Axion Paradigm with Color-Mediated Neutrino Masses.

We propose a generalized Kim-Shifman-Vainshtein-Zakharov-type axion framework in which colored fermions and scalars act as two-loop Majorana neutrino-mass mediators. The global Peccei-Quinn symmetry under which exotic fermions are charged solves the strong CP problem. Within our general proposal, various setups can be distinguished by probing the axion-to-photon coupling at helioscopes and haloscopes. We also comment on axion dark-matter production in the early Universe.

New Ambiguity in Probing CP Violation in Neutrino Oscillations.

If neutrinos get mass via the seesaw mechanism the mixing matrix describing neutrino oscillations can be effectively nonunitary. We show that in this case the neutrino appearance probabilities involve a new CP phase ϕ associated with nonunitarity. This leads to an ambiguity in extracting the "standard" three-neutrino phase δ_{CP}, which can survive even after neutrino and antineutrino channels are combined. Its existence should be taken into account in the planning of any oscillation experiment aiming at a robust measurement of δ_{CP}.

Minimal supergravity scalar neutrino dark matter and inverse seesaw neutrino masses.

We show that within the inverse seesaw mechanism for generating neutrino masses, minimal supergravity naturally provides the scalar neutrino as the lightest superparticle. We also demonstrate that such schemes naturally reconcile the small neutrino masses with the correct relic scalar neutrino dark matter abundance and accessible direct detection rates in nuclear recoil experiments. This way, inverse seesaw minimal supergravity offers a common solution to the generation of the neutrino mass and to the origin of dark matter.

Predictive flavor symmetries of the neutrino mass matrix.

Here we propose an A(4) flavor symmetry model that implies a lower bound on the neutrinoless double beta decay rate, corresponding to an effective mass parameter M{ee} > or similar to 0.03 eV, and a direct correlation between the expected magnitude of CP violation in neutrino oscillations and the value of sin{2}theta{13}, as well as a nearly maximal CP phase delta.

Decaying warm dark matter and neutrino masses.

Neutrino masses may arise from spontaneous breaking of ungauged lepton number. Because of quantum gravity effects the associated Goldstone boson - the majoron - will pick up a mass. We determine the lifetime and mass required by cosmic microwave background observations so that the massive majoron provides the observed dark matter of the Universe. The majoron decaying dark matter scenario fits nicely in models where neutrino masses arise via the seesaw mechanism, and may lead to other possible cosmological implications.

R parity violation assisted thermal leptogenesis in the seesaw mechanism.

Successful leptogenesis within the simplest type I supersymmetric seesaw mechanism requires the lightest of the three right-handed neutrino supermultiplets to be heavier than approximately 10(9) GeV. Thermal production of such (s)neutrinos requires very high reheating temperatures which result in an overproduction of gravitinos with catastrophic consequences for the evolution of the Universe. In this Letter, we let R parity be violated through a lambda(i)N(i)H(u)H(d) term in the superpotential, where N(i) are right-handed neutrino supermultiplets. We show that in the presence of this term, the produced lepton-antilepton asymmetry can be enhanced. As a result, even for N1 masses as low as 10(6) GeV or less, we can obtain the observed baryon asymmetry of the Universe without gravitino overproduction.

Supersymmetric SO10 seesaw mechanism with low B-L scale.

We propose a new seesaw mechanism for neutrino masses within a class of supersymmetric SO(10) models with broken D parity. It is shown that in such scenarios the B-L scale can be as low as TeV without generating inconsistencies with gauge coupling unification nor with the required magnitude of the light neutrino masses. This leads to a possibly light new neutral gauge boson as well as relatively light quasi-Dirac heavy leptons. These particles could be at the TeV scale and mediate lepton flavor and CP violating processes at appreciable levels.

Constraining the neutrino magnetic moment with antineutrinos from the sun.

We discuss the impact of different solar neutrino data on the spin-flavor-precession (SFP) mechanism of neutrino conversion. We find that, although detailed solar rates and spectra allow the SFP solution as a subleading effect, the recent KamLAND constraint on the solar antineutrino flux places stronger constraints on this mechanism. Moreover, we show that for the case of random magnetic fields inside the Sun, one obtains a more stringent constraint on the neutrino magnetic moment down to the level of mu(nu)< or = few x 10(-12)mu(B), similar to bounds obtained from star cooling.

How sensitive is a neutrino factory to the angle theta(13)?

We consider the impact of nonstandard interactions (NSI) of neutrinos on the determination of neutrino mixing parameters at a neutrino factory using nu(-)(e)-->nu(-)(mu) "golden channels" for the measurement of theta(13). We show how a small residual NSI leads to a drastic loss in sensitivity in theta(13), of up to 2 orders of magnitude. This can be somewhat overcome if two baselines are combined.