Institute for Nuclear Research and Nuclear Energy

The NA62 experiment at CERN has the capability to collect data in a beam-dump mode, where 400 GeV protons are dumped on an absorber. In this configuration, New Physics particles, including dark photons, dark scalars, and axion-like particles, may be produced in the absorber and decay in the instrumented volume beginning approximately 80 m downstream of the dump. A search for these particles decaying in flight to hadronic final states is reported, based on an analysis of a sample of $1.4 \times 10^{17}$ 1.4 × 10 17 protons on dump collected in 2021. No evidence of a New Physics signal is observed, excluding new regions of parameter spaces of multiple models.

Raman spectra from the same sample might differ between instruments and over time depending on the spectrometer, optical path, or sample environment, among others. There is a need to harmonize and standardize characterization by Raman spectroscopy, enabling end users to share and reuse digital spectroscopic data through FAIR databases. In this context, we present an open‐source, MIT‐licensed, Python package called ramanchada2 that collects existing and novel state‐of‐the‐art algorithms, allowing the users to generate, read, visualize, and process Raman spectra, with special emphasis on instrument calibration. A number of input formats are supported, including those from DFT simulations. This package also offers a tool for the generation of synthetic spectra based on user specifications for data augmentation and algorithm benchmarking. NeXus is introduced as an input and output format, enabling the possibility to package into a single file data and metadata, including data processing information, from multiple and even from different types of experiments, for example, XRD, Raman, and biological assays, using a harmonized structure and terminology. To facilitate Raman spectra analysis by end users, we developed “Oranchada” add‐on for data‐mining open‐source software Orange, a user‐friendly wrapper of all ramanchada2 functionalities with predefined harmonization workflows, as well as an online application for calibration.

The Landau problem and harmonic oscillator in the plane share a Hilbert space that carries the structure of Dirac’s remarkable so(2,3) representation. We show that the orthosymplectic algebra osp(1|4) is the spectrum generating algebra for the Landau problem and, hence, for the 2D isotropic harmonic oscillator. The 2D harmonic oscillator is in duality with the 2D quantum Coulomb–Kepler systems, with the osp(1|4) symmetry broken down to the conformal symmetry so(2,3). The even so(2,3) submodule (coined Rac) generated from the ground state of zero angular momentum is identified with the Hilbert space of a 2D hydrogen atom. An odd element of the superalgebra osp(1|4) creates a pseudo-vacuum with intrinsic angular momentum 1/2 from the vacuum. The odd so(2,3)-submodule (coined Di) built upon the pseudo-vacuum is the Hilbert space of a magnetized 2D hydrogen atom: a quantum system of a dyon and an electron. Thus, the Hilbert space of the Landau problem is a direct sum of two massless unitary so(2,3) representations, namely, the Di and Rac singletons introduced by Flato and Fronsdal.

Vertex algebras in higher dimensions correspond to models of quantum field theory with global conformal invariance. Any vertex algebra in dimension D admits a restriction to a vertex algebra in any lower dimension and, in particular, to dimension one. In the case when D is even, we find natural conditions under which the converse passage is possible. These conditions include a unitary action of the conformal Lie algebra with a positive energy, which is given by local endomorphisms and obeys certain integrability properties.

The YbCoC2 compound, which crystallizes in a base-centered orthorhombic unit cell in the Amm2 space group CeNiC2 structure, is unique among Yb-based compounds due to the highest magnetic ordering temperature of TN=27 K. Magnetization measurements have made it possible to plot the H-T magnetic phase diagram and determine the magnetocaloric effect of this recently discovered high-temperature heavy-fermion compound, YbCoC2. YbCoC2 undergoes spin transformation to the spin-polarized state through a metamagnetic transition in an external magnetic field. The transition is found to be of the first order. The dependencies of magnetic entropy change ΔSm(T)—have segments with positive and negative magnetocaloric effects for ΔH≤6 T. For ΔH=9 T, the magnetocaloric effect becomes positive, with a maximum ΔSm(T) value of 4.1 J (kg K)⁻¹ at TN and a refrigerant capacity value of 56.6 J kg⁻¹.

