New Fermions at the LHC and Mass of the Higgs Boson

TL;DR

This paper explores how adding vectorlike fermions at the TeV scale affects the stability and mass bounds of the Higgs boson, suggesting a lighter Higgs could indicate new physics accessible at the LHC.

Contribution

It introduces a model with vectorlike fermions that modifies Higgs mass bounds and discusses implications for LHC discoveries and vacuum stability.

Findings

Vacuum stability bound for Higgs mass lowered to 117 GeV

Upper perturbativity bound for Higgs mass is 190 GeV

Presence of vectorlike fermions could be detected at the LHC

Abstract

Unification at M_{GUT}\sim 3\times 10^{16} GeV of the three Standard Model (SM) gauge couplings can be achieved by postulating the existence of a pair of vectorlike fermions carrying SM charges and masses of order 300 GeV -- 1 TeV. The presence of these fermions significantly modifies the vacuum stability and perturbativity bounds on the mass of the SM Higgs boson. The new vacuum stability bound in this extended SM is estimated to be 117 GeV, to be compared with the SM prediction of about 128 GeV. An upper bound of 190 GeV is obtained based on perturbativity arguments. The impact on these predictions of type I seesaw physics is also discussed. The discovery of a relatively `light' Higgs boson with mass \sim 117 GeV could signal the presence of new vectorlike fermions within reach of the LHC.