Supernova deleptonization asymmetry: Impact on self-induced flavor conversion

Abstract

During the accretion phase of a core-collapse supernova (SN), the deleptonization flux has recently been found to develop a global dipole pattern (LESA-Lepton Emission Self-sustained Asymmetry). The νe number flux Fν e is much larger than Fν e in one direction, whereas they are approximately equal, or even Fν e Fν e , in the opposite direction. We use a linearized stability analysis in a simplified SN model to study the impact of the νe-νe flux asymmetry on self-induced neutrino flavor conversion. While a small lepton-number flux facilitates self-induced flavor conversion, "multiangle matter suppression" is more effective. Overall we find that for large matter densities which are relevant below the shock wave, self-induced flavor conversion remains suppressed in the LESA context and thus irrelevant for neutrino-driven explosion dynamics.

Fast neutrino flavor conversions near the supernova core with realistic flavor-dependent angular distributions

“…However, it has been recently discovered that multidimensional SN simulations exhibit a phenomenon called lepton-emission self-sustained asymmetry (LESA) [40], i.e., the lepton asymmetries of the neutrino fluxes have strong variance over various directions and this roughly hemispherical asymmetry appears to be self-stabilized. In particular, along some directions flavor asymmetries among the different species can be much milder than in the corresponding 1D simulations (see [41]). Currently, the ν angular distributions for the multi-dimensional SN models showing the LESA effects are not available in a readily usable form, but they are expected to be similar to that in 1D simulations [42].…”

Three flavor neutrino conversions in supernovae: slow & fast instabilities

“…From the solutions of equations 3.14 and 3.15, it is possible to understand the variation of the maximum growth rate κ max and the corresponding interaction strength µ onset with the chosen vacuum frequency ω j and the asymmetry parameter . The relation between them comes out to be κ max = (2/ ) 2 − 1 [36], where κ max is expressed in the units of vacuum frequency ω j . For our chosen numerical values of ω j and we find µ 2 onset > µ 1 onset and correspondingly κ 2 max > κ 1 max .…”

“…However, our focus is to understand the dynamics of the three off diagonal elements in this linear regime and to check if they qualitatively give the same picture obtained in the simple nonlinear analysis [33]. Thus the instability conditions in each of the 2 flavor systems are [36,37],…”

“…The effective matter terms can be written as λ jβ = λ l jβ + λ ν jβ , where λ l jβ and λ ν jβ corresponds to the charged leptons and neutrinos, respectively. To recover theλ, we assume an isotropic system [36] allowing us to drop the neutrino and lepton current terms (spatial parts of λ jβ ), i.e., λ j1 = λ j2 = λ j3 = 0. The charged lepton part of the temporal component of λ jβ , i.e., λ l j0 represents the usual matter term (λ) used in the literature, however now we have three λ's.…”

Collective neutrino flavor conversion: Recent developments

“…Neutrinos streaming from a SN core encounter a certain trajectory of (λ, µ) values and may never encounter any instability if λ is large, depending on the "footprint" of the unstable region in the λ-µ-plane [29,50,52,55]. In Fig.…”