Coherence of oscillations in matter and supernova neutrinos

Abstract

We study the propagation coherence for neutrino oscillations in media with different density profiles. For each profile, we find the dependence of the coherence length, Lcoh, on neutrino energy and address the issue of correspondence of results in the distance and energy-momentum representations. The key new feature in matter is existence of energy ranges with enhanced coherence around the energies E0 of “infinite coherence” at which Lcoh→∞. In the configuration space, the infinite coherence corresponds to equality of the (effective) group velocities of the eigenstates. In constant density medium, there is a unique E0, which coincides with the MSW resonance energy of oscillations of mass states and is close to the MSW resonance energy of flavor states. In the case of massless neutrinos or negligible masses in a very dense medium the coherence persists continuously. In the adiabatic case, the infinite coherence is realized for periodic density change. Adiabaticity violation changes the shape factors of the wave packets (WPs) and leads to their spread. In a medium with sharp density changes (jumps), splitting of the eigenstates occurs at crossing of each jump. We study the increase of the coherence length in a single jump and periodic density jumps — castle-wall (CW) profiles. For the CW profile, there are several E0 corresponding to parametric resonances. We outlined applications of the results for supernova neutrinos. In particular, we show that coherence between two shock wave fronts leads to observable oscillation effects, and our analysis suggests that the decoherence can be irrelevant for flavor transformations in the central parts of collapsing stars.

Quantum coherence in neutrino oscillation in matter

“…For two values of V , we have resonance in the transition processes. However, the coherence length for some values of potentials becomes infinite [15][16][17]. This effect is due to the larger mixing angle in the material medium.…”

“…In this approach, for a baseline distance more than the coherence length, the oscillation probabilities diminish. Therefore, we obtain the coherence length which in this case, depends not only on the neutrino states properties (mass squared difference, energy and its dispersion) but also on the matter potential [15][16][17]. Consequently, we obtain the l 1 -norm and analyze its behavior in terms of the baseline distance.…”

Neutrino flavor oscillations in a rotating spacetime

“…Further, the neutrino production and detection processes using wavepackets have been appropriately discussed in [64][65][66][67]. It has been noted that one can always restore the oscillation phenomenon at the detector if one can resolve the energy of the detector to the peak energy of the Gaussian wavepacket of the neutrinos.…”

The Diffuse Supernova Neutrino Background in the Standard and Double Collapse Models

“…The Mikheyev-Smirnov-Wolfenstein (MSW) effect is the effect of transformation of one neutrino species (flavor) into another one in a medium with varying density [41]. During this process, neutrinos (hereinafter, the normal hierarchy of neutrino masses is assumed) pass from one type to another according to the following formulas for the SC [21,[42][43][44]:…”