Intermediate baseline appearance experiments and three-neutrino mixing schemes

Three-neutrino mixing schemes suggested by Cardall & Fuller and Acker & Pakvasa are compared and contrasted. Both of these schemes seek to solve the solar and atmospheric neutrino problems and to account for the possible neutrino oscillation signal in the LSND experiment. These neutrino oscillation schemes have different atmospheric and solar neutrino signatures that will be discriminated by SuperKamiokande and SNO. They will also have different signatures in proposed longbaseline accelerator and reactor experiments. In particular, both of these schemes would give dramatic (and dramatically different) signals in an “intermediate baseline” experiment, such as the proposed ICARUS detector in the Jura mountains 17 km from CERN. 1 Three-mixing schemes At the present time there are three hints of neutrino mixing: the solar (e.g. [1]) and atmospheric (e.g. [2]) neutrino problems, and the signal in the LSND experiment [3]. Each of these can be solved by or interpreted as neutrino flavor oscillations. If an independent neutrino mass difference is associated with each of these three hints, four neutrino flavors are necessary. Since it is known that only three neutrino flavors participate in the weak interaction [4], the fourth neutrino flavor must be “sterile” [an SU(2) singlet]. Accounting for all three hints with only three active neutrino flavors would require that at least two of the phenomena must “share” one of the two available independent mass differences. Preprint submitted to Elsevier Preprint 1 February 2008 The possibility of a three-neutrino mixing scheme along these lines was noted by Cardall & Fuller [5]. Their scheme uses the smaller neutrino mass difference to account for the solar neutrino problem, and the larger mass difference to account for the atmospheric neutrino problem and the LSND signal. They proposed the following mass/mixing parameters: δm 2 21 ≈ 7× 10 −6 eV, (1) δm 2 31 ≈ δm 2 32 ≈ 0.3 eV, (2)