The unfinished fabric of the three neutrino paradigm
Abstract
In the current 3nu paradigm, flavor oscillations probe 3 mixing angles (theta12, theta23, theta13), one CP phase delta, and two squared mass differences delta m2>0 and Delta m2, where sign(Delta m2)=+ (-) for normal (inverted) ordering. Absolute nu masses can be probed by the effective mbeta in beta decay, by the total mass Sigma in cosmology and, if neutrinos are Majorana, by another effective mbeta beta in 0nu2beta decay. Within an updated global analysis of (non)oscillation data, we constrain these 3nu parameters, both separately and in selected pairs, and highlight the concordance or discordance among different constraints. Five oscillation parameters (delta m2, Delta m2, theta12, theta23, theta13) are consistently measured, with an overall accuracy ranging from ~1% for Delta m2 to ~6% for sin2(theta23) (due to its octant ambiguity). We find overall hints for normal ordering (at 2.5 sigma), as well as for theta23<pi/4 and for sin(delta)<0 (both at 90% C.L.), and discuss some tensions among datasets. Concerning nonoscillation data, we include the recent KATRIN constraints on mbeta, and we combine the latest 76-Ge, 130-Te and 136-Xe bounds on mbeta beta, accounting for NME covariances. We also discuss some variants related to CMB anisotropy and lensing data, which may affect cosmological constraints on Sigma and hints on sign(Delta m2). The default option, including all Planck results, irrespective of the lensing anomaly, sets upper bounds on Sigma at the level of ~10-1 eV, and further favors normal ordering up to ~3 sigma. An alternative option, that includes recent ACT results + other independent results (from WMAP and selected Planck data) globally consistent with standard lensing, is insensitive to the ordering but prefers Sigma ~(few) x 10-1 eV, with different implications for mbeta and mbeta beta searches. (Abridged)