Nuclear Theory·nucl-th

Tuesday·November 23, 2021

13 papers—5 primary·8 cross-listed

01
[Submitted on 21 Nov 2021]
Kinetic model of excitation of pairing vibrations in superfluid nuclei
V.I. Abrosimov
Excitation of pairing vibrations in superfluid nuclei is studied by using a kinetic model based on the Vlasov equation with pairing, derived from the time-dependent Hartree-Fock-Bogolyubov theory. The anomalous density response function is used to find the monopole pairing mode and the dynamic variation of the pairing gap associated with this mode. The spectroscopic factor for the excitation of monopole pairing vibrations in two-neutron transfer reaction is estimated. It is found that the pairing correlations give rise to the same coherent contribution to the semiclassical spectroscopic factor as to the corresponding quantum expression, which is essentially determined by the distribution of the neutron levels near the Fermi energy. A numerical evaluation of the reduced spectroscopic factor for the excitation of monopole pairing vibrations in two-neutron transfer reaction in superfluid nuclei shows that it does not exceed several percent of the spectroscopic factor for the transfer of two neutrons to the ground state. This estimate is in agreement with the experimental data obtained for the ratio of the cross section for the excitation of 0+state in the (p,t) reaction in the energy region of double pairing gap to the cross section for the excitation of the ground state for superfluid nuclei of the rare-earth and actinide regions.
Comments:
11 pages, 2 figures. arXiv admin note: substantial text overlap with arXiv:1912.10963
Subjects:
Nuclear Theory (nucl-th)
arXiv:
2111.10921 [pdf]
Nucl.Phys.Atom.Energy(2022)·0 citations
02
[Submitted on 22 Nov 2021]
Dynamical synthesis of 4He in the scission phase of nuclear fission
Z. X. Ren · D. Vretenar · T. Niksic · P. W. Zhao · J. Zhao · J. Meng
In the exothermic process of fission decay, an atomic nucleus splits into two or more independent fragments. Several aspects of nuclear fission are not properly understood, in particular the formation of the neck between the nascent fragments, and the subsequent mechanism of scission into two or more independent fragments. Using an implementation of time-dependent density functional theory, based on a relativistic energy density functional and including pairing correlations, we analyze the final phase of the process of induced fission of $^{240}$ Pu, and show that the time-scale of neck formation coincides with the assembly of two $α$ -like clusters (less than 1 zs = 10 $^{- 21}$ s). Because of its much larger binding energy, the dynamical synthesis of 4He in the neck predominates over other light clusters, e.g., $^{3}$ H and $^{6}$ He. At the instant of scission the neck ruptures exactly between the two $α$ -like clusters, which separate because of the Coulomb repulsion and are eventually absorbed by the two emerging fragments. The newly proposed mechanism of light charged clusters formation at scission provides a natural explanation of ternary fission.
Comments:
5 pages, 4 figures, Final version for publication
Subjects:
Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
arXiv:
2111.11075 [pdf]
PRL(2022)·70 citations
03
[Submitted on 22 Nov 2021]
Partial muon capture rates in $A = 3$ and $A = 6$ nuclei with chiral effective field theory
G. B. King🇺🇸 · S. Pastore🇺🇸 · M. Piarulli🇺🇸 · R. Schiavilla🇺🇸
Searches for neutrinoless-double beta decay rates are crucial in addressing questions within fundamental symmetries and neutrino physics. The rates of these decays depend not only on unknown parameters associated with neutrinos, but also on nuclear properties. In order to reliably extract information about the neutrino, one needs an accurate treatment of the complex many-body dynamics of the nucleus. Neutrinoless-double beta decays take place at momentum transfers on the order of 100 MeV/ $c$ and require both nuclear electroweak vector and axial current matrix elements. Muon capture, a process in the same momentum transfer regime, has readily available experimental data to validate these currents. In this work, we present results of {\it ab initio} calculations of partial muon capture rates for $^{3}$ He and $^{6}$ Li nuclei using variational and Green's Function Monte Carlo computational methods. We estimate the impact of the three-nucleon interactions, the cutoffs used to regularize two-nucleon ( $2 N$ ) interactions, and the energy range of $2 N$ scattering data used to fit these interactions.
Comments:
10 pages, 5 figures including supplemental material; Re-analyzed GFMC $^{3}$ He muon capture with updated wave functions, conclusions unchanged
Subjects:
Nuclear Theory (nucl-th)
arXiv:
2111.11360 [pdf]
PRC(2022)·15 citations
04
[Submitted on 22 Nov 2021]
Transport near the chiral critical point
Alexander Soloviev🇺🇸
The evolution of a heavy ion collision passes close to the O(4) critical point of QCD, where fluctuations of the order parameter are expected to be enhanced. Using the appropriate stochastic hydrodynamic equations in mean field near the the pseudo-critical point, we compute how these enhanced fluctuations modify the transport coefficients of QCD. Finally, we estimate the expected critical enhancement of soft pion yields, which provides a plausible explanation for the excess seen in experiment relative to ordinary hydrodynamic computations.
Comments:
8 pages, 4 figures. Proceedings for A Virtual Tribute to Quark Confinement and the Hadron Spectrum (vConf21)
Subjects:
Nuclear Theory (nucl-th)
arXiv:
2111.11375 [pdf]
EPJ Web Conf.(2022)·3 citations
05
[Submitted on 22 Nov 2021]
Anomalous plasma: chiral magnetic effect and all that
Igor A. Shovkovy🇺🇸
Chiral anomalous effects in relativistic plasmas are reviewed. The essence of chiral separation and chiral magnetic effects is explained in simple terms. Qualitative differences between the two phenomena, both of which are triggered by background electromagnetic fields, are highlighted. It is shown how an interplay of the chiral separation and chiral magnetic effects could lead to a new collective plasma mode, called the chiral magnetic wave. It is argued that the chiral magnetic wave is overdamped in weakly interacting plasmas. Its fate in a strongly interacting quark-gluon plasma is less clear, especially in the presence of a superstrong magnetic field. The observational signatures of the chiral anomalous effects are discussed briefly.
Comments:
Contribution a Festschrift celebrating the career of Peter Suranyi. 25 pages, 2 figures
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph)
arXiv:
2111.11416 [pdf]
Chapter 18 in Peter Suranyi 87th Birthday…·9 citations

Affiliations

first authorsco-authorsvia INSPIRE

Kinetic model of excitation of pairing vibrations in superfluid nuclei

Dynamical synthesis of 4He in the scission phase of nuclear fission

Partial muon capture rates in A=3 and A=6 nuclei with chiral effective field theory

Transport near the chiral critical point

Anomalous plasma: chiral magnetic effect and all that

Affiliations

Partial muon capture rates in $A = 3$ and $A = 6$ nuclei with chiral effective field theory