Nuclear Theory·nucl-th

Thursday·December 8, 2022

7 papers—1 primary·6 cross-listed

01
Time-dependent Dirac equation applied to one-proton radioactive emission
Tomohiro Oishi
Relativistic energy-density functional (REDF) theory has been developed and utilized for self-consistent meanfield calculations of atomic nuclei. The proton-emitting radioactivity can provide a suitable reference to improve the predicting ability of REDF especially on the proton-drip line. One needs to consider the quantum tunneling effect, which plays an essential role in nucleon-emitting radioactive processes. However, the relativistic quantum tunneling has been less investigated compared with the non-relativistic case. This work is devoted to a theoretical evaluation of one-proton ( $1 p$ ) radioactivity based on the relativistic Dirac formalism. For this purpose, I develop the time-dependent (TD) Dirac-spinor calculation to simulate the $1 p$ emission. By utilizing the relativistic Hartree-Bogoliubov (RHB) calculation with the DD-PCX parameters, single-proton potentials for the time-dependent Dirac spinor are determined. The TD-Dirac calculation is applied to the $1 p$ emissions from the $^{37}$ Sc and $^{39}$ Sc nuclei, which can be well approximated as the valence proton and the proton-close-shell cores. The sensitivity of $1 p$ -emission energy and decaying width to the mass number is demonstrated. Remarkable sensitivity exists due to the size of system, which affects the nuclear part of potentials and energy levels, whereas the Coulomb barrier is common with the same atomic number. The calculated $1 p$ energy and decaying lifetime are roughly consistent to the experimental limitation. The present TD-Dirac calculation is expected as applicable widely to proton-rich nuclides in order to improve the REDF by utilizing the $1 p$ -emission data.
nucl-thnucl-exPRC(2023)·5 citations
02
Life at the Landau pole
Paul Romatschke🇺🇸
If a quantum field theory has a Landau pole, the theory is usually called 'sick' and dismissed as a candidate for an interacting UV-complete theory. In a recent study on the interacting 4d O(N) model at large N, it was shown that at the Landau pole, observables remain well-defined and finite. In this work, I study both relevant and irrelevant deformations of the said model at the Landau pole, finding that physical observables remain unaffected. Apparently, the Landau pole in this theory is benign. As a phenomenological application, I compare the O(N) model to QCD, by identifying $Λ_{MS}$ with the Landau pole in the O(N) model.
↳ hep-thhep-phnucl-thAppliedMath(2024)·19 citations
03
Monopoles, spectra of overlap fermions, and eta-prime meson in external magnetic fields
Masayasu Hasegawa🇷🇺
The effects of external magnetic fields on monopoles, spectra of the overlap Dirac operator, instantons, and the mass of the eta-prime meson are examined by conducting lattice QCD simulations. The uniform external magnetic fields are applied to gauge field configurations with $N_{f}$ = 2 + 1 flavor quarks. The bare quark masses are tuned in order to obtain the physical values of the pion mass and of the ratio $\frac{m _{s}}{m _{u, d}}$ . Standard configurations and configurations with applied external magnetic fields are generated in the color confinement and deconfinement phases. The intensity of external magnetic fields varies from $e ∣ B ∣$ = 0.57 to 1.14 [GeV $^{2}$ ]. To examine the influence of external magnetic fields on monopoles, we first calculate the monopole density, measure the lengths of the monopole loops and compare them with the absolute value of the Polyakov loops. Next, using the generated configurations, we compute the eigenvalues and eigenvectors of the overlap Dirac operator, which preserves exact chiral symmetry. To investigate how external magnetic fields affect the spectra of the overlap Dirac operator, we compute spectral densities, compare fluctuations of the eigenvalues of the overlap Dirac operator with the predictions of random matrix theory, and estimate the number of instantons and anti-instantons from the topological charges. In addition, we analyze smearing effects on these observables and chiral symmetry breaking. Finally, we calculate the decay constant of the pseudoscalar meson, the chiral condensate, and the square mass of the eta-prime meson using the eigenvalues and eigenvectors. We then extrapolate the numerical results in the chiral limit and demonstrate the effects of external magnetic fields on the extrapolation results. This article presents preliminary results.
↳ hep-latnucl-exnucl-thTheor.Math.Phys.(2024)·0 citations
04
