Reconstruction of supernova νμ, ντ, (ν)over-barμ and (ν)over-barτ neutrino spectra at scintillator detectors

We present a new technique to directly reconstruct the spectra of nu(mu), nu(tau), (nu) over bar (mu), and (nu) over bar (tau) from a supernova, using neutrino-proton elastic scattering events (nu + p -> nu + p) at scintillator detectors. These neutrinos, unlike nu(e) and (nu) over bar (e), have only neutral current interactions, which makes it very challenging, with any reaction, to detect them and measure their energies. With updated inputs from theory and experiments, we show that this channel provides a robust and sensitive measure of their spectra. Given the low yields and lack of spectral information in other neutral current channels, this is perhaps the only realistic way to extract such information. This will be indispensable for understanding flavor oscillations of SN neutrinos, as it is likely to be impossible to disentangle neutrino mixing from astrophysical uncertainties in a SN without adequate spectral coverage of all flavors. We emphasize that scintillator detectors, e. g., Borexino, KamLAND, and SNO+, have the capability to observe these events, but they must be adequately prepared with a trigger for a burst of low-energy events. We also highlight the capabilities of a larger detector like LENA.