A SUSY SO(10) GUT Model with Lopsided Structure

Abstract

The standard model (SM) of elementary particles has been established for more than 30 years and tested by a large number of experiments. However, because of the naturalness problem of the electroweak symmetry breaking scale and a large number of unexplained parameters in SM, physicists have been looking for a more fundamental theory. Supersymmetry (SUSY) and grand unification are two appealing concepts that have been mostly implemented to build candidates for beyond SM theories. SUSY helps to stabilize the scale of electroweak symmetry breaking, and grand unification embeds the SM gauge groups into larger and more fundamental gauge groups.

Neutrino oscillations, signaling massive neutrinos, are the first direct evidence of beyond SM physics. A tiny neutrino mass can be elegantly explained by the seesaw mechanism. The neutrino masses from this mechanism are of Majorana type and therefore break the B-L (baryon number minus lepton number) symmetry. A favorable framework of studying neutrino masses and oscillations is the SO(10) grand unification theory (GUT) which naturally accommodates a B-L breaking. The same B-L breaking can also facilitate baryogenesis via a leptogenesis scenario. This provides an interesting correlation between these two pieces of phenomenology. This thesis presents a realistic SUSY SO(10) GUT model with lopsided structure, which generates the correct masses and mixing of neutrinos and produces the right amount of baryon asymmetry.

One of the most characteristic features of this model is the lopsided mass matrices structure. We examine observables in B decays that are sensitive to this structure, and find a specific pattern of predictions that can be used to test this type of models.