Renormalization Group Analysis of Neutrino Mass Parameters

Tools for calculating the Renormalization Group Equations for renormalizable and non-renormalizable operators in various theories are reviewed, which are essential for comparing experimental results with predictions from models beyond the Standard Model. Numerical examples for the running of the lepton mixing angles in models with non-degenerate see-saw scales are shown, in which the best-fit values of the experimentally favored LMA solution are produced from maximal or from vanishing solar neutrino mixing at the GUT scale.Comment: 6 pages, 17 figures; to appear in the proceedings of the 10th International Conference on Supersymmetry and Unification of Fundamental Interactions (SUSY02), June 17 - 23, DESY Hambur

Sneutrino Hybrid Inflation

We review the scenario of sneutrino hybrid inflation, where one of the singlet sneutrinos, the superpartners of the right-handed neutrinos, plays the role of the inflaton. In a minimal model of sneutrino hybrid inflation, the spectral index is given by $n_s \approx 1 + 2 \gamma$. With $\gamma = 0.025 \pm 0.01$ constrained by WMAP, a running spectral index $|d n_s/d \ln k| \ll |\gamma|$ and a tensor-to-scalar ratio $r \ll \gamma^2$ are predicted. Small neutrino masses arise from the seesaw mechanism, with heavy masses for the singlet (s)neutrinos generated by the vacuum expectation value of the waterfall field after inflation. The baryon asymmetry of the universe can be explained by non-thermal leptogenesis via sneutrino inflaton decay, with low reheat temperature $T_RH \approx 10^6$ GeV.Comment: 7 pages, 2 figures; talk presented at the International Workshop on The Dark Side of the Universe (DSU2006), Madrid, Spain, June 20-24, 200

Implications of Running Neutrino Parameters for Leptogenesis and for Testing Model Predictions

The running of neutrino parameters in see-saw models and its implications for leptogenesis and for testing predictions of mass models with future precision experiments are discussed using analytical approximations as well as numerical results.Comment: 5 pages, 2 figures; talk presented at 10th International Symposium on Particles, Strings and Cosmology (Pascos04), Northeastern University, Boston, August 16-22, 2004; references adde

Searches for Sterile Neutrinos at Future Electron-Proton Colliders

Sterile neutrinos are an attractive extension of the Standard Model of elementary particles towards including a mechanism for generating the observed light neutrino masses. We discuss that when an approximate protective "lepton number"-like symmetry is present, the sterile neutrinos can have masses around the electroweak scale and potentially large neutrino Yukawa couplings, which makes them well testable at planned future particle colliders. We systematically discuss the production and decay channels for sterile neutrinos at electron-proton colliders and give a complete list of the leading order signatures for sterile neutrino searches. We highlight several novel search channels and present a first look at the possible sensitivities for the active-sterile mixing parameters and the heavy neutrino masses. We also compare the performance of electron-proton colliders with the ones of proton-proton and electron-positron colliders, and discuss the complementarity of the different collider types.Comment: Conference proceedings for the DIS 2017 in Birmingham, 13 pages, 8 figures, 2 table

Impact of other scalar fields on oscillons after hilltop inflation

Oscillons are spatially localized and relatively stable field fluctuations which can form after inflation under suitable conditions. In order to reheat the universe, the fields which dominate the energy density after inflation have to couple to other degrees of freedom and finally produce the matter particles present in the universe today. In this study, we use lattice simulations in 2+1 dimensions to investigate how such couplings can affect the formation and stability of oscillons. We focus on models of hilltop inflation, where we have recently shown that hill crossing oscillons generically form, and consider the coupling to an additional scalar field which, depending on the value of the coupling parameter, can get resonantly enhanced from the inhomogeneous inflaton field. We find that three cases are realized: without a parametric resonance, the additional scalar field has no effects on the oscillons. For a fast and strong parametric resonance of the other scalar field, oscillons are strongly suppressed. For a delayed parametric resonance, on the other hand, the oscillons get imprinted on the other scalar field and their stability is even enhanced compared to the single-field oscillons.Comment: 15 pages, 6 figures, version published in JCA

GUT predictions for quark and lepton mass ratios

Group theoretical factors from GUT symmetry breaking can lead to predictions for the ratios of quark and lepton masses at the unification scale. Due to supersymmetric (SUSY) threshold corrections the viability of such predictions can depend strongly on the SUSY parameters. We derive possible new predictions for the GUT scale ratios m_\mu/m_s, y_\tau/y_b and y_t/y_b and compare them with the experimentally allowed ranges for three common SUSY breaking scenarios.Comment: Based on a talk given at SUSY 09; 5 pages, 1 figure, 2 table