Issue 8 (Volume 3) 2026

The results of the research partnership between the Flerov Laboratory of Nuclear Reactions of the Joint Institute for Nuclear Research (FLNR JINR) and the Laboratory of Fundamental Particles of the Lebedev Physical Institute (LFP LPI) are presented. The publication focuses on two areas: the search for tracks of superheavy nuclei in pallasite meteorites (OLIMPIYA experiment) and testing of various dielectric materials (glasses and micas) as detectors of heavy charged particles.

The Nearest Neighbors estimation of likelihood is implemented for the multivariate amplitude analysis of the cascades of particle decays. In this approach Monte Carlo simulated events that are used to describe data are assigned weights dependent on the parameters of the theoretical fitting model. Each of such weighted events is considered as contributing to N-dimensional probability density function (p.d.f.) in its neighborhood in the parameter space. No analytic p.d.f. or cpu-intensive re-generation of N-dimensional p.d.f. at each fit step are required. The method allows accurate accounting for reconstruction effects, demands modest cpu resources and can be effectively multi-threaded. General setup of the fit as well as toy example of the amplitude analysis of B-meson decays are demonstrated.

Being a spin-1 particle, the deuteron, when polarized, offers access to a wide range of interesting tensor observables. A quest for tensor asymmetries is at the heart of the spin physics with polarized deuterons at future colliders, and calls for frequent tensor polarization flips in storage rings or in deuterium targets.
Here we focus on the JEDI developed technique of the Fourier analysis of the horizontal polarization oscillations under continuous radiofrequency-driven spin flips. The generated in this way time-stamped oscillating helicity of stored particles paves the way to the nucleon/nucleus spin structure studies and to the search for the parity violation. Simultaneously, a whole set of tensor spin asymmetries, including the off-diagonal ones needed for searches for the T-violation beyond the Standard Model, will be produced.
A crucial ingredient is a long polarization lifetime, and we report the first analytic treatment of decoherence of the tensor polarization under continuous radiofrequency spin flips. Our principal conclusion is that at low- and intermediate-energy accelerators the deuteron polarization lifetime could be in the ballpark of several hours, making the oscillating polarization approach viable at the Nuclotron/NICA and HIAF.
We comment on a utility of the flattop spin-tensor dichroism via oscillations in the cross section of interaction of deuterons in the internal target as a monitor of the tensor polarization. Simultaneously, the dichroism effect can be used for measuring the spin precession frequences and as a comagnetometer to synchronize spin phases of colliding bunches in a collider.

Corrected: 11 August 2026 (Eq. (28) was revised; typos and grammar were corrected)

The experimental data collected by KEDR and BESIII collaborations at the energies below charm quark thresholds are compared with the massless QCD expressions for the \(e^+e^-\) annihilation R-ratio truncated at different orders of perturbation theory. The fits demonstrate the dependence of the extracted \(\alpha_s(M_Z)\) values on the orders of truncation of the corresponding approximations. The next-to-leading order, next-to-next-to-leading order and next-to-next-to-next-to-leading order fits of the combined KEDR data and BESIII data , truncated at the scale of mass of \(J/\Psi\) meson, give the following results \(\alpha_s(M_Z)=0.1151_{-0.0069}^{+0.0052}\), \(\alpha_s(M_Z)=0.1190_{-0.0081}^{+0.0064}\) and \(\alpha_s(M_Z)=0.1283_{-0.0075}^{+0.0028}\). The increasing tendency of fitted \(\alpha_s(M_Z)\) value is associated with the effects of not totally controlled within asymptotic perturbation theory expansions kinematical \(\pi^2\) contributions to R-ratio coefficients due to analytical continuation from the space-like to time-like energy regions. The applications of the fixed orders of perturbation theory expansions and careful treatment of the analytical continuation effects are commented.

Corrected:

28 July 2026 (changes have been made in Eqs. (12)–(14) and an expression has been added after them)

As a high-priority issue for sustainable global development, food security requires attention to both the quantity and quality of food. Trace elements pose a complex challenge for food security in this context; they can be beneficial as essential micronutrients or harmful as toxic contaminants that compromise food safety and public health. Consequently, advanced analytical tools, particularly elemental analysis, are employed to verify food quality, authenticity, and traceability. Since its first application in 1936 neutron activation analysis has proven to be a powerful analytical technique for determining the elemental composition of a wide variety of samples. The method's widespread adoption is due to its numerous benefits, including its multi-element character, non-destructive nature, high sensitivity and precision, ultra-low detection limits, and simple sample preparation. These advantages have led to its use in critical fields such as food safety, agriculture, and environmental monitoring. The paper provides an introduction to the biological role and toxicity of trace elements, discusses the fundamental principles, strengths, and limitations of neutron activation analysis, and presents an overview of NAA applications in food analysis, along with a summary of key findings.