Neutrinos in Stochastic Media: From Sun to Core-Collapse Supernovae

Recent work on neutrino propagation in stochastic media and its implications for the Sun and corecollapse supernovae are reviewed. It is shown that recent results from Sudbury Neutrino Observatory and SuperKamiokande combined with a best global fit value of δm2 = 5× 10−5 eV2 and tan2 θ = 0.3 rule out solar electron density fluctuations of a few percent or more. It is argued that solar neutrino experiments may be able to rule out even smaller fluctuations in the near future. Recent observation of the charged-current solar neutrino flux at the Sudbury Neutrino Observatory [1] together with the measurements of the ν⊙-electron elastic scattering at the SuperKamiokande detector [2] established that there are at least two active flavors of neutrinos of solar origin reaching Earth. Analyses of all the solar neutrino data updated after the Sudbury Neutrino Observatory results were announced indicate (in two-flavor mixing schemes) a best fit value of δm2 = 5×10−5 eV2 and tan2 θ = 0.3 [3, 4]. In calculating neutrino survival probability in matter one typically assumes that the electron density of the Sun is a monotonically decreasing function of the distance from the core and ignores potentially de-cohering effects [5]. To understand such effects one possibility is to study parametric changes in the density [6, 7] or the role of matter currents [8]. Loreti and Balantekin [9] considered neutrino propagation in stochastic media. They studied the situation where the electron density in the medium has two components, one average component given by the Standard Solar Model or Supernova Model, etc., Ne(r), and one fluctuating component, Nr e (r). The two-flavor Hamiltonian describing neutrino propagation in such a medium is given by Ĥ = (−δm2 4E cos2θ+ 1 √ 2 GF(Ne(r)+ N r e(r)) ) σz + ( δm2 4E sin2θ )