Limits on neutrino oscillations derived from the ratio of neutral- to charged-current cross sections of neutrinos measured at the CERN SPS NBB

Abstract

We present an analysis, in terms of neutrino oscillations, of the recent measurements of the ratio R of neutral-current to charged-current neutrino cross sections performed by the CDHS and CHARM Collaborations at the CERN Super Proton Synchroton narrow-band beam. The measurementswere aimed at the determination of sin 2 θ w. Our analysis is based on the observation that muon-neutrino oscillations would decrease the number of interactions with a muon in the final state. The effect of oscillations on R can be studied, comparing the actual measurements with the value of R predicted by an independent measurement of sin 2 θ w. Limits on ν μ − ν e, ν μ − ν τ , and ν μ − ν x oscillations are presented. They refer to a region of high mass squared difference of the two oscillating neutrinos ( Δm 2 > 3 eV 2). For high Δm 2 the limits on the mixing angle θ are very restrictive. In particular, for the transition ν μ − ν x (x≠e, τ) they represent the best available results for large intervals in Δm 2.