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Nuclear Theory·nucl-th

Monday·January 11, 2016

9 papers—3 primary·6 cross-listed

All9Primary3Cross-lists6
  1. 04

    Spin Polarized versus Chiral Condensate in Quark Matter at Finite Temperature and Density

    H. Matsuoka (Kochi Univ., Japan)🇯🇵 · Y. Tsue (Kochi Univ., Japan)🇯🇵 · J. da Providencia (Univ. de Coimbra, Portugal)🇵🇹 · C. Providencia (Univ. de Coimbra, Portugal)🇵🇹 · M. Yamamura (Kansai Univ., Japan)🇯🇵 · H. Bohr (Danish Technical Univ., Denmark)🇩🇰

    It is shown that the spin polarized condensate appears in quark matter at high baryon density and low temperature due to the tensor-type four-point interaction in the Nambu-Jona-Lasinio-type model as a low energy effective theory of quantum chromodynamics. It is indicated within this low energy effective model that the chiral symmetry is broken again by the spin polarized condensate as increasing the quark number density, while the chiral symmetry restoration occurs in which the chiral condensate disappears at a certain density.

    ↳ hep-phnucl-thPTEP(2016)·11 citations
  2. 05

    The Role of Nucleon Strangeness in Supernova Explosions

    T. J. Hobbs🇺🇸 · Mary Alberg🇺🇸 · Gerald A. Miller🇺🇸

    Recent hydrodynamical simulations of supernova (SN) evolution have highlighted the importance of a thorough control over microscopic physics responsible for such internal processes as neutrino heating. In particular, it has been suggested that modifications to the neutrino-nucleon elastic cross section can potentially play a crucial role in producing successful supernova explosions. One possible source of such corrections can be found in a nonzero value for the nucleon's strange helicity content . In the present analysis, however, we show that theoretical and experimental progress over the past decade has suggested a comparatively small magnitude for , such that its sole effect is not sufficient to provide the physics leading to supernova explosions.

    ↳ astro-ph.HEhep-phnucl-thPRC(2016)·25 citations
  3. 06

    Nucleon Charges, Form-factors and Neutron EDM

    Rajan Gupta🇺🇸 · Tanmoy Bhattacharya🇺🇸 · Vincenzo Cirigliano🇺🇸 · Huey-Wen Lin🇺🇸 · Boram Yoon🇺🇸

    We present an update of our analysis of statistical and systematic errors in the calculation of iso-vector scalar, axial and tensor charges of the nucleon. The calculations are done using flavor HISQ ensembles generated by the MILC Collaboration at three values of the lattice spacing ( and fm) and three values of the quark mass ( and MeV); and clover fermions for calculating the correlation functions, i.e., we use a clover-on-HISQ lattice formulation. The all-mode-averaging method allows us to increase the statistics by a factor of eight for the same computational cost leading to a better understanding of and control over excited state contamination. Our current results, after extrapolation to the continuum limit and physical pion mass are , and . Further checks of control over all systematic errors, especially in , are still being performed. Using results for the flavor-diagonal charges, , and , we analyze contributions of the quark electric dipole moment to the neutron EDM and the consequences for split SUSY model.

    ↳ hep-latnucl-thPoS(2016)·3 citations
  4. 07

    Magnetic dipole excitations of Cr

    H. Pai · T. Beck · J. Beller · R. Beyer · M. Bhike · V. Derya · U. Gayer · J. Isaak · J. Kvasil · B. Loher · V. O. Nesterenko · N. Pietralla and 14 other authors

    The low-lying -strength of the open-shell nucleus Cr has been studied with the method of nuclear resonance fluorescence up to 9.7 MeV, using bremsstrahlung at the superconducting Darmstadt linear electron accelerator S-DALINAC and Compton backscattered photons at the High Intensity -ray Source (HIS) facility between 6 and 9.7 MeV of the initial photon energy. Fifteen states have been observed between 3.6 and 9.7 MeV. Following our analysis, the lowest state at 3.6 MeV can be considered as an isovector orbital mode with some spin admixture. The obtained results generally match the estimations and trends typical for the scissors-like mode. Detailed calculations within the Skyrme Quasiparticle Random-Phase-Approximation method and the Large-Scale Shell Model justify our conclusions. The calculated distributions of the orbital current for the lowest -state suggest the schematic view of Lipparini and Stringari (isovector rotation-like oscillations inside the rigid surface) rather than the scissors-like picture of Lo Iudice and Palumbo. The spin M1 resonance is shown to be mainly generated by spin-flip transitions between the orbitals of the -shell.

    ↳ nucl-exnucl-thPRC(2016)·28 citations
  5. 08

    Solar opacity calculations using the super-transition-array method

    M. Krief · A. Feigel · D. Gazit (Hebrew U.)

    A new opacity model based on the Super-Transition-Array (STA) method for the calculation of monochromatic opacities of local thermodynamic equilibrium plasmas, was developed. The atomic code, named STAR (STA-Revised), is described and used to calculate spectral opacities for a solar model implementing the recent AGSS09 composition. Calculations are carried throughout the solar radiative zone. The relative contributions of different chemical elements and atomic processes to the total Rosseland mean opacity are analyzed in detail. Monochromatic opacities and charge state distributions were compared with the widely used Opacity-Project (OP) code, for several elements near the radiation-convection interface. STAR Rosseland opacities for the solar mixture show a very good agreement with OP and the OPAL opacity code, throughout the radiation zone. Finally, an explicit STA calculation of the full AGSS09 photospheric mixture, including all heavy metals was performed. It was shown that due to their extremely low abundance, and despite being very good photon absorbers, the heavy elements do not affect the Rosseland opacity.

    ↳ astro-ph.SRnucl-thphysics.atom-phApJ(2016)·23 citations

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