Mu-tau neutrino refraction and collective three-flavor transformations in supernovae

Abstract

We study three-flavor collective neutrino transformations in the dense-neutrino region above the neutrino sphere of a supernova core. We find that two-flavor conversions driven by the atmospheric mass difference and the 13-mixing angle capture the full effect if one neglects the second-order difference between the and refractive index. Including this ''mu-tau matter term'' provides a resonance at a density of 3 10 7 g cm ÿ3 that typically causes significant modifications of the overall e and e survival probabilities. This effect is surprisingly sensitive to deviations from maximal 23-mixing, being different for each octant.

Role of dense matter in collective supernova neutrino transformations

“…On the other hand, for iron-core SNe, during the accretion phase the matter density can reach values and can have such a profile that it is important. The possibility of such large matter densities had led some of us to speculate that the second-order difference between the ν µ and ν τ refractive effect could sometimes play an interesting role for three-flavor collective transformations [21]. It is easy to show, however, that the density requirement for this mu-tau effect to be important implies that the multiangle matter effect can not be avoided.…”

“…The neutrinos streaming from a supernova (SN) core or from the accretion torus of coalescing neutron stars are so dense that the neutrino-neutrino interaction causes collective flavor transformations [1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24,25,26,27,28]. At the same time, the density of ordinary matter is also very large, suppressing normal flavor conversions unless the neutrinos encounter an MSW resonance [29,30,31,32].…”

Collective neutrino oscillations in nonspherical geometry

“…Only recently has it been fully appreciated that this condition is sufficient even if a dense background of ordinary matter provides a much larger interaction energy so that naively neutrinoneutrino interactions would seem negligible [14,15]. Following this crucial insight, nonlinear oscillation phenomena in the supernova (SN) context have been studied over the past two years in a long series of papers [15,16,17,18,19,20,21,22,23,24,25,26,27,28,29,30,31].…”

“…• relative to the radial direction and then used a neutrino-neutrino interaction strength consistent with this assumption [27]. This implementation of the single-angle approximation has the advantage that one can use the same numerical code as for multi-angle simulations, simply restricting oneself to a single angular bin.…”

Upper limits on the diffuse supernova neutrino flux from the SuperKamiokande data

“…The hierarchy is defined as normal (inverted) if the third mass eigenstate -the one whose electron component is sin 2 θ 13 -is the heaviest (lightest). The net conversion probability is due to a combination of effects of neutrino-neutrino coherent scattering [22,23,24,25,26,27,28,29,30,31,32,33,34,35,36] and of matter-driven resonant conversion (see e.g., [37,38,39]). The neutrino-neutrino effects swap the energy spectra of the electron and non-electron components of the flux for the inverted mass hierarchy and above a certain critical energy, E c .…”