Date and time: Monday, March 22nd at 11:00 CET
Speaker: Mario Fernández Navarro (SOTON ESR)
Title: Active-sterile neutrino oscillations in very low reheating scenarios
Abstract: Most neutrino oscillation experiments are well explained through the mixing of the three standard neutrino flavours of the SM, but some anomalies in short baseline oscillation experiments remain unexplained. These anomalies may be explained by the existence of an extra, sterile neutrino state, leading to the so-called 3+1 framework. However, this 3+1 scenario is highly constrained by cosmological observations, which favour the standard three-neutrino case. Here we present a way to accommodate the 3+1 scenario with the cosmological observations by suppressing the thermalisation of the sterile neutrino in the early Universe. We address this problem by considering an exotic cosmological scenario where we assume that a very late reheating process took place before BBN. In this scenario, the radiation epoch starts at temperatures of order MeV, in such a way that neutrinos may decouple from the cosmic plasma before they are fully thermalised.