M. M. Guzzo

Status of the solution to the solar neutrino problem based on nonstandard neutrino interactions

We analyze the current status of the solution to the solar neutrino problem based both on (a) nonstandard flavor-changing neutrino interactions (FCNI) and (b) nonuniversal flavor diagonal neutrino interactions (FDNI). We find that FCNI and FDNI with matter in the Sun as well as in the Earth provide a good fit not only to the total rate measured by all solar neutrino experiments but also to the day-night and seasonal variations of the event rate, as well as the recoil electron energy spectrum measured by the SuperKamiokande Collaboration. This solution does not require massive neutrinos and neutrino mixing in vacuum. Stringent experimental constraints on FCNI from bounds on lepton flavor violating decays and on FDNI from limits on lepton universality violation rule out

Probing flavor changing neutrino interactions using neutrino beams from a muon storage ring

{\ensuremath{\nu}}_{e}\ensuremath{\rightarrow}{\ensuremath{\nu}}_{\ensuremath{\mu}}

Status of a hybrid three neutrino interpretation of neutrino data

transitions induced by new physics as a solution to the solar neutrino problem. However, a solution involving

Global analysis of the post-SNO solar neutrino data for standard and nonstandard oscillation mechanisms

{\ensuremath{\nu}}_{e}\ensuremath{\rightarrow}{\ensuremath{\nu}}_{\ensuremath{\tau}}

Massless “just-so” solution to the solar neutrino problem

transitions is viable and could be tested independently by the upcoming B factories if flavor violating tau decays would be observed at a rate close to the present upper bounds.

Neutrino decay and solar neutrino seasonal effect

We discuss the capabilities of a future neutrino factory based on intense neutrino beams from a muon storage ring to explore the non-standard neutrino matter interactions, which are assumed to be sub-leading effects in the standard mass induced neutrino oscillations. The conjunction of these two mechanisms will magnify fake CP violating effect in the presence of matter which is not coming from the CP phase in the neutrino mixing matrix. We show that such fake CP violation can be observed in neutrino factory experiments by measuring the difference between the neutrino and anti-neutrino probabilities. In order to perform such test, we consider three neutrino flavors, admitting the mixing parameters in the range consistent with the oscillation solution to the atmospheric and the solar neutrino problems, as well as with the constraints imposed by the reactor neutrino data. We show that with a 10 kt detector with 5 years of operation, a stored muon energy E_\mu \ge 20 GeV, 2 \times 10^{20} muon decays per year, and a baseline L \sim 732 km, such a neutrino facility can probe the non-standard flavor changing neutrino interactions down to the level of (10^{-3}-10^{-2})~G_F, in both \nu_\mu \to \nu_\tau/ \bar \nu_\mu \to \bar \nu_\tau and \nu_e \to \nu_\tau/\bar \nu_e \to \bar \nu_\tau modes.

Constraining the violation of the equivalence principle with IceCube atmospheric neutrino data

We re-analyse the non-standard interaction (NSI) solutions to the solar neutrino problem in the light of the latest solar as well as atmospheric neutrino data. The latter require oscillations (OSC), while the former do not. Within such a threeneutrino framework the solar and atmospheric neutrino sectors are connected not only by the neutrino mixing angle #13 constrained by reactor and atmospheric data, but also by the flavour-changing (FC) and non-universal (NU) parameters accounting for the solar data. Since the NSI solution is energy-independent the spectrum is undistorted, so that the global analysis observables are the solar neutrino rates in all experiments as well as the Super-Kamiokande day-night measurements. We find that the NSI description of solar data is slightly better than that of the OSC solution and that the allowed NSI regions are determined mainly by the rate analysis.     

Second-order corrections to neutrino two-flavor oscillation parameters in the wave packet approach

What can we learn from solar neutrino observations? Is there any solution to the solar neutrino anomaly which is favored by the present experimental panorama? After SNO results, is it possible to affirm that neutrinos have mass? In order to answer such questions we analyze the current available data from the solar neutrino experiments, including the recent SNO result, in view of many acceptable solutions to the solar neutrino problem based on different conversion mechanisms, for the first time using the same statistical procedure. This allows us to do a direct comparison of the goodness of the fit among different solutions, from which we can discuss and conclude on the current status of each proposed dynamical mechanism. These solutions are based on different assumptions: ~a! neutrino mass and mixing, ~b! a nonvanishing neutrino magnetic moment, ~c! the existence of nonstandard flavor-changing and nonuniversal neutrino interactions, and ~d! a tiny violation of the equivalence principle. We investigate the quality of the fit provided by each one of these solutions not only to the total rate measured by all the solar neutrino experiments but also to the recoil electron energy spectrum measured at different zenith angles by the Super-Kamiokande Collaboration. We conclude that several nonstandard neutrino flavor conversion mechanisms provide a very good fit to the experimental data which is comparable with ~or even slightly better than! the most famous solution to the solar neutrino anomaly based on the neutrino oscillation induced by mass.

Random magnetic fields inducing solar neutrino spin-flavor precession in a three generation context

We study the effect of the non-resonant, vacuum oscillation-like neutrino flavor conversion induced by non-standard flavor changing and non-universal flavor diagonal neutrino interactions with electrons in the sun. We have found an acceptable fit for the combined analysis for the solar experiments total rates, the Super-Kamiokande (SK) energy spectrum and zenith angle dependence. Phenomenological constraints on non-standard flavor changing and non-universal flavor diagonal neutrino interactions are considered.

Quantum flavor oscillations extended to the Dirac theory

Abstract We consider the possibility of solar neutrino decay as a sub-leading effect on their propagation between production and detection. Using current oscillation data, we set a new lower bound to the ν 2 neutrino lifetime at τ 2 / m 2 ≥ 7.2 × 10 − 4 s . eV − 1 at 99 % C.L. Also, we show how seasonal variations in the solar neutrino data can give interesting additional information about neutrino lifetime.