Nuclear Theory·nucl-th
15 papers—7 primary·8 cross-listed
[Submitted on 1 Jul 2020]
Sebastian Kubis · Włodzimierz Wójcik · Noemi Zabari
It is shown that recently proposed RMF model with and meson interaction agrees with the observational data and presents an interesting structure with phase transition in the outer part of neutron star core.
[Submitted on 1 Jul 2020]
Patrick Carzon🇺🇸 · Skandaprasad Rao🇺🇸 · Matthew Luzum🇧🇷 · Matthew Sievert🇺🇸 · Jacquelyn Noronha-Hostler🇺🇸
Recent measurements have established the sensitivity of ultracentral heavy-ion collisions to the deformation parameters of non-spherical nuclei. In the case of Xe collisions, a quadrupole deformation of the nuclear profile led to an enhancement of elliptic flow in the most central collisions. In Pb collisions a discrepancy exists in similar centralities, where either elliptic flow is over-predicted or triangular flow is under-predicted by hydrodynamic models; this is known as the -to- puzzle in ultracentral collisions. Motivated by low-energy nuclear structure calculations, we consider the possibility that Pb nuclei could have a pear shape deformation (octupole), which has the effect of increasing triangular flow in central PbPb collisions. Using the recent data from ALICE and ATLAS, we revisit the -to- puzzle in ultracentral collisions, including new constraints from recent measurements of the triangular cumulant ratio and comparing two different hydrodynamic models. We find that, while an octupole deformation would slightly improve the ratio between and , it is at the expense of a significantly worse triangular flow cumulant ratio. In fact, the latter observable prefers no octupole deformation, with for Pb, and is therefore consistent with the expectation for a doubly-magic nucleus even at top collider energies. The -to- puzzle remains a challenge for hydrodynamic models.
[Submitted on 2 Jul 2020]
Eun Jin In · Youngman Kim · Panagiota Papakonstantinou · Seung-Woo Hong
The location of the neutron drip line, currently known for only the lightest elements, remains a fundamental question in nuclear physics. Its description is a challenge for microscopic nuclear energy density functionals, as it must take into account in a realistic way not only the nuclear potential, but also pairing correlations, deformation effects and coupling to the continuum. The recently developed deformed relativistic Hartree-Bogoliubov theory in continuum (DRHBc) aims to provide a unified description of even-even nuclei throughout the nuclear chart. Here, the DRHBc with the successful density functional PC-PK1 is used to investigate whether and how deformation influences the prediction for the neutron drip-line location for even-even nuclei with 8<=Z<=20, where many isotopes are predicted deformed. The results are compared with those based on the spherical relativistic continuum Hartree-Bogoliubov (RCHB) theory and discussed in terms of shape evolution and the variational principle. It is found that the Ne and Ar drip-line nuclei are different after the deformation effect is included. The direction of the change is not necessarily towards an extended drip line, but rather depends on the evolution of the degree of deformation towards the drip line. Deformation effects as well as pairing and continuum effects treated in a consistent way can affect critically the theoretical description of the neutron drip-line location.
[Submitted on 2 Jul 2020]
Using the idea of the instanton approach to quantum tunneling we try to obtain a method of calculating spontaneous fission rates for nuclei with the odd number of neutrons or protons. This problem has its origin in the failure of the adiabatic cranking approximation which serves as the basis in calculations of fission probabilities. Selfconsistent instanton equations, with and without pairing, are reviewed and then simplified to non-selfconsistent versions with phenomenological single-particle potential and seniority pairing interaction. Solutions of instanton-like equations without pairing and actions they produce are studied for the Woods-Saxon potential along realistic fission trajectories. Actions for unpaired particles are combined with cranking actions for even-even cores and fission hindrance for odd-A nuclei is studied in such a hybrid model. With the assumed equal mass parameters for neighbouring odd-A and even-even nuclei, the model shows that freezing the K {\pi} configuration leads to a large overestimate of the fission hindrance factors. Actions with adiabatic configurations mostly show not enough hindrance; instanton-like actions for blocked nucleons correct this, but not sufficiently.
[Submitted on 1 Jul 2020]
Fatema. H. Obeed · Ali. K. Hasan
In this work the excited energy levels, reduced transition probabilities, , intrinsic quadrupole moments and deformation parameters have been calculated for Zn isotopes with neutrons (N=32,34,36 and 38 ). Nushellx code has been applied for all energy states of (fp-shell) nuclei. Shell-model calculations for the zinc isotopes have been carried out with active particles distributed in the lp, 0f and lp orbits outside doubly-magic closed "56Ni"core nucleus. By using (f5p) model space and (f5pvh) interaction, the theoretical results have been obtained and compared with the available experimental results. The excited energies values, electric transition probability B(E2), intrinsic quadrupole moment (Q) and deformation parameters () have been appeared at complete agreement with the experimental values. As well as, the energy levels have been confirmed and determined for the angular momentum and parity of experimental values which have not been well established and determined experimentally. On the other hand, it has been predicted some of the new energy levels and electric transition probabilities for the Zn isotopes under this study which were previously unknown in experimental information.
[Submitted on 1 Jul 2020]
We study the meson photoproduction on protons and nuclei at the near-threshold center-of-mass energies below 11.4 GeV (or at the corresponding photon laboratory energies below 68.8 GeV). We calculate the absolute excitation functions for the non-resonant and resonant photoproduction of mesons off protons at incident photon laboratory energies of 63--68 GeV by accounting for direct () and two-step () production channels within different scenarios for the non-resonant total cross section of elementary reaction and for branching ratios of the decays . We also calculate an analogous functions for photoproduction of mesons on C and Pb target nuclei in the near-threshold center-of-mass beam energy region of 9.0--11.4 GeV by considering respective incoherent direct () and two-step (, ) production processes within a nuclear spectral function approach. We show that a detailed scan of the total photoproduction cross section on a proton and nuclear targets in the near-threshold energy region in future high-precision experiments at the proposed high-luminosity electron-ion colliders EIC and EicC in the U.S. and China should give a definite result for or against the existence of the non-strange hidden-bottom pentaquark states and (1, 2, 3) as well as clarify their decay rates.
[Submitted on 1 Jul 2020]
We calculate the -matrices of elastic pion-nucleon () scattering up to fourth order in SU(3) heavy baryon chiral perturbation theory. The pertinent low-energy constants are determined by fitting to phase shifts below 200 MeV pion laboratory momentum in the physical region. The scattering lengths and scattering volumes are extracted from the chiral amplitudes, and turn out to be in good agreement with those of other approaches and the available experimental values. We also discuss the subthreshold parameters and the related issues. On the basis of the various phase shifts, the threshold parameters and the subthreshold parameters, the convergence of the chiral expansion is analyzed in detail. The calculation provides the possibility to consider explicitly more complex processes involving strangeness.
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