Neutrino Oscillation from Hidden GRB Jets

Collapsars are the likely progenitors of Long Gamma-Ray Burst (lGRBs). lGRBs have been observed to last for thousands to tens of thousands of seconds, thus making unlikely the neutrino-driven engine as the main mechanism for driving the jets. In this context, the Blandford-Znajek mechanism seems likely to explain the production of rotational-axis directed jets without the need for large accretion rates. These engines, require magnetic fields between $10^{12}$ G $< B < 10^{15}$ G threading the innerdisk, Kerr-BH region to exist. We derive the neutrino self-energy and the effective potential up to O(1/$M_W^4$) in a weakly and highly magnetized GRB fireball flow which is made up of electrons, protons, neutrons and their anti-particles. We consider neutrino energies of 1-100 MeV which are produced during stellar collapse, merger events or in the fireball itself by electron-positron annihilation, inverse beta decay and nucleonic bremsstrahlung processes. Many of these neutrinos propagate through the fireball and may oscillate resonantly. Using two-neutrino mixing we study the possibility of these oscillations.