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Nuclear Theory·nucl-th

Monday·November 9, 2015

7 papers—5 primary·2 cross-listed

All7Primary5Cross-lists2
  1. 01

    [Submitted on 5 Nov 2015]

    A new approach to barrier-top fission dynamics

    G.F. Bertsch · J.M. Mehlhaff

    We proposed a calculational framework for describing induced fission that avoids the Bohr-Wheeler assumption of well-defined fission channels. The building blocks of our approach are configurations that form a discrete, orthogonal basis and can be characterized by both energy and shape. The dynamics is to be determined by interaction matrix elements between the states rather than by a Hill-Wheeler construction of a collective coordinate. Within our approach, several simple limits can be seen: diffusion; quantized conductance; and ordinary decay through channels. The specific proposal for the discrete basis is to use the quantum numbers of the axially symmetric Hartree-Fock approximation to generate the configurations. Fission paths would be determined by hopping from configuration to configuration via the residual interaction. We show as an example the configurations needed to describe a fictitious fission decay . We also examine the geometry of the path for fission of U, measuring distances by the number of jumps needed to go to a new partition.

    Comments:
    Write-up of a talk given at the Workshop "Compound-nuclear reactions 2015" Tokyo, Oct. 19-23, 2015; 11 pages and 11 figures. To be published in European Journal of Physics, Web of Conferences
    Subjects:
    Nuclear Theory (nucl-th)
    arXiv:
    1511.01936 [pdf]
    EPJ Web Conf.(2016)·3 citations
  2. 02

    [Submitted on 5 Nov 2015]

    Nucleon Polarisabilities at and Beyond Physical Pion Masses

    Harald W. Griesshammer (George Washington U.)🇺🇸 · Judith A. McGovern (U. of Manchester)🇬🇧 · Daniel R. Phillips (Ohio U.)🇺🇸

    We examine the results of Chiral Effective Field Theory (EFT) for the scalar- and spin-dipole polarisabilities of the proton and neutron, both for the physical pion mass and as a function of . This provides chiral extrapolations for lattice-QCD polarisability computations. We include both the leading and sub-leading effects of the nucleon's pion cloud, as well as the leading ones of the resonance and its pion cloud. The analytic results are complete at NLO in the -counting for pion masses close to the physical value, and at leading order for pion masses similar to the Delta-nucleon mass splitting. In order to quantify the truncation error of our predictions and fits as \% degree-of-belief intervals, we use a Bayesian procedure recently adapted to EFT expansions. At the physical point, our predictions for the spin polarisabilities are, within respective errors, in good agreement with alternative extractions using experiments and dispersion-relation theory. At larger pion masses we find that the chiral expansion of all polarisabilities becomes intrinsically unreliable as approaches about MeV---as has already been seen in other observables. EFT also predicts a substantial isospin splitting above the physical point for both the electric and magnetic scalar polarisabilities; and we speculate on the impact this has on the stability of nucleons. Our results agree very well with emerging lattice computations in the realm where EFT converges. Curiously, for the central values of some of our predictions, this agreement persists to much higher pion masses. We speculate on whether this might be more than a fortuitous coincidence.

    Comments:
    39 pages LaTeX2e (pdflatex) including 12 figures as 16 .pdf files using includegraphics. Version approved for publication in EPJA includes modifications, clarifications and removal of typographical errors in refereeing and publication process
    Subjects:
    Nuclear Theory (nucl-th); High Energy Physics — Lattice (hep-lat); High Energy Physics — Phenomenology (hep-ph)
    arXiv:
    1511.01952 [pdf]
    EPJA(2016)·53 citations
  3. 03

    [Submitted on 6 Nov 2015]

    Leading three-baryon forces from SU(3) chiral effective field theory

    Stefan Petschauer🇩🇪 · Norbert Kaiser🇩🇪 · Johann Haidenbauer🇩🇪 · Ulf-G. Meißner🇩🇪 · Wolfram Weise🇩🇪

    Leading three-baryon forces are derived within SU(3) chiral effective field theory. Three classes of irreducible diagrams contribute: three-baryon contact terms, one-meson exchange and two-meson exchange diagrams. We provide the minimal non-relativistic terms of the chiral Lagrangian, that contribute to these diagrams. SU(3) relations are given for the strangeness S=0 and -1 sectors. In the strangeness-zero sector we recover the well-known three-nucleon forces from chiral effective field theory. Explicit expressions for the lambda-nucleon-nucleon chiral potential in isospin space are presented.

    Comments:
    14 pages, 5 figures, 4 tables; v2: published version, minor changes
    Subjects:
    Nuclear Theory (nucl-th)
    arXiv:
    1511.02095 [pdf]
    PRC(2016)·64 citations
  4. 04

    [Submitted on 2 Nov 2015]

    Jet-induced modifications of the characteristic of the bulk nuclear matter

    P. Marcinkowski · M. Słodkowski · D. Kikoła · J. Sikorski · J. Porter-Sobieraj · P. Gawryszewski · B. Zygmunt

    We present our studies on jet-induced modifications of the characteristic of the bulk nuclear matter. To describe such a matter, we use efficient relativistic hydrodynamic simulations in (3+1) dimensions employing the Graphics Processing Unit (GPU) in the parallel programming framework. We use Cartesian coordinates in the calculations to ensure a high spatial resolution that is constant throughout the evolution of the system. We show our results on how jets modify the hydrodynamics fields and discuss the implications.

    Comments:
    2 pages, 3 figures, SQM2015 proceedings submitted to Journal of Physics: Conference Series (JPCS) - IOP Conference Series
    Subjects:
    Nuclear Theory (nucl-th)
    arXiv:
    1511.02137 [pdf]
    J.Phys.Conf.Ser.(2016)·2 citations
  5. 05

    [Submitted on 6 Nov 2015]

    Operator analysis of effective spin-flavor interactions for L=1 excited baryons

    Cintia Willemyns🇦🇷 · Carlos Schat🇦🇷

    We match the non-relativistic quark model, with both flavor dependent and flavor independent effective quark-quark interactions, to the spin-flavor operator basis of the 1/Nc expansion for the L=1 non-strange baryons. We obtain analytic expressions for the coefficients of the 1/Nc operators in terms of radial integrals that depend on the shape and relative strength of the spin-spin, spin-orbit and tensor interactions of the model, which are left unspecified. We obtain several new, parameter-free relations between the seven masses and the two mixing angles that can discriminate between different spin-flavor structures of the effective quark-quark interaction. We discuss in detail how a general parametrization of the mass matrix depends on the mixing angles and is constrained by the assumptions on the effective quark-quark interaction. We find that, within the present experimental uncertainties, consistency with the best values of the mixing angles as determined by a recent global fit to masses and decays does not exclude any of the two most extreme possibilities of flavor dependent (independent) quark-quark interactions, as generated by meson (gluon) exchange interactions.

    Comments:
    36 pages, 9 figures
    Subjects:
    Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph)
    arXiv:
    1511.02215 [pdf]
    PRD(2016)·6 citations

Affiliations

first authorsco-authorsvia INSPIRE