2 research outputs found
Collective neutrino flavor transitions in supernovae and the role of trajectory averaging
Non-linear effects on supernova neutrino oscillations, associated with
neutrino self-interactions, are known to induce collective flavor transitions
near the supernova core for theta_13 \neq 0. In scenarios with very shallow
electron density profiles, these transformations have been shown to couple with
ordinary matter effects, jointly producing spectral distortions both in normal
and inverted hierarchy. In this work we consider a complementary scenario,
characterized by higher electron density, as indicated by post-bounce
shock-wave simulations. In this case, early collective flavor transitions are
decoupled from later, ordinary matter effects. Moreover, such transitions
become more amenable to both numerical computations and analytical
interpretations in inverted hierarchy, while they basically vanish in normal
hierarchy. We numerically evolve the neutrino density matrix in the region
relevant for self-interaction effects. In the approximation of averaged
intersection angle between neutrino trajectories, our simulations neatly show
the collective phenomena of synchronization, bipolar oscillations, and spectral
split, recently discussed in the literature. In the more realistic (but
computationally demanding) case of non-averaged neutrino trajectories, our
simulations do not show new significant features, apart from the smearing of
``fine structures'' such as bipolar nutations. Our results seem to suggest
that, at least for non-shallow matter density profiles, averaging over neutrino
trajectories plays a minor role in the final outcome. In this case, the swap of
nu_e and nu_{\mu,\tau} spectra above a critical energy may represent an
unmistakable signature of the inverted hierarchy, especially for theta_{13}
small enough to render further matter effects irrelevant.Comment: v2 (27 pages, including 9 eps figures). Typos removed, references
updated. Minor comments added. Corrected numerical errors in Eq.(6). Matches
the published versio
Effect of Collective Flavor Oscillations on the Diffuse Supernova Neutrino Background
Collective flavor oscillations driven by neutrino-neutrino self interaction
inside core-collapse supernovae have now been shown to bring drastic changes in
the resultant neutrino fluxes. This would in turn significantly affect the
diffuse supernova neutrino background (DSNB), created by all core-collapse
supernovae that have exploded in the past. In view of these collective effects,
we re-analyze the potential of detecting the DSNB in currently running and
planned large-scale detectors meant for detecting both electron neutrinos and
antineutrinos. The next generation detectors should be able to observe DSNB
fluxes. Under certain conducive conditions, one could learn about neutrino
parameters. For instance, it might be possible to determine the neutrino mass
hierarchy, even if theta_{13} is almost zero.Comment: Ver3 (24 pages, 4 figures and 4 tables): Reference added. Figure 1
corrected. Misprints corrected. Acknowledgment added. No changes in results.
Supercedes the version published in JCA