The European Physical Journal A最新文献

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.

We investigate the multi-channel 4-body scattering system using regularized 2- and 3-body contact interactions. The analysis determines the sensitivity of bound-state energies, scattering phase shifts and cross-sections on the cutoff parameter ((lambda )), and on the energy gaps between scattering thresholds. The latter dependency is obtained with a 2-body scale fixed to an unnaturally large value and a floating 3-body parameter. Specifically, we calculate the binding energies of the shallow 3- and 4-body states, dimer-dimer and trimer-atom scattering lengths, and the trimer-atom to dimer-dimer reaction rates. Employing a potential renormalized by a large 2-body scattering length and a 3-body scale, we find all calculated observables to remain practically constant over the range (6,text {fm}^{-2}<lambda <10,text {fm}^{-2}). Divergences in scattering lengths emerge for critical 3-body parameters at which thresholds are degenerate. For those critical points where the dimer-dimer and trimer-atom thresholds overlap, we predict an enhancement of the inelastic over the elastic scattering event. Such an inversion between elastic- and rearrangement-collision probabilities indicates a strong sensitivity of the 4-body reaction dynamics on the 3-body parameter at finite 2-body scale. As this enhancement is found here for all considered cutoffs but not in earlier studies which employ different renormalization schemes, we conclude that the sole cutoff variation does not necessarily imply non-perturbative changes in reaction rates. We conjecture the enhancement to follow from specific combinations of the finite 2-body range and the 3-body parameter.

High-performance scintillator materials are needed for particle identification and measurements of energy and momentum of electromagnetic particles in modern nuclear physics experiments. As an example, the US Electron-Ion Collider, a unique collider with diverse physics topics, requires electromagnetic calorimetry enabling high-quality electron identification and detection in the momentum range of 0.3 to tens of GeV. The highest resolution in electromagnetic calorimeters can be provided by homogeneous materials, e.g., lead tungstate crystals. Inorganic glass scintillators have been investigated as an attractive and cost-effective alternative to crystals, that is also easier and faster to manufacture in mass production. In this paper, we discuss progress in the fabrication and characterization of recent scintillating glass samples on both test bench and beam tests. The results are well-reproduced by simulation and are discussed in the context of the Electron-Ion Collider experimental requirements and bench-marked against lead tungstate crystals.

The evolutionary path of massive stars begins at helium burning. Energy production for this phase of stellar evolution is dominated by the reaction path 3(alpha rightarrow ^{12}) C((alpha ,gamma )^{16})O and also determines the ratio of (^{12})C/(^{16})O in the stellar core. This ratio then sets the evolutionary trajectory as the star evolves towards a white dwarf, neutron star or black hole. Although the reaction rate of the 3(alpha ) process is relatively well known, since it proceeds mainly through a single narrow resonance in (^{12})C, that of the (^{12})C((alpha ,gamma )^{16})O reaction remains uncertain since it is the result of a more difficult to pin down, slowly-varying, portion of the cross section over a strong interference region between the high-energy tails of subthreshold resonances, the low-energy tails of higher-energy broad resonances and direct capture. Experimental measurements of this cross section require herculean efforts, since even at higher energies the cross section remains small and large background sources are often present that require the use of very sensitive experimental methods. Since the (^{12})C((alpha ,gamma )^{16})O reaction has such a strong influence on many different stellar objects, it is also interesting to try to back calculate the required rate needed to match astrophysical observations. This has become increasingly tempting, as the accuracy and precision of observational data has been steadily improving. Yet, the pitfall to this approach lies in the intermediary steps of modeling, where other uncertainties needed to model a star’s internal behavior remain highly uncertain.

⁶He, known as a Borromean nucleus with a 2n-halo structure, and its mirror partner ⁶Be, the lightest 2p emitter, provide an excellent framework for exploring soft dipole resonance and nuclear structure. Despite previous studies on these nuclei, the potential presence of soft dipole resonance ((J^pi = 1^-)) had rarely been predicted before. In this work, we will investigate the presence of (1^-) resonance states in the complex energy plane, focusing on how the soft dipole resonance impacts the E1 transitions/response. Using the Gamow coupled-channel method for three-body calculations, we analyze the structures and soft dipole resonance of ⁶He and ⁶Be mirror systems, further exploring the E1 transition strengths of ⁶He through Green’s function method. The results show that the structural properties of ⁶He and ⁶Be show similar behavior. Notably, there are significant di-nucleon correlations in the (0^+) ground-state of both nuclei. Additionally, we observed a significant enhancement in E1 transition strengths at the energy corresponding to the (1^-) state. This indicates the presence of relative motion between the valence nucleons and the core.

This Eur. Phys. J. A volume 58 is dedicated to the life and work of Dr. Franz Käppeler from Karlsruhe Institute for Technology (KIT) who died on 20 November 2021, after a short illness. He was one of the leading experimentalists in the field of experimental nuclear astrophysics in Germany and worldwide for decades. Many of the authors of this volume knew Franz personally and many others were directly or indirectly inspired by his work and personality. All references in this introductory article refer to publications in this volume, not necessary to actual work by Dr. Käppeler.

A complex interplay between mixing and nucleosynthesis is at work in asymptotic giant branch (AGB) stars. In addition to the slow neutron capture process (s-process), the intermediate neutron capture process (i-process) can develop during proton ingestion events (PIEs). In this paper, after quickly reviewing the different modes of production of heavy elements in AGB stars that have been identified so far, we investigate the synthesis of actinides and other short-lived radioactive nuclei (SLRs, (^{60})Fe, (^{107})Pd, (^{126})Sn, (^{129})I, (^{135})Cs, and (^{182})Hf) during i-process nucleosynthesis. AGB stellar models with initial masses (1 le M_textrm{ini}/M_{odot }le 3), metallicities (-3 le ) [Fe/H] ( le 0), and different overshoot strengths were computed with the stellar evolution code STAREVOL. During PIEs, a nuclear network of 1160 isotopes is used and coupled to the transport equations. We found that AGB models with [Fe/H] (<-2) can synthesize actinides with abundances sometimes greater than solar values. The (^{60})Fe yield scales with the initial metallicity, while the (^{107})Pd, (^{126})Sn, (^{129})I, (^{135})Cs, and (^{182})Hf yields follow a similar pattern as a function of metallicity, with a production peak at [Fe/H] (simeq -1.3). At [Fe/H] (<-1), the fraction of odd Ba isotopes (f_textrm{Ba,odd}) is predicted to vary between 0.6 and 0.8 depending on the initial mass and metallicity. Nuclear uncertainties on our 1(~M_{odot })  [Fe/H] (=-2.5) model lead to (f_textrm{Ba,odd}) ranging between 0.27 and 0.76, which is clearly above the s-process value. AGB stars experiencing PIEs appear to be potential producers of actinides and SLRs, particularly at low metallicity (except for (^{60})Fe). Galactic chemical evolution modelling is required to assess their possible contribution to the galactic enrichment.

In the (U(3) times U(3)) quark NJL model, (tau ) lepton decays with the production of scalar mesons (f_0(pi ,K)) and neutrinos are studied, where (f_0=f_0(500), f_0(980)). It is shown that these decays mainly occur via contact channels and channels with axial-vector mesons (a_1(1260)), (K_1(1270)) and (K_1(1400)). All mesons are considered as quark-antiquark states in this case. The obtained results can be considered as predictions for future experiments. The obtained estimates for the branching fractions of the (tau rightarrow pi ^-2pi ^0 nu _tau ) decay taking into account the contributions of the (rho pi ) and (f_0(500)pi ) states are in satisfactory agreement with experimental data.