Large mass splittings for fourth generation fermions allowed by LHC Higgs exclusion

TL;DR

This paper investigates how a heavy Higgs boson influences the mass differences and decay channels of fourth generation fermions, potentially altering search strategies at the LHC.

Contribution

It demonstrates that a heavy Higgs allows large mass splittings in fourth generation fermions, enabling new decay channels and affecting experimental search strategies.

Findings

Heavy Higgs (>800 GeV) permits large mass splittings.

Large splittings enable W-emission decay channels.

W-emission channels can change LHC search strategies.

Abstract

In the context of the Standard model with a fourth generation, we explore the allowed mass spectra in the fourth generation quark and lepton sectors as functions of the Higgs mass. Using the constraints from unitarity and oblique parameters, we show that a heavy Higgs allows large mass splittings in these sectors, opening up new decay channels involving W emission. A Higgs heavier than $ \sim 800 GeV $ would in fact necessitate either a heavy quark decay channel t'-> b'W/b'-> t' W or a heavy lepton decay channel \tau' -> \nu' W as long as the mixing between the third and fourth generations is small. This mixing tends to suppress the mass splittings and hence the W-emission channels. The possibility of the W-emission channel could substantially change the search strategies of fourth generation fermions at the LHC and impact the currently reported mass limits.