A muon-neutrino beam leaves the source pure and arrives as a mixture. Drag the baseline, energy, mass splitting and mixing angle to see flavour drain away and come back:
P = sin2(2θ) · sin2(1.27 · Δm2 L / E),
with Δm2 in eV2, L in km and E in GeV.
Survival stays a muon neutrino
0.0001
0.0139 % of the beam
Appearance changed flavour
0.9999
99.99 % of the beam
First oscillation maximum
296.9 km
The detector sits at 0.99 of that distance.
Baseline L295 km
Beam energy E0.6 GeV
Mass splitting2.50e-3 eV²
Mixing angle θ45.00°
Amplitude sin2(2θ) = 1.0000 · L/E = 491.7 km/GeV
Tip: the pattern is set by L divided by E, not by distance alone — halve the energy and a fixed detector slides a full oscillation down the curve.