Figure 1
Credit: Adapted from [5]

Figure 1: The flavor content of the neutrino mass eigenstates. The splitting between ν3 and ν2 (or ν1) (labelled here by 1, 2, and 3) is responsible for oscillation at 500 km/GeV (relevant to neutrinos arriving from the Earth’s atmosphere), whereas the splitting between ν2 and ν1 leads to an oscillation at the scale of 15,000 km/GeV (relevant to neutrinos arriving from the sun). νe appearance at the T2K experiment is primarily controlled by the size of sin2 θ13, the fraction of νe in the ν3 mass eigenstate.