Constraining neutrino oscillation parameters with current solar and atmospheric data

Abstract

We analyze the impact of recent solar and atmospheric data in the determination of the neutrino oscillation parameters, taking into account that both the solar ν e and the atmospheric ν µ may convert to a mixture of active and sterile neutrinos. We use the most recent global solar neutrino data, including the 1496-day Super-K neutrino data sample, and we investigate in detail the impact of the recent SNO neutral current, spectral and day/night data by performing also an analysis using only the charged current rate from SNO. We confirm the clear preference of the pure active LMA solution of the solar neutrino problem and obtain that the LOW, VAC, SMA and Just-So 2 solutions are disfavored with a ∆χ 2 = 9, 9, 23, 31, respectively. Furthermore, we find that the global solar data constrains the admixture of a sterile neutrino to be less than 44% at 99% C.L..A pure sterile solution is ruled out with respect to the active one at 99.997% C.L.. By performing an improved fit of the atmospheric data, we also update the corresponding regions of oscillation parameters. We find that the recent atmospheric Super-K (1489-day) and MACRO data have a strong impact on constraining a sterile component in atmospheric oscillations: if the ν µ is restricted to the atmospheric mass states only a sterile admixture of 16% is allowed at 99% C.L., while a bound of 35% is obtained in the unconstrained case. Pure sterile oscillations are disfavored with a ∆χ 2 = 34.6 compared to the pure active case.In the appendix we discuss the implications of the first 145.1 days of KamLAND data on the determination of the solar neutrino parameters. The inclusion of KamLAND enhances the rejection of non-LMA-MSW solutions by 13 units in ∆χ 2 . The bound on the sterile neutrino fraction is practically unaffected in the boron-fixed case, while it improves from 61% to 51% in the boron-free case.

Testing the statistical compatibility of independent data sets

“…The interested reader can find precise definitions of the parameters, applied approximations, an extensive discussion of physics aspects, and references in Refs. [3,5,10]. Here we are interested mainly in the statistical aspects of the analysis, and therefore we consider a simplified scenario.…”

Implication of a vanishing element in the3+1scenario

“…Adding one sterile neutrino to the standard 3 generation framework gives rise to two possible mass spectra -the 2+2 in which two pairs of mass states are separated by a difference ∼ eV 2 and 3+1 in which a single predominantly sterile state differs by ∼ eV 2 from the three active states [2]. Subsequently the 2+2 schemes were found to be incompatible with the solar and atmospheric neutrino data [3]. The MiniBoone experiment was designed to test this and its antineutrino data confirmed the LSND anomaly [4].…”

Neutrinos in Anomaly Mediated Supersymmetry Breaking with R-parity Violation

“…(4.10) is numerically smaller than the term dependent on A. When this condition is fulfilled the following approximated expressions for the two heaviest neutrinos are valid for Λ 2 = Λ 3 2) and as before, we approximate the atmospheric and the solar mass differences by m 2 ν 3 and m 2 ν 2 respectively. In this way, the quadratic growing of the solar mass with ǫ 2 is clear, and the quadratic decreasing of the atmospheric mass is also clear knowing that the term proportional to A is positive and larger than the negative term proportional to B.…”

“…The analysis of the solar neutrinos leads to the 3σ level limits [2] (see also [3] while the atmospheric neutrino data shows that 0.34 < ∼ sin 2 θ atm < ∼ 0.66…”