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Nuclear Theory·nucl-th

Thursday·October 8, 2020

4 papers—2 primary·2 cross-listed

All4Primary2Cross-lists2
  1. 01

    M1 resonance in Pb within the self-consistent phonon-coupling model

    V. Tselyaev · N. Lyutorovich · J. Speth · P.-G. Reinhard

    The main goal of the paper is to investigate theoretically the experimentally observed fragmentation of the isovector resonance in Pb within a self-consistent model based on an energy-density functional (EDF) of the Skyrme type. This fragmentation (spread of the strength) is not reproduced in a conventional one-particle--one-hole () random-phase approximation (RPA) and thus has to be investigated in the framework of more complicated models. However, previously applied models of this type were not self-consistent. In the present work, we use a recently developed renormalized version of the self-consistent time blocking approximation (RenTBA) in which the phonon configurations are included on top of the RPA configurations. We have determined several sets of the parameters of the modified Skyrme EDF fitted within the RenTBA and RPA and have found the necessary condition of producing the fragmentation of the resonance in Pb in our model. We present also the results of the RenTBA and RPA calculations for the first excited states of the natural parity modes in Pb obtained with these modified parametrizations.

    nucl-thPRC(2020)·16 citations
  2. 02

    Numerical Simulation of GUE Two-Point Correlation and Cluster Functions

    Adam James Sargeant

    Numerical simulations of the two-point eigenvalue correlation and cluster functions of the Gaussian unitary ensemble (GUE) are carried out directly from their definitions in terms of deltas functions. The simulations are compared with analytical results which follow from three analytical formulas for the two-point GUE cluster function: (i) Wigner's exact formula in terms of Hermite polynomials, (ii) Brezin and Zee's approximate formula which is valid for points with small enough separations and (iii) French, Mello and Pandey's approximate formula which is valid on average for points with large enough separations. It is found that the oscillations present in formulas (i) and (ii) are reproduced by the numerical simulations if the width of the function used to represent the delta function is small enough and that the non-oscillating behaviour of formula (iii) is approached as the width is increased.

    nucl-thcond-mat.stat-mechBraz.J.Phys.(2021)·0 citations
  3. 03

    The Fragmentation Spectrum from Space-Time Reciprocity

    Duff Neill🇺🇸

    Analyzing the single inclusive annihilation spectrum of charged hadrons in collisions, I confront the hadronization hypothesis of local parton-hadron duality with a systematic resummation of the dependence on the small energy fraction. This resummation is based on the reciprocity between time-like and space-like splitting processes in -dimensions, which I extend to resum all the soft terms of the cross-section for inclusive jet production. Under the local-parton-hadron duality hypothesis, the resulting distribution of jets essentially determines the spectrum of hadrons as the jet radius goes to zero. Thus I take the resummed perturbative jet function as the non-perturbative fragmentation function with an effective infra-red coupling. I find excellent agreement with data, and comment on the mixed leading log approximation previously used to justify local parton-hadron duality.

    ↳ hep-phnucl-thJHEP(2021)·9 citations
  4. 04

    The Positive-Parity Baryon Spectrum and the Role of Hybrid Baryons

    Tanjib Khan🇺🇸 · David Richards🇺🇸 · Frank Winter🇺🇸

    We calculate the low-lying spectra for the positive-parity and at two pion masses of 358 and 278 MeV using an isotropic clover action with two degenerate light-quaark and one strange-quark flavors through the application of the generalized variational method within the distillation framework. The spectrum exhibits the general features observed in previous calculations using an anisotropic clover lattice, with a counting of states at least as rich as the quark model. Furthermore, we identify states that are hybrid in nature, where gluonic degrees of freedom play a structural role, indicatinng that such states appear a feature of the excited baryon spectrum, irrespective of the lattice action, or the precise details of the smearing of the lattice interpolating operators used to identify such states.

    ↳ hep-lathep-phnucl-thPRD(2021)·26 citations

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