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Nuclear Theory·nucl-th

Friday·April 16, 2021

7 papers—6 primary·1 cross-listed

All7Primary6Cross-lists1
  1. 01

    [Submitted on 15 Apr 2021]

    Jülich-Bonn-Washington Model for Pion Electroproduction Multipoles

    Maxim Mai🇺🇸 · Michael Döring🇺🇸 · Carlos Granados🇺🇸 · Helmut Haberzettl🇺🇸 · Ulf-G. Meißner🇩🇪 · Deborah Rönchen🇩🇪 · Igor Strakovsky🇺🇸 · Ron Workman🇺🇸

    Pion electroproduction off the proton is analyzed in a new framework based on a general parametrization of transition amplitudes, including constraints from gauge invariance and threshold behavior. Data with energies and below are included. The model is an extension of the latest Jülich-Bonn solution incorporating constraints from pion-induced and photoproduction data. Performing large scale fits ( data) we find a set of solutions with which allows us to assess the systematic uncertainty of the approach.

    Comments:
    27 pages, 14 figures
    Subjects:
    Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex)
    arXiv:
    2104.07312 [pdf]
    PRC(2021)·46 citations
  2. 02

    [Submitted on 15 Apr 2021]

    Possible bound nuclei beyond the two-neutron drip line in the region

    C. Pan🇨🇳 · K. Y. Zhang🇨🇳 · P. S. Chong🇨🇳 · C. Heo🇨🇳 · M. C. Ho · J. Lee🇨🇳 · Z. P. Li🇨🇳 · W. Sun🇨🇳 · C. K. Tam🇨🇳 · S. H. Wong🇨🇳 · R. W.-Y. Yeung🇨🇳 · T. C. Yiu🇨🇳 · S. Q. Zhang🇨🇳

    Possible bound nuclei beyond the two-neutron drip line in the region are investigated by using the deformed relativistic Hartree-Bogoliubov theory in continuum with density functional PC-PK1. Bound nuclei beyond the drip lines of Ba, Ce, Sm, Gd and Dy are predicted, forming peninsulas of stability in nuclear landscape. Near these peninsulas, several multi-neutron emitters are predicted. The underlying mechanism of the peninsulas of stability is investigated by studying the total energy, Fermi surface, quadrupole deformation and the single-neutron spectrum in the canonical basis. It is found that the deformation effect is crucial for forming the peninsulas of stability, and pairing correlations are also essential in specific cases. The dependence on the deformation evolution is also discussed. The decay rates of multi-neutron radioactivity in Ba and Sm isotopic chains are estimated by using the direct decay model.

    Comments:
    21 pages, 6 figures
    Subjects:
    Nuclear Theory (nucl-th)
    arXiv:
    2104.07337 [pdf]
    PRC(2021)·47 citations
  3. 03

    [Submitted on 15 Apr 2021]

    The kinks in charge radii across = 82 and 126 revisited

    M. Bhuyan🇲🇾 · B. Maheshwari🇮🇳 · H. A. Kassim🇲🇾 · N. Yusof🇲🇾 · S. K. Patra🇮🇳 · B. V. Carlson🇧🇷 · P. D. Stevenson🇬🇧

    We revisit the studies of the isotopic shift in the charge radii of {\it even-even} isotopes of Sn and Pb nuclei at = 82, and 126, respectively, within the relativistic mean-field and Relativistic-Hartree-Bogoliubov approach. The shell model is also used to estimate isotopic shift in these nuclei, for the first time, to the best of our knowledge. The ground state single-particle energies () are calculated for non-linear NL3 \& NL3 and density-dependent DD-ME2 parameter sets compared with the experimental data, wherever available. We establish a correlation between the filling of single-particle levels and the isotopic shift in occupation probabilities. The obtained from the relativistic mean-field and Relativistic-Hartree-Bogoliubov approaches are in line with those used in the shell model and experimental data for both the Sn and Pb isotopic chains. The shell model calculated isotopic shift agrees with relativistic mean-field and Relativistic-Hartree-Bogoliubov approaches that explain the experimental data quite well.

    Comments:
    Published in Journal of Physics G: Nuclear and Particle Physics
    Subjects:
    Nuclear Theory (nucl-th)
    arXiv:
    2104.07392 [pdf]
    J.Phys.G(2021)·15 citations
  4. 04

    [Submitted on 15 Apr 2021]

    Finite Range Interactions in Constrained Molecular Dynamics

    Massimo Papa

    Many-body correlations developed in the constrained molecular dynamics approach in the frame-work of the CoMD model are analyzed in the case of a finite range effective interaction. The study is performed in the case of infinite nuclear matter at zero temperature. A comparison with the predictions in the mean - field limit, which is taken as a reference case, highlights non-negligible differences concerning the produced Equation of State (EoS)for symmetric and asymmetric NM. A procedure is illustrated able to determine the necessary corrections of the effective interaction parameters in the CoMD model in such a way to reproduce the chosen reference EoS saturation properties. Even if the obtained numerical results are strictly valid for the CoMD model, the rather general feature of the discussed correlations gives a wider meaning to the obtained differences which are strongly related to the nucleon wave function space localization characterizing every semi-classical quantum molecular dynamics approach. Finally, the relevance of the constraint on the primary light cluster production is shortly illustrated in an appendix section.

