Solar Neutrino Observables Sensitive to Matter Effects

Abstract EN

We discuss constraints on the coefficient AMSW which is introduced to simulate the effect of weaker or stronger matter potential for electron neutrinos with the current and future solar neutrino data.

The currently available solar neutrino data leads to a bound AMSW=1.47+0.54−0.42(+1.88−0.82) at 1σ (3σ) CL, which is consistent with the Standard Model prediction AMSW=1.

For weaker matter potential (AMSW<1), the constraint which comes from the flat 8B neutrino spectrum is already very tight, indicating the evidence for matter effects.

However for stronger matter potential (AMSW>1), the bound is milder and is dominated by the day-night asymmetry of 8B neutrino flux recently observed by Super-Kamiokande.

Among the list of observables of ongoing and future solar neutrino experiments, we find that (1) an improved precision of the day-night asymmetry of 8B neutrinos, (2) precision measurements of the low-energy quasi-monoenergetic neutrinos, and (3) the detection of the upturn of the 8B neutrino spectrum at low energies are the best choices to improve the bound on AMSW.