PaperPanorama

Nuclear Theory·nucl-th

Wednesday·February 5, 2020

7 papers—2 primary·5 cross-listed

All7Primary2Cross-lists5
  1. 01

    Large- analysis of magnetic and axial two-nucleon currents in pionless effective field theory

    Thomas R. Richardson🇺🇸 · Matthias R. Schindler🇺🇸

    We analyze magnetic and axial two-nucleon contact terms in a combined large- and pionless effective field theory expansion. These terms play important roles in correctly describing, e.g., the low-energy cross section of radiative neutron capture and the deuteron magnetic moment. We show that the large- expansion hints towards a hierarchy between the two leading-order magnetic terms that matches that found in phenomenological fits. We also comment on the issue of naturalness in different Lagrangian bases.

    nucl-thhep-phPRC(2020)·10 citations
  2. 02

    Constraining input parameters of AMPT model with meson production

    Katyayni Tiwari🇮🇳 · Md. Nasim🇮🇳

    A Multi-Phase Transport Model (AMPT) has been extensively used to understand the physics behind the experimental observation. Like other models, the outcome of the AMPT model depends on the initial parameters. Therefore, one needs to choose suitable initial parameters before using the model. Lund string fragmentation function has been used to create quark-antiquarks pairs in the AMPT model. The Lund string fragmentation parameters determine the yields and transverse momentum () spectra of particles produced in nucleus-nucleus collisions. The values of Lund string fragmentation parameters were determined by fitting the charged particle yield and spectra measured in the experiment. In this paper, we have shown the yield of strange quarks carrying hadrons, e.g. mesons, are more sensitive to Lund string fragmentation parameters compared to non-strange pions. Using meson spectra measured at RHIC, we have obtained new sets of Lund parameters for Au+Au collisions at = 11.5, 39, and 200 GeV. We have found that using the same set of parameters, we can explain -meson yield at = 39 and 200 GeV, however, we need a different set of parameters for = 11.5 GeV. This suggests that at low energy, = 11.5 GeV, the underlying mechanism for particle production is different compared to top RHIC energies. We have also predicted invariant yield of and mesons as a function of in U+U collisions at = 196 GeV to be measured by STAR experiment.

    nucl-thNPA(2020)·4 citations
  3. 03

    Thermal modifications of quarkonia and heavy quark diffusion from a comparison of continuum-extrapolated lattice results to perturbative QCD

    Anna-Lena Lorenz🇩🇪 · Heng-Tong Ding🇨🇳 · Olaf Kaczmarek🇨🇳 · Hiroshi Ohno🇯🇵 · Hauke Sandmeyer🇩🇪 · Hai-Tao Shu🇩🇪

    We investigate the in-medium modifications of heavy quarkonia in the vector channel and the heavy quark diffusion coefficient by comparing Euclidean correlators from the lattice to a perturbative spectral function. On the lattice side, we work with continuum extrapolated data from four different large and fine lattices with Clover-improved Wilson fermions in the quenched approximation at five temperatures (0.75, 1.1, 1.3, 1.5 and 2.25). On the perturbative side, we use a combination of pNRQCD and vacuum asymptotics to describe the spectral function. After accounting for systematic errors, we obtain a spectral function that is suited to describe the bound state region. This spectral function describes charmonium well without a resonance peak at any of our analyzed temperatures above , while we observe a thermally broadened resonance peak for bottomonium that is only melted at our largest temperature, . For the transport contribution we assume a Breit-Wigner shaped peak and find that the drag coefficient of charm quarks is larger than that of bottom quarks.

    ↳ hep-lathep-phnucl-exnucl-thPoS(2020)·5 citations
  4. 04

    Free energy of a Holonomous Plasma

    Chris P. Korthals Altes🇫🇷 · Hiromichi Nishimura🇯🇵 · Robert D. Pisarski🇺🇸 · Vladimir V. Skokov🇺🇸

    At a nonzero temperature T, a constant field generates nontrivial eigenvalues of the thermal Wilson line. We discuss contributions to the free energy of such a holonomous plasma when the coupling constant, , is weak. We review the computation to by several alternate methods, and show that gauge invariant sources, which are nonlinear in the gauge potential , generate novel contributions to the gluon self energy at . These ensure the gluon self energy remains transverse to , and are essential in computing contributions to the free energy at for small holonomy, . We show that the contribution from off-diagonal gluons is discontinuous as the holonomy vanishes. The contribution from diagonal gluons is continuous as the holonomy vanishes, but sharply constrains the possible sources which generate nonzero holonomy, and must involve an infinite number of Polyakov loops.

    ↳ hep-phhep-latnucl-thPRD(2020)·16 citations
  5. 05

    QCD equation of state at vanishing and high baryon density: Chiral Mean Field model

    Anton Motornenko🇩🇪 · Jan Steinheimer🇩🇪 · Volodymyr Vovchenko🇩🇪 · Stefan Schramm🇩🇪 · Horst Stoecker🇩🇪

    The thermodynamic properties of high temperature and high density QCD-matter are studied using the Chiral SU(3)-flavor parity-doublet Polyakov-loop quark-hadron mean-field model, CMF. The CMF model provides a proper description of lattice QCD data, heavy-ions physics, and static neutron stars. The behavior of lines of constant pressure with increase of baryon density is discussed. The rapid change of pressure behavior at suggests a strong contribution of baryons to thermodynamic properties at this region. The position of this region is very close to the radius of convergence for a Taylor expansion of the QCD pressure. The role of mesons and unstable hadrons in the hydrodynamic expansion of strongly interacting matter is also discussed.

    ↳ hep-phastro-ph.HEnucl-thNPA(2021)·6 citations
  6. 06

    Fate of Light Scalar Mesons

    N.N. Achasov🇷🇺

    It is shown that all predictions for the light scalars, based on their four-quark nature, are supported by experiment. The future research program is outlined also.

    ↳ hep-phhep-exnucl-thPhys.Part.Nucl.(2020)·8 citations
  7. 07

    Chiral pasta

    Andreas Schmitt🇬🇧

    Interiors of neutron stars are ultra-dense and may contain a core of deconfined quark matter. Such a core connects to the outer layers smoothly or through a sharp microscopic interface or through an intermediate macroscopic layer of inhomogeneous mixed phases, which is globally neutral but locally contains electrically charged domains. Here I employ a nucleon-meson model under neutron star conditions that shows a first-order chiral phase transition at large densities. In the vicinity of this chiral transition I calculate the free energies of various mixed phases - different 'pasta structures' - in the Wigner-Seitz approximation. Crucially, chirally broken nuclear matter and the approximately chirally symmetric phase (loosely interpreted as quark matter) are treated on the same footing. This allows me to compute the interface profiles of bubbles, rods, and slabs fully consistently, taking into account electromagnetic screening effects and without needing the surface tension as an input. I find that the full numerical results tend to disfavor mixed phases compared to a simple step-like approximation used frequently in the literature and that the predominantly favored pasta structure consists of slabs with a surface tension .

    ↳ hep-phastro-ph.HEnucl-thPRD(2020)·28 citations

Affiliations

first authorsco-authorsvia INSPIRE