Nuclear Theory·nucl-th

Tuesday·February 22, 2022

9 papers—8 primary·1 cross-listed

01
[Submitted on 18 Feb 2022]
The need for a local nuclear physics feature in the neutron-rich rare-earths to explain solar $r$ -process abundances
Nicole Vassh · Gail C. McLaughlin · Matthew R. Mumpower · Rebecca Surman
We apply Markov Chain Monte Carlo to predict the masses required to form the observed solar $r$ -process rare-earth abundance peak. Given highly distinct astrophysical outflows and nuclear inputs, we find that results are most sensitive to the $r$ -process dynamics (i.e. overall competition between reactions and decays), with similar mass trends predicted given similar dynamics. We show that regardless of whether fission deposits into the rare-earths or not, our algorithm consistently predicts the need for a local nuclear physics feature of enhanced stability in the neutron-rich lanthanides.
Subjects:
Nuclear Theory (nucl-th)
arXiv:
2202.09437 [pdf]
9 citations
02
[Submitted on 20 Feb 2022]
Van der Waals equation of state for asymmetric nuclear matter
A.I. Sanzhur (Institute for Nuclear Research, Kyiv, Ukraine)
The application of van der Waals equation of state to the asymmetric nuclear matter is considered in a critical state region. The corrections to the van der Waals pressure and free energy due to the Fermi statistics are obtained starting from the Thomas--Fermi entropy expression which ensures the fulfilment of Nernst theorem. The derived corrections account for the effective nucleon mass and neutron-proton isotopic asymmetry. The parameters of van der Waals equation of state are deduced taking the experimental value of critical temperature for symmetric nuclear matter and testing the model of van der Waals with statistics corrections included against the theory of Skyrme energy density functional. Critical line in pressure-temperature-composition space is considered. Incompressibility coefficient is determined along the critical line as a function of nuclear matter composition. Jump in the value of specific heat upon crossing critical line is discussed.
Comments:
15 pages, 2 figures, 2 tables, published in Nucl. Phys. At. Energy
Subjects:
Nuclear Theory (nucl-th)
arXiv:
2202.09749 [pdf]
Nucl.Phys.Atom.Energy(2022)·4 citations
03
[Submitted on 21 Feb 2022]
Scale symmetry and composition of compact star matter
Long-Qi Shao🇨🇳 · Yong-Liang Ma🇨🇳
The dense compact star matter is studied by using the skyrmion crystal approach. The chiral effective theory used includes the lightest scalar meson, the lowest-lying vector mesons as well as pions. Consistency with the vector manifestation and the dilaton limit fixed point at high density constrains the anomalous dimension of the gluon field $1.0 ≲ ∣ γ_{G^{2}} ∣ ≲ 2.0$ and leads to the significance of the scale symmetry breaking in the intrinsic parity-odd part of the effective theory. The speed of sound $v_{s}^{2} ≃ 1/3$ and the polytropic index $γ ≃ 1$ -- both satisfy the conformal limits -- after the dilaton limit fixed point at high density but the matter is still in the hadronic phase. This means that neither the conformal speed of sound nor the smallness of the polytropic index can be used as a criterion of the onset of quark matter. These conclusions are significant for constructing the equation of state of nuclear matter.
Comments:
6 pages, 5 figures
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph)
arXiv:
2202.09957 [pdf]
PRD(2022)·11 citations
04
[Submitted on 21 Feb 2022]
Role of Tensor Interaction as Salvation of Cluster Structure in $^{44}$ Ti
Chikako Ishizuka · Hiroki Takemoto · Yohei Chiba · Akira Ono · Naoyuki Itagaki
