Newsfeeds

Journal of Physics G: Nuclear and Particle Physics - latest papers

Latest articles for Journal of Physics G: Nuclear and Particle Physics

IOPscience

  • Testing quantum entanglement via quantum state tomography with muons
    Entanglement is a fundamental pillar of quantum mechanics. Probing quantum entanglement and testing Bell inequality with muons can be a significant leap forward, as the muon is arguably one of the best elementary particles that can be manipulated and detected over a wide range of energies, e.g. from approximately 0.3–102 GeV, corresponding to velocities from 0.94 to nearly the speed of light. In this work, we present a realistic proposal and a comprehensive study of quantum entanglement in a state composed of different-flavor fermions in muon–electron scattering. The polarization density matrix for the muon–electron system is derived using a kinematic approach within the relativistic quantum field theory framework. Entanglement in the resulting muon–electron qubit system and the violation of the Bell inequality can be observed with a high event rate. This paves the way for performing quantum tomography with muons.

  • Searching for long-lived particles in free neutron experiments
    We explore the decay of free neutrons into exotic long-lived particles, whose decays could be detected in the next-generation free neutron experiments. We show that such a possibility is viable as long as the exotic particle is highly mass-degenerate with the neutron, avoiding exclusion by large-volume detectors. We estimate the number of observable events and identify the most promising final states from both theoretical and experimental perspectives. Our analysis highlights the unique capability of the HIBEAM-NNBAR experiment at the European spallation source to probe this unexplored region of parameter space, opening a new avenue for exploring physics beyond the Standard Model. We estimate that several events per year could be observed in the NNBAR experiment.

  • 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.

  • 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+.

  • 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.