The GSI oscillation mystery

In this talk, a short discussion of the GSI anomaly is given. We discuss the physics involved using a comparison with pion decay, and explain why the observed oscillations cannot be caused by standard neutrino mixing.Comment: 3 pages, 1 figure; part of the proceedings of the "International School of Nuclear Physics, 31st Course, 'Neutrinos in Cosmology, in Astro-, Particle- and Nuclear Physics' " in Erice, Italy, 16 - 24 September 200

Running of Radiative Neutrino Masses: The Scotogenic Model - REVISITED

A few years ago, it had been shown that effects stemming from renormalisation group running can be quite large in the scotogenic model, where neutrinos obtain their mass only via a 1-loop diagram (or, more generally, in many models in which the light neutrino mass is generated via quantum corrections at loop-level). We present a new computation of the renormalisation group equations (RGEs) for the scotogenic model, thereby updating previous results. We discuss the matching in detail, in particular in what regards the different mass spectra possible for the new particles involved. We furthermore develop approximate analytical solutions to the RGEs for an extensive list of illustrative cases, covering all general tendencies that can appear in the model. Comparing them with fully numerical solutions, we give a comprehensive discussion of the running in the scotogenic model. Our approach is mainly top-down, but we also discuss an attempt to get information on the values of the fundamental parameters when inputting the low-energy measured quantities in a bottom-up manner. This work serves the basis for a full parameter scan of the model, thereby relating its low- and high-energy phenomenology, to fully exploit the available information.Comment: 44 pages, 13 figures; continuation of 1205.0008 [hep-ph]; content matches published version; v3 corrected a minor typo in Eq. (25

Explicit and spontaneous breaking of SU(3) into its finite subgroups

We investigate the breaking of SU(3) into its subgroups from the viewpoints of explicit and spontaneous breaking. A one-to-one link between these two approaches is given by the complex spherical harmonics, which form a complete set of SU(3)-representation functions. An invariant of degrees p and q in complex conjugate variables corresponds to a singlet, or vacuum expectation value, in a (p,q)-representation of SU(3). We review the formalism of the Molien function, which contains information on primary and secondary invariants. Generalizations of the Molien function to the tensor generating functions are discussed. The latter allows all branching rules to be deduced. We have computed all primary and secondary invariants for all proper finite subgroups of order smaller than 512, for the entire series of groups \Delta(3n^2), \Delta(6n^2), and for all crystallographic groups. Examples of sufficient conditions for breaking into a subgroup are worked out for the entire T_{n[a]}-, \Delta(3n^2)-, \Delta(6n^2)-series and for all crystallographic groups \Sigma(X). The corresponding invariants provide an alternative definition of these groups. A Mathematica package, SUtree, is provided which allows the extraction of the invariants, Molien and generating functions, syzygies, VEVs, branching rules, character tables, matrix (p,q)_{SU(3)}-representations, Kronecker products, etc. for the groups discussed above.Comment: 62 pages, 5 figures; the corresponding software package SUtree can be downloaded from http://theophys.kth.se/~amerle/SUtree/SUtree.html New in v2: Nice figure added, references added, explicit transformation matrices between different embeddings calculated, software package update

Getting Information on |U_{e3}|^2 from Neutrino-less Double Beta Decay

We consider the possibility to gain information on the lepton mixing matrix element |U_{e3}| from an improved experimental limit on the effective neutrino mass governing neutrino-less double beta decay. We show that typically a lower limit on |U_{e3}| can be set. Furthermore, we give the values of the sum of neutrino masses and |U_{e3}| which are allowed and forbidden by an experimental upper limit on the effective mass. Alternative explanations for neutrino-less double beta decay or Dirac neutrinos would be required if future measurements showed that the values lie in the respective regions. Moreover, we argue that a measurement of |U_{e3}| from neutrino-less double beta decay is very difficult due to the expected errors on the effective mass and the oscillation parameters.Comment: 17 pages, 7 figures; Comments and references added; to appear in AHEP (Advances in High Energy Physics