Stars as Laboratories for Fundamental Physics - MPP Theory Group

390 Chapter 10
10.9 Future Experiments
10.9.1 Superkamiokande
If some form of neutrino oscillations are the explanation for the measured
solar flux deficits relative to standard predictions, how are we
ever going to know for sure One needs to measure a signature which
is characteristic only for neutrino oscillations. The most convincing
case would be a measurement of the “wrong-flavored” neutrinos, i.e.
the ν µ or ν τ appearance rather than the ν e disappearance. Other clear
signatures would be a deformation of the 8 B spectrum or a diurnal or
seasonal flux variation.
The latter cases can be very well investigated with the Superkamiokande
detector which is scheduled to begin its operation in April of
1996. It is a water Cherenkov detector like Kamiokande, with about
20 times the fiducial volume. With about twice the relative coverage
of the surface area with photocathodes and a detection threshold as
low as 5 MeV it will count about 30 events/day from the solar boron
neutrino flux, as opposed to about 0.3 events/day at Kamiokande.
Fig. 10.20. Expected signal at night relative to the average daytime signal
in a water Cherenkov detector as a function of the angle between the
Sun and the detector nadir. The large-angle example is for sin 2 2θ = 0.7
and ∆m 2 ν = 1×10 −5 eV 2 , the small-angle case for sin 2 2θ = 0.01 and
∆m 2 ν = 0.3×10 −5 eV 2 . Also shown are the existing Kamiokande measurements
and the expected Superkamiokande error bars after 1 month and 1 year
of running, respectively. (Adapted from Suzuki 1995.)