    Comments:
    The proposed interaction if applied to the dynamics of finite systems gives problems related to pairing effects. Changes are under investigation
    Subjects:
    Nuclear Theory (nucl-th)
    arXiv:
    2104.07421 [pdf]
    0 citations
  5. 05

    [Submitted on 15 Apr 2021]

    Two Particles with Zero-Range Interaction in a Magnetic Field

    Johannes Kirscher🇬🇧 · Brian C. Tiburzi🇺🇸

    Energy levels are investigated for two charged particles possessing an attractive, momentum-independent, zero-range interaction in a uniform magnetic field. A transcendental equation governs the spectrum, which is characterized by a collective Landau-level quantum number incorporating both center-of-mass and relative degrees of freedom. Results are obtained for a system of one charged and one neutral particle, with the interaction chosen to produce a bound state in vanishing magnetic field. Beyond deriving the weak-field expansion of the energy levels, we focus on non-perturbative aspects. In the strong-field limit, or equivalently for a system in the unitary limit, a single bound level with universal binding energy exists. By contrast, excited states are resonances that disappear into the continuum as the magnetic field is raised beyond critical values. A hyperbola is derived that approximates the number of bound levels as a function of the field strength remarkably well.

    Comments:
    8 pages, 3 figures, v2 presentation improved, results unchanged
    Subjects:
    Nuclear Theory (nucl-th); High Energy Physics — Lattice (hep-lat); High Energy Physics — Phenomenology (hep-ph)
    arXiv:
    2104.07565 [pdf]
    PLB(2021)·1 citation
  6. 06

    [Submitted on 15 Apr 2021]

    Intermediate mass dileptons as pre-equilibrium probes in heavy ion collisions

    Maurice Coquet🇫🇷 · Xiaojian Du🇩🇪 · Jean-Yves Ollitrault🇫🇷 · Soeren Schlichting🇩🇪 · Michael Winn🇫🇷

    The production of dileptons with an invariant mass in the range 1 GeV < M < 5 GeV provides unique insight into the approach to thermal equilibrium in ultrarelativistic nucleus-nucleus collisions. In this mass range, they are produced through the annihilation of quark-antiquark pairs in the early stages of the collision. They are sensitive to the anisotropy of the quark momentum distribution, and also to the quark abundance, which is expected to be underpopulated relative to thermal equilibrium. We take into account both effects based on recent theoretical developments in QCD kinetic theory, and study how the dilepton mass spectrum depends on the shear viscosity to entropy ratio that controls the equilibration time. We evaluate the background from the Drell-Yan process and argue that future detector developments can suppress the additional background from semileptonic decays of heavy flavors.

    Comments:
    10 pages, 7 figures; computation of the effective area is defined more rigorously, figures are updated accordingly. Added paragraph on page 7, discussing the impact of inhomogeneities in transverse density profile. Added paragraph in the conclusion on page 9, on fitting the invariant mass spectrum with a power function
    Subjects:
    Nuclear Theory (nucl-th); High Energy Physics — Experiment (hep-ex); High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex)
    arXiv:
    2104.07622 [pdf]
    PLB(2021)·58 citations
  7. 07

    [Submitted on 14 Apr 2021] (cross-list from hep-ph)

    Nucleon off-shell structure and the free neutron valence structure from A=3 inclusive electron scattering measurements

    E.P. Segarra🇺🇸 · J.R. Pybus🇺🇸 · F. Hauenstein🇺🇸 · T. Kutz🇺🇸 · D. Higinbotham🇺🇸 · G.A. Miller🇺🇸 · E. Piasetzky🇮🇱 · A. Schmidt🇺🇸 · M. Strikman🇺🇸 · L.B. Weinstein🇺🇸 · O. Hen🇺🇸

    Understanding the differences between the distribution of quarks bound in protons and neutrons is key for constraining the mechanisms of SU(6) spin-flavor symmetry breaking in Quantum Chromodynamics (QCD). While vast amounts of proton structure measurements were done, data on the structure of the neutron is much more spars as experiments typically extract the structure of neutrons from measurements of light atomic nuclei using model-dependent corrections for nuclear effects. Recently the MARATHON collaboration performed such an extraction by measuring inclusive deep-inelastic electron-scattering on helium-3 and tritium mirror nuclei where nuclear effects are expected to be similar and thus be suppressed in the helium-3 to tritium ratio. Here we evaluate the model dependence of this extraction by examining a wide range of models including the effect of using instant-form and light-cone nuclear wave functions and several different parameterizations of nucleon modification effects, including those with and without isospin dependence. We find that, while the data cannot differentiate among the different models of nuclear structure and nucleon modification, they consistently prefer a neutron-to-proton structure function ratio of at of with a typical uncertainty () of and for isospin-independent and isospin-dependent modification models, respectively. While strongly favoring SU(6) symmetry breaking models based on perturbative QCD and the Schwinger-Dyson equation calculation, the MARATHON data do not completely rule out the scalar di-quark models if an isospin-dependent modification exist.

    Comments:
    6 pages, 4 figures
    Subjects:
    High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
    arXiv:
    2104.07130 [pdf]
    8 citations

Affiliations

first authorsco-authorsvia INSPIRE