Four Generations and Higgs Physics

TL;DR

This paper explores the implications of a hypothetical fourth generation of particles on Higgs physics, revealing significant effects on production, decay, and observable signals, consistent with current experimental bounds.

Contribution

It identifies a specific parameter space for a fourth generation that aligns with experimental data and predicts distinctive Higgs phenomenology and exotic signals.

Findings

Higgs production rates are enhanced by the fourth generation

Higgs decay channels include exotic signatures like same-sign dileptons

Electroweak precision data constrains Higgs mass to 115-315 GeV

Abstract

In the light of the LHC, we revisit the implications of a fourth generation of chiral matter. We identify a specific ensemble of particle masses and mixings that are in agreement with all current experimental bounds as well as minimize the contributions to electroweak precision observables. Higgs masses between 115-315 (115-750) GeV are allowed by electroweak precision data at the 68% and 95% CL. Within this parameter space, there are dramatic effects on Higgs phenomenology: production rates are enhanced, weak-boson-fusion channels are suppressed, angular distributions are modified, and Higgs pairs can we observed. We also identify exotic signals, such as Higgs decay to same-sign dileptons. Finally, we estimate the upper bound on the cutoff scale from vacuum stability and triviality.