Decoherence in supernova neutrino transformations suppressed by deleptonization
Abstract
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.
Cite
@article{arxiv.0706.2498,
title = {Decoherence in supernova neutrino transformations suppressed by deleptonization},
author = {Andreu Esteban-Pretel and Sergio Pastor and Ricard Tomas and Georg G. Raffelt and Gunter Sigl},
journal= {arXiv preprint arXiv:0706.2498},
year = {2008}
}