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Journal of Physics G: Nuclear and Particle Physics - latest papers
Latest articles for Journal of Physics G: Nuclear and Particle Physics
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Seniority-two valence-shell building blocks of the octupole phonon
The relative ordering of J− levels of multiplets resulting from two-body excitations, which include a Jπ = 3− state that can contribute to the octupole phonon, are investigated in a simplistic shell-model approach. To calculate the relative level ordering, harmonic oscillator wavefunctions and a residual δ interaction are used. The simplistic approach confirms for the particle-particle channel, the often stated preference of the Δj = 3, Δl = 3 subshell combination over the Δj = 3, Δl = 1 subshell combination through an enhanced energy gain. Furthermore, it is shown that, in the particle–hole channel, the gain is less pronounced for the Δj = 3, Δl = 3 subshell configuration. In combination with the overall structure of an oscillator shell, these results explain the comparatively low excitation energy for 3 excitations observed for the octupole-soft proton and neutron numbers predicted by various models.
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Surface and curvature tensions in relativistic mean-field models
The present paper shows a simple method to obtain fittings for the surface and curvature tensions. The method uses the nuclear mass of a spherical, fully ionized atom and a simple expression for the binding energy such that a least square fit is found when confronted with the atomic mass evaluation 2020. The fittings are then used to evaluate the pasta phase free energy per particle, which is confronted with the one obtained with a Thomas–Fermi fitting. The results are very encouraging and suggest that this recipe can be safely used whenever the surface and curvature tensions are necessary.
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Electromagnetic moments in the Sn-Gd region determined within nuclear DFT
Within the nuclear density functional theory framework, employing the Skyrme UNEDF1 functional and incorporating pairing correlations, we determined the spectroscopic electric quadrupole and magnetic dipole moments of the ν11/2− and π7/2+ configurations in heavy, deformed, open-shell odd nuclei with 50 ≤ Z ≤ 64. The notions of self-consistent shape and spin polarisations due to odd nucleons responsible for generating total electric quadrupole and magnetic dipole moments were transformed into detailed computational procedures. The alignment of intrinsic angular momentum along the axial symmetry axis, necessitating signature and time-reversal symmetry breaking, followed by the restoration of rotational symmetry, proved to be essential components of the method. In contrast, the restoration of particle number symmetry yields modifications of only about 1%. With the isovector spin-spin terms of the functional previously adjusted in near doubly magic nuclei across the mass chart, the calculations were parameter-free. Effective charges and g-factors were not employed. A reasonably good agreement was achieved between the calculated and measured electric quadrupole moments. A similarly fair description of the magnetic dipole moments was obtained for the intruder configurations ν11/2− alongside a poor description of those for π7/2+.
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Sensitivity of the neutrino transmission coefficient at high energies to the Earth’s density profile
The flux of atmospheric and astrophysical neutrinos measured in ultra-high-energy (UHE) neutrino detectors is strongly dependent on the description of the propagation and absorption of the neutrinos during the passage through Earth to the detector. In particular, the attenuation of the incident neutrino flux depends on the details of the matter structure between the source and the detector. In this paper, we will investigate the impact of different descriptions for the density profile of Earth on the transmission coefficient, defined as the ratio between the flux measured in the detector and the incoming neutrino flux. We will consider five different models for the Earth’s density profile and estimate how these different models modify the target column density and transmission coefficients for different flavors. The results are derived by solving the cascade equations taking into account the neutral current interactions and tau regeneration. A comparison with approximated solutions is also presented. Our results indicated that the predictions are sensitive to the model considered for the density profile, with the simplified three layer model providing a satisfactory description when compared with the Preliminary Reference Earth Model results. Our results also showed that the more simplified models with two or one layer fail mainly for neutrinos that cross a small column of matter and are not good approximations for the neutrino propagation. These findings highlight the importance of using realistic Earth density models in UHE neutrino analyses, as simplified models may lead to misestimations in the predicted attenuation effects.
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Impact of soft QCD effects over intrajet azimuthal anisotropies
Observations of collective signatures within jets of particles have been recently reported by measurements at the Large Hadron Collider at CERN laboratory, providing insights on the minimum conditions required for forming a Quark Gluon Plasma state. A quantitative comparison with data measurements on intrajet azimuthal anisotropies and predictions from PYTHIA event generator soft quantum chromodynamics (QCD) model parameter tunes: Monash, CP5, and QCD-scheme colour reconnection (CR) is presented. Energetic jets with transverse momentum over 550 GeV from proton–proton collisions at 13 TeV are reconstructed. Results from predictions using the standard E-scheme (ES) and jet axis choice are compared with those from the winner-take-all (WTA) frame. Significant differences are present between predictions from WTA and ES frames at the lowest and highest intrajet charged particles multiplicities ( ), with the QCD-scheme CR tune showing the smallest variation between frames. Predictions for v2 at the highest are consistent with the data measurements at a 2.3σ uncertainty level. These results set new guidance towards the search for intrajet collective effects and understanding of nonperturbative QCD dynamics originated from a single parton.