Finite width effects on the azimuthal asymmetry in proton-nucleus collisions in the Color Glass Condensate
Pedro Agostini🇵🇱 · Tolga Altinoluk🇵🇱 · Néstor Armesto🇪🇸
We perform a numerical analysis of the two particle azimuthal correlations at central rapidities generated in $p$ A collisions within the framework of the Color Glass Condensate. We extend the standard computations to include the subeikonal corrections which stem from considering the finite longitudinal width of the dense target. For practical reasons, we only consider the next-to-next-to-eikonal corrections instead of using the all-order expressions for the inclusive two gluon production cross section. We show that the subeikonal terms that we account for in the two gluon yields contribute to both even and odd harmonics, the latter being absent in the standard Color Glass Condensate calculations performed at eikonal accuracy. Our analysis confirms the vanishing of the subeikonal effects with increasing collision energy and when going to forward rapidities, as expected.
↳ hep-phnucl-thPLB(2023)·21 citations
05
Understanding globular cluster abundances through nuclear reactions
P Adsley🇺🇸 · M Williams🇨🇦 · D S Harrouz🇫🇷 · D P Carrasco-Rojas🇺🇸 · N de Séréville🇫🇷 · F Hammache🇫🇷 · R Longland🇺🇸 · B Bastin🇫🇷 · B Davids🇨🇦 · T Faestermann🇩🇪 · C Fougères🇫🇷 · U Greife🇺🇸 and 15 other authors
Globular clusters contain multiple stellar populations, with some previous generation of stars polluting the current stars with heavier elements. Understanding the history of globular clusters is helpful in understanding how galaxies merged and evolved and therefore constraining the site or sites of this historic pollution is a priority. The acceptable temperature and density conditions of these polluting sites depend on critical reaction rates. In this paper, three experimental studies helping to constrain astrophysically important reaction rates are briefly discussed.
↳ nucl-exastro-ph.GAastro-ph.SRnucl-thJ.Phys.Conf.Ser.(2023)·1 citation
06
Transfer Reactions in Nuclear Astrophysics
Philip Adsley
Transfer reactions are an important tool in nuclear astrophysics. These reactions allow us to identify states in nuclei and to find the corresponding energies, to determine if these states can contribute to astrophysical nuclear reactions and ultimately to determine the strength of that contribution. In this paper, the basic details of how transfer reactions may be used in nuclear astrophysics are set out along with some common pitfalls to avoid.
↳ nucl-exnucl-thEPJ Web Conf.(2023)·1 citation
07
Collisional flavor instability in dense neutrino gases
Zewei Xiong (GSI)🇩🇪 · Lucas Johns (Berkeley)🇺🇸 · Meng-Ru Wu (Academia Sinica)🇹🇼 · Huaiyu Duan (UNM)🇺🇸
Charged-current neutrino processes such as $ν_{e} + n ⇌ p + e^{-}$ and $ν ˉ_{e} + p ⇌ n + e^{+}$ destroy the flavor coherence among the weak-interaction states of a single neutrino and thus damp its flavor oscillation. In a dense neutrino gas such as that inside a core-collapse supernova or the black hole accretion disk formed in a compact binary merger, however, these "collision" processes can trigger large flavor conversion in cooperation with the strong neutrino-neutrino refraction. We show that there exist two types of collisional flavor instability in a homogeneous and isotropic neutrino gas which are identified by the dependence of their real frequencies on the neutrino density $n_{ν}$ . The instability transitions from one type to the other and exhibits a resonance-like behavior in the region where the net electron lepton number of the neutrino gas is negligible. In the transition region, the flavor instability grows exponentially at a rate $\propto n_{ν}^{1/2}$ . We find that the neutrino gas in the black hole accretion disk is susceptible to the collision-induced flavor conversion where the neutrino densities are the highest. As a result, large amounts of heavy-lepton flavor neutrinos may be produced through flavor conversion, which can potentially have important ramifications in the subsequent evolution of the remnant.
↳ hep-phastro-ph.HEnucl-thPRD(2023)·69 citations

Affiliations

first authorsco-authorsvia INSPIRE

Time-dependent Dirac equation applied to one-proton radioactive emission

Life at the Landau pole

Monopoles, spectra of overlap fermions, and eta-prime meson in external magnetic fields

Finite width effects on the azimuthal asymmetry in proton-nucleus collisions in the Color Glass Condensate

Understanding globular cluster abundances through nuclear reactions

Transfer Reactions in Nuclear Astrophysics

Collisional flavor instability in dense neutrino gases

Affiliations