7 research outputs found
A realistic pattern of fermion masses from a five-dimensional SO(10) model
We provide a unified description of fermion masses and mixing angles in the
framework of a supersymmetric grand unified SO(10) model with anarchic Yukawa
couplings of order unity. The space-time is five dimensional and the extra flat
spatial dimension is compactified on the orbifold ,
leading to Pati-Salam gauge symmetry on the boundary where Yukawa interactions
are localised. The gauge symmetry breaking is completed by means of a rather
economic scalar sector, avoiding the doublet-triplet splitting problem. The
matter fields live in the bulk and their massless modes get exponential
profiles, which naturally explain the mass hierarchy of the different fermion
generations. Quarks and leptons properties are naturally reproduced by a
mechanism, first proposed by Kitano and Li, that lifts the SO(10) degeneracy of
bulk masses in terms of a single parameter. The model provides a realistic
pattern of fermion masses and mixing angles for large values of . It
favours normally ordered neutrino mass spectrum with the lightest neutrino mass
below 0.01 eV and no preference for leptonic CP violating phases. The right
handed neutrino mass spectrum is very hierarchical and does not allow for
thermal leptogenesis. We analyse several variants of the basic framework and
find that the results concerning the fermion spectrum are remarkably stable.Comment: 30 pages, 7 figures, 4 table
Unification and Phenomenology of F-Theory GUTs with U(1)_PQ
We undertake a phenomenological study of SU(5) F-theory GUT models with an
additional U(1)_{PQ} symmetry. In such models, breaking SU(5) with hypercharge
flux leads to the presence of non-GUT multiplets in the spectrum. We study the
effect these have on the unification of gauge couplings, including two-loop
running as well as low- and high-scale threshold corrections. We use the
requirement of unification to constrain the size of thresholds from KK modes of
SU(5) gauge and matter fields. Assuming the non-GUT multiplets play the role of
messengers of gauge mediation leads to controlled non-universalities in the
sparticle spectrum while maintaining grand unification, and we study the LHC
phenomenology of this scenario. We find that the MSSM spectrum may become
compressed or stretched out {by up to a factor of three} depending on the
distribution of hypercharge flux. We present a set of benchmark points whose
production cross-sections and decays we investigate, and argue that precision
kinematic edge measurements will allow the LHC to distinguish between our model
and mGMSB.Comment: 46 pages, 15 figure