Alexei Yu. Smirnov

Neutrino production coherence and oscillation experiments

A bstractNeutrino oscillations are only observable when the neutrino production, propagation and detection coherence conditions are satisfied. In this paper we consider in detail neutrino production coherence, taking π → μν decay as an example. We compare the oscillation probabilities obtained in two different ways: (1) coherent summation of the amplitudes of neutrino production at different points along the trajectory of the parent pion; (2) averaging of the standard oscillation probability over the neutrino production coordinate in the source. We demonstrate that the results of these two different approaches exactly coincide, provided that the parent pion is considered as pointlike and the detection process is perfectly localized. In this case the standard averaging of the oscillation probability over the finite spatial extensions of the neutrino source (and detector) properly takes possible decoherence effects into account. We analyze the reason for this equivalence of the two approaches and demonstrate that for pion wave packets of finite width σxπ the equivalence is broken. The leading order correction to the oscillation probability due to σxπ ≠ 0 is shown to be ~ [vg/(vg−vπ )]σxπ/losc, where vg and vπ are the group velocities of the neutrino and pion wave packets, and losc is the neutrino oscillation length.

Solar neutrinos and neutrino physics

Abstract.Solar neutrino studies triggered and largely motivated the major developments in neutrino physics in the last 50 years. The theory of neutrino propagation in different media with matter and fields has been elaborated. It includes oscillations in vacuum and matter, resonance flavor conversion and resonance oscillations, spin and spin-flavor precession, etc. LMA MSW has been established as the true solution of the solar neutrino problem. Parameters

Non-standard interactions and the CP phase measurements in neutrino oscillations at low energies

\theta_{12}

Hidden flavor symmetries of SO(10) GUT

and

Discrete symmetries and mixing of Dirac neutrinos

\Delta

Neutrino mixing and masses in SO(10) GUTs with hidden sector and flavor symmetries

m221 have been measured;

Leptonic CP violation phases, quark–lepton similarity and seesaw mechanism

\theta_{13}

Oscillations of the 7Be solar neutrinos inside the Earth

extracted from the solar data is in agreement with results from reactor experiments. Solar neutrino studies provide a sensitive way to test theory of neutrino oscillations and conversion. Characterized by long baseline, huge fluxes and low energies they are a powerful set-up to search for new physics beyond the standard 3

Scanning the Earth with solar neutrinos and DUNE

\nu

Neutrino properties, mass hierarchy, and CP-violation

paradigm: new neutrino states, sterile neutrinos, non-standard neutrino interactions, effects of violation of fundamental symmetries, new dynamics of neutrino propagation, probes of space and time. These searches allow us to get stringent, and in some cases unique bounds on new physics. We summarize the results on physics of propagation, neutrino properties and physics beyond the standard model obtained from studies of solar neutrinos.