Browsing by Author "Palomares-Ruiz, Sergio"

Now showing 1 - 2 of 2
  • Thumbnail Image
    Item
    Explaining LSND by a decaying sterile neutrino
    (2005) Palomares-Ruiz, Sergio; Pascoli, Silvia; Schwetz, Thomas; Physics; Elementary Particle Theory
    We propose an explanation of the LSND evidence for electron antineutrino appearance based on neutrino decay. We introduce a heavy neutrino, which is produced in pion and muon decays because of a small mixing with muon neutrinos, and then decays into a scalar particle and a light neutrino, predominantly of the electron type. We require values of gm4 ~ few eV, g being the neutrino-scalar coupling and m4 the heavy neutrino mass, e.g. m4 in the range from 1 keV to 1 MeV and g ~ 10-6-10-3. Performing a fit to the LSND data as well as all relevant null-result experiments, we show that all data can be explained within this decay scenario. In the minimal version of the decay model, we predict a signal in the upcoming MiniBooNE experiment corresponding to a transition probability of the same order as seen in LSND. In addition, we show that extending our model to two nearly degenerate heavy neutrinos it is possible to introduce CP violation in the decay, which can lead to a suppression of the signal in MiniBooNE running in the neutrino mode. We briefly discuss signals in future neutrino oscillation experiments, we show that our scenario is compatible with bounds from laboratory experiments, and we comment on implications in astrophysics and cosmology.
  • Thumbnail Image
    Item
    On the atmospheric neutrino oscillations, theta(13) and neutrino mass hierarchy
    (2007-11-14T10:32:54Z) Petcov, Serguey T.; Palomares-Ruiz, Sergio; Physics; Elementary Particle Theory
    We give predictions for the up-down asymmetry in the Nadir angle dependence of the ratio Nmu/Ne of the rates of the mu-like and e-like multi-GeV events measured in water-Cerenkov detectors (Super-Kamiokande, etc.) in the case of 3-neutrino oscillations of the atmospheric nu_e (antinu_e) and nu_mu (antinu_mu), driven by one neutrino mass squared difference, |Delta m^2_{atm}| = |Delta m^2_{31}| ~ (2.0 - 3.0) 10^{-3} eV^2 >> Delta m^2_{21} = Delta m^2_{sol}. This ratio is particularly sensitive to the Earth matter effects in the atmospheric neutrino oscillations, and thus to the values of sin^2(theta13) and sin^2(theta23), theta13 and theta23 being the neutrino mixing angle limited by the CHOOZ and Palo Verde experiments and that responsible for the dominant atmospheric nu_mu -> nu_tau (antinu_mu -> antinu_tau) oscillations, respectively. It is also sensitive to the type of neutrino mass spectrum which can be with normal (Delta m^2_{atm} > 0) or with inverted (Delta m^2_{atm} < 0) hierarchy.