High Scale Physics Research Articles

R-parity breaking via type II seesaw, decaying gravitino dark matter and PAMELA positron excess

We propose a new class of R-parity violating extension of MSSM with type II seesaw mechanism for neutrino masses where an unstable gravitino is the dark matter of the Universe. It decays predominantly into three leptons final states, thereby providing a natural explanation of the positron excess but no antiproton excess in the PAMELA experiment. The model can explain neutrino masses without invoking any high scale physics while keeping the pre-existing baryon asymmetry of the universe in tact.

Hidden sector renormalization of MSSM scalar masses

Running of gauge couplings in the MSSM from a unified value at high energies leads to a successful prediction of the weak mixing angle. Supersymmetric models at the TeV scale may contain further hints of high scale physics, such as the pattern of superpartner masses when evolved from the TeV scale to a high scale using the renormalization group. This running is traditionally assumed to be independent of effects in the hidden sector. In this paper we re-examine this assumption, and conclude that the predictions for scalar masses may depend sensitively on the details of the mechanism of supersymmetry breaking. We identify mass relations that persist even when such effects are taken into account.

Leptogenesis, μ–τ symmetry and [formula omitted

We show that in theories where neutrino masses arise from type I see-saw formula with three right-handed neutrinos and where large atmospheric mixing angle owes its origin to an approximate leptonic μ–τ interchange symmetry, the primordial lepton asymmetry of the Universe, εl can be expressed in a simple form in terms of low energy neutrino oscillation parameters as εl=(aΔm⊙2+bΔmA2θ132), where a and b are parameters characterizing high scale physics and are each of order ⩽10−2 eV−2. We also find that for the case of two right-handed neutrinos, εl∝θ132 as a result of which, the observed value of baryon to photon ratio implies a lower limit on θ13. For specific choices of the CP phase δ we find θ13 is predicted to be between 0.10–0.15.

Hubble-induced radiative corrections and Affleck-Dine baryogenesis

We examine the viability of the Affleck-Dine mechanism for baryogenesis under radiatively induced running of soft breaking $({\rm mass})^2$ of the flat directions stemming from non-zero energy density of the inflaton during inflation. A major difference from analogous phenomenological studies is that the horizon radius provides a natural infrared cut-off to the quantum corrections in this case. We identify different scenarios which may arise and point out that the $H_{u}L$ flat direction remains the most promising flat direction, since it is largely independent of uncertainties about high scale physics and details of the inflationary model.

New physics and the Landau pole

In scalar field theories the Landau pole is an ultraviolet singularity in the running coupling constant that indicates a mass scale at which the theory breaks down and new physics must intervene. However, new physics at the pole will in general affect the running of the low energy coupling constant, which will in turn affect the location of the pole and the related upper limit (``triviality'' bound) on the low energy coupling constant. If the new physics is strongly coupled to the scalar fields these effects can be significant even though they are power suppressed. We explore the possible range of such effects by deriving the one loop renormalization group equations for an effective scalar field theory with a dimension 6 operator representing the low energy effects of the new physics. As an independent check we also consider a renormalizable model of the high-scale physics constructed so that its low energy limit coincides with the effective theory.