Confronting solutions to the atmospheric neutrino anomaly involving large angle ${\nu }_{\mu }\to {\nu }_e$ oscillations with SuperKamiokande and CHOOZ

Abstract

Neutrino oscillation scenarios involving large angle ${\nu }_{\mu }\to {\nu }_e$ oscillations are disfavoured in the parameter range $\Delta m^2/e{V}^2>10^{-3}$ by recent results from the CHOOZ reactor-based ${\bar{\nu }}_e$ disappearance experiment. For this reason we extend our previous work on up-down asymmetries for various oscillation scenarios by computing up-down asymmetries and the R ratio for the entire conceivable range $10^{-4}-10^{-1}e{V}^2$ of $\Delta m^2$. Matter effects in the Earth play a crucial role. We perform a ${\chi }^2$ fit to the data. We find that, because of the matter effect, the three-flavour maximal mixing model provides a reasonable fit to SuperKamiokande and CHOOZ data provided that the relevant $\Delta m^2$ is in the range $4\times 10^{-4}<\Delta m^2/e{V}^2<1.5\times 10^{-3}$.

Comments: 16 pages, 8 figures, Latex; numerical error for one of the cases considered is corrected; conclusions are unchanged