No Arabic abstract
This letter proposes an alternative quantum mechanical picture for the observed phenomena of neutrino oscillations. It is assumed in the following that neutrinos interact via diabatic (or localised) interactions with a new particle field, which changes their flavor. Furthermore, it is assumed that each neutrino flavor state can only have a single associated mass thereby making them fundamental particles of nature. The effective masses associated with matter interactions replace the concept of neutrino mixing angles. Preliminary evidence that left-handed neutrinos and right-handed antineutrinos oscillate differently is presented, implying charge-parity violation. Given the apparent anomalous observations of some neutrino oscillation experiments, which have led to speculations about the existence of a fourth (sterile) neutrino, it is worth examining the oscillation behavior predicted by alternative mechanisms to determine if they more naturally explain the available data.
In the last decades, a very important breakthrough has been brought in the elementary particle physics by the discovery of the phenomenon of the neutrino oscillations, which has shown neutrino properties beyond the Standard Model. But a full understanding of the various aspects of the neutrino oscillations is far to be achieved. In this paper the theoretical background of the neutrino oscillation phenomenon is described, referring in particular to the paradigmatic models. Then the various techniques and detectors which studied neutrinos from different sources are discussed, starting from the pioneering ones up to the detectors still in operation and to those in preparation. The physics results are finally presented adopting the same research path which has crossed this long saga. The problems not yet fixed in this field are discussed, together with the perspectives of their solutions in the near future.
We study distances of propagation and the group velocities of the muon neutrinos in the presence of mixing and oscillations assuming that Lorentz invariance holds. Oscillations lead to distortion of the $ u_mu$ wave packet which, in turn, changes the group velocity and the distance $ u_mu$ travels. We find that the change of the distance, $d_{osc}$, is proportional to the length of the wave packet, $sigma_x$, and the oscillation phase, $phi_p$, acquired by neutrinos in the $pi-$ and $K-$ meson decay tunnel where neutrino wave packet is formed: $d_{osc} propto sigma phi_p$. Although the distance $d_{osc}$ may effectively correspond to the superluminal motion, the effect is too tiny ($sim 10^{- 5}$ cm) to be reconciled with the OPERA result. We analyze various possibilities to increase $d_{osc}$ and discuss experimental setups in which $d_{osc}$ (corresponding to the superluminal motion) can reach an observable value $sim 1$ m.
Heavy neutral leptons (HNLs) are hypothetical particles, motivated in the first place by their ability to explain neutrino oscillations. Experimental searches for HNLs are typically conducted under the assumption of a single HNL mixing with a single neutrino flavor. However, the resulting exclusion limits may not directly constrain the corresponding mixing angles in realistic HNL models -- those which can explain neutrino oscillations. The reinterpretation of the results of these experimental searches turns out to be a non-trivial task, that requires significant knowledge of the details of the experiment. In this work, we perform a reinterpretation of the ATLAS search for promptly decaying HNLs to tri-lepton final states. We show that in realistic HNL models, the actual limits can vary by several orders of magnitude depending on the free parameters of the model. Marginalizing over the unknown model parameters leads to an exclusion limit on the total mixing angle which can be up to 3 orders of magnitude weaker than the limits reported in arXiv:1905.09787. This demonstrates that the reinterpretation of results from experimental searches is a necessary step to obtain meaningful limits on realistic models. We detail a few steps that can be taken by experimental collaborations in order to simplify the reuse of their results.
We study a model for the mass matrices of the leptons. We are ablte to relate the mass eigenvalues of the charged leptons and of the neutrinos to the mxiing angles and can predict the masses of the neutrinos. We find a normal hierarchy -the masses are 0.004 eV, 0.01 eV and 0.05 eV. The atmospheric mixing angle is given by the mass ratios of the charged leptons and of the neutrinos. We find 38 degrees, consistent with the experiments. The mixing element, connecting the first neutrino with the electron, is found to be 0.05.
We derive for the first time an effective neutrino evolution Hamiltonian accounting for neutrino interactions with external magnetic field due to neutrino charge radii and anapole moment. The results are interesting for possible applications in astrophysics.