Oscillation searches via neutrino-electron scattering.

Several years ago Rosen and Kayser' pointed out that vz-v, oscillations could alter the observed cross sections in neutrino-electron scattering experiments. Their basic point was that cr(v, e) is about six times larger than o.(v„e ) due to the weak-charged-current amplitude which contributes to the former but not the latter. So, if vz-v, oscillations occur during source to target traversal, one will measure what appears to be an enhancement of cr(" zv"e) and a decrease in o("v,"e). (The quotation marks indicate that the initially pure neutrino beam may have evolved to a combination of v„v„, etc. , due to oscillations. ) Such an effect could confuse the interpretation of neutrino scattering data in, for example, determinations of sin t9~ or searches for extra Z' bosons. Of course, once such a possibility is recognized, those measurements can instead be used to search for oscillations. In this paper, the Rosen-Kayser scenario' is reexamined for the purpose of seeing whether it can compete with more direct probes of oscillations. We shall show that present (and past) o(v„e) (o.(v„e)) experiments are not nearly as sensitive to v„-v, (v„-v, ) oscillations as dedicated oscillation experiments. As a corollary, one can be confident that the average value sin OII =0.223+0.018 presently extracted from o.(v„e) [cr(v„e )] data is relatively free of uncertainties from oscillations. However, a recently proposed high-statistics LAMPF (Clinton P. Anderson Meson Physics Facility at Los Alamos) experiment that would determine sin HII, to +0.002 via a precision measurement of the ratio