Abstract: We discuss the systematic decomposition of the dimension nine neutrinoless double beta decay operator, focusing on mechanisms with potentially small contributions to neutrino mass, while being accessible at the LHC. We first provide a (d = 9 tree-level) complete list of diagrams for neutrinoless double beta decay. From this list one can easily recover all previously discussed contributions to the neutrinoless double beta decay process, such as the celebrated mass mechanism or “exotics”, such as contributions from left-right symmetric models, R-parity violating supersymmetry and leptoquarks. More interestingly, however, we identify a number of new possibilities which have not been discussed in the literature previously. Contact to earlier works based on a general Lorentz-invariant parametrisation of the neutrinoless double beta decay rate is made, which allows, in principle, to derive limits on all possible contributions. We furthermore discuss possible signals at the LHC for mediators leading to the short-range part of the amplitude with one specific example. The study of such contributions would gain particular importance if there were a tension between different measurements of neutrino mass such as coming from neutrinoless double beta decay and cosmology or single beta decay.

Abstract: Preliminary results of MINOS experiment indicate that theta(23) is not maximal. Global fits to world neutrino data suggest two nearly degenerate solutions for theta(23): one in the lower octant (LO: theta(23) < 45 degrees) and the other in the higher octant (HO: theta(23) > 45 degrees). v(mu) -> v(e) oscillations in superbeam experiments are sensitive to the octant and are capable of resolving this degeneracy. We study the prospects of this resolution by the current T2K and upcoming NOvA experiments. Because of the hierarchy-delta(CP) degeneracy and the octant delta(CP) degeneracy, the impact of hierarchy on octant resolution has to be taken into account. As in the case of hierarchy determination, there exist favorable (unfavorable) values of delta(CP) for which octant resolution is easy (challenging). However, for octant resolution the unfavorable delta(CP) values of the neutrino data are favorable for the anti-neutrino data and vice-verse. This is in contrast to the case of hierarchy determination. In this paper, we compute the combined sensitivity of T2K and NOvA to resolve the octant ambiguity. If sin(2)theta(23) – 0.41, then NOvA can rule out all the values of theta(23) in HO at 2 sigma C.L., irrespective of the hierarchy and delta(CP). Addition of T2K data improves the octant sensitivity. If T2K were to have equal neutrino and anti-neutrino runs of 2.5 years each, a 2 sigma resolution of the octant becomes possible provided sin(2) theta(23) <= 0.43 or >= 0.58 for any value of delta(CP).

Abstract: A new Higgs-like boson with mass around 126 GeV has recently been discovered at the LHC. The available data on this new particle is analyzed within the context of two-Higgs doublet models without tree-level flavour-changing neutral currents. Keeping the generic Yukawa structure of the Aligned Two-Higgs Doublet Model framework, we study the implications of the LHC data on the allowed scalar spectrum. We analyze both the CP-violating and CP-conserving cases, and a few particular limits with a reduced number of free parameters, such as the usual models based on discrete Z(2) symmetries.