Acquiring adequate sensory information and using it to provide motor control are important issues in the process of creating walking robots. The objective of this article is to present control algorithms for the optimization of the walking cycle of an innovative walking robot named “Big Foot”. The construction of the robot is based on minimalist design principles—only two motors are used, with which Big Foot can walk and even overcome obstacles. It is equipped with different types of sensors, with some of them providing information necessary for the realization of an optimized walk cycle. We examine two laws of motion—sinusoidal and polynomial—where we compare the results with constant angular velocity motion. Both proposed laws try to find balance between minimizing shock loads and maximizing walking speed for a given motor power. Experimental results are derived with the help of a 3D-printed working prototype of the robot, with the correct realization of the laws of motion being ensured by the use of a PD controller receiving data from motor encoders and tactile sensors. The experimental results validate the proposed laws of motion and the results can be applied to other walking robots with similar construction.

To find a high purity flux for low background experiments is one of the most challenging problems. In this work, we report the production process of a highly purified ammonium acetate flux solution for low background experiments. A sub-distilled method has been used to purify initial precursors from contamination for the syntheses of final product. As a result, a high purity ammonium acetate solution was synthesized with a minimum content of elements which collectively represent the main source of background radiation (K < 2.3 × 10–8 g/g, Th < 2.6 × 10–11 g/g and U < 1 × 10–11 g/g). An Estimation of the impurity content of the product has been performed with Instrumental neutron activation analysis, inductively coupled plasma atomic emission spectrometry and inductively coupled plasma mass spectrometry.

Numerically the positron lifetime values for a graphene coated metal, in particular, copper, iron, and tungsten substrate were obtained. Similarly, such values for a single vacancy filled with impurities, hydrogen or helium, coming from the irradiation with proton or alpha particles, respectively are also reported. We have for a graphene-Cu - 131ps, graphene-Fe - 119 ps, and for graphene-W - 126 ps, while for a single metal vacancy near the graphene coating we have - 194 ps, 186 ps, 209 ps, correspondingly. A comparison is made with the case of a metal slabs under same conditions. The momentum distribution shape S and W parameters have also been calculated, and reported here. A general trend discussion in relation to the dependence of the S and W parameters, as well as the positron lifetime on the number of impurities in the single metal vacancy is given. This results have been obtained within the Local Density Approximation method. A modeling relevant to the reactor plasma dusting from the walls is performed by molecular dynamics simulation of the impact of energetic copper clusters on the surface coated with the graphene. A protective influence of the graphene coating leads to the decreased destruction of the bulk from the impacting cluster.

In this work, two new perovskites of composition BaFe0.875Re0.125O3−δ and BaFe0.75Ta0.25O3−δ, designed from ab-initio calculations to fulfill different requisites of cathode materials for solid-oxide fuel cells (SOFC), were prepared and studied from the structural point of view from neutron powder diffraction (NPD) data. They are both derivatives of BaFeO3 hexagonal perovskite (space group P6 3 /mmc), typified as the 6H polytype, stabilized when the perovskite tolerance factor slightly overpasses the unity. Whereas BaFe0.875Re0.125O3−δ keeps this structural type, as demonstrated in this crystallographic study from NPD data at 295 and 4 K, with unit-cell parameters a = 5.70177(7); c = 14.0334(2) Å at 295 K, the second material, BaFe0.75Ta0.25O3−δ, is cubic and can be defined in the Pm-3m space group, corresponding of the perovskite arystotype, with a = 4.05876(3) Å. A conspicuous oxygen deficiency is observed, with a refined stoichiometry of 2.86(3) per formula unit. The anisotropic displacement factors for oxygen atoms in this last material are flattened disks perpendicular to the (Fe,Ta)-O-(Fe,Ta) direction, suggesting a dynamic tilting of the octahedra that could be related to the oxygen motion via oxygen vacancies across the structure. This is a pre-requisite for functional mixed-ionic-electronic (MIEC) materials performing as cathodes in SOFC.

