Two gallium data sets, spin flavour precession and KamLAND

Abstract

We reexamine the possibility of a time modulation of the low energy solar neutrino flux which is suggested by the average decrease of the Ga data in line with our previous arguments. We perform two separate fits to the solar neutrino data, one corresponding to ‘high’ and the other to ‘low’ Ga data, associated with low and high solar activity, respectively. We therefore consider an alternative to the conventional solar+KamLAND fitting, which allows one to explore the much wider range of the θ12 angle permitted by the KamLAND fitting alone. We find a solution with parameters Δm221 = 8.2 × 10−5 eV2, tan2θ = 0.31 in which the ‘high’ and the ‘low’ Ga rates lie far apart and are close to their central values and is of comparable quality to the global best fit, where these rates lie much closer to each other. This is an indication that the best fit in which all solar and KamLAND data are used is not a good measure of the separation of the two Ga data sets, as the information from the low energy neutrino modulation is dissimulated in the wealth of data. Furthermore, for the parameter set proposed one obtains an equally good fit to the KamLAND energy spectrum and an even better fit than the ‘conventional’ LMA one for the reactor antineutrino survival probability as measured by the KamLAND.