2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/40241In a two flavour world, the usual equal $p$, equal $E$, or equal $v$ assumptions used to derive the neutrino oscillation length can be replaced by a specific definition of the velocity of the oscillating state which, unlike those assumptions, is compatible with exact production kinematics. This definition is further vindicated by the analysis of $π_{μ2}$ decay at rest.8 pages, latex, no figuresHigh Energy Physics - Phenomenologytext