arXiv subjects

Werner Rodejohann

Publications and source records attributed to Werner Rodejohann.

149 records · Page 9Linked to original sources

arXiv2004

Neutrinoless double beta decay and direct searches for neutrino mass

Study of the neutrinoless double beta decay and searches for the manifestation of the neutrino mass in ordinary beta decay are the main sources of information about the absolute neutrino mass scale, and the only practical source of information about the charge conjugation properties of the neutrinos. Thus, these studies have a unique role in the plans for better understanding of the whole fast expanding field of neutrino physics.

hep-ph↗

arXiv2004

Flavor Democracy and Type-II Seesaw Realization of Bilarge Neutrino Mixing

We generalize the democratic neutrino mixing Ansatz by incorporating the type-II seesaw mechanism with S(3) flavor symmetry. We find that bilarge neutrino mixing can naturally appear if the flavor democracy contribution is strongly suppressed due to significant cancellation between the conventional seesaw and triplet mass terms. Explicit S(3) symmetry breaking yields successful neutrino phenomenology and various testable correlations between the neutrino mass and mixing parameters. Among the results are a normal neutrino mass ordering, $0.005 \le |U_{e3}| \le 0.057$, $1 - \sin^2 2θ_{23} \ge 0.005$, positive $J_{\rm CP}$ and moderate cancellation in the effective mass of the neutrinoless double beta decay.

hep-ph↗

arXiv2003

Hierarchical Matrices in the See-Saw Mechanism, large Neutrino Mixing and Leptogenesis

We consider the see-saw mechanism for hierarchical Dirac and Majorana neutrino mass matrices m_D and M_R, including the CP violating phases. Simple arguments about the structure of the neutrino mass matrix and the requirement of successful leptogenesis lead to the situation that one of the right-handed Majorana neutrinos is much heavier than the other two, which in turn display a rather mild hierarchy. It is investigated how for the neutrino mixing one small and two large angles are generated. The mixing matrix element |U_{e3}|^2 is larger than 10^{-3} and a characteristic ratio between the branching ratios of lepton flavor violating charged lepton decays \ell_j -> \ell_i γis found. Successful leptogenesis implies sizable CP violation in oscillation experiments. As in the original minimal see-saw model, the signs of the baryon asymmetry of the universe and of the CP asymmetry in neutrino oscillations are equal and there is no connection between the leptogenesis phase and the effective mass as measurable in neutrinoless double beta decay.

hep-ph↗

arXiv2002

Leptogenesis, mass hierarchies and low energy parameters

Leptogenesis in a left-right symmetric model is investigated for all possible neutrino mass hierarchies. The predictions of the model for low energy parameters as measured in neutrinoless double beta decay and in oscillation experiments are compared. The preferred values of the Majorana phases and limits on the smallest mass state are given. The main observation is that for the inverse hierarchy observable CP violation in oscillation experiments as well as a sizable signal in neutrinoless double beta decay can be expected. In a degenerate scheme, one Majorana phase is bounded to be around pi/2 or pi, and this ambiguity can easily be tested through neutrinoless double beta decay. The dependence of the baryon asymmetry on the different "Dirac" and "Majorana" phases is analyzed and a possibility to avoid the gravitino problem is discussed.

hep-ph↗

arXiv2000

Bounds on effective Majorana neutrino masses at HERA

The lepton-number violating process e p \to nu_e l l' X mediated by Majorana neutrinos is studied for the HERA collider for (l l') = (e tau), (mu tau), (mu mu) and (tau tau). Only the muonic decay of the tau is considered. The direct limit on the effective muon Majorana mass, is improved significantly to 4.0 times 10^3 GeV and for the first time direct limits on the analogous effective masses connected with the tau sector are given, namely 4.2 times 10^3 GeV for , 4.4 times 10^3 GeV for and 2.0 times 10^4 GeV for . We find that a more general analysis for an upgraded HERA could improve this values by a factor of up to 40, yet still being orders of magnitude worse than indirect limits.

hep-ph↗