Establishing a nu(mu,tau) component in the solar neutrino flux

We point out that the recoil electron kinetic energy spectra in the v-epsil on elastic scattering are different for incident nu(e) or nu(mu,tau), and h ence one can in principle establish the existence of the nu(mu,tau) compone nt in the solar neutrino flux by fitting the shape of the spectrum. This wo uld be a new model-independent test of the solar neutrino oscillation in a single experiment, free from astrophysical and nuclear physics uncertaintie s. For the Be-7 neutrinos, it is possible to determine the nu(mu,tau) compo nent at BOREXINO or KamLAND, if the background is sufficiently low. Note th at this effect is different from the distortion in the incident neutrino en ergy spectrum, which has been discussed in the literature.