Decoherence in supernova neutrino transformations suppressed by deleptonization

In the dense-neutrino region at 50-400 km above the neutrino sphere in a supernova, neutrino-neutrino interactions cause large flavor transformations. We study when the multi-angle nature of the neutrino trajectories leads to flavor decoherence between different angular modes. We consider a two-flavor mixing scenario between nu_e and another flavor nu_x and assume the usual hierarchy F(nu_e)>F{antinu_e)>F(nu_x)=F(antinu_x) for the number fluxes. We define epsilon=(F(nu_e)-F(antinu_e))/(F(antinu_e)-F(antinu_x)) as a measure for the deleptonization flux which is the one crucial parameter. The transition between the quasi single-angle behavior and multi-angle decoherence is abrupt as a function of epsilon. For typical choices of other parameters, multi-angle decoherence is suppressed for epsilon>0.3, but a much smaller asymmetry suffices if the neutrino mass hierarchy is normal and the mixing angle small. The critical epsilon depends logarithmically on the neutrino luminosity. In a realistic supernova scenario, the deleptonization flux is probably enough to suppress multi-angle decoherence.Comment: 17 pages, 12 figures. Misprint in Eq (14) correcte

Collective flavor transitions of supernova neutrinos

We give a very brief overview of collective effects in neutrino oscillations in core collapse supernovae where refractive effects of neutrinos on themselves can considerably modify flavor oscillations, with possible repercussions for future supernova neutrino detection. We discuss synchronized and bipolar oscillations, the role of energy and angular neutrino modes, as well as three-flavor effects. We close with a short summary and some open questions.This work was supported by the Deutsche Forschungsgemeinschaft (SFB 676 “Particles, Strings and the Early Universe: The Structure of Matter and Space-Time) and by the European Union (contracts No. RII3-CT-2004-506222)

Supernoves com a laboratoris de propietats de neutrins

194 páginas. Tesis Doctoral del Departamento de Física Teórica, de la Universidad de Valencia, y el Instituto de Física Corpuscular (IFIC). Fecha de lectura: 07-13-2009La tesis que aquí se presenta pretende ser un análisis de diversos aspectos de fenomenología de neutrinos en dos escenarios diferentes. Por un lado se trata el estudio de las posibles interacciones no estándar de neutrinos en experimentos terrestres de acelerador y reactor. Por otro lado se discute la propagación de neutrinos en supernova, teniendo en cuenta los nuevos descubrimientos que muestran la importancia que el propio fondo de neutrinos tiene en la evolución de éstos. Este análisis se presenta tanto en ausencia como en presencia de interacciones no estándar.Peer reviewe