Higgs boson mass bounds in the presence of a very heavy fourth quark generation

TL;DR

This paper investigates how a very heavy fourth quark generation would alter the theoretical bounds on the Higgs boson mass, using lattice simulations of a Higgs-Yukawa model that mimics the Standard Model's Higgs-fermion interactions.

Contribution

It provides the first numerical evaluation of Higgs mass bounds considering a heavy fourth quark generation within a chirally invariant lattice framework.

Findings

Heavy fourth quark generation raises the Higgs mass upper bound.

The presence of a fourth generation lowers the Higgs mass lower bound.

Results differ significantly from the three-generation Standard Model scenario.

Abstract

We study the effect of a potential fourth quark generation on the upper and lower Higgs boson mass bounds. This investigation is based on the numerical evaluation of a chirally invariant lattice Higgs-Yukawa model emulating the same Higgs-fermion coupling structure as in the Higgs sector of the electroweak Standard Model. In particular, the considered model obeys a Ginsparg-Wilson version of the underlying ${SU}(2)_L\times {U}(1)_Y$ symmetry, being a global symmetry here due to the neglection of gauge fields in this model. We present our results on the modification of the upper and lower Higgs boson mass bounds induced by the presence of a hypothetical very heavy fourth quark doublet. Finally, we compare these findings to the standard scenario of three fermion generations.