Cosmic ray studies with the KM3NeT neutrino telescope

The origin, propagation, and interaction of high-energy Cosmic Rays (CRs) with the atmosphere are not yet fully understood. In particular, we lack precise measurements of the CR hadronic interactions in the very forward region. This work focuses on the investigation of the CR secondary particle properties via the study of high-energy atmospheric muons. Muon detection is performed underwater with the KM3NeT neutrino telescopes. In this work, the simulation of atmospheric muons for the KM3NeT experiment was performed. This simulation was compared with KM3NeT data from the partially deployed detectors already taking data underwater. The simulation included the most recent models available: Sibyll 2.3d for the high-energy hadronic interaction and GSF for CR flux. During my PhD, I contributed to the development of atmospheric muon simulation software for the Cherenkov neutrino telescopes. In particular, I developed an alternative code for the muon propagation in water that allowed to cross-check the standard KM3NeT software and resolve the issues it was affected by. I developed a framework to tune the parameters of the fast muon generator MUPAGE on the CORSIKA full MC simulations that includes the recent models mentioned above. The framework results demonstrated that the tuned MUPAGE represents the CORSIKA results and can be used as a fast alternative to the full MC simulations. The fast generation allows the simulation of muons with the same statistics as in the real data. This goal is not achievable with the full simulations and the CPU resources available. Then, I performed studies on systematic uncertainties. The uncertainties include that on CR flux and its composition, high-energy hadronic interaction model, light attenuation length in seawater, and detector response simulation. Finally, I compared the KM3NeT data with the MC simulations including all systematic uncertainties mentioned above. The comparison revealed the discrepancy between the real data and the MC predictions for the underwater muon flux. There are ∼40% more muons in the data with respect to MC. Hence, the mismatch is of the same order as for the GeV muons at sea level (the muon puzzle). Muons detected with KM3NeT originate from the very first interactions of CRs in the atmosphere, while GeV muons at sea level are mostly originate in the lower parts of the atmosphere after several steps of the EAS cascade development. Thus, the measurement performed in this work provides new insights and the test-bench for possible solutions to the muon puzzle. The KM3NeT detectors are rapidly growing. The detector performance for the atmospheric muon detection grows both in terms of statistics, but also, what is more important for this study, it improves in the quality of the muon track reconstruction. More energy is absorbed in the detector volume and more light is emitted, which allows better direction and energy reconstruction. The framework developed during my thesis is provided to the Collaboration as the internally available code with all necessary documentation. This allows this work to be continued in the near future by the collaborators in order to extend the analysis for the larger and better KM3NeT detectors. The main KM3NeT goals are related to the neutrinos detection and, in this aspect, the atmospheric muons are only background. Its precise knowledge improves, however, the systematics of the main physics analysis. Also atmospheric muons are the most copious events and, thus, they provide a facility for the reconstruction code tests and the detector response studies. Therefore, better knowledge about true flux of these events allows to tune the other detector properties

Frequency conditions for the global stability of nonlinear delay equations with several equilibria

In our adjacent work, we developed a spectral comparison principle for compound cocycles generated by delay equations. In particular, this principle allows to derive frequency conditions (inequalities) for the uniform exponential stability of such cocycles by means of their comparison with stationary problems. Such inequalities are hard to verify analytically since they contain resolvents of additive compound operators and to compute the resolvents it is required solving a first-order PDEs with boundary conditions involving both partial derivatives and delays. In this work, we develop approximation schemes to verify some of the arising frequency inequalities. Beside some general results, we mainly stick to the case of scalar equations. By means of the Suarez-Schopf delayed oscillator and the Mackey-Glass equations, we demonstrate applications of the theory to reveal regions in the space of parameters where the absence of closed invariant contours can be guaranteed. Since our conditions are robust, so close systems also satisfy them, we expect them to actually imply the global stability, as in known finite-dimensional results utilizing variants of the Closing Lemma which is still awaiting developments in infinite dimensions

Retrieving refractive index of single spheres using the phase spectrum of light-scattering pattern

We analyzed the behavior of the complex Fourier spectrum of the angle-resolved light scattering pattern (LSP) of a sphere in the framework of the Wentzel-Kramers-Brillouin (WKB) approximation. Specifically, we showed that the phase value at the main peak of the amplitude spectrum almost quadratically depends on the particle refractive index, which was confirmed by numerical simulations using both the WKB approximation and the rigorous Lorenz-Mie theory. Based on these results, we constructed a method for characterizing polystyrene beads using the main peak position and the phase value at this point. We tested the method both on noisy synthetic LSPs and on the real data measured with the scanning flow cytometer. In both cases, the spectral method was consistent with the reference non-linear regression one. The former method leads to comparable errors in retrieved particle characteristics but is 300 times faster than the latter one. The only drawback of the spectral method is a limited operational range of particle characteristics that need to be set a priori due to phase wrapping. Thus, its main application niche is fast and precise characterization of spheres with small variation range of characteristics.Comment: 16 pages, 9 figures, 2 table

Electrically-Detected ESR in Silicon Nanostructures Inserted in Microcavities

We present the first findings of the new electrically-detected electron spin resonance technique (EDESR), which reveal the point defects in the ultra-narrow silicon quantum wells (Si-QW) confined by the superconductor delta-barriers. This technique allows the ESR identification without application of an external cavity, as well as a high frequency source and recorder, and with measuring the only response of the magnetoresistance, with internal GHz Josephson emission within frameworks of the normal-mode coupling (NMC) caused by the microcavities embedded in the Si-QW plane

Evolutionary relationships of Red Jungle Fowl and chicken breeds

Published results were reassessed and original data are provided regarding the origin and relatedness of four postulated chicken breed lineages, egg-type, game, meat-type and Bantam, to each other and to the basic ancestral species of jungle fowls, Gallus gallus. A system approach was employed concerning the planning of the experiments. One element of the system approach is the choice of the breeds to be compared with G. gallus. These breeds were supposed to represent major evolutionary branches of chickens. Four experiments on genetic relationships were conducted using different estimation criteria including morphological discrete characters, body measurements, biochemical markers, and the activity of serum esterase-1. The greatest similarity was found between G. gallus and the egg-type breeds of Mediterranean roots and/or true Bantams. This fact might testify that the indicated chicken groups occupied earlier stages in the evolution from the wild progenitor to the present biodiversity of chickens in the world