LSND Anomalies Research Articles

Combining LSND and atmospheric anomalies in a three-neutrino picture

We investigate the three-neutrino mixing scheme for solving the atmospheric and LSND anomalies. We find the region in the parameter space that provides a good fit to the LSND and the SK atmospheric data, taking into account the CHOOZ constraint. We demonstrate that the goodness of this fit is comparable to that of the conventional fit to the solar and atmospheric data. Large values of the LSND angle are favoured and $\sin^2(2\theta_{\rm LSND})$ can be as high as 0.1. This can have important effects on the atmospheric electron neutrino ratios as well as on down-going multi-GeV muon neutrino ratios. We examine the possibility of distinguishing this scheme from the conventional one at the long baseline experiments. We find that the number of electron neutrino events observed at the CERN to Gran Sasso experiment may lead us to identify the scheme, and hence the mass pattern of neutrinos.

Cornering (3+1) sterile neutrino schemes

Using the most recent atmospheric neutrino data, as well as short-baseline, long-baseline and tritium $\beta$-decay data we show that the joint interpretation of the LSND, solar and atmospheric neutrino anomalies in (3+1) sterile neutrino schemes is severely disfavored, in contrast to the theoretically favored (2+2) schemes.

Four-neutrino scenarios

The main features of four-neutrino 3+1 and 2+2 mixing schemes are reviewed, after a discussion on the necessity of at least four massive neutrinos if the solar, atmospheric and LSND anomalies are due to neutrino oscillations.

Implications of mirror neutrinos for early universe cosmology

The exact parity model (EPM) is, in part, a theory of neutrino mass and mixing that can solve the atmospheric, solar and LSND anomalies. The central feature of the neutrino sector is three pairs of maximally mixed ordinary and mirror neutrinos. It has been shown that inter-family ordinary-mirror neutrino oscillations can generate large neutrino asymmetries in the epoch of the early universe immediately prior to big bang nucleosynthesis (BBN). The large neutrino asymmetries generically suppress the production of mirror neutrinos, and a sufficiently large (Formula presented) asymmetry can directly affect light element synthesis through nuclear reaction rates. In this paper we present a detailed calculation of neutrino asymmetry evolution driven by the six-flavor EPM neutrino sector, focusing on implications for BBN. © 2000 The American Physical Society.