Nuclear Theory·nucl-th

Wednesday·February 14, 2024

8 papers—5 primary·3 cross-listed

01
[Submitted on 11 Feb 2024]
Alpha-like correlations in $^{20}$ Ne, comparison of quartetting wave function and THSR approaches
G. Röpke · C. Xu · B. Zhou · Z. Z. Ren · Y. Funaki · H. Horiuchi · M. Lyu · A. Tohsaki · T. Yamada
$^{20}$ Ne can be considered as a double-magic $^{16}$ O core nucleus surrounded by four nucleons, the constituents of an $α$ -like quartet. Similar to other nuclei ( $^{212}$ Po, $^{104}$ Ti, etc.) with a quartet on top of a double-magic core nucleus, significant $α$ -like correlations are expected. Correlations in the ground state of $^{20}$ Ne are investigated using different approaches. The quartetting wave function approach (QWFA) predicts a large $α$ -like cluster contribution near the surface of the nuclei. The Tohsaki-Horiuchi-Schuck-Röpke (THSR) approach describes $α$ -like clustering in nuclear systems. The results of the QWFA in the Thomas-Fermi and shell-model approximation are compared with THSR calculations for the container model. Results for the $α$ formation probability and the rms radii are shown.
Comments:
15 pages, 15 figures. arXiv admin note: text overlap with arXiv:1810.01274
Subjects:
Nuclear Theory (nucl-th)
arXiv:
2402.07962 [pdf]
EPJA(2024)·8 citations
02
[Submitted on 13 Feb 2024]
A=3 (e,e') $x_{B} \geq 1$ cross-section ratios and the isospin structure of short-range correlations
A. Schmidt · A. W. Denniston · E. M. Seroka · N. Barnea · D.W. Higinbotham · I. Korover · G.A. Miller · E. Piasetzky · M. Strikman · L.B. Weinstein · R. Weiss · O. Hen
We study the relation between measured high- $x_{B}$ , high- $Q^{2}$ , Helium-3 to Tritium, $(e, e^{'})$ inclusive-scattering cross-section ratios and the relative abundance of high-momentum neutron-proton ( $n p$ ) and proton-proton ( $pp$ ) short-range correlated (SRC) nucleon pairs in three-body ( $A = 3$ ) nuclei. Analysis of this data using a simple pair-counting cross-section model suggested a much smaller $n p / pp$ ratio than previously measured in heavier nuclei, questioning our understanding of $A = 3$ nuclei and, by extension, all other nuclei. Here we examine this finding using spectral-function-based cross-section calculations, with both an \textit{ab initio} $A = 3$ spectral function and effective Generalized Contact Formalism (GCF) spectral functions using different nucleon-nucleon interaction models. The \textit{ab initio} calculation agrees with the data, showing good understanding of the structure of $A = 3$ nuclei. An 8\% uncertainty on the simple pair-counting model, as implied by the difference between it and the \textit{ab initio} calculation, gives a factor of 5 uncertainty in the extracted $n p / pp$ ratio. Thus we see no evidence for the claimed ``unexpected structure in the high-momentum wavefunction for hydrogen-3 and helium-3''.
Comments:
6 pages, 4 figures
Subjects:
Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
arXiv:
2402.08199 [pdf]
PRC(2024)·3 citations
03
[Submitted on 13 Feb 2024]
Elastic Electron Scattering from Deformed and Oriented Odd-A Nuclei
Pedro Sarriguren
Interference terms between monopole and quadrupole Coulomb form factors that contribute to the cross-section of electron scattering from polarized nuclei are studied within the plane wave Born approximation. By experimentally exploring the effect of this nuclear response, valuable insights into the sign of the quadrupole deformation can be obtained. The nuclear structure is evaluated numerically using a self-consistent deformed Hartree-Fock approximation with Skyrme effective interactions and accounting for pairing correlations. To illustrate the practical applicability, several examples of odd-A nuclei with different spins and deformations are examined. Comparison of unpolarized and polarized cross-sections becomes a tool to discriminate between the oblate and prolate nature of the nuclear shape, providing a deeper understanding of the nuclear deformation.
Comments:
13 pages, 30 figures
Subjects:
Nuclear Theory (nucl-th)
arXiv:
2402.08304 [pdf]
PRC(2024)·3 citations
04
[Submitted on 13 Feb 2024]
A novel solution to the hyperon-puzzle in neutron stars
