Flavor Physics in an SO(10) Grand Unified Model

Abstract

In supersymmetric grand-unified models, the lepton mixing matrix can possibly affect flavor-changing transitions in the quark sector. We present a detailed analysis of a model proposed by Chang, Masiero and Murayama, in which the near-maximal atmospheric neutrino mixing angle governs large new b → s transitions. Relating the supersymmetric low-energy parameters to seven new parameters of this SO(10) GUT model, we perform a correlated study of several flavor-changing neutral current (FCNC) processes. We find the current bound on B(τ → µγ) more constraining than B(B → X s γ). The LEP limit on the lightest Higgs boson mass implies an important lower bound on tan β, which in turn limits the size of the new FCNC transitions. Remarkably, the combined analysis does not rule out large effects in B s −B s mixing and we can easily accomodate the large CP phase in the B s −B s system which has recently been inferred from a global analysis of CDF and DØ data. The model predicts a particle spectrum which is different from the popular Constrained Minimal Supersymmetric Standard Model (CMSSM). B(τ → µγ) enforces heavy masses, typically above 1 TeV, for the sfermions of the degenerate first two generations. However, the ratio of the third-generation and first-generation sfermion masses is smaller than in the CMSSM and a (dominantly right-handed) stop with mass below 500 GeV is possible.