The determination of the strong coupling constant $\alpha _{\mathrm{s}} (m_{\mathrm{Z}})$ α s ( m Z ) from H1 inclusive and dijet cross section data [1] exploits perturbative QCD predictions in next-to-next-to-leading order (NNLO) [2–4]. An implementation error in the NNLO predictions was found [4] which changes the numerical values of the predictions and the resulting values of the fits. Using the corrected NNLO predictions together with inclusive jet and dijet data, the strong coupling constant is determined to be $\alpha _{\mathrm{s}} (m_{\mathrm{Z}}) =0.1166\,(19)_{\mathrm{exp}}\,(24)_{\mathrm{th}}$ α s ( m Z ) = 0.1166 ( 19 ) exp ( 24 ) th . Complementarily, $\alpha _{\mathrm{s}} (m_{\mathrm{Z}})$ α s ( m Z ) is determined together with parton distribution functions of the proton (PDFs) from jet and inclusive DIS data measured by the H1 experiment. The value $\alpha _{\mathrm{s}} (m_{\mathrm{Z}}) =0.1147\,(25)_{\mathrm{tot}}$ α s ( m Z ) = 0.1147 ( 25 ) tot obtained is consistent with the determination from jet data alone. Corrected figures and numerical results are provided and the discussion is adapted accordingly.

The measurement of the jet cross sections by the H1 collaboration had been compared to various predictions including the next-to-next-to-leading order (NNLO) QCD calculations which are corrected in this erratum for an implementation error in one of the components of the NNLO calculations. The jet data and the other predictions remain unchanged. Eight figures, one table and conclusions are adapted accordingly, exhibiting even better agreement between the corrected NNLO predictions and the jet data.

The response function of the BGO, NaI (Tl) and LaBr3(Ce) scintillation detectors to monoenergetic gamma quanta was built on the basis of Monte Carlo simulations using the GEANT4 toolkit and calibration measurements with gamma radiation sources of different energies. The response function consists of seven components: the first six constitute the detector’s response to a direct hit of monoenergetic gamma radiation and depend on the properties of the detector (size, material, energy resolution, etc.), and the seventh component represents the effect of surrounding materials on the measured gamma spectrum. For each component of the function, the analytical form of the energy dependence is determined and its parameters are found when registering gamma quanta with energies in the range from 0.3 MeV to 10 MeV.

We introduce a symmetric operad whose algebras are the operator product expansion (OPE) Algebras of quantum fields. There is a natural classical limit for the algebras over this operad and they are commutative associative algebras with derivations. The latter are the algebras of classical fields. In this paper we completely develop our approach to models of quantum fields, which come from vertex algebras in higher dimensions. However, our approach to OPE algebras can be extended to general quantum fields even over curved space–time. We introduce a notion of OPE operations based on the new notion of semi-differential operators. The latter are linear operators Γ:M→N between two modules of a commutative associative algebra A, such that for every m∈M the assignment a↦Γ(a·m) is a differential operator A→N in the usual sense. The residue of a meromorphic function at its pole is an example of a semi-differential operator.

A study of the reaction of inelastic scattering of 14.1 MeV neutrons by 23 Na nuclei was carried out at the TANGRA facility using the tagged neutron method. In this work, the energies of visible g-transitions are determined, the yields of g -quanta are obtained, the angular distributions of g -quanta for 23 Na are measured. The results obtained are in good agreement with the data of other published experimental works.

We present the detailed dynamical model of a 3D printed walking robot with a minimal number of degrees of freedom (DOF). The robot has only two DOF, but despite that, it is capable of moving forward (or backwards) by walking, rotating to an arbitrary angle, going around obstacles, and even climbing stairs, in accordance with its size. Following a tendency of an increased popularity of robots in the education process, the prototype finds application in specialized educational methods for work with children with autism or development problems.