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Nuclear Theory·nucl-th

Wednesday·April 8, 2015

8 papers—5 primary·3 cross-listed

All8Primary5Cross-lists3
  1. 06

    More on Heisenberg's model for high energy nucleon-nucleon scattering

    Horatiu Nastase🇧🇷 · Jacob Sonnenschein🇮🇱

    We revisit Heisenberg's model for nucleon-nucleon scattering which admits a saturation of the Froissart bound. We examine its uniqueness, and find that up to certain natural generalizations, it is the only action that saturates the bound. We find that we can extract also sub-leading behaviour for from it, though that requires a knowledge of the wavefunction solution that is hard to obtain, and a black-disk model allows the calculation of as well. The wavefunction solution is analyzed perturbatively, and its source is interpreted. Generalizations to several mesons, addition of vector mesons, and curved space regimes are also found. We discuss the relations between Heisenberg's model and holographic models that are dual to QCD-like theories.

    ↳ hep-thhep-exhep-phnucl-thPRD(2015)·16 citations
  2. 07

    Solving the inhomogeneous Bethe-Salpeter Equation in Minkowski space: the zero-energy limit

    T. Frederico (ITA, S. Jose' dos Campos, Brazil)🇧🇷 · G. Salme' (INFN Rome, Italy)🇮🇹 · M. Viviani (INFN Pisa, Italy)🇮🇹

    For the first time, the inhomogeneous Bethe-Salpeter Equation for an interacting system, composed by two massive scalars exchanging a massive scalar, is numerically investigated in ladder approximation, directly in Minkowski space, by using an approach based on the Nakanishi integral representation. In this paper, the limiting case of zero-energy states is considered, extending the approach successfully applied to bound states. The numerical values of scattering lengths, are calculated for several values of the Yukawa coupling constant, by using two different integral equations that stem within the Nakanishi framework. Those low-energy observables are compared with (i) the analogous quantities recently obtained in literature, within a totally different framework and (ii) the non relativistic evaluations, for illustrating the relevance of a non perturbative, genuine field theoretical treatment in Minkowski space, even in the low-energy regime. Moreover, dynamical functions, like the Nakanishi weight functions and the distorted part of the zero-energy Light-front wave functions are also presented. Interestingly, a highly non trivial issue related to the abrupt change in the width of the support of the Nakanishi weight function, when the zero-energy limit is approached, is elucidated, ensuring a sound basis to the forthcoming evaluation of phase-shifts.

    ↳ hep-phcond-mat.str-elnucl-thEPJC(2015)·25 citations
  3. 08

    Evolution of E2 transition strength in deformed hafnium isotopes from new measurements on Hf, Hf, and Hf

    M. Rudigier🇩🇪 · K. Nomura🇩🇪 · M. Dannhoff · R-B. Gerst · J. Jolie · N. Saed-Samii · S. Stegemann · J-M. Régis · L. M. Robledo · R. Rodríguez-Guzmán · A. Blazhev · Ch. Fransen · N. Warr · K. O. Zell

    The available data for E2 transition strengths in the region between neutron-deficient Hf and Pt isotopes are far from complete. More and precise data are needed to enhance the picture of structure evolution in this region and to test state-of-the-art nuclear models. In a simple model, the maximum collectivity is expected at the middle of the major shell. However, for actual nuclei, this picture may no longer be the case, and one should use a more realistic nuclear-structure model. We address this point by studying the spectroscopy of Hf. We remeasure the 2^+_1 half-lives of 172,174,176Hf, for which there is some disagreement in the literature. The main goal is to measure, for the first time, the half-lives of higher-lying states of the rotational band. The new results are compared to a theoretical calculation for absolute transition strengths. The half-lives were measured using \gamma-\gamma and conversion-electron-\gamma delayed coincidences with the fast timing method. For the determination of half-lives in the picosecond region, the generalized centroid difference method was applied. For the theoretical calculation of the spectroscopic properties, the interacting boson model is employed, whose Hamiltonian is determined based on microscopic energy-density functional calculations. The measured 2^+_1 half-lives disagree with results from earlier \gamma-\gamma fast timing measurements, but are in agreement with data from Coulomb excitation experiments and other methods. Half-lives of the 4^+_1 and 6^+_1 states were measured, as well as a lower limit for the 8^+_1 states. We show the importance of the mass-dependence of effective boson charge in the description of E2 transition rates in chains of nuclei. It encourages further studies of the microscopic origin of this mass dependence. New data on transition rates in nuclei from neighboring isotopic chains could support these studies.

    ↳ nucl-exnucl-thPRC(2015)·19 citations

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first authorsco-authorsvia INSPIRE