Implications of neutrino data circa 2005

TL;DR

This paper integrates solar, reactor, and atmospheric neutrino data within a three-neutrino framework to update the oscillation parameters, highlighting robust determinations of $ riangle m^2_{12}$ and $ heta_{12}$ from solar and KamLAND data, while constraining $ heta_{13}$ subdominantly. It clarifies how global fits can be approximated by simple data-driven arguments and discusses the implications for solar fluxes, Borexino, and CPT tests. The authors also examine non-oscillation probes—cosmology, $eta$-decay, and neutrinoless double-beta decay—to bound the absolute neutrino mass scale and the Majorana nature, addressing current experimental limits and tensions (notably the Klapdor claim). Overall, the work connects oscillation physics with direct mass measurements and cosmology, outlining how future experiments could sharpen mass hierarchies and test new physics scenarios.

Abstract

Adopting the 3 neutrino framework, we present an updated determination of the oscillation parameters. We perform a global analysis and develope simple arguments that give essentially the same result. We also discuss determinations of solar neutrino fluxes, capabilities of future experiments, tests of CPT, implications for neutrino-less double-beta decay, beta decay, cosmology.

Figures (7)

• Figure 1: Summary of present information on neutrino masses and mixings from oscillations.
• Figure 2: Best-fit regions at $90,~99$ and $99.73\%$CL. Fig. \ref{['fig:2005']}a assumes CPT invariance and combines solar $\nu$ data (dashed red contours) with reactor $\bar{\nu}$ data (dotted blue contours). In fig. \ref{['fig:2005']}a we show how data determine the high- and low-energy limits of $P(\nu_e\to\nu_e)$, as precisely described in the text,
• Figure 3: Test of CPT-violating neutrino masses. We show the separate fit for $\Delta m^2$ in neutrinos and $\Delta\bar{m}^2$ in anti-neutrinos, marginalized with respect to the mixing angles $\theta_{12}$ and $\theta_{23}$. The atmospheric fit includes data from SK, K2K, Macro. The solar fit includes data from SNO, SK, Gallex, Sage, Homestake, KamLAND. These plots update the original results in fig.s 5 and 6 of CPT
• Figure 4: The energy-dependent survival probability predicted by LMA, and how experimental data restrict the low-energy and high-energy limits of $P(\nu_e\to \nu_e,E_\nu)$.
• Figure 6: $99\%$ CL expected ranges for the parameters $m_{\rm cosmo}=m_1+m_2+m_3$ probed by cosmology (fig. \ref{['fig:cosmobeta']}a) and $m_{\nu_e}\equiv (m\cdot m^\dagger)^{1/2}_{ee}$ probed by $\beta$-decay (fig. \ref{['fig:cosmobeta']}b) as function of the lightest neutrino mass. The darker lines show how the ranges would shrink if the present best-fit values of oscillation parameters were confirmed with negligible error.