Background: The $^{44}$ Ti nucleus has been known to have a $^{40}$ Ca+ $α$ cluster structure, and inversion doublet structure has been observed; however, $α$ cluster structure tends to be washed out when the breaking of the $α$ cluster is allowed due to the spin-orbit interaction. Nevertheless, $α$ clustering in medium-heavy nuclei is quite a hot subject recently. Purpose: The tensor interaction has been known to play an essential role in the strong binding of the $^{4}$ He nucleus, which induces the two-particle-two-hole (2p2h) excitation. Since this excitation is blocked when another nucleus approaches, it is worthwhile to show whether the tensor effect works to keep the distance between $^{4}$ He and $^{40}$ Ca and becomes the salvation of the clustering in $^{44}$ Ti. Methods: The spin-orbit effect is included in the cluster model by using the antisymmetrized quasi cluster model (AQCM) developed by the authors. We have also developed an improved version of the simplified method to include the tensor contribution ( $i$ SMT), which allows us to estimate the tensor effect within the cluster model. The competition of these two is investigated in the medium-heavy mass region for the first time. Results: According to AQCM, the spin-orbit interaction completely breaks the $α$ cluster and restores the symmetry of $j j$ -coupling shell model when the $α$ cluster approaches the $^{40}$ Ca core. On the other hand, $i$ SMT gives a large distance between $α$ and $^{40}$ Ca due to the tensor effect. Conclusions: In $^{44}$ Ti, because of the strong spin-orbit and tensor contributions, two completely different configurations ( $j j$ -coupling shell model and cluster states) almost degenerate, and their mixing becomes important.
Comments:
7 pages, 4 figures
Subjects:
Nuclear Theory (nucl-th)
arXiv:
2202.10016 [pdf]
PRC(2022)·7 citations
05
[Submitted on 21 Feb 2022]
Lorentz-covariant kinetic theory for massive spin-1/2 particles
Xin-Li Sheng🇨🇳 · Qun Wang🇨🇳 · Dirk H. Rischke🇩🇪
We construct a matrix-valued spin-dependent distribution function (MVSD) for massive spin-1/2 fermions and study its properties under Lorentz transformations. Such transformations result in a Wigner rotation in spin space and in a nontrivial matrix-valued shift in space-time, which corresponds to the side jump in the massless case. We express the vector and axial-vector components of the Wigner function in terms of the MVSD and show that they transform in a Lorentz-covariant manner. We then construct a manifestly Lorentz-covariant Boltzmann equation which contains a nonlocal collision term encoding spin-orbit coupling. Finally, we obtain the spin-dependent distribution function in local equilibrium by demanding detailed balance.
Comments:
7 pages, 1 figure
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph)
arXiv:
2202.10160 [pdf]
PRD(2022)·31 citations
06
[Submitted on 21 Feb 2022]
Spectroscopic properties of 4He within a multiphonon approach
G. De Gregorio · F. Knapp · N. Lo Iudice · P. Veselý
Bulk and spectroscopic properties of 4He are studied within an equation of motion phonon method. Such a method generates a basis of n-phonon (n = 0, 1, 2, 3...) states composed of tensor products of particle-hole Tamm-Dancoff phonons and then solves the full eigenvalue problem in such a basis. The method does not rely on any approximation and is free of any contamination induced by the center of mass, in virtue of a procedure exploiting the singular value decomposition of rectangular matrices. Two potentials, both derived from the chiral effective field theory, are adopted in a self-consistent calculation performed within a space including up to three phonons. The latter basis states are treated under a simplifying assumption. A comparative analysis with the experimental data points out the different performances of the two potentials. It shows also that the calculation succeeds only partially in the description of the spectroscopic properties and suggests a recipe for further improvements.
Comments:
Accepted for publication on Phys. Rev. C
Subjects:
Nuclear Theory (nucl-th)
arXiv:
2202.10266 [pdf]
PRC(2022)·11 citations
07
[Submitted on 21 Feb 2022]
Benchmark calculations of infinite neutron matter with realistic two- and three-nucleon potentials
A. Lovato🇺🇸 · I. Bombaci🇮🇹 · D. Logoteta🇮🇹 · M. Piarulli🇺🇸 · R. B. Wiringa🇺🇸
