LMA MSW solution of the solar neutrino problem and first KamLAND results

The first KamLAND results are shown to be in very good agreement with the predictions made on the basis of the solar neutrino data and the LMA realization of the MSW mechanism. We perform a combined analysis of the KamLAND (rate, spectrum) and the solar neutrino data with a free boron neutrino flux f B . The best fit values of neutrino parameters are Δ m 2 = 7.3 × 10 −5 eV 2 , tan 2 θ = 0.41 and f B = 1.05 with the 1σ intervals: Δ m 2 = (6.2 – 8.4) × 10 −5 eV 2 , tan 2 θ = 0.33 – 0.54. We find the 3σ upper bounds: Δ m 2 < 2.8 × 10 −4 eV 2 and tan 2 θ < 0.84, and the lower bound Δ m 2 > 4 × 10 −5 eV 2 . At 99% CL the KamLAND spectral result splits the LMA region into two parts with the preferred one at Δ m 2 < 10 −4 eV 2 . The higher Δ m 2 region is accepted at about the 2σ level. We show that effects of non-zero 13-mixing, sin 2 θ 13 ⩽ 0.04, are small, leading to a slight improvement of the fit in the higher Δ m 2 region. At the best fit point we predict for SNO: CC/NC = 0.33 +0.05 −0.03 and A DN SNO = 2.8±0.8% (68% CL), and A DN SNO < 9% at the 3σ level. Further improvements in the determination of the oscillation parameters are discussed and implications of the solar neutrino and KamLAND results are considered.