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

TL;DR

This paper investigates how a hypothetical fourth fermion generation could alter the theoretical bounds on the Higgs boson mass, using lattice simulations of a Higgs-Yukawa model that mimics the Standard Model's fermion couplings.

Contribution

It provides a numerical analysis of the impact of a potential fourth fermion generation on Higgs mass bounds within a chirally invariant lattice framework, extending the standard three-generation scenario.

Findings

Fourth generation significantly modifies Higgs mass bounds

Heavy fourth quark doublet influences upper and lower bounds

Results compared to the three-generation case

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.