We present the equation of state of infinite neutron matter as obtained from highly-realistic Hamiltonians that include nucleon-nucleon and three-nucleon coordinate-space potentials. We benchmark three independent many-body methods: Brueckner-Bethe-Goldstone (BBG), Fermi hypernetted chain/single-operator chain (FHNC/SOC), and auxiliary-field diffusion Monte Carlo (AFDMC). We find them to provide similar equations of state when the Argonne $v_{18}$ and the Argonne $v_{6}^{'}$ nucleon-nucleon potentials are used in combination with the Urbana IX three-body force. Only at densities larger than about 1.5 the nuclear saturation density ( $ρ_{0} = 0.16 fm^{- 3}$ ) the FHNC/SOC energies are appreciably lower than the other two approaches. The AFDMC calculations carried out with all of the Norfolk potentials fitted to reproduce the experimental trinucleon ground-state energies and $n d$ doublet scattering length yield unphysically bound neutron matter, associated with the formation of neutron droplets. Including tritium $β$ -decay in the fitting procedure, as in the second family of Norfolk potentials, mitigates but does not completely resolve this problem. An excellent agreement between the BBG and AFDMC results is found for the subset of Norfolk interactions that do not make neutron-matter collapse, while the FHNC/SOC equations of state are moderately softer.
Comments:
15 pages, 3 figures. arXiv admin note: text overlap with arXiv:1908.04426
Subjects:
Nuclear Theory (nucl-th); High Energy Astrophysical Phenomena (astro-ph.HE); Nuclear Experiment (nucl-ex)
arXiv:
2202.10293 [pdf]
PRC(2022)·48 citations
08
[Submitted on 21 Feb 2022]
Pion-induced radiative corrections to neutron beta-decay
Vincenzo Cirigliano🇺🇸 · Jordy de Vries🇳🇱 · Leendert Hayen🇺🇸 · Emanuele Mereghetti🇺🇸 · André Walker-Loud🇺🇸
We compute the electromagnetic corrections to neutron beta decay using a low-energy hadronic effective field theory. We identify and compute new radiative corrections arising from virtual pions that were missed in previous studies. The largest correction is a percent-level shift in the axial charge of the nucleon proportional to the electromagnetic part of the pion-mass splitting. Smaller corrections, comparable to anticipated experimental precision, impact the $β$ - $ν$ angular correlations and the $β$ -asymmetry. We comment on implications of our results for the comparison of the experimentally measured axial charge with first-principle computations using lattice QCD and on the potential of $β$ -decay experiments to constrain beyond-the-Standard-Model interactions.
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Lattice (hep-lat); High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex)
arXiv:
2202.10439 [pdf]
PRL(2022)·65 citations
09
[Submitted on 21 Feb 2022] (cross-list from astro-ph.HE)
Prospects for Distinguishing Supernova Models Using a Future Neutrino Signal
Jackson Olsen🇺🇸 · Yong-Zhong Qian🇺🇸
The next Galactic core-collapse supernova (SN) should yield a large number of observed neutrinos. Using Bayesian techniques, we show that with an SN at a known distance up to 25 kpc, the neutrino events in a water Cherenkov detector similar to Super-Kamiokande (SK) could be used to distinguish between seven one-dimensional neutrino emission models assuming no flavor oscillations or the standard Mikheyev-Smirnov-Wolfenstein effect. Some of these models could still be differentiated with an SN at a known distance of 50 kpc. We also consider just the relative distributions of neutrino energy and arrival time predicted by the models and find that a detector like SK meets the requirement to distinguish between these distributions with an SN at an unknown distance up to $\sim 10$ kpc.
Comments:
12 pages, 2 figures
Subjects:
High Energy Astrophysical Phenomena (astro-ph.HE); High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
2202.09975 [pdf]
PRD(2022)·14 citations

Affiliations

first authorsco-authorsvia INSPIRE