Present and Future Contributions of Reactor Experiments to Mass Ordering and Neutrino Oscillation Studies

Oscillations of Active Neutrinos at Short Baseline in the Model with Three Decaying Sterile Neutrinos

To study the oscillations of active neutrinos in the framework of the model with three active and three sterile neutrinos, the analytical expressions are obtained for the appearance and survival probabilities of different neutrino flavors taking into account the decaying sterile neutrinos contributions. In the framework of the considered phenomenological neutrino model, we make an interpretation of the experimentally detected XENON1T-excess of electronic recoil events in the energy range of 1–7 keV as a result of the radiative decay of a sterile neutrino with a mass of about 7 keV. Estimations of the decay parameters for the radiative decay of Majorana sterile neutrinos due to the magnetic dipole transitions into the active neutrino states are made. The value of the parameter of active and sterile neutrinos mixing has been derived from the Baksan Experiment on Sterile Transitions (BEST) experimental data. The graphical dependences for the probabilities of appearance and survival of muonic and electron neutrinos at short baseline (SBL) are presented with the use of that gained from the experimental data estimations of the model parameters.

Phenomenological Effects of CPT and Lorentz Invariance Violation in Particle and Astroparticle Physics

It is well known that a fundamental theorem of Quantum Field Theory (QFT) set in flat spacetime ensures the CPT invariance of the theory. This symmetry is strictly connected to the Lorentz covariance, and consequently to the fundamental structure of spacetime. Therefore it may be interesting to investigate the possibility of departure from this fundamental symmetry, since it can furnish a window to observe possible effects of a more fundamental quantum gravity theory in a “lower energy limit”. Moreover, in the past, the inquiry of symmetry violations provided a starting point for new physics discoveries. A useful physical framework for this kind of search is provided by astroparticle physics, thanks to the high energy involved and to the long path travelled by particles accelerated by an astrophysical object and then revealed on Earth. Astrophysical messengers are therefore very important probes for investigating this sector, involving high energy photons, charged particles, and neutrinos of cosmic origin. In addition, one can also study artificial neutrino beams, investigated at accelerator experiments. Here we discuss the state of art for all these topics and some interesting new proposals, both from a theoretical and phenomenological point of view.