Constraints on Supersymmetric Flavour Models from b->s gamma

TL;DR

This paper investigates how deviations from minimal flavour violation in supersymmetric models affect the b->s gamma decay rate, revealing conditions under which these deviations relax existing experimental bounds.

Contribution

It introduces a detailed analysis of non-zero off-diagonal Yukawa and sfermion matrices at the GUT scale and their impact on flavour observables in CMSSM-like theories.

Findings

Large down-squark sector expansion parameter relaxes b->s gamma bounds.

Slepton sector expansion parameter must be smaller to satisfy tau-> mu gamma constraints.

Departure from MFV can significantly alter supersymmetric flavour phenomenology.

Abstract

We consider the effects of departures from minimal flavour violations (MFV) in the context of CMSSM-like theories. Second and third generation off-diagonal elements in the Yukawa, sfermion, and trilinear mass matrices are taken to be non-zero at the GUT scale. These are run down together with MSSM parameters to the electroweak scale. We apply constraints from fermion masses and CKM matrix elements to limit the range of the new free parameters of the model. We determine the effect of the departure from MFV on the branching ratio of b->s gamma. We find that only when the expansion parameter in the down-squark sector is relatively large there is a noticeable effect, which tends to relax the lower limit from b->s gamma on the universal gaugino mass. We also find that the expansion parameter associated with the slepton sector needs to be smaller than the corresponding parameter in the down-squark sector in order to be compliant with the bound imposed by the branching ratio of tau-> mu gamma.