Academic training less at CERN

SNO webpage

It is sensitive to the high part(*) of the ν energy spectrum, via the reactions:
CC: νd -> epp (it measures Φ(ν_e))
NC: νd -> νnp (it measures Φ(ν_e+μ+τ))
ES: νe -> νe (it measures all fluxes, but the electron neutrino dominates by a factor of 6)

ES gives poor energy information (since energy is shared between electron and neutrino) but gives directionality. Solar Standard Model expects 3 events/day.
CC gives energy and direction information. One expect spectrum distorsion in case of oscillations. SSM predicts 30 events/day.
NC gives no directionality nor energy information. SSM predicts 30 events/day. To detect neutrons, in principle one could use recombination into deuterium (with emission of gammas) but efficiency is very low. So, SNO uses two methods: Helium-3 proportional counters, and Chlorine Salt diluted in the heavy water.

(*) The solar "matter effect" is important for the high-energy ⁸B neutrinos, not the low-energy pp neutrinos.

Solar neutrino flavor change is ν_e -> ν_x, where ν_x is some combination of ν_μ and ν_τ: this is a 2-neutrino system.
In fact, for the typical ⁸B energy of 8 MeV and Δm²_sol~8*10^-5 eV², the interaction term with matter (which is due to &nu_ee charged current interactions) dominates, and ν_e is with very good approximation an eigenstate of H.
For pp neutrinos (~0.2 MeV), instead, the vacuum hamiltonian dominates.
Explaination:
- the interaction term is G_FN_e~0.75*10^-5 eV²/MeV (multiplied by a matrix in which only the electron element is filled)
- the vacuum term is the mixing matrix multiplied by the factor Δm²_sol/4E.

So, the boron neutrinos mix inside the Sun; outside of the Sun, in the travel to Earth, nothing oscillates anymore.

Results from solar neutrinos: Δm²_sol~8*10^-5 eV², θ_sol~34 degrees.

This has implication on reactor antineutrinos.
With Δm²_sol~8*10^-5 eV², the fractional importance of interaction energy (independent of neutrino energy) and vacuum energy (Δm²_sol/4E), for E~few MeV, is negligible.
So, reactor experiments at large distance see an energy averaged oscillation, and should see substantial disappearance of the antineutrino flux.
In fact, KamLAND (~180 km from reactor) sees only 66% of the flux.
Flavor change with Δm²_sol and θ_sol fits both the solar and reactor data.