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Abstract：A Quantum Field Theory (QFT) formalism for neutrino oscillations is presented. The neutrino emission and detection are identified with the charged-current vertices of a single second-order Feynman diagram for the underlying process, enclosing neutrino propagation between these two points. The L-dependent master formula for the charged lepton production rate is derived, which provides the QFT basis for analyzing neutrino oscillations. It is demonstrated that our QFT formula coincides with the conventional one under some assumptions for some particular choice of the underlying process. The presented formalism also leads to the expected result for Racah’s process involving neutrino oscillation into antineutrino (and vice versa). The corresponding L-dependent effective Majorana neutrino mass is studied. Further, techniques are developed for constructing amplitudes of neutrino-related processes in terms of the neutrino mass matrix, with no reference to the neutrino mixing matrix. The proposed approach extensively uses Frobenius covariants within the framework of Sylvester’s theorem on matrix functions. It is maintained that fitting experimental data in terms of the neutrino mass matrix can provide better statistical accuracy in determining the neutrino mass matrix compared to methods using the neutrino mixing matrix at intermediate stages. Finally, the quasi-Dirac scenario for neutrino mixing is considered. Under simplified assumptions for the 6x6 neutrino mixing matrix, an impact of neutrino oscillation data on the observation of neutrinoless double-beta decay is discussed.
About the Speaker: Professor Fedor Šimkovic works at the Department of Nuclear Physics and Biophysics at the Faculty of Mathematics, Physics and Informatics of Comenius University. He is well known for the theoretical achievements in the field of neutrino and nuclear physics, in particular for the calculation of the nuclear matrix element of neutrinoless double beta decay. He also participates in experiments in top neutrino physics research and in designing software for processing and interpretation of data from neutrino experiments NEMO3/SuperNEMO (0vββ), Baikal-GVD (neutrino space telescope) and JUNO (research into neutrino oscillations).