Effects of a potential fourth fermion generation on the upper and lower Higgs boson mass bounds

TL;DR

This study investigates how a hypothetical fourth fermion generation could alter the theoretical bounds on 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 analysis of the impact of a fourth fermion generation on Higgs mass bounds within a chirally invariant lattice framework.

Findings

Fourth generation heavy quarks significantly modify Higgs mass bounds.

Results differ from the standard three-generation scenario.

The model maintains chiral symmetry using Ginsparg-Wilson fermions.

Abstract

We study the effect of a potential fourth fermion 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.