Flavour physics with a 4th generation

TL;DR

This paper reviews recent developments in flavour physics involving a hypothetical fourth generation of particles, discussing constraints, predictions for key observables, and implications for lepton flavour violation and CP violation.

Contribution

It provides an overview of the impact of a fourth generation on flavour observables and discusses potential experimental constraints and signals.

Findings

Predictions for Br(B_s -> mu+ mu-) and Br(K -> pi nu nubar)

Analysis of S(psi phi) in the B_s system

Discussion of epsilon'/epsilon as a constraint

Abstract

We present an overview of recent work on flavour physics in the presence of a sequential fourth generation. We will discuss shortly the constraints on the new parameters and in the reminder present predictions for observables like Br(B_s -> mu+ mu-), Br(K -> pi nu nubar) and the indirect CP violation S(psi phi) in the B_s system. We will further stress the importance of epsilon'/epsilon as a possible constraint once reliable lattice results for B_6 and B_8 become available. Lepton flavour violation is also briefly discussed in view of prospects for tau physics at an upgraded flavour factory as well as upcoming experiments for mu -> e gamma and mu-e conversion in nuclei.