Neutrino-induced reactions in core-collapse supernovae: Effects on the electron fraction

Abstract

Neutrino induced reactions are a basic ingredient in astrophysical processes like star evolution. The existence of neutrino oscillations affects the rate of nuclear electroweak decays which participates in the chain of events that determines the fate of the star. Among the processes of interest, the production of heavy elements in core-collapse supernovae is strongly dependent upon neutrino properties, like the mixing between different species of neutrinos.In this work we study the effects of neutrino oscillations upon the electron fraction as a function of the neutrino mixing parameters, for two schemes: the 1 + 1 scheme (one active neutrino and one sterile neutrino) and the 2 + 1 scheme (two active neutrinos and one sterile neutrino). We have performed this analysis considering a core-collapse supernovae and determined the physical conditions needed to activate the nuclear reaction chains involved in the r-process. We found that the interactions of the neutrinos with matter and among themselves and the initial amount of sterile neutrinos in the neutrinosphere might change the electron fraction, therefore affecting the onset of the r-process. We have set constrains on the active-sterile neutrino mixing parameters. They are the square-mass-difference ∆m 2 14 , the mixing angle sin 2 2θ 14 , and the hindrance factor ξs for the occupation of sterile neutrinos. The calculations have been performed for different values of Xα, which is the fraction of α-particles. For Xα = 0 the r-process is taking place if ∆m 2 14 ≥ 2 eV 2 , sin 2 2θ 14 < 0.8 and ξs < 0.5. For larger values of Xα the region of parameters is strongly reduced. The present results are compared to results available in the literature.

Titanium and Iron in the Cassiopeia A Supernova Remnant

“…The mapping took place when the supernova shock had moved out of the iron core and propagated into the Si-S rich shell at t < 1 s. We note that our 1D methods employed for modeling the collapse, core bounce, and initial explosion do not capture the full physics of the central engine (for a discussion, see Fryer et al 2018), and this is a source of uncertainty in our yields calculations. The details of the engine change the shock trajectories, and neutrino chemistry can change Y e values (Saez et al 2018;Fu-jimoto & Nagakura 2019). The nature of the shock affects mostly the yields after the shock falls below NSE (before it falls out of NSE, the yields are set by the equilibrium values, not the time-dependent evolution).…”

“…The latter point, the Y e values, could alter our results as well (see, e.g., Magkotsios et al 2010). Although more detailed models have addressed neutrino interactions and the evolution of Y e , the neutrino physics is not yet sufficiently accurate to model this correctly (Saez et al 2018). In light of this, any nucelosynthetic calculation under these conditions is subject to uncertainty.…”

“…They also assumed a single value of Y e based on the progenitor composition outside a cutoff radius in their preferred model, which was chosen to better match the Cas A remnant. Neutrino processing may affect the final yields, but assuming a single value of Y e is not realistic (Saez et al 2018;Fujimoto & Nagakura 2019). Couch et al (2015) simulated the last few minutes of Si-shell burning in 3D before modeling the collapse and explosion, which they also ran in 3D with a single octant and a network of 21 isotopes.…”

Neutrino interactions in liquid scintillators including active-sterile neutrino mixing

“…The consequences of the existence of sterile neutrinos in different astrophysical scenarios have being examined in previous works [25,26], among others. In particular, in the context of SN, several authors have already analysed the effects of the inclusion of a sterile neutrino upon the fraction of free neutrons, the baryonic density, the electron fraction of the material, and nucleosynthesis processes [27,14,28,5,29,30]. In particular, in reference [31], the SN events produced via proton and electron elastic scattering in scintillators are studied.…”