The European Physical Journal A最新文献

This article provides a comprehensive review of the evolution of the nuclear shape concept, a cornerstone in nuclear physics. Tracing its historical development from the early 20th century, we highlight key milestones and paradigm shifts that have shaped our understanding. The review explores the transition from the initial spherical model to the introduction of nuclear deformation, emphasizing the contributions of the liquid drop model and the unified model. The pivotal role of nuclear shapes in elucidating various nuclear phenomena and their profound impact on both theoretical and experimental nuclear physics are discussed in depth. The article underscores the relevance of nuclear shape in contemporary physics, particularly in light of groundbreaking findings from ultra-relativistic heavy ion collisions. These recent results illustrate the enduring significance of nuclear shape in advancing our comprehension of nuclear structure and reactions.

The deuteron is the lightest spin-1 nucleus, consisting of a weakly bound system of two spin-(frac{1}{2}) nucleons. One intriguing characteristic of the deuteron is the tensor polarized structure, which cannot be naively constructed combining the proton and neutron structure. The tensor structure of the deuteron provides unique insights into the quarks and gluons distributions and their dynamics within the nucleus. It can be studied experimentally through inclusive and semi-inclusive Deep Inelastic Scattering (DIS) of electrons on tensor polarized deuterons. One-dimensional (longitudinal-momentum-dependent) tensor structure functions are extracted from the inclusive DIS, whereas three-dimensional with additional transverse-momentum-dependent tensor structure functions are extracted from the semi-inclusive DIS. Experimentally, achieving high tensor polarization for such measurements has been a challenge. Significant progress has recently been made in enhancing the tensor polarization for polarized deuteron target, opening up a new window for experimental studies of the deuteron tensor structure. In this article, we discuss the tensor structure functions of the deuteron and the experimental schemes to extract these functions at Jefferson Lab, highlighting the potential measurements of the transverse-momentum-dependent tensor structure functions.

The MAXED and GRAVEL unfolding algorithms have been used to determine cross-sections, with the NAXSUN method developed at JRC-Geel. This study explores the potential of a particular type of artificial neural network, the multilayer perceptron (MLP), as an alternative to traditional unfolding algorithms. By generating a training dataset using the TALYS 2.0 code and testing the MLP model on real experimental data, we compared the effectiveness of MLP in unfolding neutron-induced reactions cross sections involving indium and rhenium isotopes. The results were benchmarked against those obtained using standard unfolding algorithms and TALYS 2.0 simulations, demonstrating the advantages and limitations of the ANN approach. The obtained results show a much-reduced corridor of uncertainty in the derived cross-section curves compared to previous work using traditional unfolding techniques.

A new method is proposed for fitting non-relativistic binary-scattering data and for extracting the parameters of possible quantum resonances in the compound system that is formed during the collision. The method combines the well-known R-matrix approach with the analysis based on the semi-analytic representation of the Jost functions. It is shown that such a combination has the advantages of both these approaches, namely, the number of the fitting parameters remains relatively small (as for the R-matrix approach) and the proper analytic structure of the S-matrix is preserved (as for the Jost function method). It is also shown that the new formalism, although closely related to the R-matrix method, has the benefit of no dependence on an arbitrary channel radius. The efficiency and accuracy of the proposed method are tested using a model single-channel potential. Artificial “experimental” data generated with this potential are fitted, and its known resonances are successfully recovered as zeros of the Jost function on the appropriate sheet of the Riemann surface of the energy.

This work presents the Trojan Horse Method (THM) as a powerful technique for measuring nuclear reaction cross sections at astrophysical energies. We then explore the impact of THM-derived reaction rates on the predictions of Standard Big Bang Nucleosynthesis (SBBN) using the PRIMAT code. Primordial abundances are shown for the single rate impact and, for the first time, also for all the THM rates together. The result shows significant differences with the use of THM rates, which in some cases goes in the direction of improving the agreement with the observations with respect to the use of only reaction rates from direct data, especially for the (^7hbox {Li}) and deuterium abundances, which are still open issues for SBBN.

With (gamma )-ray tracking arrays, the angular correlation and, especially, the linear polarization of (gamma ) rays can be measured with high precision. However, because of the complexity of these spectrometers, measuring angular distributions is more involved. The techniques and associated formalisms were developed and established in the 1950s. The experimental setups of that era were relatively simple when compared to the advanced (gamma )-ray tracking arrays available today. This paper aims to review and refine these techniques, unify the nomenclatures and, specifically, adapt them for use with the newest tracking arrays. In addition, new methods for producing the required response functions for these arrays are introduced.

Photons as quantum bits have been amongst the first physical systems to be used for experimentally demonstrating some of the basic concepts in quantum computing starting from entanglement, to teleportation, to the realisation of a two-qubit CNOT gate and more recently for demonstrating quantum advantage using light. Photons can thus be used as qubits and are a potential platform for a future quantum computer. It is hard to predict which platform will win the race, perhaps none of them will surpass the others. What is for sure is that light can not be ignored altogether as this is the building block for communications and for propagating information in general, and thus for quantum information, in particular over long distances through optical fibres or via satellites. We will first develop what are the different ways of encoding qubits with photons and why photons are interesting systems with a great potential. We will then review some of the pioneering works up to what has been achieved more recently and we will conclude by what perspectives one can hope for using photonic qubits. Implicitly, in this work, we take the stand-point of a future fault-tolerant quantum computer using photons. In this review, some of the experimental technologies will be mentioned and briefly described but the reader will refer to further readings for more information onto how to produce, control and detect photonic qubits. It is also worth stating that this review has to be seen more as a first introduction to the subject.

Selected experimental results on nuclear structure and reaction studies are presented which have been obtained using Digital INGA at TIFR employing the BARC-TIFR Pelletron Linac Facility. These results demonstrate how the use of stable heavy-ion beams available at this facility together with state-of-the-art instrumentation produced many important results covering diverse aspects of nuclear structure with varying angular momentum as well as reaction dynamics related to weakly bound nuclei. Finally, we discuss the future directions of nuclear structure research with the INGA project.

Elastic electron scattering from deformed nuclei is described within the distorted-wave Born approximation (DWBA) by employing charge densities which reflect, respectively, the prolate and oblate shapes of the target nucleus. Clear evidence for the shape dependence of the differential cross section and of the electronic spin asymmetry is found at scattering angles in the vicinity of the first diffractive cross section minimum. As an example, results for the (^{27})Al nucleus at collision energies between 150 and 500 MeV are provided.