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

BICEP2 implications for single-field slow-roll inflation revisited

It is generally believed that in single-field slow-roll inflation, a large tensor-to-scalar ratio $r > 0.1$ requires inflaton field values close to or above the Planck scale. Recently, it has been claimed that $r > 0.15$ can be achieved with much smaller inflaton field values $\Delta \phi < M_{Pl}/10$. We show that in single-field slow-roll inflation, it is impossible to reconcile $r > 0.1$ with such small field values, independently of the form of the potential, and that the recent claim to the contrary is based on an invalid approximation. We conclude that the result of the BICEP2 measurement of $r > 0.1$, if confirmed, truly has the potential to rule out small-field models of single-field slow-roll inflation.Comment: 9 pages, 2 figures, v3: references and note on arXiv:1404.3398v2 adde

One-Loop Right-Handed Neutrino Threshold Corrections for Two-Loop Running in Supersymmetric Type I Seesaw Models

The renormalization group (RG) running of the neutrino mass operator is required for comparing the predictions of neutrino models at high energy with the experimental data at low energies. In the type I seesaw scenario with n_G right-handed neutrinos, the RG running is also performed in the effective theories above and between the thresholds given by the masses of the right-handed neutrinos. At these thresholds, the effective theories are matched. When calculating the two-loop RG running, the matching has to be performed at the one-loop level. In this work, we calculate the one-loop matching formulae in the MSSM extended by n_G right-handed neutrinos using supergraph techniques. Moreover we present a general formula for one-loop matching of superpotential operators which can readily be applied to any supersymmetric theory where chiral superfields are integrated out.Comment: 15 pages, 4 figures; version to appear in JHE