Stars as Laboratories for Fundamental Physics - MPP Theory Group

Neutrino Oscillations 289
8.2.4 Experimental Oscillation Searches
Because neutrino masses must be very small the oscillation length involves
macroscopic scales. Numerically, it is
l osc = 2.48 m
E ν
1 MeV
1 eV 2
∆m 2 . (8.24)
Therefore, the modulation of the flavor content of a neutrino beam can
occur on large, even astronomical length scales.
There exists a large number of oscillation searches using terrestrial
neutrino sources (reactors, accelerators); for detailed references see Particle
Data Group (1994). In Fig. 8.5 (curves a–f) I show the most
restrictive limits on oscillations between the known neutrinos where
Fig. 8.5. Experimental limits on neutrino masses and mixing angles. Reactors,
ν e disappearance: (a) Bugey 4 (Achkar et al. 1995), superseding the
Gösgen limits (Zacek et al. 1986); (b) Kurchatov Institute (Vidyakin et al.
1987, 1990, 1991). Accelerator experiments: (c) BNL Experiment 776, wideband
beam, ν e and ν e appearance (Borodovsky et al. 1992). (d) BNL Experiment
734, measurement of ν e /ν µ ratio (Ahrens et al. 1985). (e) Fermilab
Experiment 531, ν τ appearance (Ushida et al. 1986); similar constraints were
reported by the CHARM II Collaboration (1993). (f) CDHS Experiment,
ν µ disappearance (Dydak et al. 1984). (g) Anticipated range of sensitivity
for the CHORUS and NOMAD experiments which are currently taking data
at CERN (DiLella 1993; Winter 1995).