefficients of high-momentum heavy-flavor particles.
nucl-thhep-phnucl-exNPA(2018)·311 citations
04
Coexisting partial dynamical symmetries and multiple shapes
A Leviatan · N Gavrielov
We present an algebraic procedure for constructing Hamiltonians with several distinct partial dynamical symmetries (PDSs), of relevance to shape-coexistence phenomena. The procedure relies on a spectrum generating algebra encompassing several dynamical symmetry (DS) chains and a coherent state which assigns a particular shape to each chain. The PDS Hamiltonian maintains the DS solvability and quantum numbers in selected bands, associated with each shape, and mixes other states. The procedure is demonstrated for a variety of multiple quadrupole shapes in the framework of the interacting boson model of nuclei.
nucl-thquant-phJ.Phys.Conf.Ser.(2018)·2 citations
05
Energy spectra in $p$ -shell $Λ$ hypernuclei and $_{Λ}^{19} F$ and spin-dependent $Λ N$ interactions
Yoshiko Kanada-En'yo🇯🇵 · Masahiro Isaka🇯🇵 · Toshio Motoba🇯🇵
Energy spectra of $0 s$ -orbit $Λ$ states in $p$ -shell $Λ$ hypernuclei ( $_{Λ}^{A} Z$ ) and those in $_{Λ}^{19} F$ are studied with the microscopic cluster model and antisymmetrized molecular dynamics using the $G$ -matrix effective $Λ N$ ( $Λ N G$ ) interactions. Spin-dependent terms of the ESC08a version of the $Λ N G$ interactions are tested and phenomenologically tuned to reproduce observed energy spectra in $p$ -shell $_{Λ}^{A} Z$ . Spin-dependent contributions of the $Λ N$ interactions to spin-doublet splitting and excitation energies are discussed. Energy spectra for unobserved excited states in $p$ -shell $_{Λ}^{A} Z$ and $_{Λ}^{19} F$ are predicted with the modified $Λ N G$ interactions.
nucl-thPTEP(2019)·1 citation
06
Ab Initio No Core Shell Model with Leadership-Class Supercomputers
James P. Vary🇺🇸 · Robert Basili🇺🇸 · Weijie Du🇺🇸 · Matthew Lockner🇺🇸 · Pieter Maris🇺🇸 · Dossay Oryspayev🇺🇸 · Soham Pal🇺🇸 · Shiplu Sarker🇺🇸 · Hasan Metin Aktulga🇺🇸 · Esmond Ng🇺🇸 · Meiyue Shao🇺🇸 · Chao Yang🇺🇸
Nuclear structure and reaction theory is undergoing a major renaissance with advances in many-body methods, strong interactions with greatly improved links to Quantum Chromodynamics (QCD), the advent of high performance computing, and improved computational algorithms. Predictive power, with well-quantified uncertainty, is emerging from non-perturbative approaches along with the potential for guiding experiments to new discoveries. We present an overview of some of our recent developments and discuss challenges that lie ahead. Our foci include: (1) strong interactions derived from chiral effective field theory; (2) advances in solving the large sparse matrix eigenvalue problem on leadership-class supercomputers; (3) selected observables in light nuclei with the JISP16 interaction; (4) effective electroweak operators consistent with the Hamiltonian; and, (5) discussion of A=48 system as an opportunity for the no-core approach with the reintroduction of the core.
nucl-thProceedings of the International Conferen…·3 citations
07
The Tjon Band in Nuclear Lattice Effective Field Theory
Nico Klein🇩🇪 · Serdar Elhatisari🇩🇪 · Timo A. Lähde🇩🇪 · Dean Lee🇺🇸 · Ulf-G. Meißner🇩🇪
We explore the lattice spacing dependence in Nuclear Lattice Effective Field Theory for few-body systems up to next-to-next-to leading order in chiral effective field theory including all isospin breaking and electromagnetic effects, the complete two-pion-exchange potential and the three-nucleon forces. We calculate phase shifts in the neutron-proton system and proton-proton systems as well as the scattering length in the neutron-neutron system. We then perform a full next-to-next-to-leading order calculation with two-nucleon and three-nucleon forces for the triton and helium-4 and analyse their binding energy correlation. We show how the Tjon band is reached by decreasing the lattice spacing and confirm the continuum observation that a four-body force is not necessary to describe light nuclei.
nucl-thhep-lathep-phEPJA(2018)·23 citations
08
Charmonium states in strong magnetic fields
Amal Jahan CS🇮🇳 · Nikhil Dhale🇮🇳 · Sushruth Reddy P🇮🇳 · Shivam Kesarwani🇮🇳 · Amruta Mishra🇮🇳
The medium modifications of the masses of the charmonium states (J/ $ψ$ , $ψ$ (3686) and $ψ$ (3770)) in asymmetric nuclear matter in the presence of strong magnetic fields are studied using an effective chiral model. The mass modifications arise due to medium modifications of the scalar dilaton field, which simulates the gluon condensates of QCD within the effective hadronic model. The effects due to the magnetic field as well as isospin asymmetry are observed to be appreciable at high densities for the charmonium states, which can have consequences, e,g, in the production of the open charm mesons and the charmonium states, in the asymmetric heavy ion collisions at the compressed baryonic matter (CBM) experiments at the future facility at GSI. The presence of magnetic field leads to Landau quantization of the energy levels of the proton in the asymmetric nuclear matter. The effects of the anomalous magnetic moments of the proton and neutron on the masses of the charmonium states are studied and are observed to lead to larger masses of the charmonium states, as compared to when these effects are not taken into account.
nucl-thhep-phPRC(2018)·41 citations

Affiliations

first authorsco-authorsvia INSPIRE