Production process dependence of neutrino flavour conversion

We perform a covariant wavepacket analysis of neutrino oscillations taking into account the lifetime of the neutrino production process . We find that flavour oscillations in space are washed out when the neutrinos are produced from long lived resonances and what may be observed in appearance/disappearance experiments is a uniform conversion probability independent of distance. The lifetime of the resonance which produces the neutrinos acts as the the effective baseline of the experiment. For this reason the LSND experiment where neutrinos are produced from muon decay has two orders of magnitude more sensitivity to neutrino mass square difference than other experiments where the neutrinos are produced from pion or kaon decays. Using the covariant conversion probability formula we find that the region of ∆m2 and sin22θ which is allowed by LSND and all other experiments is 2.2× 10−3eV 2 < ∆m2 < 6.3eV 2 and 0.002 < sin22θ < 0.15.