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Nuclear Theory·nucl-th

Wednesday·February 16, 2022

8 papers—4 primary·4 cross-listed

All8Primary4Cross-lists4
  1. 01

    Application of complex transition density to nuclear reaction and effect of phase factor

    T. Furumoto

    Complex transition density can be constructed by a nuclear structure model with a complex basis and/or complex coefficient. In general, the complex transition density is converted to the real one with phase factor. In this study, we apply the complex transition density directly to the microscopic reaction model. We compare with scattering cross sections calculated with the real and complex transition densities in the frameworks of the optical model, the distorted wave Born approximation, and the coupled-channel (CC) calculation, respectively. In addition, we investigate the dependence of the phase factor for the transition density in the elastic and inelastic cross sections. The effect of the phase factor on the elastic and inelastic cross sections can be seen in the CC calculation. Finally, we found an important role of the phase factor in the nuclear elastic and inelastic scatterings.

    nucl-thnucl-ex0 citations
  2. 02

    In-medium isospin impurity from charge symmetry breaking in the mirror hypernuclei

    M. Schäfer🇮🇱 · N. Barnea🇮🇱 · A. Gal🇮🇱

    The separation energies in the mirror hypernuclei exhibit large charge symmetry breaking (CSB). Analyzing this CSB within pionless effective field theory while using partially conserved baryon-baryon SU(3) flavor symmetry, we deduce a induced in-medium admixture amplitude in the dominantly isospin hyperon. Our results confirm the free-space value inferred directly within the SU(3) baryon octet by Dalitz and von-Hippel in 1964 and reaffirmed in a recent QCD+QED lattice calculation. Furthermore, exploring the consequences of SU(3) flavor symmetry on the -nucleon interaction, we find that CSB is expected to impact the and spin channels in opposite directions, with the latter dominating by an order of magnitude. These observations explain a recent deduction of -nucleon CSB strengths.

    nucl-thhep-phnucl-exPRC(2022)·13 citations
  3. 03

    Many-body approximations to the superfluid gap and critical temperature in pure neutron matter

    M. Drissi · A. Rios

    We compute singlet pairing gaps and critical temperatures in pure neutron matter with different many-body approximations. Medium effects tend to reduce gaps and critical temperatures compared to the standard BCS ansatz. In the mean-field approximation, the ratio of these two quantities remains constant across a wide range of densities. This constant ratio is close to the universal prediction of BCS theory, whether three-neutron interactions are included or not. Using a more sophisticated many-body approach that incorporates the effect of short-range correlations in pairing properties, we find that the gap to critical temperature ratio in the low-density regime is substantially larger than the BCS prediction, independently of the interaction. In this region, our results are relatively close to experiments and theoretical calculations from the unitary Fermi gas. We also find evidence for a different density dependence of zero-temperature gaps and critical temperatures in neutron matter.

    nucl-thEPJA(2022)·12 citations
  4. 04

    Theoretical description of pygmy (dipole) resonances

    Edoardo G. Lanza · Andrea Vitturi

    Stable and unstable nuclei with neutron excess () show - in the isovector dipole transition strength distribution - a small hump around the neutron emission threshold energy known as Pygmy Dipole Resonance (PDR). One of its main features is the isospin mixing allowing the experimental studies with both isovector and isoscalar probes. Different theoretical approaches and methodologies are used to deduce the characteristics of the PDR. In this Chapter, the various mean-field theories and their extensions, devoted to understand and reproduce the strength distribution of these low-lying dipole states, are summarised. Special attention is dedicated to the calculations of the inelastic cross section, aspect that is particularly important in the investigation with isoscalar probes, such as -particles or O. The relevance of the radial form factors is presented in relation to the inelastic cross-section calculations.

    nucl-thnucl-ex1 citation

Affiliations

first authorsco-authorsvia INSPIRE