A. Chorozidou · T. Gaitanos
Neutron stars offer a great opportunity to study highly compressed hadronic matter experimentally and theoretically. However, the so-called hyperon-puzzle arises at neutron star densities. The hyperon coexistence with other particles in compressed matter softens the equation of state and many widely-accepted models fail to reproduce precise observations of large neutron star masses. Here, we propose a novel mechanism to retain the stiffness of the high density state with hyperons by considering the explicit momentum dependence of their in-medium potentials. Our approach modifies conventional strangeness threshold conditions and generates new threshold effects on hyperons in high-density matter. We demonstrate these effects within the Non-Linear Derivative model, which incorporates baryon momentum-dependent fields based on empirical and microscopic studies. It turns out that even soft momentum-dependent strangeness fields do prohibit their populations in neutron star matter. The generic momentum dependence of strangeness potentials, as modeled by the non-linear derivative approach, is crucial for resolving the long-standing hyperon-puzzle in neutron stars.
Comments:
5 pages, 3 figures. To appear in Physical Review C as a letter
Subjects:
Nuclear Theory (nucl-th)
arXiv:
2402.08329 [pdf]
1 citation
05
[Submitted on 13 Feb 2024]
Finite density QCD equation of state: critical point and lattice-based $T^{'}$ -expansion
Micheal Kahangirwe🇺🇸 · Steffen A. Bass🇺🇸 · Elena Bratkovskaya🇩🇪 · Johannes Jahan🇺🇸 · Pierre Moreau🇺🇸 · Paolo Parotto🇮🇹 · Damien Price🇺🇸 · Claudia Ratti🇺🇸 · Olga Soloveva🇩🇪 · Mikhail Stephanov🇺🇸
We present a novel construction of the QCD equation of state (EoS) at finite baryon density. Our work combines a recently proposed resummation scheme for lattice QCD results with the universal critical behavior at the QCD critical point. This allows us to obtain a family of equations of state in the range $0 \leq μ_{B} \leq 700$ MeV and 25 MeV $\leq T \leq 800$ MeV, which match lattice QCD results near $μ_{B} = 0$ while featuring a critical point in the 3D Ising model universality class. The position of the critical point can be chosen within the range accessible to beam-energy scan heavy-ion collision experiments. The strength of the singularity and the shape of the critical region are parameterized using a standard parameter set. We impose stability and causality constraints and discuss the available ranges of critical point parameter choices, finding that they extend beyond earlier parametric QCD EoS proposals. We present thermodynamic observables, including baryon density, pressure, entropy density, energy density, baryon susceptibility and speed of sound, that cover a wide range in the QCD phase diagram relevant for experimental exploration.
Comments:
16 pages, 18 figures
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph)
arXiv:
2402.08636 [pdf]
PRD(2024)·38 citations
06
[Submitted on 12 Feb 2024] (cross-list from hep-ph)
Neutrinoless double beta decay rates in the presence of light sterile neutrinos
W. Dekens🇺🇸 · J. de Vries🇳🇱 · D. Castillo🇪🇸 · J. Menéndez🇪🇸 · E. Mereghetti🇺🇸 · V. Plakkot🇳🇱 · P. Soriano🇪🇸 · G. Zhou🇨🇳
We investigate neutrinoless double-beta decay ( $0 ν β β$ ) in minimal extensions of the Standard Model of particle physics where gauge-singlet right-handed neutrinos give rise to Dirac and Majorana neutrino mass terms. We argue that the standard treatment of these scenarios, based on mass-dependent nuclear matrix elements, is missing important contributions to the $0 ν β β$ amplitude. First, new effects arise from the exchange of neutrinos with very small (ultrasoft) momenta, for which we compute the associated nuclear matrix elements for the decays of $^{76}$ Ge and $^{136}$ Xe. These contributions can dominate the $0 ν β β$ rate in cases with light sterile neutrinos. The ultrasoft terms are also relevant in the more standard scenario of just three light Majorana neutrinos where they lead to a $10%$ reduction of the total $0 ν β β$ amplitude. Secondly, we highlight the importance of short-range terms associated with medium-heavy sterile neutrinos and provide explicit formulae that can be used in phenomenological analyses. As examples we discuss impact of these new effects in several explicit scenarios, including a realistic $3 + 2$ model with two right-handed gauge-singlet neutrinos.
