Physics of supernova neutrinos: flavor conversion effects

Original · EN

I review the effects of flavor conversion of neutrinos from stellar collapse due to masses and mixing, and discuss the motivations for their study. I consider in detail the sensitivity of certain observables (characteristics of the energy spectra of nuₑ and antinuₑ events) to the 13-mixing (sin²θ₁3) and to the type of mass hierarchy/ordering (sign[Delta m²₁3]). These observables are: the ratio of average energies of the spectra, rₑ =<E>/< E >, the ratio of widths of the energy distributions, rGamma = Gamma/ Gamma, the ratios of total numbers of nuₑ and antinuₑ events at low energies, S, and in the high energy tails, Rₜail. I show that regions in the space of observables rₑ, rGamma, Rₜail exist in which certain mass hierarchy and intervals of sin²θ₁3 can be identified or discriminated. Finally, I discuss the potential of studying regeneration effects on nuₑ and antinuₑ in the matter of the Earth and point out that both the observation or exclusion of these effects lead to model-independent information on sin²θ₁3 and the mass hierarchy. The extraction of this information would highly benefit from the presence of a new, large, long lived nuₑ detector, and from the progress of theoretical predictions of the fluxes and energy spectra of the neutrinos originally produced in the star.