On lepton flavour violation in realistic supergravity models

Hayes, Jonathan Geoffrey (2005) On lepton flavour violation in realistic supergravity models. University of Southampton, Doctoral Thesis.

Record type: Thesis (Doctoral)

Abstract

We study the phenomenological consequences of a string inspired effective supergravity model arising from intersecting D-branes supplemented by an additional U(1) family symmetry, detailing the scientific progress leading up to the advent of this model and giving reasons as to why one should consider it. Realistic effective supergravity models have a variety of sources of lepton flavour violation (LFV) which can drastically affect the predictions relative to the usual scenarios in the literature based on minimal supergravity and the supersymmetric see-saw mechanism. we catalogue the additional sources of LFV which occur in this model including the effect of D-terms arising from the Abelian U(1) family symmetry, non-aligned trilinear contributions from scalar F-terms, as well as non-minimal supergravity contributions and the effect of different Yukawa textures. In order to quantify these effects, we calculate the branching ratios for μ → and τ →μγ for a range of benchmark points designed to isolate the different contributions. In such theories the magnitude of the D-terms is predicted, and we find that the D-term contributions are generally dangerously large, but in certain cases such contributions can lead to a dramatic suppression of LFV rates. In the class of string models considered here, we find the surprising result that the D-terms can sometimes restore universality in effective non-minimal supergravity models.

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