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Register a new userGlobal analysis of neutrino masses, mixings and phases: entering the era of leptonic CP violation searches
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We perform a global analysis of neutrino oscillation data, including high-precision measurements of the neutrino mixing angle theta_13 at reactor experiments, which have confirmed previous indications in favor of theta_13>0. Recent data presented at the Neutrino 2012 Conference are also included. We focus on the correlations between theta_13 and the mixing angle theta_23, as well as between theta_13 and the neutrino CP-violation phase delta. We find interesting indications for theta_23< pi/4 and possible hints for delta ~ pi, with no significant difference between normal and inverted mass hierarchy.
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The neutrino parameters determined from the solar neutrino data and the anti-neutrino parameters determined from KamLAND reactor experiment are in good agreement with each other. However, the best fit points of the two sets differ from each other by about $10^{-5}$ eV$^2$ in mass-square differenc and by about $2^circ$ in the mixing angle. Future solar neutrino and reactor anti-neutrino experiments are likely to reduce the uncertainties in these measurements. This, in turn, can lead to a signal for CPT violation in terms a non-zero difference between neutrino and anti-neutrino parameters. In this paper, we propose a CPT violating mass matrix which can give rise to the above differences in both mass-squared difference and mixing angle and study the constraints imposed by the data on the parameters of the mass matrix.
CP violation, fermion masses and mixing angles including that of neutrinos are studied in an SUSY SO(10)$times Delta (48)times$ U(1) model. The nonabelian SU(3) discrete family symmetry $Delta(48)$ associated with a simple scheme of U(1) charge assignment on various fields concerned in superpotential leads to unique Yukawa coupling matrices with zero textures. Thirteen parameters involving masses and mixing angles in the quark and charged lepton sector are successfully predicted by only four parameters. The masses and mixing angles for the neutrino sector could also be predicted by constructing an appropriate heavy Majorana neutrino mass matrix without involving new parameters. It is found that the atmospheric neutrino deficit, the mass limit put by hot dark matter and the LSND $bar{ u}_{mu} to bar{ u}_{e}$ events may simultaneously be explained, but solar neutrino puzzle can be solved only by introducing a sterile neutrino. An additional parameter is added to obtain the mass and mixing of the sterile neutrino. The hadronic parameters $B_{K}$ and $f_{B}sqrt{B}$ are extracted from the observed $K^{0}$-$bar{K}^{0}$ and $B^{0}$-$bar{B}^{0}$ mixings respectively. The direct CP violation ($epsilon/epsilon$) in kaon decays and the three angles $alpha$, $beta$ and $gamma$ of the unitarity triangle in the CKM matrix are also presented. More precise measurements of $alpha_{s}(M_{Z})$, $|V_{cb}|$, $|V_{ub}/V_{cb}|$, $m_{t}$, as well as various CP violation and neutrino oscillation experiments will provide an important test for the present model and guide us to a more fundamental theory.
Within the standard three-neutrino framework, the absolute neutrino masses and their ordering (either normal, NO, or inverted, IO) are currently unknown. However, the combination of current data coming from oscillation experiments, neutrinoless double beta decay searches, and cosmological surveys, can provide interesting constraints for such unknowns in the sub-eV mass range, down to O(0.1) eV in some cases. We discuss current limits on absolute neutrino mass observables by performing a global data analysis, that includes the latest results from oscillation experiments, neutrinoless double beta decay bounds from the KamLAND-Zen experiment, and constraints from representative combinations of Planck measurements and other cosmological data sets. In general, NO appears to be somewhat favored with respect to IO at the level of ~2 sigma, mainly by neutrino oscillation data (especially atmospheric), corroborated by cosmological data in some cases. Detailed constraints are obtained via the chi^2 method, by expanding the parameter space either around separate minima in NO and IO, or around the absolute minimum in any ordering. Implications for upcoming oscillation and non-oscillation neutrino experiments, including beta-decay searches, are also discussed.
We revisit our previous work [Phys. Rev. D 95, 096014 (2017)] where neutrino oscillation and nonoscillation data were analyzed in the standard framework with three neutrino families, in order to constrain their absolute masses and to probe their ordering (either normal, NO, or inverted, IO). We include updated oscillation results to discuss best fits and allowed ranges for the two squared mass differences $delta m^2$ and $Delta m^2$, the three mixing angles $theta_{12}$, $theta_{23}$ and $theta_{13}$, as well as constraints on the CP-violating phase $delta$, plus significant indications in favor of NO vs IO at the level of $Deltachi^2=10.0$. We then consider nonoscillation data from beta decay, from neutrinoless double beta decay (if neutrinos are Majorana), and from various cosmological input variants (in the data or the model) leading to results dubbed as default, aggressive, and conservative. In the default option, we obtain from nonoscillation data an extra contribution $Deltachi^2 = 2.2$ in favor of NO, and an upper bound on the sum of neutrino masses $Sigma < 0.15$ eV at $2sigma$; both results - dominated by cosmology - can be strengthened or weakened by using more aggressive or conservative options, respectively. Taking into account such variations, we find that the combination of all (oscillation and nonoscillation) neutrino data favors NO at the level of $3.2-3.7sigma$, and that $Sigma$ is constrained at the $2sigma$ level within $Sigma < 0.12-0.69$ eV. The upper edge of this allowed range corresponds to an effective $beta$-decay neutrino mass $m_beta = Sigma/3 = 0.23$ eV, at the sensitivity frontier of the KATRIN experiment.
Assuming the Majorana nature of massive neutrinos, we generalize the Friedberg-Lee neutrino mass model to include CP violation in the neutrino mass matrix M_ u. The most general case with all the free parameters of M_ u being complex is discussed. We show that a favorable neutrino mixing pattern (with theta_12 approx 35.3^circ, theta_23=45^circ, theta_13 eq 0^circ and delta=90^circ) can naturally be derived from M_ u, if it has an approximate or softly-broken mu-tau symmetry. We also point out a different way to obtain the nearly tri-bimaximal neutrino mixing pattern with delta=0^circ and non-vanishing Majorana phases.
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