Comments:
v2 corresponds to the published version; added user-friendly Mathematica NB for computation of lifetimes for $^{76}$ Ge and $^{136}$ Xe
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
2402.07993 [pdf]
JHEP(2024)·32 citations
07
[Submitted on 13 Feb 2024] (cross-list from cond-mat.mtrl-sci)
Effect of electron-phonon coupling on thermal transport in metals: a Monte Carlo approach for solving the coupled electron-phonon Boltzmann transport equations
Jie Peng · W. Ryan Deskins · Maria Helena Braga · Anter El-Azab
In this work, the effect of electron-phonon (e-ph) coupling on both electron and phonon transport of metals is investigated via first principles calculations. A Monte-Carlo (MC) approach for solving the coupled electron-phonon Boltzmann transport equations is developed to investigate thermal conductivity of metals. In this approach, the anisotropic electron band structure, phonon dispersion in the full Brillouin zone, and mode-dependent thermal relaxation time of electrons and phonons are calculated from first principles. Using this approach, MC simulations of coupled e-ph thermal transport at different temperatures in {\alpha}-U and Ag are performed. These two materials were selected as a way to demonstrate the applicability of the method in different fields. The results indicate that the electron relaxation time due to phonon scattering is orders of magnitude smaller than the phonon relaxation time due to electron scattering. The results also show that, in phonon thermal transport, the impact of ph-e scattering is almost negligible and the ph-ph scattering dominates phonon transport. At high temperature, the electrons dominate thermal transport in both {\alpha}-U and Ag. However, at low temperature, the phonon contribution to the total thermal conductivity of {\alpha}-U is significant. Moreover, the Lorenz ratio deviates from the Sommerfeld value at low to intermediate temperatures, where the Wiedemann-Franz law is not applicable. Finally, we show that the Ag electronic thermal conductivity shows a stronger size effect than its phonon thermal conductivity.
Comments:
36 Pages, 14 Figures
Subjects:
cond-mat.mtrl-sci (cond-mat.mtrl-sci); Nuclear Theory (nucl-th)
arXiv:
2402.08150 [pdf]
AIP Adv.(2025)·0 citations
08
[Submitted on 13 Feb 2024] (cross-list from hep-ph)
Constraints on Variation of the Weak Scale from Big Bang Nucleosynthesis
Anne-Katherine Burns🇺🇸 · Venus Keus🇮🇪 · Marc Sher🇺🇸 · Tim M.P. Tait🇺🇸
Recently, the EMPRESS collaboration has included new data in the extraction of the primordial $^{4}$ He abundance from Big Bang Nucleosynthesis (BBN), resulting in a determination that differs from the previous value and from theoretical expectations. There have been several studies attempting to explain this anomaly which involve variation of fundamental constants between the time of BBN and the present. Since the Higgs vacuum expectation value (vev) is the only dimensionful parameter in the Standard Model and it is already known to vary during the electroweak phase transition, we consider the possibility that the vev is slightly different during BBN compared to its present value. A modification of the vev changes not only particle masses but also affects, through mass thresholds, the QCD confinement scale. We use the recently developed PRyMordial program to study this variation and its impact on the $^{4}$ He and deuterium abundances. We find that bounds on $∣ δ v / v ∣$ are approximately $0.01$ , and that the EMPRESS result can be explained within $2 σ$ if $0.008 < δ v / v < 0.02$ , but at the cost of worsening the current $2 σ$ discrepancy in the deuterium abundance to over $3 σ$ .
Comments:
Version to be published in PRD, 12 pages, 4 figures
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Astrophysical Phenomena (astro-ph.HE); Nuclear Theory (nucl-th)
arXiv:
2402.08626 [pdf]
PRD(2024)·14 citations

Affiliations

first authorsco-authorsvia INSPIRE