# FCNC Decays of the Top Quark

## TL;DR

This paper investigates flavor-changing neutral current decays of the top quark, analyzing suppression mechanisms in the Standard Model and exploring beyond Standard Model scenarios like R-parity-violating SUSY for potential observable signals.

## Contribution

It identifies the suppression mechanisms in the Standard Model and demonstrates that R-parity-violating SUSY could produce detectable FCNC top decays.

## Key findings

- Standard Model suppresses $t\to c+h/Z$ decays significantly.
- cMSSM cannot enhance FCNC decay rates sufficiently.
- R-parity-violating SUSY allows for potentially observable FCNC signals.

## Abstract

If new physics (e.g. SUSY) does not show up as direct evidence at the LHC, it could still be observable in FCNC processes involving the $t$-quark. We take a close look at the process $t\to c + h/Z$ and show that its branching ratio in the Standard Model is subject to three mechanisms of suppression. To obtain an observable signal, one needs to evade all these mechanisms in a theory beyond the Standard Model. We show that a theory like the cMSSM cannot provide a big enough enhancement. However, in a framework like $R$-parity-violating SUSY, observable signals are a distinct possibility.