Sandhya Choubey — Page 8

arXiv1998

Effect of Flavour Oscillations on the Detection of Supernova Neutrinos

Neutrinos and antineutrinos of all three flavours are emitted during the post bounce phase of a core collapse supernova with $\numu/\nutau (\anumu/\anutau)$ having average energies more than that of $\nue(\anue)$. They can be detected by the new earth bound detector like SNO and Super-Kamiokande which are sensitive to neutrinos of all three flavours. In this letter we consider the effect of flavour oscillations on the neutrino flux and their expected number of events at the detector. We do a three-generation analysis and for the mass and mixing schemes we first consider the threefold maximal mixing model consistent with the solar and the atmospheric neutrino data and next a scenario with one $Δm^2 \sim 10^{-11} eV^2$ (solar range) and the other $Δm^2 \sim 10^{-18} eV^2$, for which the oscillation length is of the order of the supernova distance. In both these scenarios there are no matter effects in the resultant neutrino spectrum and one is concerned with vacuum oscillations. We find that though neutrino oscillations result in a depletion in the number of $\nue$ and $\anue$ coming from the supernova, the actual signals at the detectors are appreciable enhanced.

hep-ph↗

arXiv1998

Constraints on Neutrino Mixing from r-process Nucleosynthesis in Supernovae

In this paper we note that for neutrino mass squared differences in the range $10^{-4} - 10^{-1} eV^2$, vacuum neutrino oscillations can take place between the neutrino-sphere and the weak freeze-out radius in a type II supernova. Requiring that such oscillations are consistent with the r-process nucleosynthesis from supernovae one can constrain the mixing of $ν_e$ with $ν_μ$ (or $ν_τ$) down to $10^{-4} eV^2$. We first do a two-flavor study and find that the neutron rich condition $Y_e < 0.5$ is satisfied for all values of mixing angles. However if we take the criterion $Y_e < 0.45$ for a successful r-process and assume $ν_μ- ν_e$ oscillations to be operative then this mode as a possible solution to the atmospheric neutrino anomaly is ruled out in accordance with the recent CHOOZ result. Furthermore since we can probe mass ranges lower than CHOOZ the narrow range that was allowed by the CHOOZ data at 99% C.L. is also ruled out. Next we do a three-generation analysis keeping $Δm_{12}^2 \sim 10^{-5} eV^2$ or $10^{-11} eV^2$ (solar neutrino range) and $Δm_{13}^2 \approx Δm_{23}^2 \sim 10^{-4} - 10^{-1} eV^2$ (atmospheric neutrino range) and use the condition $Y_e < 0.45$ to give bounds on the mixing parameters and compare our results with the CHOOZ bound. We also calculate the increase in the shock-reheating obtained by such oscillations.

hep-ph↗