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Nuclear Theory·nucl-th

Wednesday·January 31, 2018

13 papers—6 primary·7 cross-listed

All13Primary6Cross-lists7
  1. 01

    Poincaré-covariant analysis of heavy-quark baryons

    Si-Xue Qin🇨🇳 · Craig D. Roberts🇺🇸 · Sebastian M. Schmidt🇩🇪

    We use a symmetry-preserving truncation of meson and baryon bound-state equations in quantum field theory in order to develop a unified description of systems constituted from light- and heavy-quarks. In particular, we compute the spectrum and leptonic decay constants of ground-state pseudoscalar- and vector-mesons: , , with and ; and the masses of baryons and their first positive-parity excitations, including those containing one or more heavy quarks. This Poincaré-covariant analysis predicts that such baryons have a complicated angular momentum structure. For instance, the ground states are all primarily -wave in character, but each possesses -, - and -wave components, with the -wave fraction being large in the states; and the first positive-parity excitation in each channel has a large -wave component, which grows with increasing current-quark mass, but also exhibits features consistent with a radial excitation. The configuration space extent of all such baryons decreases as the mass of the valence-quark constituents increases.

    nucl-thhep-phPRD(2018)·60 citations
  2. 02

    -Resonance in the Hydrogen Spectrum

    Franziska Hagelstein (AEC Bern)🇨🇭

    The electromagnetic excitation of the -resonance plays an appreciable role in the Lamb shift and hyperfine structure of muonic and electronic hydrogen. Its effect appears at the subleading order , together with other proton-polarizability contributions from forward two-photon exchange. We use the large- relations for the nucleon-to-delta transition form factors to compute the effect of the in the hydrogen spectrum. We pay particular attention to a subtile difference between predictions based on a direct calculation of the two-photon exchange (or Compton scattering amplitudes) and predictions based on the -production photoabsorption cross sections. The mismatch is explained by studying the dispersion relations for tree-level Compton scattering off the proton in more details.

    nucl-thhep-phFew Body Syst.(2018)·16 citations
  3. 03

    Evidence for rotational to vibrational evolution along the yrast line in the odd-A rare-earth nuclei

    H. B. Zhou · S. Huang · G. X. Dong · Z. X. Shen · H. J. Lu · L. L. Wang · X. J. Sun · F. R. Xu

    The phase transition of nuclei to increasing angular momentum (or spin) and excitation energy is one of the most fundamental topics of nuclear structure research. The odd-N nuclei with A equal 160 are widely considered belonging to the well-deformed region, and their excitation spectra are energetically favored to exhibit the rotational characteristics. In the present work, however, there is evidence indicating that the nuclei can evolve from rotation to vibration along the yrast lines while increasing spin. The simple method, named as E-Gamma Over Spin (E-GOS) curves, would be used to discern the evolution from rotational to vibrational structure in nuclei as a function of spin. In addition, in order to get the insight into the rotational-like properties of nuclei, theoretical calculations have been performed for the yrast bands of the odd-A rare-earth nuclei using the total Routhian surfaces (TRS) model. The TRS plots indicate that the 165Yb and 157Dy isotopes have stable prolate shapes at low spin states. At higher rotational frequency (larger than 0.50 MeV), a distinct decrease in the quadrupole deformation is predicted by the calculations, and the isotopes becomes rigid in the gamma deformation.

    nucl-thNucl.Phys.Rev.(2018)·0 citations
  4. 04

    Systematic few-body analysis of eta-d, eta-3He and eta-4He interaction at low energies

    A.Fix🇷🇺 · O.Kolesnikov🇷🇺

    The Alt-Grassberger-Sandhas N-body theory is used to study interaction of eta-mesons with d, 3He, and 4He. Separable expansion of the subamplitudes is adopted to convert the integral equations into the quasi-two-body form. The resulting formalism is applied to fit the existing data for low-energy eta production on few-nucleon targets. On the basis of this fitting procedure the scattering lengths a_{eta d}, a_{eta 3He}, a_{eta 4He} as well as the subthreshold behaviour of the elementary eta-N scattering amplitude are obtained.

    nucl-thPRC(2018)·6 citations
  5. 05

    Quantum mechanical description of excitation energy distribution of the reaction residue in nucleon-induced inclusive one-nucleon knockout reactions

    Kazuyuki Ogata

    Understanding of inclusive one-nucleon knockout reactions for long-lived fission fragments (LLFPs) is crucial for nuclear transmutation studies. However, the particle and heavy ion transport code system (PHITS) severely overshoots the inclusive one-nucleon knockout cross sections sigma_-1N. Therefore development of a reaction model for describing the inclusive one-nucleon knockout processes is necessary. A key is specification of the position and the momentum of a nucleon inside a nucleus to be struck by the incident nucleon. In this paper the semiclassical distorted wave model incorporating the Wigner transform of the one-body nuclear density matrix is applied to the calculation of excitation energy distributions of reaction residues. Decay of a residue is described by introducing a threshold parameter for the minimum excitation energy of it. With reasonable values of the parameter, the measured sigma_-1N for several LLFPs are reproduced by the proposed reaction model. The incident energy dependence of sigma_-1N is found to be governed by that of the nucleon-nucleon cross sections at energies higher than about 75 MeV. At low energies, the nuclear absorption and the Coulomb penetrability also become important. The energy dependence of neutron-induced sigma_-1N is predicted and found to be quite different from that of proton induced one. The proposed reaction model is shown to be promising in discussing the energy dependence of nucleon-induced inclusive one-nucleon knockout processes. The energy dependence of the measured sigma_-1p for 107Pd above 100 MeV is, however, not explained by the present calculation.

    nucl-th0 citations
  6. 06

    Isoscalar and Isovector spin response in shell nuclei

    H. Sagawa · T. Suzuki

    The spin magnetic dipole transitions and the neutron-proton spin-spin correlations in shell even-even nuclei with are investigated using shell model wave functions taking into accout enhanced isoscalar (IS) spin-triplet pairing as well as the effective spin operators. It was shown that the IS pairing and the effective spin operators gives a large quenching effect on the IV spin transitions to be consistent with observed data by experiments. On the other hand, the observed IS spin strength show much smaller quenching effect than expected by the calculated results. The IS pairing gives a substantial quenching effect on the spin magnetic dipole transitions, especially on the isovector (IV) ones. Consequently, an enhanced isoscalar spin-triplet pairing interaction enlarges the proton-neutron spin-spin correlation deduced from the difference between the isoscalar (IS) and the IV sum rule strengths. The beta-decay rates and the IS magnetic moments of shell are also examined in terms of the IS pairing as well as the effective spin operators.

    nucl-thPRC(2018)·10 citations

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first authorsco-authorsvia INSPIRE